[carbon02]

Working on my stepmothers 2.4L Alero 70,000 miles. Car starts and runs smoothly, but when you accelerate lightly from a stopsign there is no issue, when accelerating harder the car shudders and shakes like going over a wash board.

Seems to occur only from a stopped position when taking off. Doesn't occur with the car moving.

No codes stored. I've got a copy of the scantool datastream, and it looked like the IAT sensor was slow to respond to changes and it showed a momentary quick drop in temperature to nearly 0F, so I replaced it. Car shuddering still occurs.

Car at idle is running approximately 12-15% load as reported on the scantool. This seems high, but might be non related. I'm not sure how PCM's calculate load.

Short term fuel trim is -8% to 5% so I'm assuming that O2 sensor might be ok.

Car has approximately 70,000 miles. Is this a transmission issue? Any idea's from the 2.4L guys out there?

I still can't figure out how the 2.4L monitors airflow without a MAF sensor, I guess I just haven't studied this engine that much, as the car's not mine and I'm not aware of all the "quirks" of this engine family.

I'm typically over on the Intrigue Forum with the 3.5L shortstar, but it looks like this forum's fairly active.

Thanks