Tech Thread Only?

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Re: Tech Thread Only?

barrym95838
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Submitted for your approval, a diagnosis of mine from earlier today, paraphrased:
1994 Buick Century 3.1L  Customer complaint for surging.  Mashing the throttle against the Park/Neutral rev limiter causes fuel cut-out, and is unrelated to the true symptom, which is engine lugging caused by spontaneous engagement of the TCC in any gear except first.  Scoped TCC circuit and found that the clutch was engaging with no input, indicating an internal transmission concern -- the solenoid vent is restricted, or the TCC filter screen is blown, causing more flow than the solenoid can bleed off.
barrym95838
EO/EI144107
“Never attribute to malice that which can be adequately explained by stupidity.”
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Re: Tech Thread Only?

scanner
In reply to this post by scanner
scanner wrote
This is a 1998 Dodge Pickup with a 3.9L V6.   The complaint is that the engine dies intermittently, mostly after started cold in the morning.   Once the engine was warmed up, the engine would die at random times, but would restart immediately.
 
D wrote
I say PCM is bad
FiendFX wrote
If wire integrity is good, only thing left is computer???
Centralized Smog wrote
PCM is opening the circuit
barrym95838 wrote
I would recommend a replacement PCM
The other shop had replaced the ignition coil.  If I were to guess, due to the code description.   They had also changed the coolant and intake air temperature sensors.   I guess because the problem would surface mostly when it was cold.  

The fix indeed was the PCM.  I gave the consumer an estimate to replace PCM with a remanufactured unit.  He balked and then located and procured a used one locally for $160.  That was less than half of what I was quoted from my suppliers for a reman.  

I highly recommended to the consumer that the VIN on the vehicle should match the one in the PCM. I swapped out the PCM and programed the VIN using the J2534 Toolbox and CarDAQ-Plus 2 from Drew Tech.   You can get the toolbox software for free from the same place you download the drivers for you DrewTech IMClean.   http://www.drewtech.com/downloads/index.html  I suppose it didn't matter whether I programed the VIN or not, since it won't impact a BAR97 test.    

BTW, the IMClean will not work with the J2534 Toolbox.  The Toolbox doesn't even recognize the IMClean.   Some may tell you that the IMClean will work as a J-box, but it's not even J2534-1 compliant.  http://www.drewtech.com/technician/introduction/whatisj2534-history.html   The IMClean will work as an interface with some diagnostic software, but I wouldn't attempt programing with it.  

The P0420 was the catalytic converter.   I recommended a muffler shop and the consumer returned a week later for his smog inspection.   When I inspected the cat, there was an pre-OBDII cat installed.   I couldn't believe the muffler shop I had recommended, replaced the cat with wrong part.   I asked the consumer for the invoice for the catalytic converter, and he said he never got one.   Whuut???   It turned out the consumer thought my guy was charging too much, so he found a place that would do it for $50 less.  

I told the consumer that there are muffler shops that prey on the uninformed (I didn't say STUPID), and rip them off.   The rip off shop told the consumer it would cost $140 more to install the proper cat.   In the end, the consumer got his old cat reinstalled, and $70 back from the rip off shop.   After all, the rip off shop had to do the job twice.    The consumer went to recommended muffler shop to replace the catalytic converter, and the vehicle finally passed with no problem.  

Why make it simple, when it will work equally as well complicated.
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Re: Tech Thread Only?

FiendFX
Great case study. Scanner, I wanted to know your thought process on this vehicle. Just by scoping the coil and the CKP led you to the PCM?
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Re: Tech Thread Only?

scanner
FiendFX wrote
Great case study. Scanner, I wanted to know your thought process on this vehicle. Just by scoping the coil and the CKP led you to the PCM?
The thought process was pretty much what was asked and answered here through the course of the post.  

The first thing was to question the consumer about what his truck was doing, and what parts had been thrown at the truck.   He never received an invoice for the repairs performed.  

I scanned the truck, and then hooked up to ignition primary, and waited for something to happen.   Fortunately it happened once within a few minutes of running.    That was the capture I posted.   I could see that it wasn't a power supply issue.   I went looking for other signals that could impact the loss of spark.    I then looked at the cam and crank signals, and occasionally, I could feel the engine miss, but the cam and crank never dropped out.   I was pretty confident at that time that the PCM was the problem.  

