94 GT Idle Problems

nwagner811 · Jan 3, 2012

Okay guys I will try to give as much detail as I can on this.
The Problem I’m having is with the idle jumping 300 to 800 RPM, and hanging for 2-5 seconds when shifting under 3K. “When shifting over 3k theirs no jump in RPM, It will hang a bit when it comes down under 3K.”

It starts up with no problem “warm or cold” and idles at 700-800 RPM It never dies/stalls…..It’s a bit of a dog on fist the first start up “performance wise” but once it warms up 5-10 mines and she’s good to go. (I wouldn’t immediately start, and get on it anyway)…..Its drivable, drove it all summer like this.

The car has not yet been tuned nor is it chipped, so my question is it now just in need of a tune? Or is there a different problem here.

I’m aware of the Idle Problems Forum and I read over it long before I became a SN95 Member, but I want to know what you guys think.

~Modifications~
-347 Kit
-GT40 Heads
-E303 Cam
-Cobra Intake
-Aftermarket throttle body with adjustable tips mount (The throttle plate solid, and does not have a hole in it)
-Spec Stage2 Clutch
-BBK Headers Flow Master Mufflers
-Smog Pump Delete Kit
-No Cats “No sniff test in MN”
-MSD Ignition
-Bigger injectors “I’m not sure 24 or 27 or something I can’t remember”
-Bigger Fuel Pump
-Cold Air
-Short Throw Shifter
-Some other little stuff I’m forgetting

So let go over what I’ve done.
Before I did all of this the car idled at 1000RPM “wouldn’t go any lower” and jumped about 1k RPM when shifting under 3500-4K RMP, and would hang forever at 1500 RPM.
..
-Reset the computer on a few different occasions.
-Cleaned the Throttle body
-Cleaned the IAC/ then replaced it after the problem didn’t go away.
-Adjusted the TPS to .98 then turned the Idle screw “from all the way out till it just touched enough to change the voltage to .99.
- Adjusted the Idle air bypass screw to set the idle to 800RM

I have an adjustable fuel pressure regulator, but I never messed with it nor have I attempted to adjust the distributor. I felt I didn’t know enough about fuel injection to mess with them without a little direction first.
So let me know what you guys think……

So let me know what you guys think……Also all the mods with the exception of the clutch, was done by the previous owner. He made aware me of this problem before I bought the car. He thought all it needed was a tune, but I want to make sure before

Thanks in Advance
nwagner811

forcefedhatch · Jan 3, 2012

Odds are if you feel you don't know enough about the Timing on distributor, etc. odds are #1 your car needs a tune for sure! And before you attempt anything more have someone with you or go to a reputable shop to do this! When changing engine combos oem ecu tunes are null and void, your engine is basing itself off of 302 cubes when in reality it needs to feed 347 cubes. Even with a maf set up for your 24(or so) lb/hr injectors it still needs tuned for the additional needed air flow and the cam tuning is extremely important especially In the 94-95 computers! They are very touchy and one small change can make the whole system go crazy. To be honest I'm surprised it's drivable on a stock ECM and no tune.. Congrats on that one! But long story short get it tuned and base timing set by a pro. If not it could cost you your engine..

Sent from my iPhone

forcefedhatch · Jan 3, 2012

Btw that sucked writing that big of a run on sentence over a phone!

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rz5.0 · Jan 3, 2012

Get it tune. You should really think about getting bigger heads!!!

nwagner811 · Jan 3, 2012

Thanks..... It’s a strong motor “I don’t think it's even close to the performance level it could be though.”

It seems to me to be a delay. The Computer needs that extra second to go, “Oh its go time/Oh you let off the gas.”…..I just wanted to know if there’s a bigger problem here before taking it to the dyno…..

On that note anyone on here from Minnesota get there Stangs tuned?
Where? What did you think? I see a lot of mixed opinions on the shops around here.

nwagner811 · Jan 3, 2012

Yes I have thought about binger heads I’m open to suggestions.

rz5.0 · Jan 3, 2012

AFR185.. QH tune it your self.

Addermk2 · Jan 3, 2012

I would hardly suggest this guy tunes this car on his own. especially if he cant even check his own timing.

Get some larger heads, cam and a new intake... slap it all together and bring it to a tuner.

ttocs · Jan 3, 2012

I was having similar problems from time to time until I replaced the TPS and the IAC and it went away.

rz5.0 · Jan 3, 2012

Addermk2 said:
I would hardly suggest this guy tunes this car on his own. especially if he cant even check his own timing.

Get some larger heads, cam and a new intake... slap it all together and bring it to a tuner.

well its an option. Also check you fuelpressure. Its ez get a gauge hook it up disconect vac line and set. Im really suprice it runs that way.

nwagner811 · Jan 3, 2012

I’m not an expert your right Addermk2 I’m19 and still learning, but I’m more then capable to work on my own car. However I’m not arrogant enough to just do something, if I don’t know the effect it will have on it. “That’s why I joined this forum.” To ask people who have more experience than me questions.

If I didn’t work on my own stuff why would I even be on here,I would have just taken it into someone wouldn’t you think.

So you’re informing me I can adjust the timing on an EFI and it won’t cause problems. I didn’t know that…..All my other cars I’ve owned have been carburated. EFI again is something I’m in the process of learning.

This car is my daily driver “in the summer anyway” I don’t need nor have that kind of cash to replace everything you just mentioned……Plus again I’m 19, I might wrap it around a pole

rz5.0 · Jan 3, 2012

Timing is ez to set. Find your balancer find the 10* mark the one on the left of the 0 if you looking at it from the top. White out works good to mark. Hook up your timing light hook up on the # 1 wire comming of the distributor. Pull the spuot looks like a grey fuse on the passanger side by the tfi module. Turn your distibutor till you get the mark to line up on the pointer.

nwagner811 · Jan 3, 2012

Thanks RZ I’m familiar with how to adjust timing, I really just wasn’t sure about doing it on an EFI motor. “Never done it on one before” I wasn’t sure if the computer would adjust itself, or if it would cause a problem. Or if it even affects it.