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Thanks
The most common problem is ignition arcing because of no dialectric greese on the sparkplug boot. Bad spark plug, fualty injector for #3, engine compression problem on #3, ect. You got to do some troubleshooting and hope its one of the easy problems. If your due for a tune up, do one and see.
If you have a manual driven fan. I would first want to know if any modifications have been made to the engine, or the AC condensor removed or something. Has an add on transmission cooler been added?
If your positive that the engine is running cold itself and not a problem with the guage and a heater control valve not letting hot coolant enter the heater core. Please post more info about your vehicle.
Electric fan or manual? If electric fan, how long until it comes on after start up?
Automatic or manual transmission?
Modifications or add ons?
How are you determining engine temp?
Factory AC, or after makrket or none?
From what I can tell from other postings is that it can be either plugged cat, bad crank sensor, poor fuel preasure, fouled EGR, vacum leak, or a new truck....i just don't know how common any of these issues are in this model to know where to really start. Guess I have to pick one and start ruling them out one by one. Any ideas?
How common is the faulty fuel preasure issue? Rare but I have had fuel pumps briefly and intermitantly loose pressure causing random misfires. I actually had to see the failure while it happened. I even had a fuel pressure regulator fail intermitantly dropping the pressure.
Could this be a vacum, or faulty compression issue? Not a vacum issue, vacum leaks cause a lean miss and your o2 sensor would have caught that and run the engine ritch. Compression can cause misfires but I doubt that is your problem. Compression problems are rarely intermitant and are usally isolated by cyclinder and can be identified as a specific problem with one or more cyclinders.
No doubt, you got a tuffy, intermitant stuff always is. You basically have to keep trouble shooting until you find it. An intermitant coil failure or not enough output of kv spark could be it also. All the PCM knows, is that every once in a while the crank sensor is picking up a weird vibration and interpreting it as missfires. Hell, one car I finally found it, it was a loose mounting bolt for the crank sensor.
Heres a suggestion. Start with one system and eliminate it as the problem. Test it until the po300 comes back and if what ever you were testing checks out ok, move on to the next thing. Clear codes and test something else.
If you have a single or duel electric fan set up, check to see at what time the fan is coming on. A few models used a duel fan set up like on Honda's. One of the fans is controled by your AC being used.
I don't remember who posted that your vehicle has no heater control valve but only a door. I really don't care. This isn't your problem, but your vehicle does have a heater control valve.
You should be fine with a thermostat rated at 195, I would suggest not replacing it any more, this isn't your problem.
If you need help in identifying the fan clutch, it is made of aluminum about 6.5 inches in diameter with very small fins on it. It is located on your fan, between your fan and water pump.
If it's still misses and the mpg is still in the toilet I'm going to check the fuel preasure, EGR Valve and then maybe get to the CAT. Don't think its any of them as I believe a sensor light would have come on. Anyone got any other ideas? I could use the help.
Flashman3000
Not sure if this lead holds true for the SFI system. The post below is copied from
http://www.s10forum.com/forum/f107/if-your-having-a-mystery-running-like-crap-pr- oblem-268309/
The trouble-prone Sequential Central Port Injector (SCPI) fuel system was installed on GM's popular SUVs, pickup trucks and vans with 4.3L, 5.0L, and 5.7 liter engines. The defective fuel injection systems can cause GM owners to experience a "Service Engine Soon" light, misfires, rough idle, and hard start problems due to deposit build-up that cause poppet valves to stick and fail
CHECK THIS OUT here is the link to it http://www.arb.ca.gov/newsrel/nr021103.htm
took a lot of diggin there is a tsb for it the number is 99066g most gm dealers will tell you there isnt one. this is the link that shows you the tsb that i finally got a dealership to say there was after going to 4 of them.
http://www.talkabouttrucks.com/group...ges/71004.html
As I read this I believe it applies to my VIN...8TH digit is X=CSEFI any thoughts? I posted the GM Policy Letter below..maybe it will help others save some time and money.
