Check Engine light

swschrad · June 2003

sounds like the shop is either playing Warranty Payments Roulette or sticking you when they should be getting the codes out of the computer and doing a troubleshooting chain to see what is really broken or out of adjustment. if in fact they HAVE been diligently taking codes and working with Honda TS, I find it hard to see why they have done several thousand dollars worth of parts slinging with no resolution of the issues.

something is missing here.

0patience · June 2003

My question is, there is a diagnostic tool that they can hook up to the vehicle and send you on your way. It monitors the vehicle and how it runs, any time a code is triggered, it is logged and the parameters of the engine are also logged. Why haven't they done this yet?
It will then show what is happening when the check engine light comes on.

jwc2000 · July 2003

Thanks alcan for setting me straight on my last inquiry. I did type in the wrong code. To recap, I drive a 1999 Honda Accord LX with four cylinders. When the CEL came on, Auto Zone read the code and it was P1556. They couldn't tell me what this meant because it was specific to the manufacturer. I would like to have some idea of the problem before I have to take it to a dealer.

alcan · July 2003

Unfortunately, P1556 is a manufacturer specific code and Honda tends not to release information. Try reposting in one of the Honda forums. Auburn is a Honda tech who frequents them, and might be able to help you.

putt2 · July 2003

at 90000miles engine light come. friends suggest that I check out the vsv switching valve. where is the valve and where can I buy it? any info. is preciated.

dustyk · August 2003

I have an OBD II list. Are you sure you have the correct code for a Honda?

"P1556 "A" Camshaft Position Actuator Control Open Circuit Bank 1 (BMW)"

Regards,
Dusty

0patience · August 2003

From Honda's own information system. I didn't find that trouble code listed for it.
Recheck the trouble code, as it is invalid.

jacquegill · September 2003

I have a millenia 02 with 19,800. I have been fairly pleased with it so far, but a few weeks ago my "check engine" sensor came on. Checked the gas cap and even filled the car up. It goes off at times, but comes back on. Took into a mazda dealer and they say I need "de-carbonization" and that this is part of my "routine maintenance" even though it is not listed on their schedule. Also indicated that my warrenty is not valid if I don't do this. Has anyone heard of this?

swschrad · September 2003

some engines under some conditions tend to build up deposits of unburned fuel and carbon, particularly on valves and the edges of pistons and the facing ring.

was NOT aware that anybody has "secret maintenance schedules" for periodic maintenance that are not published, as that would be against the magnusson-moss warranty act as I understand it.

I strongly suspect the maintenance advisor goofed that part. it is possible to get incomplete sealing around valves, or have chunks of gunk break off and crack rings, so if you have a performance issue, it does need to be addressed.

the general decarbonization procedure I have heard of, and used to do periodically for no demonstrated good reason on a couple of old mopars in the 70s other than "clean is good," is to slowly trickle petroleum solvent into the carburetor throat, choking on the evil white smoke, until the car stalled out. then you turn the key off, go someplace else for a half hour or so, start the car, and drive a bit until you stop smogging out the neighborhood. there is probably a modified procedure for FI engines, maybe introducing what is essentially penetrating oil through a vacuum hose, because carburetors are hard to find on the engine these days.

0patience · September 2003

jacquegill,
Need to know what trouble code they got to come to that conclusion.
De-carbonizing is not listed as routine maintenance, so I guess you can draw your own conclusion from that.

randor · September 2003

I have a '97 Suburban with a 5.7L V8 that has 106,000 miles on it. It has an intermittent Service Engine Soon Light for P0172 Left Bank Rich and P0175 Right Bank Rich. When the light comes on it exhibits a change in driveability-it surges at level throttle at highway speeds and seems to have less power overall. When the light is off it runs normally. The 02 sensors have been replaced, the cats check out ok for back pressure, and the fuel injection was given a ProVac service, and it was given a complete tune up and new filters. It still has the intermittent condition. Any suggestions?

alcan · September 2003

Coolant temp sensor.
Leaking fuel pressure regulator diaphragm ( a PITA, the upper intake plenum has to be removed to access)

fwatson · September 2003

My '01 Mazda Millenia P with 2.5 litre V-6 engine, is still running flawlessly with more than 12000 miles on it.

