Stalls on cold start

Tiny
92LX
  • MEMBER
  • FORD MUSTANG
I have a 92 LX with the 5.0L and a vortech blower. It has 48,000 miles. The problem is on cold start, it starts up but then the rpm drops right off and stalls. The only way to keep running is to give it some gas and even then the rpms bounce from about 1200 - 500 if I can keep it at a constant above 1500 for a few minutes then it smooths out. Engine is not throwing any codes. I have put in a new EGR valve, checked for vaccuum leaks and did a good cleaning on the IAC. I have also ruled out o2 sensors. Does anyone have any other suggestions.
Wednesday, November 28th, 2007 AT 11:44 AM

12 Replies

Tiny
BLACKOP555
  • MECHANIC
  • 10,386 POSTS
Try a new coolant temp sensor. Also clean teh MAF if you have one on your vehicle, is located on the air intake hoses coming from the air filter
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Wednesday, November 28th, 2007 AT 12:25 PM
Tiny
92LX
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Thanks very much, I will try the new coolant temp sensor. The MAF is brand new.
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Wednesday, November 28th, 2007 AT 10:28 PM
Tiny
BLACKOP555
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Hope it helps, post back your results!
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Thursday, November 29th, 2007 AT 7:00 AM
Tiny
92LX
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Put in the new coolant temp sensor and no change. Now I am wondering if a vacuum leak could cause this issue. Any other ideas out there?
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Friday, November 30th, 2007 AT 7:58 PM
Tiny
BLACKOP555
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Clean up the throttle body, also check all hoses for cracks. I would not say that its vaccum related as it stops after a while, but it could be. Try some fuel additives.
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Friday, November 30th, 2007 AT 9:46 PM
Tiny
92LX
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I cleaned out the IAC and there was no change is there a chance the IAC itself is shot and is there a way to test?

Thanks for all your help.
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Friday, November 30th, 2007 AT 9:53 PM
Tiny
BLACKOP555
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Yes there is, and here is how you can check it! Take off the IAC and examine it for wear, also check for where it goes into the throttle body, it should be smooth and have no marks whatsoever, if there is some scratches on the IAC replace it, if all looks good reinstall and be sure to put NEW GASKETS on or it probably will suck air.

Now take out a volt meter and measure the counts with the engine off at the IAC and record and then start the engine and check the counts. Post back the results.
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Saturday, December 1st, 2007 AT 7:56 AM
Tiny
92LX
  • MEMBER
  • 6 POSTS
Well I decided to just go with a brand new IAC and gasket and there was no change at all. Still revs to around 1500 for 5 secs then drops below 500 and stalls?
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Saturday, December 1st, 2007 AT 10:13 PM
Tiny
BLACKOP555
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I would like you to manually adjust the idle with the screw on top of the throttle body so the engine idles a little higher. Sounds like the IAC is functioning by having the initial rev but its just dropping down too low clean out the throttle body where butterfly valve is, and then adjust the idle a bit higher.
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Sunday, December 2nd, 2007 AT 8:53 AM
Tiny
BLACKOP555
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Also im kind of curious about what sensor you replaced, did you replace the coolant temp sensor that should be located somewhere near the thermostat under the air intake hoses? Or did you replace the one located further back and to the side of the engien?
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Sunday, December 2nd, 2007 AT 8:56 AM
Tiny
92LX
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  • 6 POSTS
I replaced the coolant temp sensor located in the solid coolant line that comes from the lower intake manifold just by the thermoostat housing.
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Sunday, December 2nd, 2007 AT 11:54 AM
Tiny
BLACKOP555
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I cant think of anything else that can cause those symptoms just on cold starts, you may have a bad pcv valve, take it out and shake it if it rattles it is good, if not replace it, you could also have a cracked or rotted rubber elbo that goes from the valve to the air intake.
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Sunday, December 2nd, 2007 AT 1:35 PM

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