94 GT With A Fox Body Throttle Body Will It Work?

sidewayzgt23 · Jan 14, 2009

I just purchased a 94 5.0 with (I will not list everything)AFR heads, TFS Stage 3 Cam, and Edelbrock Performer RPM Intake. My question is that the car has been stalling out on me lately after driving for a while, turning the car off and then starting it when it is warm? My Mustang mechanic specified that the throttle body that I have (Mac 70MM) is off of a fox body motor and I should switch to the correct one to correct the problem. He said that the computer is getting confused? Everything on the car is updated and looks perfect, the car also recently passed smog. Does it just need a new TPS or IAC? I have been doing some research and it seems that other people have done this before (especially for cylinder head clearance). Why would mine be any different? Any feedback would be appreciated. Thanks :SNSign:

ronstang94 · Jan 14, 2009

lots of people use fox throttle bodies, so the fact that the throttle body is for a fox is definately not the problem. Does the car have a tune, chip, computer mod or anything? An engine with those kinds of performance parts and no tune, will run, but not very well.

KamiKaziDK · Jan 14, 2009

What brand Mass air meter is on the car? My car sat for over a year because it was misdiognosed multiple times....ended up being a bad mass air

ProKiller · Jan 14, 2009

i highly doubt its the throttle body thats causing the problem. i'd look at into the tune before looking for hardware problems.

sidewayzgt23 · Jan 14, 2009

I just purchased the car so I do not know a whole lot about it yet? The problem just started happening. I do know that it runs very nice and the car has the timing bumped 10 degrees for better performance. The problem is only when the car is re started after being driven for a while and warm. The car dyno'd at about 300HP to the wheels with the stock headers and the stock cats according to the last owner. I have no idea if the car has a performance tune yet? Is there a way to know if the car has a chip? How do I know if my MAF meter is bad? Any info is appreciated. Thanks

ronstang94 · Jan 14, 2009

try cleaning the MAF sensor. Get some electronic parts cleaner from the local auto parts store, take the MAF off of the car, spray a lot of it on the sensor on the inside, gently wipe with a q-tip, and reinstall. If the MAF is bad or just dirty there should ba a check engine light, keep in mind that if there is no check engine light someone could have removed the bulb. when you put the key in the ignition, turn the key just a little but dont start the car, the check engine light should be on. If its not, the bulb is burned out or someone removed it.

I have never had a chip or computer programmer, not enough mods to need one. I could try to tell you ways to check to see if you have one, but ill let someone who knows more about that chime in.

KamiKaziDK · Jan 14, 2009

When my MAF went out I didn't get a check engine light and I know it works just fine. But yeah, try cleaning it like he said, that never hurts, and if you happen to know someone else with a sn95, see if you can swap it out if cleaning doesn't help

MysteryMachine · Jan 14, 2009

They make actual MAF cleaning stuff you can use too

ProKiller · Jan 15, 2009

so its a hot start problem. My guess is then the car is dumping too much fuel when its warmed. I couldn't tell you a fix other than a tune. to see if it has a chip, look behind the kick panel on the passenger side. the computer is behind it, on the back of it, there should be a little cover or a chip thingy.

bumped timing to 10* or added an additional 10*? is that base timing?

sidewayzgt23 · Jan 15, 2009

I will look today to see if it has a chip. Also, I spoke with the original owner and he specified that the car was professionally tuned by his Mustang mechanic. The timing was bumped 10 degrees from base timing. The car idles at about 1000 RPM. (Is this to compensate for the stage 3 cam)? Another characteristic of the problem is that it idle is erratic. The idle will fluctuate up and down from, again, 1000 to about 1600 RPM. This is not that bad because it eventually evens out but it is annoying .. The last thing that I noticed is that the TPS and the IAC are off of a fox body to. Should I upgrade to a 94-95 or does it matter? Thank you all for your responses so far, they have been really helpful. :SNSign:

sidewayzgt23 · Jan 15, 2009

Ok, according to the last owner the motor never had any idling or stalling problems.. Now the problem is happening whether the car is warm or cold. I went to start the car this morning and it started just to stall out right away (with an erratic idle). It took about 5 starts for it to not stall and get the idle to steady out. I then drove to the store with no problem. When I went to start my car again, it stalled out on me about 3 times before steadying out again. There was a slight idle surge when hitting stop signs but it did not stall (came close a couple of times).. Do we think that this is a IAC problem? Does the TPS need to be adjusted or replaced? Thanks

sidewayzgt23 · Jan 15, 2009

Help!

