Drop in Idle and/or stall when gas released


Asked by Nov 24, 2013 at 05:16 PM about the 1989 Chevrolet C/K 1500

Question type: Maintenance & Repair

I have been working on our 89 Chevy K1500 and am still having an idle issue.  The truck idle drops and lopes and occasionally completely stalls. This usually happens when driving slow in town... backing out of parking space, letting off gas when coming to a stop sign or to park etc.  It does fine to start and accelerate.  I have done a tune up including oil and filter, fuel filter, spark plugs, wires, cap and rotor.  Ran a couple cans of SeaFoam through in fuel tank. Still having this idle/stall issue. I don't want to just start replacing random parts "hoping" to get the right one lol... I have read that throttle body regulator or fuel pressure regulator or fuel injectors or fuel pump or a possible air leak could be causing this.  PLEASE HELP!!! Where do I start?

5 Answers

okay....I suspect the throttle position sensor has gone off~ https://www.google.com/#q=1989+Chevrolet+C%2FK+1500+throttle+positio n+sensor

6 out of 6 people think this is helpful.

Your idle air control valve is either dirty or faulty.

4 out of 4 people think this is helpful.
Andrew Olsen

the problem is there are lots of possibilities. Dont go replaceing things randomly, have them tested. Possible thins are: TPS, IAC, vacuum leak, fuel pressure regulator, bad injector, worst case scenario the pcm has messed up. You have already taken care of basic tune up items so thankfully that is out of the equation. I have a love hate relationship with the gm TBI engines. I love the reliability but most problems have the same symptoms and its impossible to just look at it and replace one thing, You gotta test components

1 out of 1 people think this is helpful.
Jeremy Stone

My 95 X-71 305 engine is doing just about the same thing I've replaced every sensor u can think of but as long. As your going down the hwy it runs good so null not one person on this site can give me any insight on what it is so good luck.

Wade Miles

Having same issue. Replaced map sensor, cts, egr valve and accuator, basic tune up including rotor, cap, wires and plugs. Checked both sides of plugs after running for 2,000 miles. Both sides were chocolate brown. Cleaned iacv and it looked damm near new. I'm thinking it might be a bad wire harrness. Connectors are a little rough. Don't have a wire tester to check voltages.

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