Idling issues and in need of some help!

Ben Jones

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Okay, so I just bought this 94 gt about a month ago, only has 30k miles on it and you can eat off it its so clean, all wiring included. Has the 302, stock bottom end, but has gt40 heads ported and polished, trick flow street heat intakes ported and polished, b303 cam, 1.7 roller rockers, fenderwell cold air intake with 76 maf to a 70mm throttle body, 24# injectors, smog pump delete and thermactor holes plugged, and has moates chip in it. SO! Here's my problem.. the damn thing runs AWESOME and strong going down the road, no surges, nothing, but every time you go to shift, every time you depress the clutch, instead of the rpms falling between gears, they raise about 300rpm and stay there, any time you press the clutch in it does that and the rpms just hang for a few seconds. If you're in neutral and rev it up to any rpm it'll stay at whatever rpm you rev up to and hang there for a few seconds before falling back to an idle, sometimes it'll fall to an idle, other times it'll just cut off. Damn near EVERY time I get to a stop sign/light, or go to pull in a driveway or parking lot it'll just die, ESPECIALLY if I have the ac on. Sometimes, like if you're pumping gas, it'll be sitting there idling at 850, 900rpm, and surge and the rpms will fall to around 600 and then catch and rev to about 1200 on its own, sometimes it'll idle back down, others it'll just cut off.. I've replaced the tps (and checked voltage, its at .98) and replaced the iac on it, it has new plugs, wires, cap, and button, I've cleaned the MAF, cleaned the throttle body, played with the str8 slot screw behind the iac to adjust air, the more I unscrew it, the faster idle will get, the more you screw it in the slower it gets, I've tried both ways from bottomed out and backing off in 1.5 turn out incrimates and road testing until I got to the end of limit and its still the damn same. All vacuum lines are new, no vacuum leaks at all. I contacted the kat I bought the car from and he said it has always done the hanging rpm thing since he bought it new and he just dealt with it because he couldn't figure it out, he claims this cutting off thing has never happened, who knows if thats true or not, I don't really care, I just want to fix the damn thing! I love the car and want to keep but I can't stand something like this its driving me crazy. The cars a real head turner and its embarrassing to go anywhere on it cos the mfr will cut off at any time. I've learned to brake with the right side of my foot hanging off the side of the pedal so I can use that side of my foot to hit the gas to catch it from cutting off when I come to stop, and even when doing that, if I catch it in time b4 cutting off and tap the gas, then it revs to about 1200 and holds it for a few seconds b4 falling back to an idle, and ill have to catch it another 2 or 3x before it'll finally idle and thats embarrassing as hell sitting at a stop light with ppl looking at the car giving a thumbs up and the mfrs surging about to cut off and holding rpms. Please somebody point me in a direction. I'm at my wits end with this bitch and have no clue what else to do with it. I've ran the timing light on it also and its 10 btdc so that should be good as well. Also, if I try to do a base idle relearn, I can't run it with the iac unplugged, any time u unplug it it cuts off immediately, if u unplug it first then go to crank it it won't run at all. You boys are my last resort.. if I don't get this thing figured out soon I'm going to sell the mfr. I can't stand something that won't act right..
 

95opal

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ford IAC only no vatozone crap.
May try restrictor plate.
Tune may be off. ISC tables may need to be adjusted
 

badass98svt

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What brand TB is on there? The aftermarket Throttle Bodies will stick sometimes (pretty common). This causes the car to having a hanging idle.
Not sure if that's your problem, but it definitely could be. Your issue sounds exactly like a sticking TB.
 
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Ben Jones

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ford IAC only no vatozone crap.
May try restrictor plate.
Tune may be off. ISC tables may need to be adjusted
I've been thinking its the tune too since no codes or anything is in it, however the IAC i got came from the regular parts store.. so it's definitely what you call an el-cheapo lol I've heard of people running a restrictor plate also and also so on one thread that a guy said he had his iac completely deleted, if you were to delete it would you have to tune it to erase that table??
 
