A Mechanic's Life - Tales From Under the Hood

thecardoc3

Mr_Shiftright said:

Really? A mercedes that won't start because of a security issue but starts right up with a battery jump? *DO* tell us more!

Are you sure you want to know?
2007 C280 The Central Gateway Control module would randomly wake itself up, and that caused all of the modules in the car to wake up as if someone had used the FOB to unlock the doors. After it did that enough times it would run the battery dead and not act up right after the car was jump started. Testing required connecting the DSO to the communication network and setting it to do a deep record and save. The first module to communicate on the data bus is the one that is waking up. Using the PICO scope software to decipher the data burst allowed the digital identifier data of the faulty module to be determined. Now no manufacturers release the module data bus ID data so what we have to do is have the vehicle live, record communication while we knock modules off of the bus basically until we lose the identifier we are looking for. So, the security system was acting up and killing the battery, and then the car started when it was jumped.

Weren't we just talking about carbs a little while ago? Did I ever tell you about the Toyota that someone tried to repair himself and instead of removing the anti-tamper plug from the mixture screw, he took a punch and drove the transfer port plug into the bore and blocked off the transfer port and the fuel supply for the mixture screw.
By me removing that plug, and then fashioning a replacement for it from a wheel weight I saved him a bundle.

xwesx

thecardoc3 said:

What you described here suggests that the choke might have failed to open properly. "Then, today (didn't use it Sat/Sun), it was equally grumpy, but with a twist: It didn't want to idle at all. I started it, it ran for about two minutes, then it started choking out and started billowing black smoke as it continually decreased idle to about nothing, and finally stalled."

That BTW doesn't mean that's what happened. The choke "sticking" was a common issue, there are several others that could result in similar behavior.

Wow; tons of information! Thank you for that!

To answer an earlier question above this, it has a Holley two-barrel (it's a replacement part as the original failed while in Anchorage one day and I had to fix it before getting home. So, I called around to find a rebuild kit, struck out, but did find a store with a full carb. The original went to the store as a core. Man, that was a job just getting the thing off the intake and replacing the studs, which were in horrible shape.) with an "automatic" choke.

I think that maybe part of the problem is just the originality of the engine (e.g., really old parts - maybe slight variability in the timing chain?). How many miles might a carb see before issues with worn throttle shaft bushings? This carb went on in July of 1997 (IIRC) at about 32,000 miles on the engine. I'm at 73,855 today.

So, further update, it warmed up solidly again today. I didn't have any stalling issues after warmup, but it did sorta "hiccup" a time or two; I feathered the throttle to bump up the RPM and then it settled in to a steady idle.

xwesx

Maybe I should just take a video of the whole morning startup process. Those things are always "fascinating."

Mr_Shiftright

You know, I did that very same thing once, and it worked! (Mazda pickup).

thecardoc3

Assuming that it did work, have you tried to figure out exactly what might have happened? If there was debris of some kind restricting a fuel circuit, the backfire might have created enough pressure to disturb it and at the most cause it to be pushed back into the bowl. But it didn't get rid of it. It's usually just a matter of time before it moves and helps generate another restriction.

BTW.
I have had to repair the damage caused by similar attempts when the result was an engine fire.

Did you like the Mercedes's example? Imagine how difficult that would be to diagnose without all of the tools and a solid understanding of the overall system. We use the same routine for a loss of communication when a given module fails and starts hogging up the data bus. That doesn't even result in trouble codes in some cases since the modules are seeing communication, they just wait for their turn, which never comes.

Mr_Shiftright

I can't imagine that problem killing a perfectly good battery---I could lock and unlock a car 100 times a day and it wouldn't do that. Besides, you should be able to spot that on a parasitic draw test. How many Ma would such an event draw anyway?

I got one for you all: ((I know the answer)

Car comes in on the hook--claimed overheated and stalled.

Engine can be rotated but only partway clockwise and partway counterclockwise, then jams up.

What happened to this engine?

thecardoc3

Mr_Shiftright said:

I can't imagine that problem killing a perfectly good battery---I could lock and unlock a car 100 times a day and it wouldn't do that. Besides, you should be able to spot that on a parasitic draw test. How many Ma would such an event draw anyway?

"If" it acted up it would initially draw a little over four amps, by thirty seconds that would drop to just over two amps. At two minutes around 150ma and it would then take another fifteen and the drain would drop under 20ma. That's just about the same that is seen when the car is turned off right after being driven. The problem however was random and could go several days without acting up. When it acted up, it would keep jumping to the four amp drain because every module on the car was waking up. With every module waking up, all of the old routines for locating a parasitic drain fail to lead to the solution.

Mr_Shiftright said:

Car comes in on the hook--claimed overheated and stalled.
Engine can be rotated but only partway clockwise and partway counterclockwise, then jams up.
What happened to this engine?

