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strage idle behavior 88 spfi


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11 replies to this topic

#1 danzick

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Posted 07 February 2013 - 10:49 AM

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

Posted Image

Edited by danzick, 07 February 2013 - 10:53 AM.


#2 mikaleda

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Posted 07 February 2013 - 12:02 PM

Coolant temp sensor has a lot to do with idle IMHO I would start there

#3 markjw

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Posted 07 February 2013 - 10:23 PM

Start with checking for trouble codes.

#4 ricepapertiger

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Posted 08 February 2013 - 09:33 PM

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, 08 February 2013 - 09:37 PM.


#5 danzick

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Posted 21 March 2013 - 11:22 AM

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.



#6 mikaleda

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Posted 21 March 2013 - 11:55 AM

Check the voltage at the iac wiring harness a DIY Manuel should give you the values and what prongs to test, or you might be able to find the info on this site.

#7 mikaleda

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Posted 21 March 2013 - 11:55 AM

Oh and try cleaning your new iac

#8 86 Wonder Wedge

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Posted 23 March 2013 - 02:05 AM

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, 23 March 2013 - 02:08 AM.


#9 Cougar

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Posted 23 March 2013 - 01:11 PM

Another thing to check for is air leaks in the intake manifold gaskets.



#10 danzick

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Posted 25 March 2013 - 09:36 PM

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.



#11 mikaleda

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Posted 26 March 2013 - 09:01 AM

If the iac is open at mid range it would be like having a vacuum leak. The iac should only be open at idle

Edited by mikaleda, 26 March 2013 - 09:01 AM.


#12 ivans imports

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Posted 26 March 2013 - 09:13 AM

Check the throttle hard stop has not been messed with i get this when its trying to find its idle stop on the tps if it gets addjusted it will not see its idle contact and will serach for idle or throttle cable is to tight






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