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Discussion Starter · #1 ·
I bought this 93 LX with the idle surging a few weeks ago. Previous owner says he remembered it surging sometime after he put this professional products throttle body on it, and looking at it, I see it doesnt have a hole like the stock one.

Car ONLY surges when basically at a dead stop, at a very low speed cruise in neutral while slowing down, it doesnt surge. It ONLY does it once it warms up, it never surges when cold. Sometimes it's a couple hundred rpm surge, sometimes it's 500-1500.

Car has a C&L 73mm MAF, Professional Products 73mm TB & 24LB Injectors, Dyna-Mod & Screamin Demon Coil from Performance Distributors, shorty headers, stock air box with K&N, and thats about it really. It's a stock car that has never been apart, never had the lower intake or anything like that off.

Things I have checked/tried:

Cleaned maf wires

Adjusted TPS down (was at over 1 volt before)

Swapped to a different TPS

Pulled IAC, it IS pretty carboned up inside, but everything I keep reading says it's likely not the IAC?

Pulled upper intake and looked for vacuum leaks (although if it were avac leak I suppose it would idle bad at all times, or have a hanging idle) & swapped upper to lower gasket while it was off to be sure

Sprayed carb cleaner EVERYWHERE and never saw a difference.

Checked to make sure it had the ground on the back of the head to body.

Tried base idle reset going off of this, tried to move it several different times Summarized/Corrected Base Idle Reset Procedure

Today I swapped the C&L Maf to a known working PMASS 24LB 75mm MAF, didnt help.



I have NOT ran codes yet, check engine bulb doesnt work anymore, so I cant do it with the jumper wire. Car runs perfect at wot and part throttle, it's just a stopped idle it cant handle. I have searched this site, and plenty of others, Im at a loss here.

Would an engine coolant temp sensor cause this? I figured that would also affect WOT as well if it were?
 

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My professional products TB does the same thing. Did everything the same as your list and it never went away. About to put my old TB back on this weekend to see if it goes away.
 

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I know you checked for vac. leaks but did you also check the t-body shaft for leaks as well. I has a proproducts t-body that I had to replace for this reason. I also had a bad idle with it as well.
 

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Discussion Starter · #5 ·
Cleaned iac, it did idle better, but still had a slight surge. So I swapped Throttle Body's but left the 65mm EGR spacer on because I didnt have a stock EGR spacer, then swapped iac's with a straight plug one I had, which I ran upside down, car idled HIGH, took it off, put the original one back on, car acted like it had a vac leak, took it off, messed with the valve inside, put it back on, car idled better.

Swapped to a stock EGR spacer, deleted the EGR valve, but didnt have a voltmeter to set tps again, car wanted to idle at 1000, then driving around the following day it idled at 1200, also there is a whistling/fire alarm sound sometimes when I turn the car off. I think there might be a slight vac leak at the brake booster. I messed with the check valve, ran the car with booster unplugged, then plugged it back in and it was idling at 800.

Checked tps tonight, it was at .54, moved it to .77, but havent started the car again, since Im in the middle of swapping the exhaust, and deleting the smog.

Also, rpms go up about 200 when I press the brake pedal hard at a stop, not sure if this is normal or not, last cars I have had in recent times were modular with hydroboost, it's been years since I have had to pay this much attention to a fox.
 
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