SUBJECT:
99066F - SPECIAL POLICY ADJUSTMENT - SEQUENTIAL CENTRAL PORT
FUEL INJECTION (SCPI) FAILURES IN CALIFORNIA ONLY (YF5
EMISSION EQUIPPED)
MODELS:
CERTAIN 1996, 1997, 1998, 1999, 2000, 2001, 2002 S/T, M/L, C/K, G,
P, W4/NPR TRUCKS AND 2003 NPR TRUCKS EQUIPPED WITH 4.3L
(RPO L35 - VIN CODE W OR RPO LF6 - VIN CODE X), 5.0L (RPO L30
- VIN CODE M) OR 5.7L (RPO L31 - VIN CODE R) ENGINE AND
CALIFORNIA EMISSION EQUIPPED (RPO YF5)
This bulletin is being revised to add the 2002 and 2003 model years to the SCPI Special Policy on certain S/T, M/L, C/K, G, P and W4/NPR truck models. Please discard Special Policy Bulletin Number 99066E, dated February, 2003.
CONDITION
Some customers of 1996, 1997, 1998, 1999, 2000, 2001, 2002 model year S/T, M/L, C/K, G, P, W4/NPR trucks and 2003 NPR trucks, that are registered in California, equipped with 4.3L (RPO L35 and VIN Code W, or RPO LF6 and VIN Code X), 5.0L (RPO L30 and VIN Code M) or 5.7L (RPO L31 and VIN Code R) engine, and California emissions (RPO YF5), may experience a "Service Engine Soon" light, misfire, rough idle or hard start due to a deposit build-up on the Sequential Central Port Fuel Injector (SCPI) poppet valve(s). The deposit build-up may cause injector poppets to stick closed. Certain fuels have been found to interact with the SCPI system to cause the deposits.
SPECIAL POLICY ADJUSTMENT
This special policy covers the SCPI failure condition described above for a period of ten (10) years or 200,000 miles, whichever occurs first, from the date the vehicle was originally placed in service, regardless of ownership.
The repairs will be made at no charge to the owner. This special policy applies ONLY to repairs requiring SCPI system servicing, injector cleaning and/or MFI assembly replacement of the SCPI system. The customer should not be charged for performing a system check when it is determined that the SCPI system is not the cause of a customer complaint (labor operation T5532 is provided to submit claims for such system checks). Any additional necessary diagnosis and repairs that are not related to the SCPI condition are not covered by this special policy. The customer should be informed that any further service that is not covered by new vehicle warranty will not be covered by this policy.
VEHICLES INVOLVED
Involved are certain 1996,1997,1998,1999, 2000, 2001, 2002 S/T, M/L, C/K, G, P, W4/NPR and 2003 NPR model vehicles, registered in California, equipped with 4.3L (RPO L35 - VIN Code W, or RPO LF6 - VIN Code X),5.0L (RPO L30 - VIN Code M) or 5.7L (RPO L31 - VIN Code R) engine; and California emissions (RPO YF5). This Special Policy covers all vehicles within these model years, with these engine and emissions RPO's.
PARTS INFORMATION
Parts required to complete this special policy are to be obtained from General Motors Service Parts Operations (GMSPO). Please refer to your "involved vehicles listing" prior to ordering parts. Normal orders should be placed on a DRO Daily Replenishment Order. In an emergency, parts should be ordered on a CSO = Customer Special Order.
IMPORTANT :Isuzu Parts Ordering: In order to comply with the 10-digit Isuzu part numbering system, Isuzu dealers must add an "8" to the beginning and a "0" to the end of the listed 8-digit part numbers when ordering parts through AIPDN.
CUSTOMER NOTIFICATION
Customers will be notified of this special policy on their vehicles by General Motors (see copy of typical customer letter included with this bulletin - actual divisional letter may vary slightly).
SERVICE PROCEDURE
System Check: Use strategy-based diagnoses listed in the front of the Driveability and Emissionssection of the service manual. If the SCPI system is operating properly, inform the customer that the vehicle does not have the condition listed in the owner letter. If poor driveability conditions persist, inform the customer that any further diagnosis and repairs will be at their expense if the vehicle is outside the parameters of the new vehicle warranty.
SCPI Injector Cleaning Procedure: If diagnosis leads to sticking poppet nozzles, use the service procedure from Service Bulletin 00-06-04-003B to clean the SCPI poppet nozzles. Please note that the service bulletin term for SCPI is Central Sequential Fuel Injection (CSFI), but is referring to the same fuel system assembly. If the poppet nozzles have previously been cleaned and the sticking condition has reoccurred, refer to the correction paragraph below.
SCPI Fuel Tank Fill Pipe Assembly for 1997-99 M/L Van and 1999 - some 2000 C/K Truck: with 4.3L, 5.0L, 5.7L engines and built prior to listed VIN/Production dates on Service Bulletin 00-06-04-018: If diagnosis leads to sticking poppet nozzles on these models, use the service procedure from Service Bulletin 00-06-04-018 to replace the fuel tank fill pipe assembly, if this procedure has not been performed previously. Previous service procedure can be verified by checking GMVIS for Labor Operation L1065 on "M/L" trucks with replacement part number 15050573; or Labor Operation L1065 on "C/K" trucks with replacement part numbers 15747585 or 15747588.