But starting about a month ago, I occasionally get a "Check Engine" light for a day or so. Nothing seems wrong when this happens, and I make it a habit to tighten the fuel filler cap at least 5 clicks after each fillup. I can't make a direct connection between fueling and the light coming on. I know that it usually has to do with pollution control, and could just be a bad oxygen sensor or such.

I was wondering though if any other owners have had the light come on, and then just clear itself after maybe 3 to 4 starts. And if so have you had it checked to know what is causing it. It came on last Saturday when I was going to be close to a Mazda dealer (about 60 miles from home), but by the time I made a couple of stops elsewhere it had cleared so I just skipped the dealer visit.

Any idea on the cause of this? Is there a way to get "beep" code readouts without special equipment, and if so, where would I find a list of those codes?

Thanks for any answers.

fwatson · September 2003

You should follow the Millenia forum. It is kind of slow, but we do get some good information over there. Here is a crosspost from it. It's for the P model with 2.5 non supercharged engine. If you have the S supercharged model this doesn't apply to you.

--------------------------------------------
--------------------------------------------
Also, there is a TSB out advising not to use 93 in the P because of carbon buildup. Check post #2536 of 2584 by misty8

----------------------------------------

(Bulletin No: 01-027/02

APPLICABLE MODEL(S)/VINS

All 1995 - 2002 Millenia models with 2.5L V6 (KL)

Description

After a cold start, MIL comes on with DTC P0300 to P0306 stored in the memory. In most cases, this concern may be caused by misfire occurring in one cylinder during idle. The use of premium fuel (high-octane fuel) may be allowing carbon deposits to accumulate on the exhaust valve seat, causing momentary insufficient compression.

To correct this concern, remove carbon deposits using a suitable top engine cleaner.

Note: After removing the carbon deposits, be sure to advise the customer to use lower-octane fuel (87 or 89 octane) to help prevent future recurrences.)

--------------------------------------------
--------------------------------------------

And this is from AllData:

5- 0102702 APR 03 Engine - MIL ON/ DTC's P0300 - P0306 Set

http://alldata.com/TSB/33/02333664.html

peyton8106 · September 2003

After about 20 highway miles my transmission shifts into direct drive and won't go back into over-drive..The engine temp. is normal and the van drives okay. Transmission was serviced for fluid and filter but promlem continues. Any ideas.

sgsutn · September 2003

My mercedes c280 has 64,000 miles. Engine light I occasionally get a "Check Engine" light for a day or so. Nothing seems wrong when this happens, and I have replaced the fuel filler cap. With no luck. Is there a reset button??

andyh4 · September 2003

Hi Guys,

I have a Nissan Altima GXE,1994.From yesterday I see the Check Engine indicator ON.I used to get this indicator when the car would stand under the Sun for few hrs.This time it happend during the night.It is ON there after.I started the car today in the morning,still the indicator is ON.No fumes,no smell though.
Can any one of you tell me what the problem could be.Pls include the apprx cost.
Thanks.

Andy.

snowman · October 2003

My Taurus (2000 SES Vulcan w/ 39K) gave me check engine light. I took it to Autozone to get the code (dealer asked me $90). It was P0156. Donwstream heated O2 sensor on bank 2. AutoZone erased the code. I have been driving since then and didn't come back but pinging was back.

My car has pinging issue. It was intense during summer time. It's got worse and I emptied 20 oz Chevron techron into half way full tank, sprayed 1 can CB cleaner and 1 can TB cleaner into TB towards upper intake, cleaned up the plugs with wire brush. BTW, plugs were nice and deposit free. The car picked up some power and pinging was gone.

200 miles later I heard light pinging. But today, after AZ erased the code, it pinged and I felt performance was down. I realized that now it is using more fuel. 3 quarters of thank I've got 160 miles. I used to get 21 miles per gallon in city. How the heck donwstream heated O2 sensor on bank 2 causes more fuel consumption?

I bought Autolight 764 copper plugs but haven't installed them. Also I am planing remove the upper intake, TB and all other thing along the way and clean them.

I am not sure whay O2 sensor is givin this much early problem.

I wonder whether CB or TB cleaner has any effect on O2 sensor problem. What you guys think?

