Surging Idle- 94 Cobra

What is causing the surge?

  • Vacuum Leak

    Votes: 2 66.7%
  • Idle Air Control

    Votes: 0 0.0%
  • MAF

    Votes: 0 0.0%
  • Tune

    Votes: 1 33.3%
  • Owner (me) did something stupid

    Votes: 0 0.0%
  • Something Else

    Votes: 0 0.0%

  • Total voters
    3
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oilspill

oilspill

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I’ll take an idle anywhere under 1000 that’s stable. Few days left til it’s the kurgan teams problem!
 

ttocs

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what mods have been done to the car now? I know it says TB and some basic stuff but I don't see anything on the list that should require a tune and if it is a vac leak or something your just going to have an upset tuner and if your lucky you will be able to fix it and have it tuned same day.
 
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oilspill

oilspill

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what mods have been done to the car now? I know it says TB and some basic stuff but I don't see anything on the list that should require a tune and if it is a vac leak or something your just going to have an upset tuner and if your lucky you will be able to fix it and have it tuned same day.
Heads, kenne bell, meth for the biggest ones. All supporting mods to go with those.

He won’t be upset he knows I’m bringing it in just to fix the surging idle.
 

tinnocker

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Ttocs, what rpm did it idle at? Mine didn't surge when I got it back from the dyno tune but it idled about 1100 rpms. Maybe I am not making myself clear. I am seeking to get my idle down to at least 850-900 rpm. My reason for getting a cam was more to hear the idle at a red light than for the performance value. I have seen on Youtube where you can get a cammed up Fox Mustang to idle at 650-700 rpms, but I haven't heard (on youtube) or read about a 94-95 that has an aftermarket cam with that low idle. I asked my tuner about the idle and he blamed it on the computer and told me that I could try the idle set screw. I did and got the surge. Turn the idle up to 1000-1100 rpms, the surge is gone.
 

ttocs

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Correct me if I am wrong but I don't think most performance cams are meant to idle at 600 rpms. The stock cam, sure it is designed to have a great idle but any performance cam I have read about isn't designed to be as smooth as the stock at idle. My idle with the trickflow stage 1 has been around 850rpms when warm both with the stock ecu and now with the holley hp.
 

tinnocker

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I have my idle down to about 850-900 with the gizmo like in the picture. On a cold start it will still surge for 45 seconds or so. If I raise the rpms up to 1000-1100 the cold start surge is gone. I think the computer is set to seek a higher rpm at start but is happy after the engine is warmed a little. And you are right about a performance cam needing a higher idle, but if the idle is too high it is hard to tell if the engine has a performance cam, especially on a stage 1 cam. I guess I am content with the 850-900 rpm setting even with the 45 second surging, until I am bored some day and start to fool with it again.
 

tinnocker

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Oilspill, I know you have read a lot of posts about your problem. Have you checked to see if your throttle valve is warped or not closing all the way when you have clearance between the cable and hex set screw? If it is not closing all the way then the idle will remain high. Also, have you adjusted the slot head screw that controls the air going to the idle air control. It should be between a half to 2 turns out. Clockwise turns all the air off and should kill the engine. Turn counterclockwise to open it up 1/2 to 2 turns. Both the IDLE AIR CONTROL screw and the hex screw that controls your foot pedal will control the idle rpms. I would try a 1 to 1 1/2 turns on the hex screw and 1 1/2 turns on the IAC slot screw, it should start, and then fine tune it to the desired rpm. Don't go above 2 turns on the IAC slot headed screw. I have read these directions in many post and used them with mine. You said you would be happy with 1000 rpms at idle. This should get you there.
 
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oilspill

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Oilspill, I know you have read a lot of posts about your problem. Have you checked to see if your throttle valve is warped or not closing all the way when you have clearance between the cable and hex set screw? If it is not closing all the way then the idle will remain high. Also, have you adjusted the slot head screw that controls the air going to the idle air control. It should be between a half to 2 turns out. Clockwise turns all the air off and should kill the engine. Turn counterclockwise to open it up 1/2 to 2 turns. Both the IDLE AIR CONTROL screw and the hex screw that controls your foot pedal will control the idle rpms. I would try a 1 to 1 1/2 turns on the hex screw and 1 1/2 turns on the IAC slot screw, it should start, and then fine tune it to the desired rpm. Don't go above 2 turns on the IAC slot headed screw. I have read these directions in many post and used them with mine. You said you would be happy with 1000 rpms at idle. This should get you there.
i went as far as buying a new throttle body just to make sure this wasn't the issue...no dice! Ive adjusted the set screw in almost every position chasing a clean idle....still no dice!
 

RAU03MACH

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A lot people do not realize that climate changes cold weather
And elevation has a lot to do with it

Think as meter jets on a carb that plate may be of some help
 

dcm0123

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If you adjust the screws with the engine running, please shut it off and restart for everything to re-calibrate itself.

Do you have an adjustable fuel pressure regulator? iF so, check your fuel pressure to see if it changed.

A good tuner should be able to stop the surging.

We have a blower on a 351W with tweecer, custom cam, injectors and MAF sensor. Typically hot idle is around 1000 rpm.
 
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oilspill

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car was dropped off this morning to Kurgan Motorsports. Excited to see what they find and hopefully get a smooth running car back.

Secretly hoping for them to tell me the short block is trash so i am forced to get a dart block.
 

ttocs

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I think that might be the only thing worse to say to a shop than "I am in no hurry". I learned that one the hard way....
 
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oilspill

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Have you got an update or checked in yet?
yea i have checked in a few times of course. Trying to not be a pita but want it fixed and back!

Late last week he said "no reason this thing shouldn't be idling correctly, i am still working on it but this one is giving us hell"
 

tinnocker

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I see you are from Atlanta. Have you tried Moe's in Dallas, Ga. He is a well known tuner and has about 6 lifts in his shop. Last time I was in there he had two Mustangs from West of the Mississippi. Most shops will not let you wonder in the working area but he encourages it!
 
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oilspill

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I see you are from Atlanta. Have you tried Moe's in Dallas, Ga. He is a well known tuner and has about 6 lifts in his shop. Last time I was in there he had two Mustangs from West of the Mississippi. Most shops will not let you wonder in the working area but he encourages it!
Back when I had to pass emissions I used to take it to them to get it to pass. Not a bad experience but wasn’t perfect either.

They did some exhaust work for me and left it hanging about an inch from the ground so I had to fix it afterwards. Easy mistake but was honestly the reason I gave kurgan a call.

May end up full circle depending on what I hear this week.
 
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oilspill

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we have a verdict! Apparently my meth injection injecting ahead of the throttle body was leaking down and washing the MAF and ultimately killing it. They relocated the injection point post blower and changed the MAF and said it is idling smooth as butter. Re-tuning it this afternoon and should be able to pick the car up Friday.
 

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