Misfire

[brojam5]

I need help with my car, a mustang gt 1994. I don' know what's wrong with it. When I'm driving in the city (about 40 mph) the engine very rough but when I'm cruising in the H-way (80-95 mph) it runs smoothly. Also I noticed that it runs smooth when the engine is cold. Just got tune-up 6 months ago and I barely use it.

thanks
John
1994 gt
vortech s/c
3:73
bassani x-pipe with headers

 

[mo_dingo]

Has the CEL light come on? Have you ran the codes?

Does the car seem to run better when you go to WOT? Does it seem better when you aren't in WOT?

Do you see smoke out the tailpipes? Are you running 91-93 octane gas?

We need some more info first. Your description is a little vauge.
Scott

 

[Ronnie41]

I need help with my car, a mustang gt 1994. I don' know what's wrong with it. When I'm driving in the city (about 40 mph) the engine very rough but when I'm cruising in the H-way (80-95 mph) it runs smoothly. Also I noticed that it runs smooth when the engine is cold. Just got tune-up 6 months ago and I barely use it.

thanks
John
1994 gt
vortech s/c
3:73
bassani x-pipe with headers

Take out your MAF sensor and spray it with cleaner, had the same issue before!

 

[Gearbanger 101]

How old is the gas in your tank? Did this just start, or has it been happening for awhile?

Assuming you're not tripping any codes....

Was the car ECU tuned with the Vortech, or did you just use and FMU? It it was tuned via chip, try removing it and running around (under vacuum of course) and see if it does the same thing). If so, clean the contacts, reinstall and trying again. If it still acts up, you've probably got an issue with your chip.