Another thing that when I pull upper intake out and discover that lower one is dirty how I should clena that up?

dunkmydonut · October 2003

have a reputation for pinging.
The computer picks up signals from sensors, and uses the info to adjust timing, and injector pulse duration. If your O2 sensor is defective, it can cause your engine control sysem to pickup false readings, and send out improper commands to fuel, and ignition system. If your scanner is telling you that your O2 sensor has a problem, then that would be a good place to start. Sometimes the code is caused by a bad connection. More than likely the O2 sensor is bad. You can change the sensor, and take a chance that it's bad, or get a manual where you get auto parts, and look for one with a flow chart. That will tell you how to check each sensor for voltage and resistance in the wiring.
I think if I had the problem, I'd get the O2 sensor, and make sure the wire connection is clean.

I had to change all my O2 sensors at 8,000 miles. So your miliage is not unusual. Glad about having the warranty.

I belong to a Ford truck forum that includes Rangers with the 3.0 LV6, and the pinging is common. Most switch to higher octane gas.

fwatson · October 2003

My '02 Mazda Millenia P with 2.5L V-6 had an occasional "Check Engine" light, so I had the code read out at AutoZone. They got PO325-Knock Sensor.

His suggestion was to go to a slightly higher octane gasoline (I'm running 87) or have the computer reprogramed. I have no ping or knock even under hard acceleration, so I am going to put a couple of feelers out to see what online mechanics suggest. Thought I might get a bite here.

alcan · October 2003

This might help:

2000 Ford Taurus V6-183 3.0L VIN U SFI Vehicle Level Engine, Cooling and Exhaust Engine Technical Service Bulletins All Technical Service Bulletins Engine Controls - Spark Knock on Acceleration

Engine Controls - Spark Knock on Acceleration
Notes

Article No. 02-24-3 12/09/02

DRIVEABILITY - SPARK KNOCK ON ACCELERATION - 3.0L 2V/FFV ENGINE ONLY

TRANSAXLE - AX4N/AX4S - HARSH TRANSMISSION ENGAGEMENT - 3.0L 2V/FFV ENGINE ONLY

FORD:
2000-2001 TAURUS
1999-2000 WINDSTAR

MERCURY:
2000-2001 SABLE

Article 00-25-5 is being republished in its entirety to update the Service Procedure.

ISSUE

Some vehicles equipped with the 3.0L 2V or 3.0L FFV engine may exhibit spark knock during light accelerator tip in or heavy acceleration. 2001 2V and FFV Taurus/Sable vehicles may also exhibit a harsh Park to Drive engagement. This may be caused by the calibration of the Powertrain Control Module (PCM).

ACTION

Verify condition. Check for potential lean contributors, reprogram the Powertrain Control Module (PCM), and/or perform Octane Adjust. Refer to the following Service Procedure for details.

SERVICE PROCEDURE

Windstar vehicles: DO NOT perform PCM reprogram. Check for potential lean contributors and/or perform Octane Adjust only. Refer to the following Octane Adjust Procedure for details. If the spark knock condition, (2000/2001 Taurus/Sable), or transmission harsh engagement, (2001 Taurus/Sable) is still present after performing normal diagnostics, check for potential lean contributors and reprogram the PCM.

On a very small percentage of Taurus/Sable vehicles, it is still possible spark knock may be present after PCM reprogramming. If spark knock can be verified after PCM reprogramming, proceed with the following Octane Adjust Procedure.

Octane Adjust Procedure

Use the New Generation Star (NGS) Tester to perform an Engine Octane Adjustment using the following procedure:

1. Using NGS Service Card (11.0 level or higher) and Flash Cable, select "Service Bay Functions".

2. Select "PCM (Powertrain Control Module)".

3. Select "Module Configuration".

4. Select EEC V or PTEC Vehicle - by TSB.

5. Press trigger to continue on emission compliance authorization screens.

6. Highlight the Octane Adjust column and press trigger, then rotate the dial to change the ignition timing from "No Retard" to "Retard". Press trigger again.

7. Highlight Fuel Octane and press trigger, then rotate the dial to set the octane to 87 Octane and press trigger again.

8. Press the Start button. You should receive a message saying that the change has been successful.

NOTE FAILURE TO PRESS THE START BUTTON WILL RESULT IN CHANGES IN OCTANE ADJUSTMENT NOT BEING ACCEPTED.