Anybody?

Cory281 · Jan 16, 2009

Maybe you have a vacuum leak?

MysteryMachine · Jan 16, 2009

I would give the IAC a shot. If that don't do it change the tps as well. They tend to go bad at some point anyway. People may disagree with me. I haven't messed with my gt in a. Few years so I forget how it worked. However my Ram had idle issues and after replacing them 2 things strightened out.

Iirc they both connect to the tb correct? In that case you will need fox ones when you replave them. I don't think the sn95 ones will even bolt onto that tb as they are totally different.

Other then that a tune? I would think with that cam it def would have had to have one to run right before. Unless it never ran right and he sold it to you cause he couldn't figure it out
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sidewayzgt23 · Jan 16, 2009

I just went out and cleaned the IAC and re installed it. I then warmed my engine to operating temp (the idle was surging from 900 - 1100 RPM). I then kept the engine running and unplugged the IAC and there was no change. I am guessing that this means that it is not working. I am going out now to buy a new IAC if that is the problem?

sidewayzgt23 · Jan 16, 2009

Another Update! Well, I bought an OEM IAC and installed it. The car does not have the stalling problem anymore but it is still having difficulties. The car is set to idle at about 900 RPM because of the cam, on deceleration the idle hangs at around 1200 RMP and then slowly drops down to the 900 RPM. Do I still have to clean the IAC? Do I need to adjust the TPS? Any suggestions?

final5-0 · Jan 16, 2009

I quickly skimmed the thread and here are a few random thoughts

I've noticed you've said stuff has been changed like spark and idle speed

You also said the previous owner had it Pro Tuned

Just a guess ... but ... I'd say the spark and idle were done in the pcm

Now about that cam

The #1 cam usually will not play nice with our pcm's

I've seen others say the #2 is more radical
so
I'd kinda think a #3 would be all the more guilty of drivability issues

If the other owner said the tune took care of all drivability issues .........

I'd think you got something simple like a v leak or such goin on

O Yeah ... I'd not hose around with trying to adjust the TPS

That is a fox thing don't ya know

The ISC can really hose up your idle :Word:
Some folk have had success with their attempt to clean them

however

I've seen many say the cleaning thing did not work and after replacement,
the idle was greatly improved

Last thing

You gotta take the meter electronics apart to get these tiny wires clean

Grady

RIO5.0 · Jan 16, 2009

Throw a vacuum gage on it and see what its pulling... the lower the number the harder time its gonna have idling, Hence what Grady mentions about that cam.

Have you tried a full idle reset yet?? I had to do that when I did the Fox swap...
Read thru this and follow it to a tee.

http://www.muscularmustangs.com/maintain.php

revhead347 · Jan 17, 2009

I have that same camshaft in my car. That cam does not play nice with the stock computer. I have a piggy back chip on my car to make it run, but if I unplug it, the car idles at 1700 rpms, and stalls constantly. At idle, my car only pulls 7.5 psi of vacuum. The overlap on that cam causes the engine to not have enough vacuum to trigger the MAP at idle. I would venture to say that you have a tuning issue. I assume those are 185cc or bigger AFRs.

Kurt

MysteryMachine · Jan 17, 2009

I kinda figured it was probably a tuning issue. I found it hard to believe with that cam the previous owner didn't have any problems with it. I was giving him the benefit of the doubt.
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94 GT With A Fox Body Throttle Body Will It Work?

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