Correction: If, after cleaning the SCPI poppet nozzles, the normal service manual diagnosis still indicates that the SCPI is the cause of the customer complaint, or if the injectors have previously been cleaned and the vehicle has again experienced sticking poppet nozzles, refer to Service Bulletin 00-06-04-003B and replace the SCPI fuel assembly with the MFI fuel assembly. Please note that the service bulletin term for SCPI is Central Sequential Fuel Injection (CSFI), but is referring to the same fuel system assembly.
CLAIM INFORMATION
For vehicles repaired under this special policy, submit a claim with the information indicated.
CUSTOMER REIMBURSEMENT
Customer requests for reimbursement are for any previously paid repairs to, or replacement of, the Sequential Central Port Fuel Injection (SCPI) system. Repairs must have occurred within 10 years of the date the vehicle was originally placed in service, or 200,000 miles, whichever occurs first. The requests are to be submitted within two (2) years of the date on which the repair was paid or within two (2) years of the date of this Special Policy Bulletin, whichever is greater.
When a customer requests reimbursement, they must provide the following:
-Proof of ownership at time of repair.
-Original paid receipt confirming the amount of unreimbursed repair
Checked on the fuel guage at Autozone last night. Didn't have one for my model truck's shrader valve. Will have to look around. I'll post back with an update this weekend after I confirmed the fuel preasure. It should be around 55psi-60psi right?
I remember you posted that you did a major tune up, thats good that is out of the equation. I hope you remembered to lube the spark plug boots with tune up grease or the proper name dielectric grease? The wires you bought come prelubed but there is never enough in them.
I think your the one that posted you have a scan tool. Thats good. I'm not familure with your model, only snap on and fluke. Does you scan tool have a data read out so you can monitor incoming data to the PCM?
Book Says: Key On Engine off 55psi-61psi at normal Operating Temp
It Reads: 52-54psi at first then slowly climbs to about 58psi in about 30 seconds and holds.
Book Says: Engine On at idle it should drop 3psi-10psi
It Reads: Quivers really bad...doesnt' hold between 52psi-54psi but does drop the 3-10psi as the books states.
Running at 65mph-75mph it reads about 54psi-58psi but quivers so widliy during the run it's hard to tell. Only holds constant under a modertat/solid load of acceleration then readsbetween 56psi -58psi. It will spike occassionaly just above 60psi one time only and then settle back down to around 56-58psi until I let my foot off.
When I let my foot off the gas it drops to 50psi-52psi and quivers between the two so that I can't really read the gauge for exact preasure. Various readings between 52-56psi when traveling around the back streets under 50mph ( the gauge will be fluttering back and forth between that range unless I put my foot into it a bit and give it a smooth acceleration load.
Should the needle be realtively solid and move smoothly with the increase or decrease in preasure? It appears that the preasures are within the book specs just not sure if the readings should be steady throughout the diagnoses and not fluttering back and forth. Any thoughts?
It was running rough so i changed plugs and was getting ready to change wires and oil.I let the truck run a little after changing plugs to see if it ran better. a stong smell of gas was very noticeable and when i checked the oil it was overfull and smelled badley of gas.Anyone have any ideas on what could be wrong?
Fuel injecter stuck open flooding a cylinder where as the fuel slips by the rings and enters oil pan.
Rings are bad in a cylinder and normal fuel delivery is slipping past the rings.
First test to see if fuel pressure drops after initial prim, key on engine off. If pressure is slowly or quickly dropping, suspect fuel injecter, use a fuel pressure guage!! Next close off return fuel line to verify regulator isn't allowing pressure to bleed off excessively. Repeat first test. If pressure is dropping still, remove all spark plugs and see what cylinder is receiving constant fuel. You will have to look at each cylinder with the intake valve open, so some cranking will be needed to turn the engine. If one fuel injecter is bad, play it safe and replace all of them.