Am I really supposed to guess? What does part way mean? 50 degrees crank? 100 degrees? 200 degrees???? FWIW, something on top of a piston could do it, a bent (broken?) connecting rod could do it. Heck something could be locking any one of the accessories and its the belt(s) stopping the engine. I've seen all of these and more, including timing chain failures, balance shaft assembly failures and even some transmission failures that would lock up the crankshaft from being able to turn a full revolution.

thecardoc3

From you get what you ask for as much as you get what you pay for file. This post in one of the other threads shines the light on why its more important to have technicians who are trained to and rewarded for being able to do the work and NOT have to rely on someone or something else to tell them what to do.

_momma_sweet said:

I bought a certified pre-owned 2012 2LT Traverse with 24k miles in Oct of 2015. I was informed on the car fax that there had been 3 transmission silinoids replaced. (3rd time the problem should have been resolved I thought) The car ran great for 5 months until one morning on the way to daycare with my 3 little ones the "traction control off, service stabili track, park assist off" sensors flashed at me and the car bogged down and would barely gas out of first. We made it to daycare and when I got back in the car and cranked it up everything acted fine but the check engine light was on. Left it at the dealership for a week, they put 80 miles on it and it never acted it up so I took it back as is. Next week it happened again WITH KIDS IN THE CAR so I drove it straight to the dealership without turning it off so they could read codes while it was acting up. They replaced the ECM after a few days and said all was good. 4 days later on the way to daycare AGAIN the "traction control off/ traction control on" sensor flashed again with check engine light on. It's back at the dealership, 3rd time in one month with no resolution so far. I also found out this is the FOURTH ECM my car has had with only 35,500 miles on it. LEMON

That customers experience is directly caused by the shortage of qualified technicians. The current system punishes anyone who takes a patient, disciplined approach towards problem solving.

Mr_Shiftright

Am I really supposed to guess? What does part way mean? 50 degrees crank? 100 degrees? 200 degrees???? FWIW, something on top of a piston could do it, a bent (broken?) connecting rod could do it. Heck something could be locking any one of the accessories and its the belt(s) stopping the engine. I've seen all of these and more, including timing chain failures, balance shaft assembly failures and even some transmission failures that would lock up the crankshaft from being able to turn a full revolution.
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@thecardoc3


Why yes, you are supposed to guess---otherwise you'd be standing in front of the engine completely paralyzed and unable to decide what to do next. A technician is always "guessing" about something. Your post shows that you are already "guessing". (which was the point of my original post).

PS: Engine dropped a valve.

thecardoc3

Mr_Shiftright said:

Why yes, you are supposed to guess---otherwise you'd be standing in front of the engine completely paralyzed and unable to decide what to do next.

No, techs are NOT supposed to guess. They need to examine, evaluate, and then test to rule in or rule out what cannot be logically deduced. I've said it many times here, test, don't guess.

Mr_Shiftright said:

A technician is always "guessing" about something. Your post shows that you are already "guessing". (which was the point of my original post).
PS: Engine dropped a valve.

All I did was give you a short list of probable causes, there was no attempt to suggest that any of them were THE answer. Besides, that's all that anyone can do in a forum setting is guess if they are playing a game like that online. Even so, looks like one of the probable scenario's was close enough since a dropped valve is something on top of a piston. But that doesn't do someone any good unless they know how to test and confirm if that is what happened or not. Being a mechanic/technician isn't about knowing or being able to look up the list of possibilities for a given symptom, it's all about having the tools, training and patience to put them to effective use and prove what is going on.

Here, let's play your game again. One change, this is a Mazda RX7.

I got one for you all: ((I know the answer)

Car comes in on the hook--claimed overheated and stalled.

Engine can be rotated but only partway clockwise and partway counterclockwise, then jams up.

What happened to this engine?

Well at least you should know what it isn't.

Mr_Shiftright

By putting up your list, you have already guessed what it was NOT. Your technician brain is already sorting the answers---and eventually your diagnosis will be a drilling down--an elimination of causes, one by one.

You always have to start by guessing. You are setting up your hypotheses.

What do scientists do? They put up a theory, based on some general observation. Then, they test the theory, or theories.

thecardoc3

Guessing is telling someone they need a gas cap when their car is setting an evaporative emissions system code without doing any investigation at all.

Mr_Shiftright

True, but it's a very good guess. Foolish guessing would be actually BUYING the gas cap and being wrong.

thecardoc3

So are you going to guess about the Mazda?

Mr_Shiftright

Nope, we've been through all of the most likely possibilities already.

thecardoc3

Too bad, it was none of the above.....

roadburner

One of my tearful regrets in life is my abject failure to learn the finer points of Wankel engine fault diagnosis.

stever

Carbon.

