Rough Idle on my 5.0 - Ford Mustang Forum
 
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post #1 of 11 (permalink) Old 08-17-2011 Thread Starter
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Unhappy Rough Idle on my 5.0

Hey so my automatic 1998 mustang gt hatchback is idling really rough
jumping from 900 rpms down to 400. If anyone one has any ideas it would be great as many view points as possible
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post #2 of 11 (permalink) Old 08-17-2011
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is the car stock, or what mods are on it? sounds like it could be a vacuum leak or an issue with the mass air flow sensor or speed density which ever one it is. more than likely a vac leak with idle jumping around
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post #3 of 11 (permalink) Old 08-17-2011 Thread Starter
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yes it is stock, and that sounds just along the lines with what my buddy said we are going around checking all of the vacuum lines, but we weren't sure thanks for another input
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post #4 of 11 (permalink) Old 08-17-2011
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Have you replaced, changed or added anything on the car?
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post #5 of 11 (permalink) Old 08-17-2011
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post #6 of 11 (permalink) Old 08-18-2011
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ummmmm doesn't the 4.6 have a new kind of computer? so the 5.0 diagnostic trick wont work? he said 1998 mustang

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post #7 of 11 (permalink) Old 08-18-2011
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you need a scanner to read the codes.A big name auto parts store will usually do it for free,but sometimes they are idiots!Could be alot of things,without knowing the codes youll just be guessing.You can get a cheap scanner for @60.00.The dealer tries to charge like @80 to do it!BTW its OBD2.

1993 notch w/306 tuned w/quarterhorse,lots o'go fast parts.18x10s,18x9s FR500s and 5 lug rear disc conv.
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post #8 of 11 (permalink) Old 08-18-2011
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hell no, the stealership near me will only check the car for $98 and its not a guarantee that they will find the problem. Even if they cant find the problem, they still charge you. Also i swear that one of them wanted to joyride my baby because they wanted to keep it for an entire day. Went to this other dealership for a quote and it was $100 but they only needed the car for 1-2 hours. NOT THE ENTIRE FREAKING DAY. At first dealership, the mechanics all had smirks on their face, kind of freaky. From then on i never left my car with anyone. Im always at most 100 feet from it

sry for being of topic.

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post #9 of 11 (permalink) Old 08-18-2011
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Quote:
Originally Posted by Weasel318 View Post
ummmmm doesn't the 4.6 have a new kind of computer? so the 5.0 diagnostic trick wont work? he said 1998 mustang
Did you look at the user name and the avatar? It's an 89..
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i know, but his message said 1998. he could have gotten a new car and didn't edit his profile. you never know. plus he replied and didn't seem to have corrected it. so i assumed its a 1998. until he said otherwise i will stick with that.

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post #11 of 11 (permalink) Old 08-19-2011 Thread Starter
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SORRY About the confusion small typo! YES it is a 89, I fixed it!
It was indeed a Vacuum leak I went through and replaced all lines she runs like a champ!
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1998 , 5.0 , automatic , idle , mustang

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