1987 GMC Jimmy with 5.7L TBI crate engine troubles - Blazer Forum - Chevy Blazer Forums

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Old 10-08-2012, 12:59 AM
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Default 1987 GMC Jimmy with 5.7L TBI crate engine troubles

I've been looking at getting a Blazer or Jimmy for a while, and I finally found one I like for a good price, a 1987 GMC Jimmy Sierra Classic with a modern GM 350ci TBI crate engine. When we first went to look at it, it started right up, and ran well, other than the lack of power steering (which we have fixed, lack of fluid). Less than 5 minutes into a little test drive, it sputtered and died, from what the guy said was most likely a lack of fuel, which does seem to have been the case.

The problem now is that after adding fuel, it won't run for anything. We can get it started, but it won't idle, it just coughs and sputters as long as you are working the throttle. We replaced the fuel filter, to no avail.

The curious thing is, with what seems to be the MAP sensor electronically disconnected, it idles perfectly, and I can rev the engine up as far as it will go without trouble, and the second its plugged back in, it goes back to running only with a lot of work. But when it is unplugged, when you put it in gear, it dies, where while it is plugged in, you can keep it running once its in gear.

Another thing I noticed is that it shifts quite violently in either scenario, lurching forward or backwards when put into gear.

From what I've been reading, its quite likely it is the fuel pump, especially since the tank was run dry. Does this sound like a reasonable assumption?

I appreciate any help, Its going to take a fair bit of work to get this truck into the tip-top shape I'd like it to be in, and that it deserves to be in, and I certainly don't have the experience to do it all on my own.

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Old 10-08-2012, 11:21 PM
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if it runs with the map sensor pulled then the fuel pump is working. sadly i own a tbi and that thing has been problem free the 2 years ive owned the thing so really not quite sure of that symptom. maybe a bad map sensor, maybe googling that symptom will come up with something.

as far as the trans issue, sometimes people put shift kits in these transmissions mine slams gears likes its supposed to, even with 33 inch tires if it shifts going around a corner it will chirp the tires. or are you referring to when you first put it in gear?
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Old 10-08-2012, 11:46 PM
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Its been suggested to me that it could be the Idle Air Control valve, so I'll try pulling that and cleaning it, see if that works/helps.

As for the transmission, yeah, I'm talking about when you first put it in gear, it lurches quite a bit. I also noticed you can always change from any gear to any other gear. Is it supposed to be able to do that? Its definitely been messed with before, so its possible something is broken. Its going to need some work either way as its missing the shift indicator, and it skips from park to neutral if you aren't careful.
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1987, 57, 57l, 87, code, crate, engine, engines, gmc, hop, jimmy, knock, sierra, tbi, tranm, ups

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