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Ben Jones

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What brand TB is on there? The aftermarket Throttle Bodies will stick sometimes (pretty common). This causes the car to having a hanging idle.
Not sure if that's your problem, but it definitely could be. Your issue sounds exactly like a sticking TB.
Its a 70mm bbk throttle body on it, what do you mean by sticking, like the butterfly sticking?? Because I've checked that as well I took the spring and cables off and moved it from closed position to WOT a few times by hand and didn't feel any tight spots in it whatsoever, also took each cable and made sure it wasn't hanging up in the cable tuning and all feels fine.
 
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Ben Jones

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By the way, thank you guys for responding so quickly and trying to help I appreciate your time.
 

badass98svt

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Yes, that is what I mean by sticking. One way or another, the aftermarket TBs very often cause a hanging idle. It's not always constant either. It may only happen on hot days etc.
If you have a stock one, I'd try swapping it just to eliminate it.
You can also adjust the idle screw a hair to compensate for the issue. I've seen more than one person claim it is vacuum pulling the blade open a hair, not any actual sticking parts.
BBK is definitely not a throttle body I would recommend.



 
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Ben Jones

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Yeah most threads I see have people saying bbk isn't worth a damn, sucks because that's exactly what everything is on this car, previous owner definitely believed in bbk for some reason.. I don't have a stock TB unfortunately but was thinking about buying a 75mm one any way since the pipe behind the TB on the plenum is 75mm and I have a 76 maf I figured the 75mm TB would work, right?
 
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Ben Jones

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The hanging idle and cutting off is REALLY bad if I have the ac on. Pretty much EVERY time you come to a stop it dies.
 

badass98svt

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Can you prevent it from stalling by not pushing in the clutch and coasting as you come to a stop. Maybe downshift to slow down then stop.

The Speedo/Odometer is working normally?
 
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Ben Jones

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Can you prevent it from stalling by not pushing in the clutch and coasting as you come to a stop. Maybe downshift to slow down then stop.

The Speedo/Odometer is working normally?
Yeah the odometer and speedo both work properly, and yeah I've tried that as well, if I just knock it up into neutral, it'll hold about 1200 rpm, when you finally get to a complete stop it'll hold 1200rpm for a few seconds then fall back down and 90% of the time when it falls it just cuts off.
 
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Ben Jones

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What is yalls opinion on the SR Performance 75mm throttle body, is SR a pretty reputable company?
 

badass98svt

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I would use nothing but OEM or Accufab.
That's just my opinion.
 

Connie

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What is yalls opinion on the SR Performance 75mm throttle body, is SR a pretty reputable company?
Hello there Ben. This is Bob. I've owned my '03 GT since new, so I know ALL that's been done to it. I installed a 'TRICK FLOW' Throttle Body on it 17 years ago, and never had an issue. I have to admit that I have a BBK Cold Air Kit I installed at the same time. So, I can't say how well the SR will do. But, they are a reputable company.
 

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RAU03MACH

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Worked on a lot of bbk throttle bodys
All the same problems
Mostly bent shaftsthrough the blade
 
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Ben Jones

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Okay so driving it today, I remembered when I rode with the dude when I bought it and i remembered him babying it all the way to 3k before he'd shift it and I asked him why he drove it like it was a damn 4 cylinder and he said "oh I just wanted to hear it one last time" but he kept doing it on every shift, gradually taking it to 3k before shifting, so today I did the same thing and now I know why he was doing it, if you take it up to 3k before shifting to 2nd, 3rd and 4th, the rpms won't hang like they do under normal driving, they fall between the gears like they ought to. Which makes absolutely no sense to me... every time you go to shift it at that high rpm it does perfect. Anybody have any ideas on that? Because I sure dont.. and yeah I think ill get the accufab and stick to Motorcraft parts when I can. I might go on and buy the Motorcraft brand IAC as well. Have any of you heard of actually DELETING the IAC altogether???
 