Mr_Shiftright

As Sherlock Holmes used to say, "Choose the simplest answer first".

Or that famous saying: "If you are in Texas and you hear hoofbeats, don't say ZEBRAS!"

thecardoc3

The Mazda was a turbo charger that came apart and ended up with pieces lodged in the inlet port.

stever

Search:

causes of mazda wankle turbo charger failure

Duckdukgo hit #2 (skipped the Wikipedia entry that was the first hit):

"Evidence of carbon build up in a 1.6 HDi PSA Group engine leading to total turbocharger failure"

Turbo Dynamics

My initial search the other day skipped the turbo charger failure part and still gave me carbon.

isellhondas

I once sold a great running RX 7 to a guy I knew. The car ran and looked great!

A couple of months later he took it to a Quickie Lube where they talked him into using synthetic oil.

A couple of days later on the freeway the engine blew without warning.

He took it to a place nearby that only works on rotary Mazdas.

The first question they asked him was " You didn't put in synthetic oil did you?

I already knew that if overheated they are unforgiving and that they have a natural tendency to use a bit of oil and, again, they do not tolerate running even a quart low. I didn't know about the synthetic oil part.

Anyone know why that would affect anything?

Mr_Shiftright

If I recall correctly, the synthetic oil, when used in an engine that used to run on "regular" oil, sometimes exhibited increased oil burning, due to swelling of oil seals as well as loss of "carbon sealing"--synthetic is highly detergent.

stever

A net search yields the typical oil wars kind of stuff. The rotary burns oil "intentionally" and the synthetic doesn't lubricate the seals property. Or it deposits too much silica. Or it's too "thin" to dissipate the heat properly. Who knows.

Mr_Shiftright

Exactly. It's probably more to do with correlation than causation.

thecardoc3

Alphabet Soup??

LIN, LAN, V2V, V2I, LTE, Bluetooth, CAN, FlexRay, Ethernet, MOST, Cybersecurity, Malware, VPN, NAV, BBW, EDR, PA, BA, LA, ACC, TJA, EA, POA,

Or a sample of how much new stuff there is to study this year....

thecardoc3

stever said:

A net search yields the typical oil wars kind of stuff.

A search of service information confirms that Mazda does NOT permit synthetic, or blends with the rotary engine.

stever said:

The rotary burns oil "intentionally"

That is correct. There is no other way to lubricate the apex seals. Maintaining a proper level is really important with these.

stever said:

and the synthetic doesn't lubricate the seals property. Or it deposits too much silica. Or it's too "thin" to dissipate the heat properly.

Let's work backwards. The thinner the oil, the better it is a dissipating heat, so that's not right.
Silica? That's a contaminant that you will see an engine oil analysis. How much is listed on the oil analysis results that you have had done?
Lubrication requirements of a given product are established by meeting the API and ILSAC minimum requirements, so that's not it.

stever said:

Who knows.

Mazda does. Could be others.....

stever

Per anecdotal posts on the net, for some years, Mazda didn't specify whether you could or could not use synthetic oil in the owner's manuals.

I like the weight/hp ratio but the maintenance (and "using" oil) would kill me.

Mr_Shiftright

Mazda's RX-7 Twin Turbo didn't need an excuse to blow up--it just did it. Fabulous car, though.

thecardoc3

stever said:

Per anecdotal posts on the net, for some years, Mazda didn't specify whether you could or could not use synthetic oil in the owner's manuals.

Well, you can't believe everything you can find on the net, but here is a screen shot from the owners manual page 8-12.

stever said:

I like the weight/hp ratio but the maintenance (and "using" oil) would kill me.

All engines use oil. Your rate may vary.....

thecardoc3

Mr_Shiftright said:

Mazda's RX-7 Twin Turbo didn't need an excuse to blow up--it just did it. Fabulous car, though.

Had to really study them and learn the ropes with each version. How many other cars did the manufacturers spray washer solvent into the engine during a cold crank? Which BTW had to be disabled as per a TSB.....

Mr_Shiftright

I like it when my engines use a little bit of oil--something squirting around up there in the upper cylinder. Some race engine are purposely built to use some oil.

roadburner

Mr_Shiftright said:

I like it when my engines use a little bit of oil--something squirting around up there in the upper cylinder. Some race engine are purposely built to use some oil.

All of my cars use oil to some extent. My Club Sport uses the most- at least a quart every 2,500 miles. So what?

Mr_Shiftright

Exactly---I would even (seriously) opt for a car that used a little oil.

thecardoc3

Have you ever looked at the Craigslist help wanted adds? A shop owner in Iowa shared this link.

http://rmn.craigslist.org/search/trd?query=automotive

xwesx

thecardoc3 said:

Have you ever looked at the Craigslist help wanted adds? A shop owner in Iowa shared this link.

http://rmn.craigslist.org/search/trd?query=automotive

Wow; that's sobering.