9. Exit out of Service Bay Functions.

Obtain an Authorized Modifications Decal (FPS 8262 - obtainable through DOES II, 25/pkg) and list the date, dealer number, and summary of modifications performed. Select a prominent place adjacent to the Vehicle Emission Control Information Decal suitable for installing the Authorized Modifications Decal. Clean the area, install the decal and cover it with a clear plastic decal shield.

PCM Calibration Information

SUPERSEDES: 00-25-5

WARRANTY STATUS: Eligible Under The Provisions Of Bumper To Bumper Warranty Coverage And Emissions Warranty.

OPERATION * DESCRIPTION * TIME

022403A * Check For Lean Contributors And Reprogram Powertrain Control Module 2000-2001 Taurus/Sable * 0.7 Hr.

022403B * Check For Lean Contributors And Reprogram Powertrain Control Module Then
Perform Octane Adjust Procedure 2000-2001 Taurus/Sable * 0.8 Hr.

022403C * Perform Octane Adjust Procedure Only 1999-2000 Windstar * 0.6 Hr.

DEALER CODING
CONDITION * BASIC PART NO. CODE
12A650 * 42

OASIS CODES: 497000, 503000, 504000, 615000, 615500, 615600

wynert · October 2003

My "check engine" light on the control panel has been coming on with the beeping signal. This happens intermittently while I am driving. This has been going on for one or two years. It started only on long trips but now happens even after driving a few miles. I have had the entire car checked by many different mechanics. Nobody has been able to figure out why it happens or how to turn it off.
This is a 1994 Continental with 130,000 miles on it, but besides the beeping it still drives very well. Any suggestions?

7937 · November 2003

I'm reading a lot about pinging here but I don't see any reference to knock sensors. Don't late model cars have them? The knock sensor is a piezoelectric device that responds to the unique knocking sound the engine makes when it pings and, then, sends a signal to the ECM to adjust the ignition timing to tune out the knock.

Even my humble 99 Cavalier has one.

If your vehicle is pinging and there is a knock sensor installed, I would check the operation of that sensor. Disconnect the wires to the sensor and put a scope on the sensor terminals. With a small hammer strike a sharp blow next to the sensor where it is mounted on the engine block. Do NOT hit the sensor ! An AC signal of about 1 volt should appear on the scope to indicate a working knock sensor.

fwatson · November 2003

New cars DO have knock sensors. I did not have any problem with knocking or pinging with my 2001 Mazda Millenia P (2.5L V6).

Instead, the knock sensor itself started causing the check engine light to come on at times. Mazda replaced it under warranty about 3 weeks ago and that solved the CEL problem. I guess the thing was just so sensitive that some minor vibration would cause it to send the signal to light the CEL.

cfrank3 · November 2003

This light stays on continuously. I've taken my 98 S70 GLT to an independent (I extremely dislike dealers) and he has checked it out twice. He gets the PO107 (map/baro circuit low) and PO455 (evap system leak large). He clears the system and I drive the car and Bingo! the check engine light comes on. The repairman says drive it anyway, all is well! Help! If nothing is wrong as he says, why is the light on?

irishalchemist · November 2003

Hi there,

I have a friend at work with a problem. She has a 97 Protege LX, 5 spd, L4, 1500cc, which is turning its CEL. I scanned it the first time, and found a P0505 - Idle Control problem. She mentioned that one time the CEL came on, the RPMs at idle jumped to 1000 (normally 700). I read that the IAC can be cleaned, and this sometimes fixes the problem. I reseted the CEL, and asked her to let me know when it came back, so I could confirm the code (she had left the gas cap loose one time, so I wanted to eliminate the obvious first...).

A week later, she told me the CEL came back on. I packed my scanner, and read the codes. The P0505 was there again, but this time she also had a P0421 stored. This has something to do with the catalytic converter not warming up properly (?).

My question is, can these two codes, P0505 and P0421, be related? Can something else be triggering these, like a faulty HO2S? There are no vaccum leaks, and the engine runs fine (I could not get it to idle fast when I drove it...). Any suggestions appreciated. I feel a bit bad, as she bought the car in part because I told her Protege's were great (I have one...).

TIA,

G.

opera_house_wk · November 2003

Sure, you can just keep driving. There is a vent solenoid that vents the charcoal canister. In general, I have found these placed in locations that are prone to water and contamination. They either gunk up or rust to pieces so the valve sticks. I assume the gas cap O ring has been inspected for damage as well as the seat.

