My 05 LaCrosse runs weird unless I remote start it. Running weird I mean kind of Jumpy. When you place your foot down on the throttle it'* sluggish to pick up and if you keep your foot in the same place once it reaches about 3000 RPM then all the sudden power kicks in. Now the 06 has a really weird problem my friend thinks it might be a plugged catalytic converter but the car seems to have no power when it'* going up a hill and sometimes when you're just driving you watch the tach drop about 200 RPM and then jump back up where it'* supposed to be. When you're sitting and driving down the road if you pay attention you can feel the car chug. Does anybody out there have any idea what the problems might be.

Do you have a service engine soon or Check engine light on?
Be interested to know what codes may be present....

nothing on the 05. Today i will get the code for the 06

I would check the Throttle position sensor to make sure it is working properly.

I also agree on checking for codes. Usually TPS issues need to get pretty bad before codes start tripping, but, this is also drive by wire, and it could explain everything.

This should be two separate threads so we don't get the various symptoms and diagnoses crossed up. Since we're here, the responses from Soft Ride and rjolly87 would apply in both cases.

What are the odometers reading right now?

How long have you and your friend owned these cars?

Where do these cars live?

Any recent trauma, repairs, or parts replacements?

This behavior is with the engine warmed up, correct?

This behavior is continuous, like every time you apply throttle as described above you get the results above from start to finish of your journey? . . . or does this behavior come and go during your journey?

Did this behavior start suddenly or did it get worse over a period of time?

Confirming: If you remote start it this behavior miraculously never appears?

What speed?

How many RPM?

Any codes?

At what speed for example?

In this example, where is the tach supposed to be?

When it drops down, do you feel a drop in power or a kick?

Please describe in more detail this "chug":

What speed?

What RPM?

Uphill or downhill or flat?

If this chug is recurring like surging, how often does it do this? Like 2 times per second or once a minute or shuddering through the whole car or . . . ?

On the 2005 My first guess would be the MAF sensor. My 1997 3800 had the same issue. I know they differ because yours is fly-by-wire and mine isn't, but otherwise they are pretty much the same. Mine had plenty of power cold, but when it went to closed-loop operation it had no cajones at any throttle opening until about 3,000RPM. Since it has tall gearing and it mostly drives around at 5,000'+ above sea level it was pretty awful: (1) I'm idling happily, as I always do then (2) my driver pushes the accelerator all the way down then (3) I say "well . . . . . . I suppose I should . . . start increasing . . . RPMS . . . somewhat, . . . I think I'll do . . . my "electric golf cart low on batteries" impression . . . then (4) . . . <yawn> . . . it'* been . . . five . . . or six . . . seconds and . . . it appears that . . . I'm approaching . . . 3,000 RPM so NOW I'M GOING TO WAKE UP AND GO LIKE MAD!

It was much worse in the summer. Swapped out the MAF and it was night and day.

On the 2006, my WAG based on what I know so far would be Converter clutch slipping, however, that was mostly improved out of those transaxles years before these cars were built. Go ahead and answer questions above and maybe we can home in on a better answer.

the 05 has 180,000 thousand on it the 06 has a 109000 on it. I have been driving the 05 for 3 years and have had this issue since I bought it. The 06 I just recently purchased and during test drive I didn't notice anything wrong with it until about 2 weeks after I owned it. Nothing major has happened to either one of these vehicles accident or repair wise. Both live in Minnesota. Both of these situations happen with motor cold or warm yes the cars behave like this the entire time the running on the 05 I have a better chance of the problem not happening if I remote start it about 90% of the time the remote start will stop it from happening this happens at all speeds all RPMs and there'* no code on the 05 but the 06 just popped a code now today I will see what it is on the 06 when driving you can feel a chugging happening but once or twice every second if you're paying attention cuz it'* just a slight chug forward and back then when you start to try to climb the hill when your body knows that the cars going to kick down the gear sometimes it doesn't almost seems like it'* stuck on a taller gear. That'* why my buddy thinks that it might be catalytic converter it'* not reading properly until it went to shift

For the 2005, it sounds the same as my issue. Maybe one of the guys here knows if yours cares more about MAF while cold than mine does. I can't explain the remote-start fixing it. That could be a red herring. If it hasn't had a MAF sensor replaced in 189,000 miles it would probably be a good idea to replace it anyways.

For the 2006, that sounds like the converter clutch slipping. If your code does turn out to indicate a bad cat I'll be surprised. When it starts "chugging" like this, what happens if you >>gradually<< push down on the pedal until it shifts down one gear? My guess is that the chugging will go away briefly before it shifts down.

In order to get the Chuggington stop I haven't found a way of doing that but it seems like it has no power or it'* stuck in 3rd or 4th gear on take off or trying to pass I have to let my foot all the way off the gas and then slam it down in order for it to act right

How does someone drive a vehicle like this for 3 years? In doing so, you may have created more problems than you originally had.....

First of all, it'* hard to believe there are no codes set on the '05.....

Second, you need to drive this with a scan tool on it to determine if it'* an engine problem, or transmission problem, or you may have more than one problem and it could be both.....

Strikes me as TPS, but still just guessing. It'd be easier to have an example of the speed and RPM this happens at.

That having been said, I agree with Tech II that this needs to be evaluated with a read of what the computer is thinking at the time.