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89 Chevy Silverado K1500 High Idle & Hesitation

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Oct 12, 2021, 10:19 PM

Post #1 of 2 (110 views)
89 Chevy Silverado K1500 High Idle & Hesitation Sign In

Okay So Got a 89 K1500 Silverado 5.7L 350 V8 Automatic, it starts a little rough idles sorta high it seems and I have to rev it up a while after starting or the engine will die, after warming it up the idle improves a little and it will actually idle NOW after so many parts have been replaced, but it still sometimes dies backing up or going forward from a start after shifting into Drive, oh.. Automatic Transmission.., And When I'm at a full stop and hit the gas it has slow acceleration, hesitation and is a little jerky , drove it to O'Reillys earlier today and it died three times in the parking lot just when I was trying to backup and then when I shifted into drive, if it doesn't die and it moves forward in Drive then there's an initial jerk and starts out with slow acceleration..

Now I'll List The New Parts ...

NEW Computer, New Throttle Body, New Throttle position Sensor, New idle air control Valve, new fuel pump relay, new spark plugs, distributor cap, distributor rotor, new fuel filter, EGR Valve, Map Sensor, knock sensor, collant temp sensor, new plug wires a few years ago, new starter and alternator a few years ago.. its been sitting for a few years, went through most of the gas got more gas expensive non ethanol gas in there and added a couple bottles of Iso heet, added Marvel's mystery oil to the oil..., and I put a new oxygen sensor in closest to the engine.. which helped a lot but not enough.. Is there another oxygen sensor on there somewhere? Have already dumped about 2300 dollars into this truck trying to get it going and the money is pretty much all gone now.. between the like over 2000 in parts and labor to a mechanic that couldn't figure it out plus the parts and additives I've put in since I got it back.. , I haven't personally checked for vacuum leak, um.. I'm kinda curious about the air intake could something like that be clogged up somewhere with pine needles or mud or leaves or something, could that be it or, is there another Oxygen Sensor on the 89 k1500 or um.. I'm not sure what the status of the ignition coil is.. Wish I could figure out the issue before I have to keep throwing endless hopefully very cheap parts at it until something sticks..

Any Advise..??

(This post was edited by JohnTheSavage on Oct 13, 2021, 8:47 AM)

Tom Greenleaf
Ultimate Carjunky / Moderator
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Oct 13, 2021, 1:37 AM

Post #2 of 2 (94 views)
Re: 89 Chevy Silverado K1500 High Idle & Hesitation Sign In

All that, $2,300 bucks and you didn't say which engine this has. 3 possible, all have TBI unless altered?
Quote you ">I haven't personally checked for vacuum leak<"
It's old enough to have several IMO is the most likely cause so what's stopping you?
Quit the parts tossing it's confusing everything first tell us how many miles on this thing if known?

Do you know how to check for vacuum leaks? Not that hard is highly suspect if engine shows any health otherwise un "unmetered" air leak will raise idle and be lean mixture of fuel do just what you subject line says.
#1 should really be what's the state of state with this engine and some history if known. It's OLD, most trucks get beat to death, not cared for too well but it's still here so what's the story?
Sorry you tossed parts like that, no doubt cheap crap used when what was there was still better than new stuff every one of them new could be junk and the problem now or soon.

Check for vacuum leaks. This old now I'd see if this engine is any good for valve timing too you can do with a vacuum gauge. With a timing light (OMG what are those?) you can also tell how healthy a lot of this is before wasting more bucks on it,

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