While driving uphill sometimes my Alero'* rpms will pulsate. If I let off the gas it seems to quit. I took it in to a mechanic and nothing abnormal was showing up on his computer and he couldn't get it to act up on his test drive. Does anyone have any ideas? Its a 2000 Alero 3.4L with about 140,000 miles on it. Thanks!

Not a misfire?

If not, could be the TCC is dropping in and out?

You should find a place where you can recreate the problem consistently, and have the tech go for a ride with you, with his scan tool in snapshot mode....

It doesn't seem like a misfire but I don't for sure. The mechanic sounded pretty confident that is wasn't the torque converter

When was the last time a tune up was done?

A bad spark plug wire or spark plug can cause a misfire which the computer detects and will prevent the torque converter from locking up.

I've had a brand new sparkplug cause me a misfire once. Come to find out, it was cracked.

Spark plugs are about a year old. Not sure about the wires. It'd be a good idea to replace them anyway. Thanks for the info!

Replace the wires and plugs just to rule them out. Your wallet will thank you later.

Usually with a engine misfire a dtc will set and the ses light will start flashing when it occurs. Sounds like something else.

I've been trying to research this and I've learned that the valve body on the transmission could be causing this. Thoughts?

My honest opinion, take it to a good reputable shop I prefer a dealer. Yes you may spend some money, but the diag. will be correct. No sense in guessing and wasting your money.

im with mike, i have had plugs and or wires wear to the point you can feel them and not set any codes. my moms 04 imp, she let go to about 140k and the gap was like double. that set no codes either and didnt drop mileage. just was running rough