2000 Alero 2.4 bucking/jerking

Car is a 2000 Alero 2.4, Automatic, 106,000 miles.

The car had been running sluggish with poor gas mileage.

Last weekend this was done: replaced the spark plugs (worn severely), replaced transmission filter and fluid (not flushed), replaced fuel filter, and replaced battery.

The car ran fine for the first two days of driving.

I then ran 1/3 can of Seafoam through the intake and replaced the air filter.

:frown: Now, on a 5 hour road trip (mostly highway), at steady speeds the car would ocasionally "miss" 4 or 5 times, then smooth out. At a stop, in gear, the engine idles smooth, but then occasionally "hiccups", similar to the "miss" at cruise speed. Now, the engine sometimes "stumbles" on acceleration.

There are no codes set or pending, and the SES light has not illuminated. I've read posts on here about the tranny, MAF, or O2 sensors. I'm leaning toward a contaminated O2 sensor because I ran the Seafoam through it.

I'm open to comments and suggestions. Thanks, Bob

I've never heard of Seafoam doing that to an O2 sensor, but maybe it can...
I'd replace the plug wires also, or if they are fairly new, check that they are tight on the new plugs.

I've never heard of Seafoam doing that to an O2 sensor, but maybe it can...
I'd replace the plug wires also, or if they are fairly new, check that they are tight on the new plugs.

The 2.4 does not have plug wires. The ignition module/cover is bolted to the top of the engine and connects to the plugs through a "spark plug boot". When I changed the plugs, I did a thorough visual inspection of the boots, springs, and module assembly. All looked good.

After a little more troubleshooting, there may be 2 problems:

The "miss" and "stumble" are not existent when the car is driven in "3", but return if driven in "D". I afraid the new transmission fluid may have dislodged some crap, and somehow affecting the trans operation in overdrive. I'm not familiar with this trans to know the details. (However, I am intimate with the Ford AX4S)

The "hiccup" at idle in gear is always present, and would suggest an ignition or fuel problem.

Any comments/suggestions are welcome! Thanks

Thanks for that info-I have the 3.4, so I'm obviously not familiar with the 2.4.

Do you have a tach? Maybe the miss only occurs in a certain RPM band, and driving in 3rd gear versus overdrive puts you in that RPM band?

Or, as you suggest, maybe it isn't really an ignition related miss, but a transmission slip or buck. I know on the 3.4, if there is an ignition related misfire, a code will be set if it continues long enough (a few seconds in my experience).
Xeroinfinity knows a lot about these transmissions. Send him a message, he'll probably know what's up.

The 2.4 does not have plug wires. The ignition module/cover is bolted to the top of the engine and connects to the plugs through a "spark plug boot". When I changed the plugs, I did a thorough visual inspection of the boots, springs, and module assembly. All looked good.

After a little more troubleshooting, there may be 2 problems:

The "miss" and "stumble" are not existent when the car is driven in "3", but return if driven in "D". I afraid the new transmission fluid may have dislodged some crap, and somehow affecting the trans operation in overdrive. I'm not familiar with this trans to know the details. (However, I am intimate with the Ford AX4S)

The "hiccup" at idle in gear is always present, and would suggest an ignition or fuel problem.

Any comments/suggestions are welcome! Thanks

Hi. I have 2.4L Alero 2001 with same problem . The problem is occurred at 90-100 km/h and turns cruise control off(if enabled). The mpg value also falled by 20-30%. I did a visit to dealership to figure this problem out. They said , there is a problem in the gear . They're ready to fix it and price for that in Israel is starting from 2000USD . May be they're wrong ? Does anyone had same problem fixed ?
Many thanks
Michael

Hi. I have 2.4L Alero 2001 with same problem . The problem is occurred at 90-100 km/h and turns cruise control off(if enabled). The mpg value also falled by 20-30%. I did a visit to dealership to figure this problem out. They said , there is a problem in the gear . They're ready to fix it and price for that in Israel is starting from 2000USD . May be they're wrong ? Does anyone had same problem fixed ?
Many thanks
Michael

Thankx for the tip, but please look at the post dates before posting!
Appearently you didnt see the thread "Posting in Old Threads (http://www.automotiveforums.com/vbulletin/showthread.php?t=891498)"

This is closed!