What the heck ,idle on my Stang going crazy

I'm having what sounds like a very similar issue. It started happening to me after I changed to a FMS 65mm throttle body. The idle would shoot up to 1,500 or so and then slowly drop down to about 900. The problem got worse after the AFR 165's went on this past week...now it shoots up to 2,000 when I first start the car and also any time I push the clutch in (like when downshifting to neutral to roll to a stop at a red light or a drive thru). It also won't always stay at 900; sometimes it revs on its own. View attachment 525168 It's annoying and even embarassing, since other cars probably think I'm revving at them (keep in mind my foot is completely off the gas!).

I don't have any vacuum leaks either. I tried switching IAC sensors and the one I switched to is even worse, so I might go back to the one that came on it. I'd like to get this tamed, though...

HAH! I thought it was only me and it was in my mind.
Would be interesting to know the solution for this one, but then again the blower sounds nice and loud until it settles.

maybe if you get it tuned, they can tune that out.

yeah, i dont think this is going to help you at all but ive been reading nonstop for the past 2-3 days about my twEECer and i read up that all that might need to be changed is the dashpot decay rate and it will bring down the rpms quicker after the tb is closed say at a stop sign/light.

i only say that cause ive been having kinda the same problems for awhile now. i was thinking it had to do with the vac with my e303.

Answers to your questions

Well, the problem is you guys bought 94 95s. I own a 95 as well. That comp is very finnicky with mods. Especially cams. I imagine the problem is extended throughout the valvetrain. The comp hates increases lift. I have learned this myself. I read in the last issue of Muscle Mustangs and Fast Fords that they offer a computer that fixes this problem with the 94-95s by Proflow. I have yet to be able to find it. I think my problem is worse than yours. My engine will stumble and die sometimes so quickly that I will not notice and hit the gas and wonder where all my 'go' went. Let me quote the letter and reply in MM&FFs:

"I own a 95 Mustang GT 5.0 with a 5spd. I recently purchased an engine kit from Trick Flow Speacialties, which included Tisted Wedge heads, Street hear intake and a came. I have not installed any of the compantnents yet, but b/c I was discussingthe system with a well-respected Ford soecialist in south florida and i was advised not to change the cam due to incompatibility problems with teh computer. Specifically I was advised that the computer installed in the 94-95 5.0 mustangs is very sensitive to cam lift and installing anything larger than ta stock will it very difficult to achieve a good idle. The cam I purchased has a lift of .499/.510 inch. Have you had any experience with this cam upgrade and is there an inexpensive solution? I really don't want to install a cam that is gonig to cause idling problems, especially here in South Fla where the a/c is used most of the year and stop and go driving is the norm.

Tim, you are correct in that driveability problems are common when larger cams are installed in 94-95s GTs./ In the past we installed a .499 list cam along with Edlbrock heads, and instake in a 94 and the idle was poor. We solved teh problem by retrofitting the car with a 89-93 EEC computer which is sold by Pro Flow. This solved the problem and restored driveability."


Well, that is the article I found, and I have yet to find this computer they spea of. Hope that was helpful. Anything else you need, just reply.