Our state has just switched from tailpipe emissions testing to the OBD-II connector test. Just ignoring the light is not always an option.

Mr_Shiftright · November 2003

opera, could you elaborate a bit on the change in emissions testing in your state?

opera_house_wk · November 2003

Has just proposed a policy of doing the emissions check using the OBDII connector instead of the tailpipe test on the dyno for late model vehicles. Start date is Jan. 5, 2004. I imagine they would have an attitude if the computer was reset just before you drove in. They say this is an effort to speed up testing delays. About 2 years ago I read that states were considering this on www.obdiicsu.com the Colorado State University site that was doing testing on this to see if it was effective. This site has some interesting case studies on emissions failures and solutions.

0patience · November 2003

Most states will be adopting the scan method for the emissions testing. Starting in 2004 most vehicles will be using the CAN protocal and everything that the emissions testing will need to know will be available through a scantool.
for those wondering what the CAN protocal is, it is Controller Area Network and will replace OBD2. And yes, those of you who have OBD2 scantools, they will be obsolete, unless they are upgradeable, but most aren't. Good news, huh?
The dyno testing will go by the wayside and you will pull into an emissions test site, they will plug in, download the info and you will pass or fail.

swschrad · November 2003

and one could say that their fine set of english-measurement wrenches has also gone obsolete with the metrification of the world.

if you have an commodore computer in the attic, it's also a paperweight. and they're trying to kill the CD now.

stuff happens, technologies change, the world moves on. if you want to keep the old stuff alive as a hobby, like rebuilding 1924 radios, cool, watch your favorite auction site for killer deals on barely-used scantools.

and if anybody finds any good used or NOS type-20 vacuum tubes, let me know, it would be nice to bring one to a local museum and maybe get a chance to play the original RCA theremin as a result.

dunkmydonut · November 2003

has been the norm here in Ma. for quite a while. There are surprising facts about the test. If your abs light is on, you can still pass. If your air bag light is on, you still pass. If your emission or cel light is on, it depends on your exhaust readings that are picked up through your obd II plug as to whether or not you pass. The emission test is only performed every other year, while the regular safety, where they jack up the front end and look for play, check horn etc. is done evey year. Confusing, huh? I think next we'll have to undergo a physical by the techs while our car is up in the air. Excuse the greasy finger prints on your butt. I don't think the feds will rest, till they've taken all the fun out of driving. I think I see black helicopters hovering over the house as I type. I'd better go!

0patience · November 2003

That would all depend on the inspector.In most states, that I know of, If the CEL is on, it is an auto failure. In states that do safety & emissions the SRS or ABS light on is an auto failure.
If they are doing a safety inspection and passing a vehicle with an SRS or ABS light on, then they are taking a personal liability, not to mention breaking the law.

swschrad · November 2003

my apartments are under the flight path between ANG flight headquarters in St. Paul and Camp Ripley. this is daily traffic to and fro.

and geez, it all started after I complained about emissions stuff messing up on my 76 buick........

:-D

... but seriously folks, if you had lazy 02 sensors, it seems to me there's no way you could legally pass if the test was any good. and the CEL won't light up on lazy sensors, only open ones, right?

7937 · November 2003

Should light up I reckon because there are two O2 sensors - one upstream of the cat. convertor and one downstream of the convertor. The ECM reads the differential of the two sensors and should pick up a problem and display the CEL if a sensor is lazy. Unless both are lazy....... No I dunno...

0patience · November 2003

It is possible that the light won't light on a "lazy" O2 sensor, but if it is OBD2, then it is possible that it would show on the scan tool.
There are alot of variables that OBD2 doesn't account for, that CAN will.

swschrad · November 2003

you should be able to identify the lazy 02 sensors, they will be the nearly-straight lines in the plot, or the numbers that don't "bounce" around. should be a sawtooth pattern back and forth around a half volt as they overshoot and catch up and overshoot the other way next pulse. the input is integrated (i.e. normalized by a capacitor across the sensor wires, or by software averaging of several successive values) at the computer itself before being used to control the engine. the ODB-II should also allow reading the values each pulse directly. I have a little kit scanner requiring a laptop computer for display and control that allows plotting the values for each 02 sensor over time.

7937 · November 2003

That does not mean the CEL light wil be displayed if both sensors are lazy. Most people do not have access to scan tools and depend on the CEL to report a problem. So, it would appear as if there is a problem here. The only valid test in this case would be a tail pipe emission test or so it would seem to me.

