Why is my engine misfiring?

SHO. 3.0L 6cyl MTX 147K. Engine runs for about 20 minutes. Gets up to operating temp. Then starts misfiring (speed up, slows down. Jerking the car around.) When it cools down, it stops. Just started happening a week ago. If I shut down while hot and try to start. It is hard to start (lights fade, hard to turn over. Like the battery is almost dead) then it turns over and misfires. If it is cool, runs perfect. It is definitely heat related. Coolant is fine, oil is fine. Battery is a year old and tested good. Could this be a thermostat, head gasket (no white smoke), alternator (alternator was replaced 3 years ago)?

Tim

Awesome! I am pretty sure it wasn't the alternator or thermostat. I was hoping it wasn't electrical. It doesn't appear to be. Here is what I did. I researched and figured either the ignition coil or the coolant temperature control sensor. So I opened the hood to look at them. The coolant temp. Control in the car looked different than the one in the picture I had of it. Same with the ignition coil. So I removed the connectors and took them both out. Blew out the dust from the connectors and cleaned them up a bit and put them back in. Just drove the car for 90 minutes, fast, slow, stop and go, highway, city. Not a problem. But, if it happens again, I will replace the ignition control module. All three just kind of sit top of the intake manifold or the throttle body. Hopefully, car is safe to drive now. What do you think before I get in rush hour traffic in the morning? Thanks for the help!

You think it is safe to drive? Its my everyday commute car.

Ahhh. The wonders of electronics. So it started again, but this time the check engine light came on and then the car stalled. Had to wait 5 mins for it to cool down enough to start. Got it home, pulled the engine control module (really easy) and took it in to get a replacement (internet said it was available at the store, but it wasn't - had to go to a store about 10 miles away). While I was at the store, they tested it (about 10 times to get it hot) and it tested good so I thought. Replace the ignition coil and the guy at the store said that was probably the cause. So I bought a coil and put it in. Didn't solve it. So I drove the 10 miles, picked up the module and put it in. Mathiaso was exactly right. It was the ignition control module. The moral of the story. Sometimes tests are wrong and the guy at the autoparts store is wrong too. But I saved a ton doing this myself with reman'ed parts. Thanks guys!

So. After all of this stuff, it wasn't the ignition control module at all. The car went back to doing misfiring and hesitating like a person learning to drive a manual. Then stalling. It was the Camshaft Position Sensor. I also found the oil leak. There is a gasket around the crankshaft flywheel and that is leaking, getting oil all over the sensor and the sensor was failing. A $30 part.

Benn driving it for a few months and now the car won't start. It will crank but not start. I have had it at two shops and they can't find the problem. They both tell me the plugs aren't getting a spark, but they tested everything on it and it tested good. They can't figure it out and gave the car back to me. I thought it was the cam position sensor that failed again (the cranking but not starting is the indicator) since I used a reman'ed part, but both shops said it tested good.

Coil, cables, ignition. Etc have all been tested. Timing belts checked out OK too

Any ideas?

I drove my '94 Taurus from NC to AZ with no problems. Now that I'm here in AZ, though, my speedometer has stopped working and my entire car jerks violently whenever I'm doing anything BUT accelerating, including braking, coasting, or even sometimes when I ease off the gas a little bit. When I get up to highway speeds, 60+, everything gets better. My speedometer suddenly works, my transmission is fine, I have no problems. When I slow down again, the transmission acts up again, though not as badly, and the speedo keeps working until I come to a dead stop, like at a red light.

I have two more days of pretty serious driving ahead of me before I can stop long enough for a serious repair job. There's a mechanic across from my hotel and I can stay a day - is this the kind of repair that can be done in that time? And if I keep driving it until Tuesday, will I be okay?

Yeah, but will it hurt to wait to do it? Can I keep driving or will I blow up?

About 250 miles.

While driving, my car seems to "skip". I am thinking maybe needs a tune-up or alternator? I don't know much about cars and don't have much money. Any posts from someone would be greatly appreciated. I can take the car to the shop on payday Fri. But I would like to give them some kind of idea what it might be. Also it cranks up okay, it just seems after I have got to a "cruising" speed that is when it starts the "skipping". THANK YOU in advance for your help. Greg W.-- Alabama

When I'm driving 50-60 mph and I need to pass another vehicle (2-lane hwy) when I accelerate faster the car jerks strongly. As I continue this I lose pick-up and it takes a long time to pass the car. All the other times I drive the car (besides passing) it operates fine. I took the car to my local ford dealer, nothing showed on the computer scan. They recomended a tune-up, the fuel injectors cleaned, and a new fuel filter. My check-engine light is always off. I installed new plugs, a new fuel filter, and had the injectors cleaned professionally. I still have the jerking problem. Any Help appreciated Thanks!