Finally it happened to me: '93 will not start

[LMP]

After 13 years where problems were mostly suspension and a few occasional codes, MAF, TPS and EGR partly failed (one coil) , yesterday, after parking the car the day before in full health, it just would not fire up in the morining: it seemed to want to fire up for a second then would endlessly crank and crank with no further sign of life.
Got codes 53,54,55,56.....so I would assume that my EGR has something to do with it....lol
Will update on this

[james kremer]

Sounds like you were almost looking forward to it....LOL.

[LMP]

UPDATE...if I can say so....
NOt much time to look at that problem recently but I understand the question mark over the head of those who have the same problem: car worked perfectly returning home and next morning, would not fire up.

- spark is AOK...so crank sensor works (at least that is what I thought...see further down). PCM is not required for spark in "bypass mode" so at this point PCM was still a suspect.
- No pulse on injectors: put the scope on one injector and no voltage voltage ever comes across it: 12V is there but no ground from PCM, neither at KEY ON, neither while starting.
- Checked TPSensor ..AOK.....cause if faulty at high voltage, PCM thinks full throttle (over 80%) is applied as driver wanting to clear a flooded engine and this cuts the injectors...so no joy here.
- checked ground on ignition module as suggested: tested OK initially but removed corrosion anyway and installed additional ground strap: no joy.
--and if car is left there overnight and I start the next morning , it will fire up and run for 1 second than stall....back to square 1. If I feed propane into the intake, it will run for a few seconds until propane is exhausted

...now....according to the "book", this could be a genuine crankshaft sensor failure: thee are 2 separate pickups in this sensor: a 18x and a 3x...and "the book" says if the 3x fails while engine running, it will continue without problem...but once stopped, it will not start again and injectors will not fire.
These are "hall effect" sensors..hence true electronics, ..hence due to fail.
Next step I'll hook the scope on the 18x and 3x signal wires and report on what I see....plug C111 is actually mounted rotated 180° from the book...at least colored wires give a clue....

..... my wife's Sportage has just started to bug on spark 2...and son just bought a 1992 Z-34...please don't laugh...ah OK, laugh.

ALso all EGR solenoids had popped a code: 53,54,55 and QuadDrver B also (56). THe EGR valve was known faulty on one solenoid for a LONG time...but tests show condition (electrically) has not changed..but ah yes....2 of the small screws that keep the EGR valve in one piece were broken...(?!?) so only one remained and the solenoids coils were surely skewed at an angle from the plungers keeping them from operating properly..so OK 53,54,55... I decided it was time to straighten that up and have a brand new one from e-bay---1/3 price of aftermarket here in Canada...

Update again
Scope read a definite pulse train from the 18x spark reference signal from CPS..but nothing that can be considered as a clear signal from the 3x (fuel reference) section..and this would definitely kill the injectors according to "the book"...have to rely on something...

Although both signals pass through a "buffer" in the ignition module and reading was taken after the buffer, I abide by the evidence and will change the CPS...I "suppose" the buffer is OK....and we will see if that logic is a valid asumption.

[LMP]

UPDATE AND REQUEST FOR OPINION:
Well I have a new crank position sensor....still a lot of spark, and fuel pressure tested AOK...but still no trig on the injectors. I have tested trigging the injectors by pulsing contact D out of the ignition module (as per chart A3 in service manual) and it does trig the injectors and at same time it turns the fuel pump ON. Playing this game several times provides enough fuel in the intake manifold to let the engine start for a split second after that....so ECM is sensitive to impulses and does its job running the pump and the injectors when it senses pulses.
What puzzles me is that although the fuel pump runs for a second at KEY ON, the injectors --at least those front ones I have tested -- do not turn ON at same time although the book says they should to prime the engine.
Nevertheless, my next step will be to install a new --well , salvaged -- ignition module....just because the crank sensor signal is amplified or buffered in that module -- ( there are in fact 2 sensors in the crank position sensor - the half crank sensor signal that is used for the fuel could be totally independant of the ignition but it has been blended in this module).
My feeling is I'll end up with a lot of spare parts..

[LMP]

Well..could not get part from salvage in my area....so decided to test the ignition module on electronic test bed....(should have done that first!) .
CHecked the operation of the 2 crank sensor buffers .....found one normal and the other (for the fuel sync) DEAD: output (intended to trig the ECM) stays HIGH whatever the status of the input signal....so that is why I did not get the 3x signal in my first trials.....and I thought it was the sensor....while it was the buffer I had supposed OK....LESSON: NEVER suppose: verify! (I thought I had learned that a thousand times)
will send test details to any interested...or better, when I have time, will do a little drawing and post it here.
..ahh...for the record...this afternoon have stopped at the GM dealer servbice department here..asked if they had an apparatus to verify the module; replied it cannot be tested.....crap!....
Looking for a replacement on e-bay and other sources now. Will NOT buy NEW locally at $350 + (aftermarket) and 400+++ at GM...

p.s. Notice there were absolutely no DTC codes relevant of this condition.....
BTW, I have replaced the EGR valve that was due for replacement for years....this one was throwing the same codes all of the time..initially only one but lately all of them: 53,54,55 and 56. I just cut the bolts and drilled through the EGR adapter base and used normal nut and bolt instead of studs. www.avigex.ca/xport/newegr.jpg Much easier.

[GregA]

Hey LMP,

Sounds like some mighty fine troubleshooting to me!

Is there any way to get that PCM disassembled and look at the insides? That "Buffer/Driver" is probably just a transister or driver IC (chip), and MAY be able to be replaced.

