94 gt idle issues..

[Smurfstang88]

Hey guys, so as some of you know i picked up this 94 gt a little while ago and unfortunately since ive started driving it more ive noticed one kind of real issue that i have been holding off posting about since i wanted to fix it myself but here we are.. so i noticed the day after i got it of course, after it gets up to temp and i sit there at idle sometimes it would want to die or would die when i turn the wheel.. so immediately i did a base idle reset and since then i have yet to actually have it die when turning the wheel.. but then as i drove it more i noticed it would still do it every once in a while if i sat in a parking lot with the ac on and if i blipped the gas all of the sudden the idle would jump all around and try to die but this doesnt happen every time.. so i cleaned the iac it got pretty clean looking and the problem persisted. Then i cleaned the maf and sprayed the little filament thing lightly and it all looked much cleaner. And cleaned the throttle body.. now since then it has idled around 1100-1200 rpms and will not come down below that, and before cleaning all that it sat at a happy 800ish rpms. Also i notice the throttle as driving hangs up around 1500 rpms when i push the clutch in and wont come back down until i come from a stop which is strange to me.. anyways im wondering why its now idling so high after all that and i also tried to adjust the idle screw on the iac and it does nothing.. i also unplugged it of course and it had no effect aside from the car not hanging at 1500 rpms while unplugged.. anyways this is why my foxbody was carbed i kind of miss that motor.. also yes i have considered air leaks and dont see anything too obvious but i dont feel thats the issue since obviously the more i mess with this stuff it has an effect, just not a good one… thanks For any input you might have guys

 

[General karthief]

You've been around here long enough to know the 'surging idle checklist'.
Vacuum leaks can be sneaky, smoke test it. You'd be surprised.

 

[manicmechanic007]

The checklict is worth a shot because it gets people thinking
You realize however, there is no idle reset procedure in the Ford manuals
You will not see me, ever never ever, play with the screw on the throttle plate
It is simply not acceptable and will get you fired? at the dealer
If you think your plate is maladjusted, you need a new one
Back in 1985 and 1986 there was a procedure
Long since gone with the coated plates
If yours hunts for idle or runs crappy it is something else

 

[Smurfstang88]

You've been around here long enough to know the 'surging idle checklist'.
Vacuum leaks can be sneaky, smoke test it. You'd be surprised.

This is true, but id love to smoke test it but i never acquired one of those and dont think i know anyone that has one unfortunately.. however i do not feel it is a vacuum leak especially since all i did was clean the maf and other components and yet the problem actually got worse, much worse. I just got done driving it and can practically drive without my foot on the gas .. in fact now when i go to change gears it goes up in rpm before i shift which is odd. Also would really like to know how it is possible for the car to refuse to idle down until the car is at almost a complete stop, how can that be? Also im not writing off vacuum leaks being a possibility its just that me cleaning these components clearly made the issue actually a whole lot worse which tells me im in the right direction id think but im going to have to try to also test the vacuum the old fashion spray soapy water way i guess..

 

[Smurfstang88]

Also i tried unplugging the maf sensor while running and it brought down the rpm to around 800.. also not really surging just wrong idle rpm and it wont adjust.. i have a new motorcrap iac coming so i will see if it does anything and maybe i will swap the maf sensor too and I’ll just bring it back if it doesnt fix it haha..

 

[WhiteCobra95]

Based on the sequence of events, it sounds like cleaning the MAF might be the source of your grief. Please let us know how it goes if you make the swap.

The SN95 5.0s seem to have a lot of idle issues in general. My Cobra hunts at idle with the A/C on, but it's fine with the A/C off. It did that before I started modifying things and it's still mostly stock. I'm not exactly sure what it's related to, but our cars are missing the baro sensor that the earlier cars have. That makes me wonder if it does some estimation for ambient pressure based on MAF vs. throttle position and then uses that to correct the IAC positions. If this relationship is off, which would shift the modeled air density, then the IAC gains could be off and over/under compensate.

 

[Smurfstang88]

Based on the sequence of events, it sounds like cleaning the MAF might be the source of your grief. Please let us know how it goes if you make the swap.

The SN95 5.0s seem to have a lot of idle issues in general. My Cobra hunts at idle with the A/C on, but it's fine with the A/C off. It did that before I started modifying things and it's still mostly stock. I'm not exactly sure what it's related to, but our cars are missing the baro sensor that the earlier cars have. That makes me wonder if it does some estimation for ambient pressure based on MAF vs. throttle position and then uses that to correct the IAC positions. If this relationship is off, which would shift the modeled air density, then the IAC gains could be off and over/under compensate.