My 86 Honda Prelude failed its emission test because of a lazy O2 sensor without me being aware that there was a problem. No CEL was displayed. But then it only has one O2 sensor and does not have OBD2.

When OBD2 came out it was said to be the answer to all these types of problems. It's like Microsoft software. Each new version has its own set of problems and bugs. I wait with bated breath for the next version of on-board vehicle diagnostic software/hardware.

swschrad · November 2003

in which clippy tells you to never click on OK...

pjmycon · November 2003

Purchased a 2003 Town and Country this summer. Has 8000 miles and "Check Engine" light came on. Went to dealer and they said it was a computer fluke. Now it's back on again after only ten days. Any suggetions as to how to handle this problem and the dealer? First time new car buyer.

pnh21 · November 2003

CEL on means that there is something wrong. Take it back to the dealer and tell them that you are afraid to drive it and ask for a loaner until they fix the problem.

amosmoses1 · December 2003

A friend owns a Saturn SL2, I believe 1998. The "Check Engine" light has been coming on, and AutoZone's "computer diagnosis" shows the following error code/message:
+++++++++++++++++++++++++++++++++++++++++++++++++

Auto Zone
Thu Dec 18 09:14:55 2003

Auto Zone #3038
58400 Belleview Rd
Plaquemine, LA 70764
(225) 687-8854

Number Crossed : P0420
Cross
Reference parts found:

TROUBLECODE OBDII (ALPHA) P CODE

TROUBLESHOOTING P0420
The PCM has determined that the catalyst system efficiency for bank 1
is
below threshold for the current engine operating conditions. (Bank 1
identifies the location of cylinder #1, while bank 2 identifies the
cylinders on the opposite bank).
+++++++++++++++++++++++++++++++++++++++++++++++++

I understand that with neither he nor I being mechanically inclined, this will need to be handled by a professional, but what I would like to know is if someone could give me an idea what is the likely problem with this vehicle. To me, it would seem that there is a problem with the catalytic converter, something with the pollution abatement system. Does this look to anyone like this system may be getting "fouled", and if so does this usually require a whole new system installation?

Many thanks!

0patience · December 2003

The catalyst monitor test is performed once per drive cycle if all test conditions are met. The main enable criteria to enable a catalyst test are: a steady TP sensor reading and calculated temperature of catalytic converter (using ECT sensor, IAT sensor, load and run time) indicating system is fully warmed up. Once the enable criteria are met, 50 samples of the sensor voltage amplitudes are collected. The results of the 50 samples are averaged and converted to a millivolt (mV) reading which indicates the efficiency of the converter. The catalyst monitor tests consist of two stages. Stage one voltage ranges from -555 mV to a positive 550 mV When this value goes above 0 mV indicating stage one has failed, the stage two test will start to be used in determining the efficiency. When stage two reaches the fail threshold the MIL (SERVICE ENGINE SOON) lamp will be illuminated and a DTC 0420 will be set. The Scan tool can display the current value in millivolts for stage one as well as indicate if the stage one test has passed or failed. Whenever DTCs are cleared or the battery has been disconnected the results of stage one will be reset to a -555 mV.

DTC PARAMETERS
The stage one will fail when the catalyst efficiency becomes less than 75% efficient. After stage one fails, the 50 sample test results are used by stage two. When the results of stage two are greater than the fail threshold mV (catalyst efficiency below about 70%), the MIL (SERVICE ENGINE SOON) telltale lamp will be illuminated and a DTC P0420 will be set.

Probable causes of a DTC P0420 are:
Exhaust system leaks between the front and rear sensors or rear sensor leaking.
Catalyst deteriorated due to excessive time operating vehicle with a catalyst damaging misfire.
Contamination of converter due to incorrect sealant, fuel, or fuel additive.
IMPORTANT: A catalyst monitor test will not be performed if a fault exists in the rear or front oxygen sensor circuits.

