QuestionQUESTION: I have a 1990 GMC Sierra. It has 200000 miles and has started to intermittenly stall. Here is the situation: After then engine is warm (Not a cold run) the motor just cuts out as if I turned the key.(No hesitation/sputtering... just a solid shut down) I still have power. (After pulling to the side of the road I tried to start and the starter turned over) The first time that this happened I let it sit over night. When I returned I tryed to start it and it fired right up. Two weeks went by and the same thing happened. But this time it was a couple days before it started up. When running, it runs smooth and well. It has new plugs and wires. New fuel pump. Any ideas?
ANSWER: If I am right in stating, from what you have said, that it never fails to start or run when cold, only when hot, then it almost has to be "hot soak." This is when an electronic component ceases to function as a result of having become too hot. What you need to do, by way of diagnosis, is to check the spark the next time it happens. If you have good strong spark, then it is probably the MAF sensor. If there is no spark, then it is most likely the ignition module, which is located under the distributor cap. A mechanic could check the coil, cap and rotor, even the ignition pick-up coil, with an ohm-meter first, then, if they were all within spec, change the module. If you have changed the cap and rotor recently, I would probably change the module; the pickup coils on these later fuel-injected engines rarely fail. If you haven't had that sort of maintenance done, I'd be tempted to change the distributor for a rebuilt one complete with cap and coil, thereby eliminating everything that could go wrong with the distributor. The coil could go bad, but it's an e-coil, and they seldom do, although I used to sell them to optimists regularly. That spot at the back of the engine in Chevys is the warmest spot under the hood, so this is not terribly uncommon.
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QUESTION: Alright, so you are brilliant. I took the truck out for a long drive and it stalled and won’t start up again. We found out that it wasn’t getting spark so we changed the distributor like you said and it fired right up. However, after it stalled we had to tow it about 1 mile (It’s automatic). And now that it is up and running it doesn’t want to shift into the passing gear. (It didn’t have this problem when I was taking it for the long drive before it stalled…it had good pickup) Right now it has good pickup from a stop light, but it has hardly no acceleration when going about 30 mph and up. I can get it driving at about 70 mph but there is just little power/acceleration... worse than if I was driving a 4 cylinder pickup. I had the timing set at a dealership ($90!!) and it still has the same problem. ANY IDEAS???
ANSWER: It is possible that you damaged the trans by towing it, it can happen, but it is pretty unusual. If it won't shift down when you floor it, the first thing to check is the kickdown cable. GM overdrive transmissions (I'm assuming that you have an overdrive trans) use a pair of cables, one to kick down and one to shift up. They don't have a vacuum modulator. If one of those cables got rearranged while you were working on the car and has kinked or is not connected properly, then the symptoms would be about what you are describing. If you don't have overdrive, then I would suspect that the vacuum hose to the modulator on the transmission has been damaged or disconnected somehow while the truck was being worked on. Also, I would be suspicious that the firing order of the plug wires got confused. The correct firing order is usually cast into the intake manifold in the front where you can read it. Chevrolet numbers their cylinders with no. 1 the front dr.side, no. 2 the front pass. side, number three the second on the dr. side, no.4 the second on the pass. side, and so on. Find the wire that goes to no.1 and then go around the cap checking which plug each wire goes to and comparing that to the order they're supposed to be in according to the manifold. You'd think that the dealer would have picked up on this when timing it, but they only time the no. 1 cylinder, as that is the one the timing marks reference to, and may not have bothered to check the firing order. I hope you didn't damage the trans. The fact that you're down on power really makes me think that the firing order is off, it is really easy to do (I did it last time I changed a set of wires, but knew it was off as soon as I drove it, 'cause all I had done was change wires so it couldn't have been anything else).
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QUESTION: I got a print offline for the wires and they look right. It actually runs "normal" at low speeds, (it could race off the line) but once i get above 30 or so it just doesnt have the pickup that it once had (i know that it was going into passing gear right before the last time that it stalled).... If you have any more information about the cables it would be greatly appreicated (location and such) and if any other ideas come to mind. Thanks once again for all your help!!!
Answer I honestly can't think of anything else, other than that the transmission may be damaged. It might be time to let someone look at the trans and see what they can see. But, please don't take it to a transmission shop; find a good mechanic who understands and works on transmissions and let him look at it (he can check everything else while he's at it). If you don't know a good mechanic, go to your local parts jobber store (not Pep Boys or any other chain, a REAL parts store) and ask them to recommend someone; they know from experience who is good and who is not.
