Hi Guys,
My 2001 has recently developed a hesitation at low rpm's in 1st, 2nd and 3rd gear. This hesitation is like a "rough patch" between 800 and 2000 rpm.
If I pull away smoothly and slowly, no problem.
If I attempt moderate to hard acceleration, the car surges and hesitates alarmingly. Reducing the throttle position smooths the acceleration. Above 2000 rpm there is not a problem. This does not seem to be such an issue when the engine is cold - however, I don't push a cold engine to work hard.
I'd really appreciate your input here.

 

Hmm. Sounds like a metering problem maybe. Check for small vacuum leaks on the manifold and all of the destinations for the small hoses. Then use throttle body cleaner on the IAC valve and the throttle body. If the IAC doesn't close when you open the throttle but the computer is expecting it to then it can give too much air for the fuel being metered.

 

Thanks Sixshooter. I'll check into that. I recently had the head gasket changed to stop an oil leak. I wonder if there's a connection there.
Meanwhile, it has been suggested that this may be caused by a defective mass air flow sensor. I'd hate to change the MAF only to find that wasn't the problem.

 

Start simple. Check every hose and every ground. Check all of the harness plugs to make sure they are seated.

Vacuum leaks can be found with throttle body or brake cleaner. The idle will rise or fall if any of that is ingested by the engine so you can find a leak with a little searching and squirting.

 

There is a ground strap from the back of the head to the shelf under the heater hoses and a harness ground on or near the throttle body (varies by year).

 

I changed the spark plugs, wires and coil boots, and the hesitation is gone. Probably, the most likely problem was the spark plugs.

 

I worked on a friend's Chrysler recently that behaved this way because of plugs.