Mr_Shiftright

Pretty much the same anywhere you look on CL.

isellhondas

Speaking of blowing up, has anyone beside myself heard an early Mazda rotary backfire like a cannon going off ten minutes after being turned off?

Mr_Shiftright

When I first heard that I seriously looked for a foxhole.

roadburner

The real early Mazdas used a thermal reactor(the same kind we used to ashcan on mid '70s Bimmers). They'd backfire on downshifts more often than not.

thecardoc3

isellhondas said:

Speaking of blowing up, has anyone beside myself heard an early Mazda rotary backfire like a cannon going off ten minutes after being turned off?

Yes. We had one do it inside the shop.

Mr_Shiftright

It really does sound like a gunshot. Has a real "crack" to it.

isellhondas

I was in a shop in Salt Lake City once and a guy who looked to be in his mid seventies had a Mazda
Rotary Pickup up on a lift changing the oil when it went off!

It literally shook the building and this old guy passed all of us as we ran out of the shop.

It comes from gas slowly dripping into that heavy "blast furnace" that was part of the emission system.

People would get home from work, park in their garage sit down to dinner or whatever and ten minutes later there were enough fumes built up and KABOOM!

I've seen car batteries and A/C pressure hoses go off too but nothing like an old Rotary Mazda!

roadburner

isellhondas said:

It comes from gas slowly dripping into that heavy "blast furnace" that was part of the emission system.

That's the reason that "Remove and discard thermal reactor" was Number One on the to-do list of BMW and Mazda owners of that vintage- along with the air pump and EGR on '70s BMWs, but I digress...

thecardoc3

There were "anti-after burn" valves and controls on these that failed and caused the backfire, both the kind with the prolonged delay, as well as during deceleration.

The idle circuit is the primary fuel feed when the engine is idling and it also feeds fuel during deceleration. The problem with that is there isn't enough air to get that fuel to burn so it just passes into the exhaust. (REM the Yugo carb thread) Some manufacturers added a control solenoid that would block off the idle circuit during decel and when shutting a car off to prevent fuel from being fed to the engine that would not get used. Others like Mazda opted to use control valves to allow air to bypass the throttle during deceleration and when the car was turned off, which leaned out the mixture.

When these controls failed, that resulted in a very rich air/fuel charge entering the exhaust. During deceleration as long as the A/F ratio was too rich to ignite, nothing happened. But when the car was turned off, the cooling of the exhaust allowed fresh air to be pulled in and that would lean out that very rich mixture until it reached one that could ignite.

thecardoc3

What/where does twelve years as an automotive technician get someone today? This post from another forum shares some insight.

"As a younger veteran of this industry, I feel that I may be
starting to lose my optimism that we might never be taken
seriously(by clients AND employers) as an educated,
respectable crowd of people providing a necessary service.
Is it really too much to ask for a well trained, dependable,
thorough driveability technician to want to make $60k a
year? I don't want to have to bust my hump week in and week
out to hope to flag 40 hours or better for $24/frh"

I looked up the averages for where he lives for all walks of life. He wouldn't qualify for a mortgage for the average home, and yet he is in the 90th percentile for this trade. When you understand the big picture, he is right at the point where he is becoming the master technician the consumer needs the shops to have and don't be surprised if he is out of the trade completely in a very short period of time. The economics of the situation aside, re-read his thoughts. The worst damage being done comes not from just being under-appreciated by his employer, but by the consumers he strives to help.

stever

The tech can always go back to school and become a doc, dentist, cop or farm worker.( therichest.com)

Being a dentist tech can be a lucrative, rewarding profession, but it also brings with it long hours, reluctant, if not downright difficult patients employers and customers, and no guarantee of success or stability.

Welcome to everyone's world, Mr. Younger Veteran Tech.

thecardoc3

"Welcome to everyone's world, Mr. Younger Veteran Tech."

So on top of everything else EVERYONE has to spend 10% or more of their take home pay on improving themselves on a yearly basis. I didn't know that. (sarc)

stever

Sure, continuing ed is a biggie in the professions. No joke.

Few docs own their own practice any more. The billing overhead alone kills them. Lexus/Nexus subscriptions aren't cheap for accountants or lawyers. I'm paying $1,200 a year just for net bandwidth so I can work.

Need a tissue for the crocodile tears flowing in here?

thecardoc3

$1200 a year? Is that all? Try doubling that for just the mobile bandwidth that we eat up.
But you were right about one thing. "The tech can always go back to school and become a doc, dentist, cop or farm worker" he can indeed, and since you are making no effort to persuade him otherwise....