89 Mustang LX, rough idle and runs terrible.

[Ericdano]

Here is the story.

About a month ago, while getting on the freeway, the Mustang started surging. Then pretty much was sputtering and then died. And I couldn't get it started. In fact, turning the key did absolutely nothing at all. It didn't even try to turn over.

Had it towed, and when it arrived at the shop, it started right up like nothing was wrong. The Mech kept it for a day, and could find absolutely nothing wrong with it.

This Sunday, I drove down to a friends house, the Mustang drove perfectly. Hung out for about 10 minutes, then went and tried to start the car. It was trying to start, but it was really difficult. Took about 6 times, one of which the car started and then immediately died. After I got the car started, it was terrible. Noisy, wanted to die if I took my foot off the gas, no power at all, stuttering while driving.

Got it to the shop, and there was even a little bit of smoke inside. Now, the mech has had it for 3 days. He thought it was perhaps the catalytic converters that had given out and were clogging the exhaust, but now he has no clue what is the matter with it.

Anyone? Ideas?

[MagicRat]

I bet it's something in the ignition system which runs fine when cold but fails as it warms up. Bad ignition coils will do this, as will (occasionally) a bad ignition module.

I don't think its the cats. They clog from overheating, and tend to stay clogged, so the car wouldn't suddenly start running better. But one can do an exhaust pressure test. A tester is screwed into the exhaust in place of the oxygen sensor.

[fordtrucksonly]

Ive seen weak fuel pumps cause it.