You asked all the right questions, and everyone that responded came to the same conclusion.  
Why make it simple, when it will work equally as well complicated.
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Re: Tech Thread Only?

barrym95838
Administrator
This post was updated on .
In reply to this post by barrym95838
Submitted for your approval, a diagnosis of mine from earlier today, exact wording:
1976 Chevy Van.  Customer complaint for inoperative headlights.  Underhood and underdash areas are both full of electrical fires waiting to happen, due to poorly routed, misrouted, improperly spliced, and improperly insulated wiring -- the extent of the mayhem is beyond the scope of a proper repair, short of complete wiring harness replacement. THIS van is dangerous to drive anywhere, in the night or day.

Inoperative headlights were traced to a defective dimmer switch and charcoalized connector -- both need to be replaced, along with dozens of other defective or marginal electrical components, too numerous to list on a single piece of paper.
barrym95838
EO/EI144107

“Never attribute to malice that which can be adequately explained by stupidity.”
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Re: Tech Thread Only?

FiendFX
In reply to this post by scanner
scanner,

thanks for that insight.
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Re: Tech Thread Only?

scanner
This was an easy one.   Customer came in for an oil change and check engine light this morning.   OBDII code P0303.  I got her out in less than an hour.   It's nice to have a parts store that delivers to you within 30 minutes after you place an order online.  

Here's the waveform.   I used an AESwave uScope to capture the problem.   Not bad for a scope that only costs $129.



Why make it simple, when it will work equally as well complicated.
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Re: Tech Thread Only?

barrym95838
Administrator
You didn't specify what you were scoping.  Are we looking at coil primary or injector?

barrym95838
EO/EI144107
“Never attribute to malice that which can be adequately explained by stupidity.”
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Re: Tech Thread Only?

scanner
barrym95838 wrote
You didn't specify what you were scoping.  Are we looking at coil primary or injector?



Primary ignition, I tried using an inductive paddle pickup for the secondary, but it wouldn't go.  It wouldn't work with my Vantage Pro either.
Why make it simple, when it will work equally as well complicated.
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Re: Tech Thread Only?

barrym95838
Administrator
Did you get my PM, scanner?  I think it need a toon up, a smog sensor, and a caddilac converter.

barrym95838
EO/EI144107
“Never attribute to malice that which can be adequately explained by stupidity.”
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Re: Tech Thread Only?

none
In reply to this post by scanner
The primary triggering looks right to me but what do I know. I would think the coil for number three cyl. is bad since there is very little oscillation happening after the ground opens.  Did I guess correctly?

Of coarse it could also be a bad CO2 sensor or EKG valve too Michael.  "There's the problem Vern. Its your catastrophic converter."  
I've hit rock bottom but I brought a pick and a shovel and I'm ready to dig!
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Re: Tech Thread Only?

barrym95838
Administrator
Yeah, the evidence suggests that there is a good primary event, but no spark is jumping any significant gap, ergo the missing oscillations at the nose of the burn line.  It would have to be a shorted secondary winding or a fouled plug.

I would remove and carefully check the plug, and if it looked good the coil would have to be the chief culprit.

I would also try to gain some brownie points with the customer by checking the tire pressures and the fluids, especially the blinker fluid.

barrym95838
EO/EI144107
“Never attribute to malice that which can be adequately explained by stupidity.”
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Re: Tech Thread Only?

scanner
In reply to this post by none
none wrote
The primary triggering looks right to me but what do I know. I would think the coil for number three cyl. is bad since there is very little oscillation happening after the ground opens.  Did I guess correctly?
That is exactly what was wrong with it.   I replaced the coil.

Of coarse it could also be a bad CO2 sensor or EKG valve too Michael.  "There's the problem Vern. Its your catastrophic converter."
Those were the first things I checked.   The CO2 sensor on the car read more than 15%, and the EKG was beating regularly.   No need to call for the crash cart.  

barrym95838 wrote
Yeah, the evidence suggests that there is a good primary event, but no spark is jumping any significant gap, ergo the missing oscillations at the nose of the burn line.  It would have to be a shorted secondary winding or a fouled plug.

I would remove and carefully check the plug, and if it looked good the coil would have to be the chief culprit.
Yes, you guys nailed it.   It was the coil.

