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What are the symptoms of a bad IAC valve/motor?

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Old 08-15-2003, 05:20 AM   #1
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Default What are the symptoms of a bad IAC valve/motor?

Title says it all. I changed several things out and fixed my nasty rich problem. But I still don't know what caused it.

The IAC was definitely broken, pintle jammed out, and the vette would barely run. It got 12 mpg at cruise, sounded lilke it was firing 10 degrees retarded on 6 cylinders, and spit raw fuel into the exhaust when lettting off the throttle.

I guesss i'll put my broken iac back on tomorrow to see if it acts up again. If that's the case, then i chickened out and took my new injectors back off when i shouldn't have.
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Old 08-15-2003, 05:32 AM   #2
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Default Re: What are the symptoms of a bad IAC valve/motor? (CentralCoaster)

I had the same problem a few months ago and it starts to surge when idling or when your driving normal and put it in neutral, some times the engine dies. But it only happened at low rpms, i.e 1000rpm or less.

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Old 08-15-2003, 06:46 AM   #3
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Default Re: What are the symptoms of a bad IAC valve/motor? (Darkness)

A bad IAC, especially on a MAF vehicle can cause all kinds of drivability issues. The most common symptoms are surging/hunting idle, or an idle that’s way out of spec (400rpm, or 1500rpm), stalling when coming to a stop, causing the ECM to have an erratic integrator value, accompanied with a moderately swinging A/F ratio. Your description of having an extremely rich A/F & “spitting raw fuel out” on de-acceleration, I would not associate that with a bad IAC! Sounds like you installed much larger Lbs/Hr injectors than stock, didn’t adj the fuel pressure, &/or install a custom chip. Perhaps you have a (NEW) bad injector(s) that leaks or are stuck open? The Accel injectors have gained a bad rep already for leaks and serious performance degradation over short periods of operation!

BTW: running that rich will ruin you engine fast, don’t’ drive it till ya fix it!
Just my 2-cents!

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Old 08-15-2003, 09:51 AM   #4
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Default Re: What are the symptoms of a bad IAC valve/motor? (CentralCoaster)

I don't see any relationship between IAC and your problems. IAC affects idle quality and stability only. It sure sounds like problems with those injectors.
Hope you get solved soon Kevin. Good Luck :cheers:
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Old 08-15-2003, 05:21 PM   #5
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Default Re: What are the symptoms of a bad IAC valve/motor? (Darkness)

Okay here's a question for you all. My wife and I have an 84 vette stock no mods has the same surging and dieing issue at below 1000 rpm's I know that the car is running rich, what are the solutions. I know 84's do not have a MAF in them does anyone have an idea. I found that the EGR Valve Silonoid connector is pretty bad. Still making connection but not a pretty site. It is kinda of a search and destroy mission with this car since it is new to us and we are learning the 84 crossfire "quarks". Please help looking forward to getting back to 2 vehicles again. :banghead:
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Old 05-06-2012, 10:10 PM   #6
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What about engine reving to max rpm at start up. I pulled my out it was very dirty, so I cleaned it and put it back in and had the same result. But this could be a symtom of bad IAC.
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Old 05-06-2012, 11:47 PM   #7
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Read the rules about reviving a thread over 45 days old BWD111.

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