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91' Mustang cold start problems


dalecm's Avatar
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12-04-02, 05:55 PM   #1  
dalecm
91' Mustang cold start problems

I have a 91' LX Convertable with the 5.0L engine and manual transmission. It has 115K miles and has seen good care. Recently it won't idle worth a darn on a cold start. I replaced plugs, plug wires, dist. cap and rotor to no avail. Checked the PCV valve and timing. It runs great when warm and starts great when warm also. Any suggestion?

 
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12-04-02, 06:25 PM   #2  
davidf
Does it have a carb?If so ,choke or hot air stove pipe system is not right.

 
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12-04-02, 10:39 PM   #3  
knuckles
All Mustangs have been EFI since 1987.

Check your IAT & ECT sensors as well as your idle air control valve.

 
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12-05-02, 05:40 AM   #4  
Joe_F
I agree with Knuckles

 
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12-05-02, 08:53 AM   #5  
fordman30
MUSTANG

My grandma sable was doing the same thing so I put a idle air control valveand it was fix.But, remember to carry your vin# to the dealer so they give you the right one .It is a easy fix 2 bolts out and 1 plug to unplug.10 min tops....have a merry x-mas

 
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12-05-02, 01:49 PM   #6  
actually, the 86 gt was the first year for multiport injection and computer, the 85's had the 4bbl holley carb and the roller cam.

Anyway, this is a very very very common problem with mustang 5.0's there was a huge discussion on this here:

http://www.corral.net/forums/showthr...threadid=10805

would suggest checking it out, you can run yourself in circles with this one.

 
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12-06-02, 10:05 AM   #7  
Joe_F
Mid 1984 also had fuel injection in the GT350 special edition model that year. Vin M engine as I recall. My former coworker had one.

Also, 1985 manual tranny equipped were Holley 4 barrel, 1985 autos had CFI to my knowledge.

1986 had Bosch MFI as you stated.

The Holley 4 barrels aren't worth 50 cents. Smokers, leakers, fuel wasters. The fuel injection was a vast improvement


Last edited by Joe_F; 12-06-02 at 10:30 AM.
 
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12-06-02, 05:18 PM   #8  
dalecm
Thanks

I appreciate all the suggestions. I'll let you know the results as soon as I have time to dig in to it. Should be able to get to it the week of the 9th .

Thanks again`

 
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12-07-02, 10:00 PM   #9  
dalecm
What is it?

Is the idle air control valve the same thing that the Chiltons manual call the Air Bypass Valve?

 
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12-07-02, 10:16 PM   #10  
Joe_F
Yes. The bypass term is Ford terminology.

 
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12-08-02, 12:26 AM   #11  
If you replace the valve you may need the part number off the old one. Take it with you to the parts store.

 
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12-08-02, 06:00 PM   #12  
Joe_F
Stevo is correct. It will also help the dealer find it quicker too.

 
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CAL

12-08-02, 09:23 PM   #13  
I had the same thing happen to my 1990 Ford with a 5.0L engine. Not knowing much about EFI, I brought it to the local Ford dealer, who replaced the air bypass valve and that solved the problem. However, I was not too happy after I found out what that valve is and where it is located, because the dealer charged me $ 265 for labor to replace it and $94 for the valve!

 
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12-20-02, 08:29 AM   #14  
dalecm
Resolution

Well......I finally got the correct part after three trips to the local auto parts store. It did take about five minutes to replace and I paid about $75 for the part. Cold starts are about 95% better. The idle seems a little low, but it runs when cold without having to work the gas pedal constantly.

Thanks everyone

 
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12-20-02, 08:36 AM   #15  
fordman30
Did the idle air control valve fix the problem ? And you are very welcome...Have a Merry Christmas and New Year

 
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12-20-02, 08:52 AM   #16  
dalecm
Yes it was the idle air control valve. Sorry I didn't include that info.

Thanks again

 
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