I would also try to gain some brownie points with the customer by checking the tire pressures and the fluids, especially the blinker fluid.
There was a hole in the reservoir, and the customer declined repairs, so the vehicle left without turn signals.  

Here's the after waveform

Why make it simple, when it will work equally as well complicated.
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Re: Tech Thread Only?

Kevin
In reply to this post by smgmn
i agree, we need to keep this about our industry. and seperate every thing else into a different area
EO/EI/BA certifications ASE Master Certified Chrysler Master Certified Ford Certified Wyotech Graduate Sequoia Institute Graduate 20+ year experience
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Re: Tech Thread Only?

Midnightdrummer
In reply to this post by smgmn
Anyone want to shoot me some ideas on a car?

1991 Corvette L98 5.7L (Vin 8)

Starts up and runs, if throttle is pressed bogs out and backfires. Shorted A/G terminals and receive a C41 - Loss of ECM serial data. Has new (Reman) ECM. Same issue as last one. Googled and see lots of the same issue with really no answers.

Checked fuses - good.
Went down the trouble shooting trouble tree to check continuity between the serial wires - has continuity
Same trouble tree to check short to ground and short to power - no shorts

If battery is disconnected and reconnected, vehicle runs fine until shut off and restarted. I read the CCM polls the ECM and waits for a response, if no response is heard, something happens with the injectors.


This is pretty much the trouble tree I followed except this is off Google and I used AllData so the names of the connectors are different but same procedure. This thing is stuck in my garage with the dash all apart and getting pretty frustrated with this thing. Any ideas would be awesome.

Diagnosis:
 Jump ALDL TERM "G" and "A"
 IGN ON
 Press "TRIP RESET" until "4.0" displays in Trip Monitor
 Note Speedo, does it say "ERR"?

NO
 A SHORT will take down the whole link. An OPEN will take down only the device(s) that becomes OPEN circuited.

 Possible inop TRIP controller.
 Loss of English/Metric TEMP display on C68 HVAC control head.
 Loss of "Check Gauges" function.

YES
 IGN OFF
 DIS red (VIN8) or blue (VINJ/LT5) ECM connector
 DIS white CCM CON
 CON Digital Volt Meter (DVM) between CCM TERM WC13 (800 TAN) and ECM CON TERM R11/B15 (VIN8/J)
 Continuity?

NO
 Repair OPEN in CKT 800 to CCM PIN WC13

YES
 CON DVM between CCM TERM WD12 (800 TAN) and ECM CON TERM R11/B15 (VIN8/J)
 Continuity?
NO
 Repair OPEN in CKT 800 to CCM PIN WD12

YES
 CON Digital Volt Meter (DVM) between CCM TERM WC13 (800 TAN) and GND.
Continuity?

YES
 Repair SHORT to GND in CKT 800

NO
 CON TEST LIGHT between CCM TERM WC13 (800 TAN) and GND.
 IGN ON
Test Light ON?

YES
 Repair SHORT to B+ in CKT 800

NO
 Repeat test from first "YES", except use use ECM TERM R5 where R11, and B20 where B15, is specified



I may have missed something I've tried so I will add to this as I think of more details. Thanks guys!
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Re: Tech Thread Only?

scanner
Midnightdrummer wrote
Anyone want to shoot me some ideas on a car?

1991 Corvette L98 5.7L (Vin 8)

Starts up and runs, if throttle is pressed bogs out and backfires. Shorted A/G terminals and receive a C41 - Loss of ECM serial data. Has new (Reman) ECM. Same issue as last one. Googled and see lots of the same issue with really no answers.
I'm not familiar with checking codes through the speedometer display.  I would guess you saw that code for module 1.   I would think that the CCM wouldn't have any thing to do with engine control once the engine has started.

