1990 GT Running Rough - Forums at Modded Mustangs
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post #1 of 7 Old March 2nd, 2008, 07:01 PM Thread Starter
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1990 GT Running Rough

I have a 1990 GT 5.0 and when i fisrt start it, it idles rough. Then when im driving and get on it hard, it takes off rough and then starts running fine. Any one got some ideals of wat my problem might be.
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post #2 of 7 Old March 2nd, 2008, 09:18 PM
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MY motor does the same thing. I can't figure out what it is. On start up it hesitates tull its warmed up. It idles fine for 15 minutes or so then drops idle gets a tad choppy and feels slightly cammed. And a small vibration. Sound similar?

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post #3 of 7 Old March 2nd, 2008, 10:11 PM
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my buddy had the same problem from a fouled out plug, so check out the plugs and wires and cap and rotor

1995 Mustang GT 5.0
1994 Jeep Grand Cherokee 4x4 5.2
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post #4 of 7 Old March 4th, 2008, 12:05 AM
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Mine was doing the same thing. I replaced the rotor and plugs and wires and it runs like a champ again. I noticed the wires get hot from being close to the headers and this causes them to get old quick. Try to tie them up away from the headers if you can.
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post #5 of 7 Old March 4th, 2008, 12:36 AM
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check for vacuum leaks......thats one of the first things you should do when its running a lil rough
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post #6 of 7 Old March 4th, 2008, 12:53 AM
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Originally Posted by Iwannagofast View Post
check for vacuum leaks......thats one of the first things you should do when its running a lil rough
+1 on that and I will have to Star his respond. I had the same issue when I bought my car. I did these procedures and now my car works perfectly.

1. Checked for vac leaks and went ahead and replaced ALL vac hoses.
2. Removed the crappy "pinched" not gapped half ass spark plugs and replaced then.

3. Removed PCV Valve, breather filter which is located under the pcv valve, and replaced plastic grommet with a rubber one with o-rings for added strenth.

4. Adjusted my timing by advancing/retarding to best on standards.

Got rid of the rough starts, throttle response is great, doesn't crap out of starts on cold days and runs good. Also got rid of that annoying "Gas pushing" feeling or studder/spitting as it used to do.

94-95 306, B-Cam, Off-brand BBK Like Headers, H-Pipe, 3.73's, Nitrous Wet Shot 175 Shot
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post #7 of 7 Old March 4th, 2008, 08:31 AM
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If you haven't done a 10 minute tune up on your car. Then do it. Basically change out spark plugs. SP Wire. Thermostat. probably advance your timing
-/+ 15 degrees. Change your belts. Cap Rotor. Still have problems then like the last guy said check for a vacuum leak.

Whats that noise? Did I just dump the Trans!!!
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