DIAGNOSTIC AIDS
DTC P0420, once set, should remain active. However, under certain driving conditions the catalyst monitor test may pass. This condition may occur if driving the vehicle at highway speeds (high air flow) but if the P0420 is set and no exhaust leaks are found the catalytic converter should be replaced. If a misfire (P0300) is detected P0420 test will not run. Be sure to correct a misfire condition before replacing the converter.

johnboy555 · January 2004

OK! I've got a 94 GP (3.1 engine). Had it about 6 years, and have really loved the car. The problem is that after driving for about 10 min (from cold) the check engine light comes on. Of course it then jumps out of (or into) a "closed loop" (whichever isn't normal) and the gas mileage goes right into the toilet. It runs OK, but bad mileage. When we run the trouble codes it points to the EGR valve. But when I check the reader each of the solenoids comes on when it should. (The reader we use can show what each individual solenoid us doing.) I have replaced the EGR with one from a junkyard engine with 40K on it and same problem. The replacement part is about $230/employee discount.
Also..I have had the exact same problem with 2 that's right 2 '94 Chevy Cavaliers. Both with the same 3.1 engines. (Each of my daughters had one.)
Is there a problem that Gm won't admit or is there something else that could be causing this. the EGR code is the only one that comes up.

alcan · January 2004

Remove the EGR valve, cycle each solenoid, and verify the pintles are opening and fully closing. If ok, try cleaning out the carbon from the EGR passages in the intake manifold. A piece of speedo or parking brake cable chucked into a drill makes a good "rooter".

lancer04 · January 2004

I have a 1992 Grand Marguis which had the check engine light go on for the first time at 90,000 miles. Somtimes it remains on, other times flashed ever 15 seconds. Other than routine maintenance, tires, oil changes, etc, the car is all original parts.
Don't want to start putting $$$ into it now.
Any suggestions on how to start looking for the problem?

alcan · January 2004

We can't help you until you until you extract the stored diagnostic trouble codes as outlined here:

http://www.troublecodes.net/Ford/

Experience has shown that an intermittent check engine light on a pre-OBD II Ford is most often caused by a failed sensor for the EGR system. Typically sets an "Insufficient EGR Flow" code.

smootho · January 2004

99 malibu sitting for a week in drive way started 1 or 2 times to let it run so saturday i drove it to the store check engine light came on what could it be thanks for any help

jrc346 · January 2004

I do occasional work on a friends 94 Crown Vic and he also (like the 92 mentioned above) has this check engine light issue, though instead at 120,000 miles. When the light comes on, it usually stays on until the engine speed changes. The O2 Sensors have been changed, but the light still comes on, though at a completely different time (mostly during idle). The car also runs poorly when in gear while idling. It will come close to stalling out and will surge up slightly then come close to stalling again. This happens in fairly rapid successions. The thing is that my friend can't afford to get the computer read everytime the light comes on. Other times it has read a bad MAF sensor, so that was changed. Then it read that the O2 Sensors were not working efficiently (constant lean reading). However in the background there is always this other issue. Any other suggestions in where to go next? Car runs excellent while underway.
One other thing that may or may not be worth mentioning. While idling in gear the cars lights really dim and there appears to be a large draw on the battery guage. Believe it or not it has the original battery. Could this be causeing the issues?
Would a dirty EGR cause these symptoms? Where is this sensor at that monitors flow through the EGR valve? I did do a top engine clean with a product called Seafoam through the PCV inlet to the intake. With that and the new O2's the car gets better gas mileage, which is a good thing. Is it possible to extract the codes using a digital voltage meter, because that is all I own? Also I didn't see anything about the 4.6LV8 system/computer on that site. Did I miss something? Anyway thanks in advance for any information that you will be able to provide. I know I bombarded you with questions here, but I am loosing any hope in trying to help this car out.

alcan · January 2004

This should be the diagnostic info for your friend's car:

http://www.troublecodes.net/Ford/eec-iv.shtml

Around 94-95 is when most automakers started switching to OBD II, so some of the info might not apply. The easiest way to tell is by checking the underhood white emission sticker. If it doesn't say "OBD II compliant", which I don't think it will for a '94, the info above will work. If you don't have access to an analog voltmeter, use a 12V test light in it's place and count the flashes. If it is OBD II compliant, take it to any AutoZone and have them read the codes (no charge). Don't buy anything, just post the codes.

The poor idle you describe sure sounds like an EGR valve hanging open at idle and introducing exhaust gas to an already lean idle mixture. It's parameters are:
-engine coolant temp above 156F
-throttle off idle
-not wide open throttle

Retrieve and post the codes, and we'll go from there.

Check Engine light

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