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94 Olds 88 intermitent stall and no start (fixed)

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7 years 4 months ago - 7 years 2 months ago #4523 by stp396
Hi guys.I'm working on a friends 94 Olds 88 with the 3800 series 2 engine.It has an intermittent no start and intermittent stall,It has 2 codes.341 cam sensor out of range and 342 cam circuit low.The car has a 16 pin connector but but apparently is still OBD 1. I had to use my old snap on brick with the K20 key to get the codes and it said 341 not p0341.When the car doesn't start there is no spark and no fuel injection control.There is power to the injectors.Fuel pressure is 43psi(new pump).I did all my checks at the ign. mod, connector.Power and grounds all good. Sensor feed 10 volts. Cam and crank signals in and out 0.0 to 6.7 volts.Fuel control out spark ref out also good.But Ignition control out was only 0.0 to 1.2 volts.When the car runs it's 0.0 to 6.7.After I was done testing I removed the module. Only three of the coil screws were holding anything. The other three were stripped out and the aluminum mounting plate had a corner broken off and was corroded a bit but I don't believe the module uses the plate for a ground.Now my question.Am I done and I need a new module or are there other tests I need to do?It took a week and a half to test all 14 wires in the connector because the car would run fine 99% of the time.It's the most reliable intermittent problem I ever worked on! Thanks in advance guys.
Last edit: 7 years 2 months ago by stp396. Reason: fixed

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7 years 3 months ago #5178 by stp396
Well,I replaced the ICM and I now have consistent spark.So now when the car wont start I'm only missing injector pulse.I pulled the ECM down from it's hiding place under the dash and did my testing on these connectors.My powers and grounds were ok and so was the cam ,crank and fuel control signals.I had my scanner hooked up also and when the car wouldn't start there was no RPM on the scanner when cranking but there is when the car runs.Wiggling the wires and harness and tapping the ECM would neither start the car when it was having a fit nor stall the car when it was running.Do I need a computer?

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7 years 3 months ago #5179 by matt.white
Is this the motor with the two crank sensors in one? There's a 3 segment ring and an 18 segment one on the back of the balancer?
Sorry, we don't have olds here but I suspect we have that motor in a different GM.
I ask because I'm wondering not if the 18x of the crank is ok but it's missing the 3x.

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7 years 3 months ago #5180 by ScannerDanner
1. On some of these, the module housing IS the ground.
2. The cam sensor will not cause a no start on this (both spark and injector pulse will be there without it)
3. The dual crank sensor (3x and 18') signals. The 3x coordinates the 18x signal during cranking. Once the engine starts the 3x signal is no longer needed. It runs off the 18x. So if the 3x is lost, the car will not start but if it is lost while running, it will continue to run until you shut it off. The 18x signal, if it's lost the car will not run or start.
4. Are you still setting a cam sensor code?
5. The cranking rpm test is not full proof

Don't be a parts changer!

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7 years 3 months ago #5187 by stp396
Hi Matt.Hi Paul.Thank you for answering.I have 18x, 3x and cam signals all the time. At the ECM connector I have cam signal on the black wire and what they call fuel control signal on the purple and white wire all the time.The cam code is historic.There are no active codes.Having all these signals but no rpm during a no start made me think there is something wrong with the ECM. When I release the key and then retry the car usually starts and I have rpm.There is no tach in the dash.I think the earlier cars used the module for ground.This car has a short wire comming from the module connector that grounds to one of the module bolts.Either way I replaced the broken mounting plate and every thing is clean and tight now.Paul, I'm a former student(2011) and thats my 97 buick in the gm maf sensor testing video.Now that I have a little more expierience I bought the premium channel and I'm getting more out of it.Thank you.

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7 years 3 months ago #5271 by egnblack
Have you looked at scan data?

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7 years 3 months ago #5274 by matt.white
Im not forgetting your rpm pid comment, but have you confirmed power to the injectors. Just when you mention releasing the key, then next crank it fires, I'm wondering if the ignition switch is failing and not powering some circuits. Just a thought.
If you really have all inputs, and no injector control, then I'm a bit stumped sorry.

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7 years 2 months ago #6466 by stp396
Well.it was the computer.We took the ECM from the old car,also a 94, swapped the prom chips and installed it in this car.My friend has been driving it for 3 weeks now and no problems. Just for kicks we put the bad ECM in the old car and now it has starting and stalling problems.I think that verifies the fix.I want to thank everyone for their input.
The following user(s) said Thank You: Noah

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7 years 2 months ago #6469 by Noah
Nice, thank you for updating us with the fix!

"Ground cannot be checked with a 10mm socket"

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