I do not suspect a compression problem, and a compression test would not be accurate if the rings are reseated due to constant fuel entering the cylinder. If this testing reveals no excess fuel, run a compression test to find a suspected cylinder problem. Reinstall spark plugs and disconect the injecter plug for that cylinder that is suspect, and run the engine to see if fuel gets into the oil again. The running problem and fuel in the oil are most likely due to a fuel injecter stuck open. The raw fuel has probably effected compression on that cylinder. After the fix, and the engine is run for a while, the compression should come back. Good luck
At 70mph during steady acceleration it reads 58-60psi until I let off then drops to 52-54psi until I put my foot into it a bit and speed up then returns to 58-60psi. I lubed the boots extra when I put them on so I think that's out of the way.
Could and EGR and PCV valve or combo failure cause this missfire? Could an intake leak on the prone vortec series cause the same conditions? The code has not come back on since I swapped out the coil but it's still seems to be missing a bit on the highway and I'm still getting 275 miles per tank. Any thoughts? ....running out of options on this pig.
Let me explain about the EGR. Even if it were sticking open at high speed, this is when they open anyway. EGR malfunctions cause idle and low speed running problems by causing a lean condition.
The fuel preasure with the key on/engine off and at normal operating temp...guages at 52-54psi first and then slowly climbs to 56psi-58-psi and holds. This takes about 30 seconds.
Starting the engine the preasure drops to around 52-54psi at idle. The needle will be twithcing back and forth between the two and not holding on one or the other during this process. The book says this model should drop 3psi-10psi during this process as well so it seems to be in spec?
During operation under acceleration it's between 58psi-60psi. When i let my foot off and decelerate the gauge reads 52psi-54psi.
Correct me if I'm wrong but if these specs are right then my options are
1. Compression test to rule out a valve train issue
2. Vaccum leak test: intake manifold, lines...
3. PCV Valve...maybe don't really know but it's one of the only things I haven't swapped yet.
4. Distributor change out????
5. Take it out to the field and bash it in with the faulty shredder from my office. Just don't know man.
Thanks for all your past guidance and any ideas you can offer.
The shaft in your distributer might be worn causing a wobble at higher speeds and random misfires. Take the cap off and check to see if there is any side to side motion on the shaft at various positions. This problem would have showed up during a scope analysis when you had it at the dealer, if they did one. I have to tell ya, that without a scope, you sometimes have to remove the distributer and turn it with your hand to rule it out. It should turn freely out of the vehicle with no binding spots, or areas during the turn that are more difficult to keep turning it.
Flashman3000
codes came up... idle air controle valve and random missfire.
It idles very rough with a strong smell of gas also very sluggish at low rpm.cuts out at higher rpm when just reving.I replaced coils,plugs,fuel fliter,fuel injector on #2 cyl.IACV,wires,air fliter, checked fuel reg,checked all hoses,replaced battery term. checked timming still same problem.When I changed the oil it had some gas in it.Im thinking either cat or comp...........please any suggestions.
2. I am also loosing coolant without any spots showing up one the driveway. what could it be?
I have a hose on my 91 chevy s10 with the 4.3L TBI enging that broke.
It is connected to the rear of the intake manifold, it has a funny looking device that goes from hose to tubing. But the piece that broke is a threaded piece that threads into the manifold. I can get the piece out but what the heck do I order so that I get the piece that threads into the intake manifold. It is broken so no way to use it like it is. It corroded and just snapped.
The hose has to be a heater hose and I see a hose called a Dorman / Heater Hose Assembly. Will this have the threaded piece, it is a special order so I can't go and look at one. Is this what I need?
I do not see it listed anywhere in my Chiltons manual. Sure hope someone can help me!!!
Thanks
Steve
Problem I found with my 99 4.3..same code...same symptoms...same replacements....was the CSEFI harness and regulator are one component located under the intake. Had no way to really test the regulator so decided to swap it all out. My mpg went from 15-20. Also, I first had a vacum leak test with a "smoke machine" done just to re-verify my garage tactics where not off. No leaks so I went with the harness swap.
I posted a technical bulletin from GMC only released in Cali on another site stating that it was determined that the CSEFI units where faulty from the get go.You may have to go back to early Jan 08 postings to see it on this site but it should still be there for more info. Not saying this is your problem...just what worked for me.
I still have a small exhaust leak, haven't gotten to the cold air and cat back duel exhaust yet but I'm sure I can get it up 2-4 mpg afterwards. Also, if the above doesn't work, timing belt and distributor pick up may be faulty or reaching end of service life. I doubt it but it's just somthing to think about. Hope this helps.
I've used them and their manuals since the early 80's to diagnose/order unkown parts. Their manuals have "exploded" views of most any component for your vehicle giving you a shot at finding out what the OEM called it.