Problems with idle after H/C/I, any suggestions.

[astronut1885]

Hey guys. A few days ago I got my car back after doing a major series of upgrades. Since then, I've been having problems with my idle. When I let the car sit and idle, it held at around 900 RPM. After a while, it surges, and would sometimes stall. Also, if I threw a rev of any type, as soon as the car brought the RPMs down it died. To fix this, I adjusted the screw on the TB to make the car idle at 1000 RPM. now it surges a tad at startup, but otherwise functions normally, albeit at 1000 rpm. My theory about this is that my engine isn't getting enough airflow because I still have a stock TB and MAF sensor. as soon as I open the TB a tad and increase the flow, it's fine. If I take it away, it dies. Also, at one point I forgot a small vacuum line off. For the whole time it was off the car idled like a champ. As soon as I reconnected it, it started surging. Is it possible that with all my newfound flow I may be choking my motor with the stock TB and MAF, or is it something else? Suggestions welcome! See sig for mods.

 

[87'GTstang]

Have you tried the infamous 1/8" hole drilled in the TB butterfly plate? I'de hate doing it myself but a lot of people have had erratic idle or idle surge problems cured from doing it.

 

[astronut1885]

There's already a small hole in my butterfly. Also, I cleaned out my idle speed control unit yesterday, and that didn't help like it used to. It really does seem like my car is choking.

 

[5.0 Nostalgia]

If you did heads cam and intake, it could be your stock TB. A 65mm would probably be good. However, before you go spend money, you should look at other sources. TPS, vacuum lines, etc. I know I have a couple lines off my car with the GT40. Also, I have the idle adjustment plate between the TB and IAC.

 

[StreetStang37]

whats your tps voltage at? could be a ton of things. i really REALLY doubt its your throttle body. keep looking for a vaccuum leak.

 

[DropTopR]

My car just simply likes to idle high. I run the TwEECer, and i set the idle to 1000 rpm anyway. Cleaned up my idle surge problem. Also, make sure your fuel pressure is ok. The car sould be idling rich after your swap. But that's just my 2 cents.

 

[astronut1885]

My fuel reg is turned down, and my IAB is freshly cleaned. My TPS os reading 1.00 volts at idle. From what I've been reading, alot of people have problems with keeping their idle so low and have to bump it up a tad. For three hours the other day I was hunting down vac leaks, so I'm pretty sure I don't have any of those.

 

[autoXr1]

See my reply to your duplicate post on this page.

 

[astronut1885]

I saw it. very informative. I just double clicked when I posted. oops and thanks.

 

[leakyfaucet]

This probably won't cure it, but you're supposed to have the TPS set below 1 volt with the throttle closed

 

[astronut1885]

Yeah. Apparently there was no vacuum line on the AFPR either. I didn't know there had to be one and my mechanic didn't put one. My buddy saw it and we put one, and he set the fuel pressure to 41 psi vacuum off. The car got better, considering the pressure was at 30, but it's still having idle issues. Now it just plain won't come down from 1100. I can loosen the screw on the TB and it still recorrects to 1100. That, or if I go too far with the screw, it stalls. Atleast she's running for now, I know it needs another tuning session.

 

[88GTMustang]

Kinda off topic but astronut1885 have any times or HP with your car, reason im asking is when i get done with my stang soon i am going to have almost exactly the same mods you have! :d

 

[astronut1885]

No, I'll be dynoing it soon and I will be running the track this summer. My mechanic, who is a Mustang guru, says I should be around 280RWHP and should run a mid 12 quarter mile. We'll see.

I just ordered an idle adjuster plate that goes on the IAC. I heard that it will help with my crappy idle. I sure hope so...