Well mine must be having some sort of crazy coincidence or something, since i just replaced the maf sensor, and still acting exactly the same..
im still waiting for my iac valve to come in the mail. Its very odd since as said i cleaned the iac and put it back and acted the same so then i cleaned the throttle body and maf, and then this high idle problem arose.
Also want to add i wouldnt consider mine to be surging, just high idle. Even before when it idled correctly it wouldnt constantly surge, just sometimes, it would bounce around at idle and die..
I recently read something about an ac pressure relief valve i think its called? But anyways i heard that could cause problems like you mentioned with the ac running only.. i dont think thats the root of my problem though.. anyways thanks for your reply

 

[Smurfstang88]

So i just got my new motorcraft iac in and installed.. still no change. Im beyond baffled… i don’t believe in mechanical coincidences, so how in the hell can cleaning these parts wind up making the car idle up +400rpms? I cant get it to come back down no matter what.. the throttle is still hanging up.. the only think im wondering is what is the sensor thats on the rubber boot that connects the tb to the maf? I also cleaned that with electronic cleaner, and thats the only one that I haven’t messed with.. i don’t understand how unplugging the iac makes the throttle down lag disappear yet its not needing to be replaced? Also to even adjust the idle on the iac is basically impossible since they engineered it terribly you cant fit a Allen key barely between that and the oil fill, so its nearly impossible to even adjust. I have yet to try to even adjust the idle since the old one made no change and assuming this one wont either since it still has all the same problems.. i guess all i can even do now is try to find vacuum leaks but i dont have a smoke machine and have been looking and yet to see a leak. All the vacuum hoses on this car are actually still looking in good shape (at least the ones i see are) so i have my doubts unless something magically came unplugged and i dont see it.. someone please give me some advice, im becoming frustrated.. i hate throwing parts at stuff since this always happens, but i really felt like i was on the right track since all i did were those things mentioned and the problem got worse. Also its not even really drivable the way it is, idles too high and even in gear i can basically go down the road in any gear without giving it gas and that is no bueno. Again thanks for any help you have to offer

 

[manicmechanic007]

At this point your oil could be contaminated with HC's
From all the cleaning?

 

[General karthief]

Do you have a vacuum gauge?

 

[Smurfstang88]

At this point your oil could be contaminated with HC's
From all the cleaning?

HC’s? What do u mean oil contamination?

 

[Smurfstang88]

Do you have a vacuum gauge?

Cant find it, i guess I’ll go get one tomorrow since i need it for another vehicle anyways, so how should i go about using it to test it when i get it? Ive heard its pretty impossible to tell on these with one but im all ears.

 

[General karthief]

Vacuum should be about 15 hg +- depending on idle rpm and steady.
Check the vacuum line under the intake in the front, it goes to the charcoal canister, it may have broke or came off. Hard to see.

 

[Smurfstang88]

Vacuum should be about 15 hg +- depending on idle rpm and steady.
Check the vacuum line under the intake in the front, it goes to the charcoal canister, it may have broke or came off. Hard to see.

Ok thanks, also ive been looking for the line u mentioned and i do not see one, so you must be right about it being hard to see
Edit: are you talking about the 3 that connect underneath the intake boot? Just looked at them and they LOOK ok..

 

[General karthief]

It come out from under the front of the upper intake going to the passenger side by the fuel lines down to the canister. You just about have to raise the upper intake to see the nipple.

 

[Smurfstang88]

It come out from under the front of the upper intake going to the passenger side by the fuel lines down to the canister. You just about have to raise the upper intake to see the nipple.

I assume by front you mean the front of the car? I swear ive been searching nonstop and see none. I do however see the one go to the back(firewall side) of the upper intake and can feel that it is connected.. also the 3 or 4 that come through under the rubber intake boot look fine..

 

[Smurfstang88]

The second pic is of the vac line that goes to the back of the intake

 

[General karthief]

The front behind the distributor

 

[Smurfstang88]

Tested the vac and get 14-16 hg.. so im assuming no vac leaks? Replaced air temp sensor on the boot and still no change. Nothing does anything and am out of ideas of what it could be..

 

[Smurfstang88]

Finally did the eec test. Did the jumper wire method first, and for some reason could not figure out how to do the test with the car not running, anyways did the running test and for some reason i never got the code 11 but it did do the idle up egr test after the engine light blinked 4 times.. then the light never came back on. Then i got my code reader and tested it not running and came back with code “electronic drive fan circuit fault” then it said code 111 all good. Then for the running test it first said unable to obtain cylinder codes and dtc’s. Unsure what that means or why. Then tried again and it got to a point saying “throttle up to half throttle lighty then release” and so i tried that multiple times and it just was stuck on that screen saying that. Never got any codes from that.. not sure if this all is a good thing or bad thing i cant tell.