Engine dies restarts 1-2 min later

kev2

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#16
A quick test for bills concern - OBDII would code for this condition, no 12v at injectors but OBDI, IDK.

The injectors get 12v from fuse #7 which gets power from ign switch... Dia 3 in the attachment I added above....
might be a good idea to check there esp if you can get to it during acting up episode,

Having a known good ICM to swapin for testing - just like working at the dealerships. ;)
hours of testing eliminated - gotta love it.

PS: is there remote starter?
 
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#17
Swapped the ICM and ran for 1.5 hours and 40 miles with no problem. Tomorrow will drive about 100 miles and 2 hours to see a hot rod a friend is building. If that proves OK I will call it good and order a new ICM.

Thanks to both of you for all the help. And, Kev-- there is no remote starter.
 
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#18
Kev and Bill:

Drove another 100 miles with no problems using the ICM off of my '90 Buick on the '89. Going to Pick and Pull Sat to get a ICM for the '89.

I can't thank you both enough for the help you have been on both Buicks over the years. I don't think I could have solved the Cam sensor problem on the '90 Buick or the ICM on this '89 without your input. I truly enjoy learning more about these more modern systems, since my technical training dates way back to the early fifties.

Jack
 

kev2

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#19
it is a lot easier to learn the system having the old world basics than it would be to begin without that background.

I will think of some items you might want to look for at the pick and pull - just to have on the shelf....
 
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#20
I will think of some items you might want to look for at the pick and pull - just to have on the shelf....
I already have the "new style" late model ECM on both cars and new TPS on one. Both have been retrofitted to R134. The blower fan resistor replaced on one. That might be a good standby item. Neutral safety switches are problematic, but I would buy new or fix old there.
 

kev2

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#21
Cost should be a consideration - check aftermarket availability but what about HVAC modules - Wiper linkages -
 
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#22
Thanks. I'll consider those but probably just wait.

If something big dies, but they are still drive-able, the cars go to scrap yard and here in Calif we get $1000 from the state just to get old cars off the road.
 

Gus

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#23
Basically, I would carry a can of carb cleaner with me....when it dies and won't start, I would spray carb cleaner into the intake and if it starts and runs as long as you spray, then you know you have good spark, but no fuel injection(since pressure is ok).....

You need a crank signal for spark.....the ICM then takes the crank signal and sends a reference(rpm) signal to the PCM....if the PCM does not receive this signal, it will not fire the injectors......

So you have three possibilities here.....

a bad crank sensor....it can go completely out, and after awhile start working again....it can also PARTIALLY work....by that I mean, it can be getting old, and the signal it is producing is not a sharp wave form....the edge of the waveform can round off....when this happens, you can still have spark, but the ICM has a problem interpreting the the malformed wave signal, and won't produce a ref signal to the PCM, and thus no injector pulse....

Bad ICM.....it fires the coils but doesn't produce a reference signal.......

And Finally, it could be a bad PCM....these late 80's, early 90's PCM's were known for breaking down....

Two tricks that I used when dealing with a stall like this, where it didn't restart right away, were....

Get a long socket extension.....with the car not running, practice hitting the pedestal that holds the crank sensor....the belt is moving close to this....so practice lightly tapping the pedestal(not the sensor), with the car not running....when you are confident, now start the car, and with the vehicle at normal operating temp, LIGHTLY tap the pedestal, while the engine is running(be very careful of the moving belt)......if the car stalls, or the rpms are affected, you've found your problem....if nothing happens, it still doesn't eliminate the crank sensor....

The other trick is to drop down the PCM inside the car......with car at normal operating temp, apply ebrake, apply brake pedal, and put in drive.....now using your fingers, tap the top of the PCM.....once again, if the car stalls or the idle is affected, that is your problem....if nothing happens, it still does not eliminate the PCM....

Since you have another known good ICM, I would try it....if the problem still exists, it's down to the crank sensor or PCM....

Or, there is one more possibility, the female connectors in the harnesses to the cranks sensor, the ICM, and the PCM....if even one is loose, an intermittent condition can occur.....you would need to pick up a male connector, and insert it into each female connector, and then pull....this is know as a drag test.....if you do not feel a drag as you pull, that female connector is not tight enough....
 
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#24
Gus: Great explanation. Thanks.

After driving 130 miles with a known good ICM out of my '89 Buick, we concluded it was a bad ICM in the '90 Buick and picked one up at the wrecking yard. We drove 30 miles home with it installed but later that day the car ran terrible (different from the original problem). Reinstalled the known good ICM and all was well. We will return the used ICM.

Have ordered a new ICM from RockAuto. I think that will solve it. I will let you all know.
 

billr

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#25
If-and-when things get settled down with the new ICM from RA, I would love to have that old one to dissect/inspect. I'm hoping to learn more about those older GM DIS ICMs and how to test them.
 
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#26
Bill: You are welcome to have it. It is a totally sealed up unit. You may destroy it just trying to get into it.

I will have a credit at Pick and Pull (they will not return cash)upon returning that ICM we picked up yesterday.

Do you have the tinted rear door glass for your van yet? If not we could search for one at P&P and use the credit. It should be about $50, which is about what the first glass cost if memory serves.
 
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#29
Checked my records and this will be the 4th ICM ( original+3 ) on this '90 Buick in only 77,000 miles. The first two replacements (1998 at 39K and 2004 at 62K) may or may not have been necessary because this is when my sister had the car and the shops threw ECMs, coils, and ICMs at the car. No way to know which part really fixed it.

My '89 Buick (exact same engine with 200,000 miles) is still using the original ICM.

Any ideas why this '90 may be eating ICM's up so often?

I thought it was speed at first because it only died on the freeway at first. But when it died at a stop sign and I considered heat. But I dismissed that because it always restarted after about 1-2 minutes and I have always felt that an engine gets hotter in the first few minutes after shut down not cooler.
 
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#30
first thoughts on this -
1) Original ICM has been replaced with aftermarket units - imported inferior, non union components?
2) A component that interacts with ICM causing failure - ie bad ign coil?