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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: Jon87V20 on July 28, 2018, 07:45:21 PM
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Hey, guys.
A while back, my '87 Suburban V20 w/ 5.7 threw a Service Engine Soon light on me and was running really rough. When I checked the code, it was a 42. I replaced my ignition control module and that seemed to clear it up and it has been running pretty well.
Over the last few weekends I replaced all my front brake components (calipers, pads, rotors/hub assemblies, and master cylinder) so the truck had been sitting for a while.
When I took the truck out to test drive it to see how the brakes were working, I left a tool or something on the bumper and heard it fall off. I jumped out to grab it off the street and the truck suddenly shut off and would not start again. It was cranking but wouldn't fire. I popped the hood and didn't see anything out of the ordinary and tried again. It was cranking and kicking a little bit like it was trying to start but just wasn't quite able to. After sitting for a few more minutes, I just held the starter and it finally fired up and I got it back to my house.
The next day, I took it to work. No issues whatsoever. The day after that, when I started it in the morning, the SES light was on again and it ran terrible all the way to work. It took twice as much throttle to accelerate up to the speed limit etc. and seemed to be missing a lot between 1,500 and 3,000 rpm. It wasn't jerking or anything while it was missing, but you could hear in the exhaust that it wasn't firing consistently.
When I got to work I checked the code and it was 42 again. After I checked the code, I started it again and the light was off and it ran fine again. That was Tuesday and it's been fine all week driving it everyday for about an hour each direction in heavy traffic until today when I took it to the dump to get rid off some garbage. It drove fine the whole way there and then the light came on again right when I was about to park it. After shutting it off and starting it again, the light is again off, and everything is fine.
It seems to be happening so randomly that I'm wondering if this could be my ECM failing?
I found a thread on here from Vile that shows a workflow on how to isolate the fault, but I can't get it to throw the code in a situation where I can perform that process at home and what not.
Is it possible it's the ECM, or maybe the new ICM is faulty? I put the thermal paste on the ICM and everything so I don't think it's getting too hot.
From what I understand, 42 has something to do with the ECM's ability to adjust the ignition timing. Could this be an issue with the distributor itself?
Luckily for now, it seems that turning it off and back on clears it up. I haven't had another episode (yet) where it will not start back up, but I'd like to get it resolved before that happens!
Thanks, everyone in advance!
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Sounds like the pickup coil is toast. I'd replace the distributor altogether.
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Okay. Thanks, Vile. Are there any brands in particular I should consider above others, or are they about the same as far as quality goes?
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If you are buying local, just get whatever is readily available at the parts store you use.
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Here is the diagnostic strategy for DTC 42
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hey vile do you have these diagnostics on your pc for all of them?
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One more question. Can I buy one of those distributors with the internal coil as a replacement, or does it have to be the same one with the external coil? Just thought it might be nice to get some clutter out of that area if possible.
Thanks!
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hey vile do you have these diagnostics on your pc for all of them?
What exactly are you asking?
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One more question. Can I buy one of those distributors with the internal coil as a replacement, or does it have to be the same one with the external coil? Just thought it might be nice to get some clutter out of that area if possible.
Thanks!
Although you could make it work, they are not interchangeable in that way.
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say for the "tech" section ? or are they there already?
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Unfortunately I don't have the time to pull all every diagnostic strategy, too many variables. They can be found in the drivability and emissions manuals.
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So I haven't had the time to go pick up a new distributor yet. Today I was driving home, and the truck stalled badly for about one second (going sixty on the freeway) and then I felt it give itself a bunch of throttle momentarily. Next time I had to stop in the gridlock, I noticed the engine was idled up quite a bit. It was trying to idle at 1,500 (in neutral) and 1,200 (in drive). It stayed like this for quite a while but eventually came back down to about 800 (in drive).
It seemed to be okay until later on in the day I was in traffic again and it gave itself a bunch of throttle again. I put in neutral because I was going to give it a light revving to see if it would calm down again. When I put it in neutral, the idle dropped sharply like it was going to shut off and I saw the SES light blink and go out. I had to keep my foot on the pedal to keep it running. It was missing terribly until I got out of traffic.
When I got it home, I popped the hood and I think I'm hearing some rod-knock now. I got down on the ground and got close to the oil pan and it's definitely coming from the bottom-end. Needless to say, I'm feeling really discouraged at this point. I still need to get the rear differential rebuild on this and the steering still needs attention...
Part of me wants to sell it, but I'm kind of attached to this truck and also I spend about $1,100 on the transmission a few months ago, put in a new steering gearbox, and replaced everything for the front brakes and I don't want to just eat it on all that.
Do you think it's better to pick up a long-block, or get this one rebuilt?
In the meantime, is there any of those products that thicken up the oil and what not helpful to keep this going for now?
This may seem like a silly question but is it dangerous to drive it like this? If it throws a rod on the highway, is it possible it will lock up the rear end and put me in my grave, or would the transmission let go of the engine when it stopped moving?
Thanks.
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if it is indeed the engine it will be cheaper to stop driving it now and a little easier to remove the engine when the time comes. it will also be cheaper to rebuild the engine vs buying a long block. but it you want more power anyway then think about what the OEM engine can do
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If you just replaced the transmission, I would check your flex plate bolts. Take the infection cover off and tighten all 3 bolts very tight.
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The transmission was rebuilt and installed professionally at a shop earlier this year, but I'll still get under there and check when I get a chance. That would be great if that were the case!
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Take a close look at the face of the flexplate while you are there. Make sure there are no sub-concentric cracks (rust tracks) propagating around the disc in the area of the crankshaft rear flange.
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BD, I already looked at it before you posted that. I'll check it out again before I pull it out of the truck to be sure.
However, I did try putting some 10w40 and some STP honey in there to try and prolong the death and it actually seemed to get worse. It's now constant instead of every few seconds. I primed the oil filter before startup, but the noise was fairly loud on the first startup after the oil change. It did quiet down but like I said before, very constant now.
I'm looking around for an inexpensive long-block for it right now. So far, the best deal I've come across is on Jegs for about $1,600.
I ended up buying another daily driver so I can take my time on the truck and do it right. I wanted to have time to go through the engine bay and clean up in there and possibly do some painting. Maybe redo some vacuum lines and wiring too. There's oil paste on everything because I think the timing cover has been leaking since I bought it. I wouldn't be able to do that if I had to rush through it in one weekend so it seemed worth buying another DD.