Have you tried to communicate with the ECM using a scanner?  
Why make it simple, when it will work equally as well complicated.
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Re: Tech Thread Only?

barrym95838
Administrator
In reply to this post by Midnightdrummer
My aftermarket scan tool has pretty decent OBD-1 coverage, so if the car was in front of me, I would start with live data from as many modules as possible.  If nothing jumped out at me in the live data or there was unexpected lack of communication, I would have to resort to pin voltage diagrams and my Vantage Pro, paying particular attention to powers and grounds.  Was there a specific incident that you can track down that may have triggered the problem, where it was fine before and not fine after?  Traffic accident, leaky windshield, engine or suspension work, stereo or alarm installation, jump start, etc.?

barrym95838
EO/EI144107


P.S.  I am reminded of a super-charged Thunderchicken from a few years back.  Idle was rock solid, but it spit and coughed when the RPM was raised to 2000 RPM.  I finally traced it to a full-fielded alternator ... when the system voltage crossed a certain threshold, the engine computer started panicking and freaking out.  Alternator replaced;  problem solved.
“Never attribute to malice that which can be adequately explained by stupidity.”
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Re: Tech Thread Only?

Midnightdrummer
scanner wrote
Have you tried to communicate with the ECM using a scanner?
When I was out of work for a couple months I had to sell off my Solus, and my work is too cheap to buy OBD1 adapters for theirs, so unfortunately I've been trying to do what I can without a scanner. If it comes down to it Ill ask my buddy for his, but I recall him using it on a 93 Vette and the data was pretty limited, although never know it might be helpful. I'm up for anything at this point.

barrym95838 wrote
My aftermarket scan tool has pretty decent OBD-1 coverage, so if the car was in front of me, I would start with live data from as many modules as possible.  If nothing jumped out at me in the live data or there was unexpected lack of communication, I would have to resort to pin voltage diagrams and my Vantage Pro, paying particular attention to powers and grounds.  Was there a specific incident that you can track down that may have triggered the problem, where it was fine before and not fine after?  Traffic accident, leaky windshield, engine or suspension work, stereo or alarm installation, jump start, etc.?

P.S.  I am reminded of a super-charged Thunderchicken from a few years back.  Idle was rock solid, but it spit and coughed when the RPM was raised to 2000 RPM.  I finally traced it to a full-fielded alternator ... when the system voltage crossed a certain threshold, the engine computer started panicking and freaking out.  Alternator replaced;  problem solved.
What makes it a little tougher is I acquired this car from my father, who bought it from another guy for next to nothing. It has had this problem for awhile, and the guy he bought it from had a parts cannon, so it has MANY new parts on it from the fuel pump, injectors, distributor, plugs, wires, etc. He couldn't figure it out, but I figured "How hard can it be" and took it on. He didn't give us any info on what could have triggered the issue. I believe it has about 200k on it though, but its bone stock.

Just last night I took the dash apart to reveal the CCM (Man what a bitch) so I could go through the trouble tree and see if there were any opens or shorts. It passed every step which left me stumped. I'd have more motivation if this car didn't make every simple job such a PITA. Maybe tomorrow night Ill hook the CCM up again and see how it runs. Maybe all my fiddling around closed an open circuit or something.

Before I resorted to pulling the dash apart, I did check a couple grounds (Can't remember the numbers). The one near the oil filter and the way down and under the ECM. Loosened, clean best I could, and retightened, with no change.

I will also keep that Thunderbird in mind Barry. That's very interesting.....

I appreciate the help and suggestions guys!
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Re: Tech Thread Only?

barrym95838
Administrator
Does your work have a Solus too, Midnight?  I still have all of the OBD-1 adapters for my Solus, but I can't use them because some n-word stole my freshly-updated Solus and OBD-2 adapter from the shop about six years ago, and I've given up hope on being able to recover it.  I'll box up everything I have and USPS all of it to your home address ... just say the word, and it's yours, gratis.

barrym95838
EO/EI144107
“Never attribute to malice that which can be adequately explained by stupidity.”
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Re: Tech Thread Only?

scanner
In reply to this post by Midnightdrummer
Midnightdrummer wrote
When I was out of work for a couple months I had to sell off my Solus, and my work is too cheap to buy OBD1 adapters for theirs, so unfortunately I've been trying to do what I can without a scanner.
Dude, you have no business trying to repair that vehicle with only a paper clip and a Google search.  

If it comes down to it Ill ask my buddy for his, but I recall him using it on a 93 Vette and the data was pretty limited, although never know it might be helpful. I'm up for anything at this point.
A SnapOn Brick would give you enough information to diagnose the Vette.  A Tech 1 or Mastertech scanner would probably get you the most information.     To do the driveability part, you need to be able to view at least Block Learn, Integrator, and O2 data, under different conditions.  
Why make it simple, when it will work equally as well complicated.
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