94 gt idle issues..

manicmechanic007

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When the tester says to perform a brief WOT
You also need to actuate the brake and the power steering switch
That should shoot the test past that stage, and output codes at that point
Look for a super star 2 or a NGS for cheap one of these days
3 digit codes means it has quite a bit of self test capability
 
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Smurfstang88

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When the tester says to perform a brief WOT
You also need to actuate the brake and the power steering switch
That should shoot the test past that stage, and output codes at that point
Look for a super star 2 or a NGS for cheap one of these days
3 digit codes means it has quite a bit of self test capability
Well it did not say to brief wot, it said to slowly go to half throttle then let off.. what about the brake and power steering? And my code reader is actually a fairly good one, just mostly meant for obd2 but came with adapters.. i still dont get why my jumper wire test is seemingly unsuccessful
 

manicmechanic007

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The factory Ford testers are the super star 2 and the new generation star
They will both tell you to perform a brief wide open throttle (in the middle of the running test)
Your tester God knows what it is thinking about with a moderate acceleration curve
Those old ones, prior to 1996 Fords, can be tested with a home made star tester, but most people are not savvy enough to get one to function
The early ones you had to latch and unlatch (that is your jumper wire's function I believe)
So, then, does your OBD tester plug in to the STI (data link connector) on your 1994?
 

Smurfstang88

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The factory Ford testers are the super star 2 and the new generation star
They will both tell you to perform a brief wide open throttle (in the middle of the running test)
Your tester God knows what it is thinking about with a moderate acceleration curve
Those old ones, prior to 1996 Fords, can be tested with a home made star tester, but most people are not savvy enough to get one to function
The early ones you had to latch and unlatch (that is your jumper wire's function I believe)
So, then, does your OBD tester plug in to the STI (data link connector) on your 1994?
Gotcha, and yes mine connects to that grey sti wire as well
 

manicmechanic007

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So, that tester should be good enough
Does it have anything on the menu like freeze frame data or live data?
In other words, can it test PIDS? Parameter identification data?
Like monitoring the O2 sensors switching?
 

Smurfstang88

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Also ive been reading up on my issue, and it seems tons of people have had these problems over the years with sn95 cars as well as some foxs and they either put an iac restrictor plate, or they just unplug their iac.. i do not like fixes like these since the thing ran just fine the way it is from factory and nothing should have changed aside from a very mild cam.. anyways alot of people say they unplug them to get rid of that rpm hanging between shifts, i just want mine fixed right because im somewhat particular and like things done right, so im wanting to know what else can i do?? This really shouldnt be such a complicated issue its so ridiculous. Also my new iac i tried to adjust the screw and after about 10 minutes of removing that rubber plug that protects you from even adjusting the screw, it is basically a rubber glue plug that rips to shreds. Anyways i tried to turn it in either direction with the right size allen key and couldnt get it to turn, and the damn thing stripped out completely, why the hell is it plastic? Id think a part that was 80$ wouldnt be such junk but not surprised these days, but couldnt get it to lower the idle on the old iac turned the screw all the way in each direction and nothing even changes the idle..
 

Smurfstang88

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How bout a pic of this plug you're talking about.
This is the white rubber plug, and behind it contains the “idle adjustment screw” for these years of cars apparently. Also i just messed with it some more and was able to get the screw freed up after I hammered a torx bit into it which was able to actually grab the plastic good enough to turn it.. anyways I adjusted it out as far as it could go and still only got the idle down to 1100rpms with it unplugged. Makes no difference in rpm speed whether its plugged in or not, but it solves the hanging rpm problem completely. Only thing i can think of is someone adjusted the throttle stop screw thing in the past and me cleaning the maf undid their “fix” and now its needing to be adjusted again but i have my doubts and i really dont want to mess with that throttle stop stud.
 

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Smurfstang88

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I was just reading another thread back from the stone ages and this guy sounds like he had my exact problem down to the T. Ill include a pic of one of his posts, and of course, unfortunately it was never resolved or at least never posted an update..
Edit: i just checked my tb butterfly, and it looks closed all the way so i dont thing the stop screw was adjusted..
 

