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strage idle behavior 88 spfi


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so my car doesnt run as good as it used to, seems to have mid range miss, but good top end. i noticed this when i noticed the idling problems it has. when i first start it up, it idles at about 2200. i can let it sit and idle for 10 mins and it will stay idling at like 2200 even if i mess with the gas pedal. as soon as i actually drive it, i stop at a stop light and this is what it does

 

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Edited by danzick
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Mine has been doing this. It used to start up just fine, and a few days before I pulled the motor to reseal it, it had a suuuuper bad startup and idle. Got the motor back in, and I have been trying to remedy a very similar issue.

 

If I'm in Park or Neutral, idle is a little more stable than yours around 1000rpm. In Drive or Reverse, it will drop the revs down to around 600 and be on the verge of stalling.

 

I cleaned out the IAC valve, helped a teensy bit.

 

As for the Coolant Temp Sensor, I'm gonna try that and see if it helps.

Edited by ricepapertiger
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  • 1 month later...

any more ideas? its got a coolant temp sensor i got from napa about 8k ago. doubt its that. im getting an IAC code, and ive tried swapping them out and had no luck. its also really lacking on the mid range. runs great wide open, but is pretty hesetant in the midrange and i find myself wide open a lot because of it. its also off and on. does it sometimes and other times ill pull to a stop light and it idles perfectly.

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The wiring can be bad as well at the IAC plug/harness (right there by the TB), that was my IAC problem.

 

And it sounds like the ECM is trying to compensate/stabilize the idle.. Is/Was your A/C OR defrost on in that video? Does it make a difference if you hit the A/C or defrost? Does yours work/ do you have it still installed and hooked up?

 

Also, check for corrosion in/around the coil terminals.. could be getting a bad tach signal to the ECM..

 

Also, have someone do a charging system test/alternator test to make sure the diodes are still good (little to no AC voltage ripple). "Pulsing" voltage can wreck havoc on the system, especially the MAF since it's wired right to the IGN circuit (not powered from the ECM)

 

Or just trying unplugging the CTS, TPS and MAF sensors.. it'll still run, and should run pretty well (since it's "flying blind") or atleast more stable.

Edited by 86 Wonder Wedge
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thanks for the replys guys. sorry i forgot this forum does not send you an email notification when you get a post to a thread. no the AC was not on in the video and yes it does have AC. also, what would the IAC valve have to do with mid range? the midrange bothers me more than the surging idle.

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