Intermittent loss of power '88 Sierra V-6

[gaander]

I have just purchased my first GMC pickup. It is an '88 Sierra 1500, extended cab, long bed. The seller told me that the engine in it now is a rebuilt 4.3L, V-6 with approximately 28,xxx miles onn it. He gave me "all the receipts he had from all the repairs". The last receipt was from '06 and was for a tune-up. He told me that "she does not run so great when it is raining out. This is not true, It can be sunny or rainy and she'll act up.

This is the best way I can explain what is happening; You can be driving along and everything is just fine then out of nowhere it's like she falls on her face. Does not die just losses all power. Now it has gotten worse. When this happens and I come to a complete stop the engine will rough idle then die. But starts right back up. After resarting 98% of the time she still has no power.
I have taken her to my mechanic and he spent four nights on her. He told me something about the right fuel injector was shutting off when she got real hot and some other stuff that I did not really understand then he replaced the ECM and said she ran fine for him around town. I drove it the next day and it didn't even have time to heat up then it lost power while driving about 35mph and proceeded to die at the next stoplight.

I was planning on taking my misses to a Memorial Day Weekend-camping, float trip but that cannot be done until this is resolved. We appreciate you taking the time to read this and any suggestions are greatly appreciated as well.

Thanks,
Greg

[leolkfrm]

if its doing it on a regular basis, take your mechanic on a ride with his diagnotic tool hooked up so he can watch the readings, It may give a better idea what is happening. Also was it a refurbished ECM? Sometimes they aren't fixed right when on the bench and may be another bad one.

[gaander]

My mechanic said that he drove it until it acted up with all his guages, etc. hooked up and this is where he came up with the ECM being bad. The one he replaced had junkyard makings on it and the original stickers. The first ECM he put in was bad so he got another new ECM non-referbished. Thank you for your time and help.

Greg

[gaander]

I replaced the fuel pump relay then we went on our trip. 3 1/2 hours each way. Ran great the whole trip until we were about 50 miles from the house on the way back. She started losing power again. This time I pulled off the road & let her cool off. Then took the breather off to find out that the right injector was not working. I got her home and put in a used injector, from the junk yard, to replace the right one that was not working all the time. This worked somewhat better for that day. Then I waited a week or so and tried to start her up again. I actually had to put my foot in it and got it started but it kept trying to die everytime I took my foot off the gas pedel. Then I put the original injector back in and she started right up and idled kind of rough but did not die. She ran bad just like before, loosing power & etc. But she ran.

After all this I am thinking it has got to be the injector? I had originally thought it was an electrical problem. Not anymore. I think I will go buy a few new injectors and see if that fixes the problem. I'll let you all know what the verdict is.

[ukrkoz]

several things come to mind:
1. you'll better off really troubleshooting the source of the problem, instead of guessplacing parts.
2. electrical supply to fuel pump cuts off periodically, shutting down the engine(negative is fast to oxydize, check it 1st)
3. we had a little devil like this in one of our eclipses. just did not like humid weather. we even knew exactly which contact it was, and will wiggle it and all comes back to life. car had close to 260K miles on it, was not worth fiddling with repairs. was throttle position sensor wire.

Troubleshooting Engine Performance Problems: Part 1

fortunately, they had much less electronics in 88, should not be that hard to scout the problem. good luck, friend.

[blu95]

this might sound off the wall but does the truck have an aftermarket radio or any extra goodys or toys my 95 started doin what seems to be the exact same thing i replaced part after part checked all the grounds an everything the i had BUDDY (JACKA@#) put my headunit in for as a favor he owed me then later i proceed to add amps mids highs subs all the good stuff then the problems started another freind thats was helping me try to get the issues fixed noticed that (JACKA@#) used a power wire from the ECM for power to the headunit the truck would get completly stupid at time we foud the factory harness got an adapter fixed rats nest been fine ever since cept the fuel gauge kinda strange i thought