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Smurfstang88

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The plate is supposed to close all the way
The throttle air bypass or IAC is what lets air around the plate to make it idle
I am aware of this, and as best i can tell it is closed all the way, at least by eye. Is there a way to make sure it is with a feeler guage or something? I really have my doubts about that being the case though since its a non molested basically untouched car and i know the original owner and 2nd and only other owner and am qhite sure they wouldnt have ever messed with it.. is it possible to have a vac leak yet not show up on the vac guage? Im still really trying to wrap my head around how it ran fine aside from occasionally going haywire and surging bad and stalling, to me replacing some sensors and cleaning the tb and now it idles super high, just doesnt make sense.
 

manicmechanic007

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Unmetered air causes bad surge. Sure a vacuum leak does not always show up on a vacuum gauge reading. The throttle plate should never be adjusted. If yours is idling high, the IAC might be stuck open or you might have a leak in the hose between the maf and the throttle plate
 

Smurfstang88

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Unmetered air causes bad surge. Sure a vacuum leak does not always show up on a vacuum gauge reading. The throttle plate should never be adjusted. If yours is idling high, the IAC might be stuck open or you might have a leak in the hose between the maf and the throttle plate
Pretty sure i figured it out. I believe someone adjusted the idle up with the screw you arent supposed to touch because it was having problems staying running because the maf was dirty or something. So when i cleaned it it then idled even higher. I looked closely at the throttle stop screw and it had burrs on the threads and was shiny from someone effin with it.. i was able to just turn it out just a little bit and got the idle pretty much where i want it and it is running fantastic without the IAC plugged in no throttle hanging. Ill get one of those restrictor plates so that way i can hopefully plug it back in. As mentioned the iac isnt stuck, its new.. and no holes are present in that boot i checked. Sometimes you just have to throw out the rule book of what you “should and shouldn't do” or else you will never get your problem fixed
 
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Smurfstang88

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So you turned the idle screw to lower the idle rpms and it runs ok with the iac unplugged and it's fixed now?
Yes that is correct! I turned the throttle stop screw which is apparently not supposed to be messed with because the tps voltage but i claim bs on that because mine is just fine..But i will be trying the iac restrictor plate (I’ll include a pic of it for anyone wondering) i need it to be plugged in because without the iac plugged in, trying to have A/c while idling doesnt go so well.. but anyways from what i read many of these sn95s need that plate to stop the hanging throttle while driving, and the rpms shooting up 200 rpm between shifts.. I’ll update when i receive the plate and let you all know how it works in case other people have this issue in the future..
 

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dcm0123

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Responding to follow this. Have a similar problem.
Also had same problemw ith high idle when you let off accelerator and turnined the screw so it would idle lower.
You should be OK as long as you do not have cold start problems.

Where did you buy the IAC restrictor plate?
 
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Smurfstang88

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Responding to follow this. Have a similar problem.
Also had same problemw ith high idle when you let off accelerator and turnined the screw so it would idle lower.
You should be OK as long as you do not have cold start problems.

Where did you buy the IAC restrictor plate?
The delayed idle down after you let off the throttle will not be solved be adjust either screw. You will notice as soon as you disconnect the iac plug, that hanging throttle issue completely disappears (if nothing else is wrong with it). Not sure if you are having a high idle problem like me where it only ever idles down to like 1200rpm, but if that screw on the iac motor doesnt lower it enough after you turn it counter clockwise 2 turns then either you have a vac leak or the throttle stop screw had been messed with.

I got the iac plate off ebay, just search your year car iac restrictor plate and it should come up, make sure the seller isnt in china, i made that mistake and i probably wont see it until next year lol.
 

Smurfstang88

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Also with the iac unplugged, one thing that is an issue is if you have A/c, forget about running the A/c while sitting there at idle, the IAC is needed for that to happen successfully. Hopefully with the plate its a good balance between allowing the iac to do its job while also not keeping the rpms hanging between shifts..