But I am an "old electronics" guy - I used to replace just "pieces" of stuff (TVs, radios, etc.) to fix them - instead of replacing a whole control module.

Let us know what happens.

Take Care,

[LMP]

Greg this buffer is in the Ignition module--that is in this 3" x 6" wafer under the coils.

See this: www.avigex.ca/xport/IgnitionModule.jpg
The electronics themselves are contained in a 1/4" x 2" x 1.5" sealed envelope. Indeed I would replace that internal buffer with a 741 but the 3x inj. sync. signal , according to the diagram, is also used internally for the spark timing but for limited time only--at start-up for synchronisation ; it seems I just cannot bypass this module...too bad.

[GregA]

Originally Posted by LMP

Greg this buffer is in the Ignition module--that is in this 3" x 6" wafer under the coils. ... The electronics themselves are contained in a 1/4" x 2" x 1.5" sealed envelope. ...too bad.

I guess they don't want us to fix these things, just buy a new one. Bummer!

Take Care,

[LMP]

BACK ALIVE: Received ignition module (brand new with wire bundle) at 7:30 this morning; installed and car fired up right away.
Total cost (for this item):$130 canadian, including 24$ extra broker predatory charges by UPS....I agree they were fast though.
THough the ignition module was the culprit, notice spark was absolutely correct but the fuel injectors would not fire. I hope this can help others caught with such confusing symptoms....

[nicke66]

Originally Posted by LMP

BACK ALIVE: Received ignition module (brand new with wire bundle) at 7:30 this morning; installed and car fired up right away.
Total cost (for this item):$130 canadian, including 24$ extra broker predatory charges by UPS....I agree they were fast though.
THough the ignition module was the culprit, notice spark was absolutely correct but the fuel injectors would not fire. I hope this can help others caught with such confusing symptoms....

Congratulations!
For the average car owner, leaving the car to an average skilled mechanical, this would probebly cost a lot of more $$$$$ ending up with every sensor and control mudule brand new in the car...

[mobby]

I had same issues but.. My solve was buying a new PCM (computer) for the Van.. Mine was giving wrong diagnostic readings and codes.. After I check all the wiring it turned out I was only getting 5.7 volts to my camshaft sensor.. That right there told me it was computer.

Replaced it and all is well now, except for another issue in another posting..

[drepalla]

Congratulations on getting it running again !
I am just stirring at your EGR replacement, it looks "different"
How much did you pay for it?

[LMP]

Yes: you have a '95 (3.8??) and this model uses the "linear" egr, www.avigex.ca/xport/egrlin.jpg that is a single solenoid moving a pintle up and down progressively opening the exhaust transfer.
'93 uses a "digital" EGR, that is how they call it, made with three separate solenoids each opening a port of different dimention. www.avigex.ca/xport/egr3.jpg IN fact, just as a 3 bit binary word, the ports have opening size of say 1,2,4, and the various combinaisons of ports give 8 different settings like this (0 is closed)
0+0+0 = 0
0+0+1 = 1
0+2+0 = 2
0+2+1 = 3
4+0+0 = 4
4+0+1 = 5
4+2+0 = 6
4+2+1 = 7
I got mine brand new on e-bay and total cost with shiping was 110 C$...a third of aftermarket price around here.

These 2 models are not interchangeable.
BTW, after all was back on the road, I kept having CEL codes for the EGR......I checked and one of the connectors of the plug had been pulled almost out of the socket...it is hard to get that plug out as they have managed to position the locking tab on the back when it is almost unreacheable and you have to use a mirror to figure it out..and obviously I had pulled a little bit too agressively on the wire bundle......anyway I repositioned the contact correctly in the plug and everything is fine now.

[drepalla]

Thanks for the reply !
Yes, I have a '95 3.8 canadian model. (Everything in french)
I learned from your previous post that the ECM gets some feedback from the EGR in order to verify that the EGR is actually working, and eventually gives a code for a low EGR flow if the problem is peristent. I think mine is currently sticky, and when the ECM is trying to regulate, it "jumps", resulting in overcompensation, giving some rouch back and forth kicks to the vehicle when cruising at about 50-60mph under 2000 RPM. (4rth gear and lockup on, easy on the gaspedal) I guess I start with a good cleanup job with brake cleaner or something equivalent, but replacement is prolly unevitable, since it is an 11 year old part

[nicke66]

Originally Posted by drepalla

Thanks for the reply !
Yes, I have a '95 3.8 canadian model. (Everything in french)
I learned from your previous post that the ECM gets some feedback from the EGR in order to verify that the EGR is actually working, and eventually gives a code for a low EGR flow if the problem is peristent. I think mine is currently sticky, and when the ECM is trying to regulate, it "jumps", resulting in overcompensation, giving some rouch back and forth kicks to the vehicle when cruising at about 50-60mph under 2000 RPM. (4rth gear and lockup on, easy on the gaspedal) I guess I start with a good cleanup job with brake cleaner or something equivalent, but replacement is prolly unevitable, since it is an 11 year old part

I have a 3.8 Trans Sport (sold new in Cananda) and had to repace the EGR-valve 1½ years ago. The problem with my valve was the sensor giving feedback to the ecm. I think this is the common problem with the valve, not a sticky pintle. It is not possible to replace only the sensor, or clean it, so replacing the EGR-valve is the only thing to do. A new valve here in Sweden is probleby nearly 400 US $, but I did find a new at ebay for 90 $.