A couple of small (IAC related?) HO bugs

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A couple of small (IAC related?) HO bugs

April 05, 2007, 03:14:31 PM

Since we completed my HO conversion exactly 1 month ago to the day, I have been extremely pleased with it. She runs really strong and gets great gas mileage while doing it (20-23 average). But there have been a couple of small bugs I would like to ask about...well, mainly just one:

Sometimes when the car is stopped and she idles kinda low, she won't want to move. If anyone has driven a car that doesnt like going when it's cold, this is exactly what it feels like (dad's Chevelle used to do that). However, my car will do it even when she's fully warmed up. I haven't been able to find any correlations with this other than she normally does it when she idles at low rpm. 750-850rpms seem to be the sweet spot for the car, but sometimes she will idle lower than that (and it gives off a slight shake) and that's typically when she does this. Sometimes there will be a slight popping noise too. I believe it's just the IAC since I'm pretty sure its the original one off of my SO. I originally thought that maybe it was just the low 2.73 gears bogging the car down, but if that was the case, the car would do it every time. I also thought it may just be the SO fuel pump, but the engine runs flawlessly even during the 1 or 2 times she has seen 5,000 rpm at full throttle, so I doubt it's that.

My other bug, which may very well be related to the above problem, is that she always idles higher in Park. While she normally likes 750-850 rpm in any other gear, in Park, she will idle anywhere from 900-1100 rpm; but if she starts up at 1100, she will slow her way down to 900-1000. I dont know if it's supposed to do that or not. If it's a problem, I would think it's also an IAC problem.

Any help here is greatly appreciated!

A couple of small (IAC related?) HO bugs

Reply #1 – April 05, 2007, 03:37:07 PM

interestingly i ALSO feel like my idle tends to sit a little higher than before. i gotta go find that procedure for "re-learning" the idle. i have the digi-dash so 1000 rpm = the first 5 bars, 4 bars = 800 rpm. goes right down the 3 bars once in gear, eventually after start up will settle at 5 bars but i can hear the engine isnt actually spinning quite that fast (remember its give or take 199 RPM :hick: ), and it might even register 4 bars. but occassionally sitting at a red light for a long time ill put it in neutral so i can just take my foot off the brake and it will come up to 5 or even 6 bars, so like 1100-1200 rpm. it will settle down again but it does spike.

somewhere i thought i read that an idle reset might be necessary. i dont know why youre getting bogging/bad response though. i think my IAC is good, the car always idled smooth and at the right speed. you could always try thoroughly cleaning it out, never know....

i gotta go to class so hopefully someone will post the idle re-learn link, if i dont find it first. try that, king. i plan on doing it this weekend, since i will be home because of Easter. if anything i worry about my transmission. idling high is like powerbraking it (albiet to a very small extent) but i still dont like it. thats why i put my car in N at stoplights. actually anytime i know ill be stopped for more than ~30 seconds i shift it out. i should get a tranny cooler, then i wouldnt have to do that anymore. ive got so many idiosyncrasies ive developed with this car so that interior piece dont break or get worn out, i dont wear out the seats, etc that i practically cant let anyone else drive the car!!!:hick:

A couple of small (IAC related?) HO bugs

Reply #2 – April 05, 2007, 03:42:06 PM

The old SO used to stall when I'd first start her up in the cold, so maybe that was also the IAC. It's just weird that my response problem doesnt happen everytime, and never happens at any time other than launch. Thanks for the info.

BTW, my favorite thing about the Sport package over the LX - buttstuffog guages. :)

A couple of small (IAC related?) HO bugs

Reply #3 – April 05, 2007, 04:52:35 PM

The IAC is easy to clean. Give that a shot and see where you are.
My '86 would constantly die when I started it and ran rough, cleaned the IAC and all was well.

Other than that, I'd check the vacuum lines to make sure none became pinched or cut when you did the HO swap. I pinched and split the small line that ran from the manifold to the FPR without knowing it.

A couple of small (IAC related?) HO bugs

Reply #4 – April 05, 2007, 06:08:36 PM

Could be the map,Vac leak,cleaning the IAC isn't a bad idea!,

A couple of small (IAC related?) HO bugs

Reply #5 – April 05, 2007, 11:21:34 PM

Alright, thanks for the tips guys! I wont get to it this weekend, but hopefully next weekend.

A couple of small (IAC related?) HO bugs

Reply #6 – April 10, 2007, 01:31:49 PM

Interesting....replacing my ignition switch has SOLVED my bogging/low idle problems. In the past 2 days, she has not once idled [too low] rough or bogged! Any comments? I certainly wasnt expecting this.