Idle problem

[dojodragon]

Well I finished the P.I. swap and the dyno numbers were good I guess, 252 rwhp. Now I have comp cams 262, headers, cold air, sct tune and the rest is stock. The car idles around 800-850, and for the most part idles perfect. But sometimes it just drops and stalls. I checked it for vacuum leaks and have none. Besides 9 out of 10 times it idles perfect. I cleaned the iac and still no change. Just wondering if anyone has had this problem? Also one more question while I have your attention, after I drive it for 15 mins and shut it off it has a hard time starting. It has plenty of power but cranks over and over with what seems like no spark. After I try for a min or two it starts just fine, I think it might be a crank sensor. I think there are two and I don't know how to test them. Any help will be appreciated.

 

[MustangMatt96GT]

TPS Sensor

 

[freefallin98]

Ive got the same problem with mine. But I havent checked the IAC yet..wtf is a TPS sensor?

 

[vermilion]

on the throttle body theyres a electrical connector that has 2 torx tip fastners or philips tip screws. that swivel sensor can sometimes gunk up from carbon. clean it with throttle body cleaner along the corners of the throttle body plate. or just remove & reinstall/replace it. try it out. disconnect neg terminal first.

 

[dojodragon]

I think it might be the tps because it starts easier if I just touch the gas a little, by opening up the throttle body a little. I think that tps is telling something that the flap is closed and not to give any gas. Does that make sense? Also where can i get a tps cheap?

 

[AaRoN]

Ive got the same problem with mine. But I havent checked the IAC yet..wtf is a TPS sensor?

Throttle position sensor O0

 

[vermilion]

any parts store has them.. up to 30$

 

[myk]

...for the most part idles perfect. But sometimes it just drops and stalls. I checked it for vacuum leaks and have none. I cleaned the iac and still no change. Also, after I drive it for 15 mins and shut it off it has a hard time starting. It has plenty of power but cranks over and over with what seems like no spark. After I try for a min or two it starts just fine...

This is the closest thread I could find to the problem I'm currently having in my '98 GT. I don't mean to be negative, but what's to rule out a bad fuel pump? The shop manual and chilton book seems to point to a failing pump. The TPS or IAC would be the easy fix and that's what I'm hoping for, I just want some ideas to help figure this out. Thanks in advance...

 

[SonicStang]

I don't mean to be negative, but what's to rule out a bad fuel pump? The shop manual and chilton book seems to point to a failing pump.

Can you hear your FP when turning the key?

 

[vermilion]

fuel pump should prime with keys turned onto accessory. although, you could ride down the street and car cuts off mysteriously. usuaully thats the sign of poopie fuel pump.

 

[myk]

Can you hear your FP when turning the key?
[/quote]

Yes I can. Although I've been at a couple of lights where the car just stalled. Just like the original poster, I'd try to start the car but it would only do it after a few minutes of trying. Yesterday, I tried to start the car cold and it had a really hard time starting. Any chance it could be the inertia/fuel cut off switch?

Thanks again, guys...

 

[myk]

Well, replaced the fuel pump cut-off/inertia switch. I really didn't think it was the problem, but it was $20 so I figured why not. I'm still leaning towards the fuel pump, especially when I can't hear the pump turn on/prime consistently when I turn the key "on." Any other ideas? I'm gonna' feel really dumb if I buy a new pump, put it on and still have the hard start/stalling problems...