joemomma

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I've got the same issue. If you run a higher idle speed, it won't die when you come to a stop. Not a fix per se, more of a band-aid. I'm all stock engine-wise except shorty headers. Adjust the air screw on the TB, not the threaded throttle stop. FWIW, my idle is right at 1000RPM.
 

tvsn95

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Okay, so I just bought this 94 gt about a month ago, only has 30k miles on it and you can eat off it its so clean, all wiring included. Has the 302, stock bottom end, but has gt40 heads ported and polished, trick flow street heat intakes ported and polished, b303 cam, 1.7 roller rockers, fenderwell cold air intake with 76 maf to a 70mm throttle body, 24# injectors, smog pump delete and thermactor holes plugged, and has moates chip in it. SO! Here's my problem.. the damn thing runs AWESOME and strong going down the road, no surges, nothing, but every time you go to shift, every time you depress the clutch, instead of the rpms falling between gears, they raise about 300rpm and stay there, any time you press the clutch in it does that and the rpms just hang for a few seconds. If you're in neutral and rev it up to any rpm it'll stay at whatever rpm you rev up to and hang there for a few seconds before falling back to an idle, sometimes it'll fall to an idle, other times it'll just cut off. Damn near EVERY time I get to a stop sign/light, or go to pull in a driveway or parking lot it'll just die, ESPECIALLY if I have the ac on. Sometimes, like if you're pumping gas, it'll be sitting there idling at 850, 900rpm, and surge and the rpms will fall to around 600 and then catch and rev to about 1200 on its own, sometimes it'll idle back down, others it'll just cut off.. I've replaced the tps (and checked voltage, its at .98) and replaced the iac on it, it has new plugs, wires, cap, and button, I've cleaned the MAF, cleaned the throttle body, played with the str8 slot screw behind the iac to adjust air, the more I unscrew it, the faster idle will get, the more you screw it in the slower it gets, I've tried both ways from bottomed out and backing off in 1.5 turn out incrimates and road testing until I got to the end of limit and its still the damn same. All vacuum lines are new, no vacuum leaks at all. I contacted the kat I bought the car from and he said it has always done the hanging rpm thing since he bought it new and he just dealt with it because he couldn't figure it out, he claims this cutting off thing has never happened, who knows if thats true or not, I don't really care, I just want to fix the damn thing! I love the car and want to keep but I can't stand something like this its driving me crazy. The cars a real head turner and its embarrassing to go anywhere on it cos the mfr will cut off at any time. I've learned to brake with the right side of my foot hanging off the side of the pedal so I can use that side of my foot to hit the gas to catch it from cutting off when I come to stop, and even when doing that, if I catch it in time b4 cutting off and tap the gas, then it revs to about 1200 and holds it for a few seconds b4 falling back to an idle, and ill have to catch it another 2 or 3x before it'll finally idle and thats embarrassing as hell sitting at a stop light with ppl looking at the car giving a thumbs up and the mfrs surging about to cut off and holding rpms. Please somebody point me in a direction. I'm at my wits end with this bitch and have no clue what else to do with it. I've ran the timing light on it also and its 10 btdc so that should be good as well. Also, if I try to do a base idle relearn, I can't run it with the iac unplugged, any time u unplug it it cuts off immediately, if u unplug it first then go to crank it it won't run at all. You boys are my last resort.. if I don't get this thing figured out soon I'm going to sell the mfr. I can't stand something that won't act right..
Soo what does your Wide Band read at idle ??
 
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Ben Jones

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I've got the same issue. If you run a higher idle speed, it won't die when you come to a stop. Not a fix per se, more of a band-aid. I'm all stock engine-wise except shorty headers. Adjust the air screw on the TB, not the threaded throttle stop. FWIW, my idle is right at 1000RPM.
That's exactly what I've done to mine for the time being until I can figure this shit out
 

cobrajeff96

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FWIW I had zero problems with both OEM and later with Accufab. Shot in the dark, but TPS might have a part to play in this.
 

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