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Car my sister is driving (2000 impala ls with a 3.8) has a slow accelleration problem. Engine does not get above 2000 rpms and car will not go above 50 mph.

is it surging or skipping? SES light on?

also this is the wrong section this is for 2000-2005 bonne's it should be in other 3800 powered cars i believe, a mod will take care of that when they see it.

I just talked to her. She says durning accelleration, the engine sounds normal until she gets above 30 mph. After 30 mph, the engine starts to "chug" and then straightens out at 50 mph. Check engine light was on due to a bad plug (it's out now). They changed all the plugs and one wire (the one on the cylinder with the bad plug). Her boyfriend was wondering if this one wire is not making a good connection somewhere. The fuel filter has not been changed in a while but I don't know if that has any effect (it does on diesel engines).

I'll be seeing her this weekend and she'll have the car. Hopefully I can get a better idea what's up.

swampthing wrote:also this is the wrong section this is for 2000-2005 bonne's it should be in other 3800 powered cars i believe, a mod will take care of that when they see it.

Noted for future reference.

find out what plugs and try to get him to get napa beldin wires I don't think it's recommended to only change one.


get it scanned again and see if the code is still there

I have already told them to do that much. I should also add all the plugs have been changed.

The most common causes are a plugged cat, and low fuel pressure.

yeah plugged cat sounds about right. same thing happened to my buddy's grand prix.
replaced the cat under warranty and was good as new.

I think that when she had this bad plug,depending on how long she drove it with the miss,the raw fuel probably clogged the convertor.Or you have a low fuel pressure,both are easy to check.

I think there was a misunderstanding when I talked to her. I thought all the plugs and wires were done and they weren't. One wire was broke and seemed to have been the problem.

Anyway, now seems like we got transmission trouble. I drove the car for about a 1/2 hour today. Shifting seems delayed and kind of weak or slow. Car also seems weak in second and/or third gear At one point, I kick to pedal to floor from a stop. The car accelerated to about 30 mph, and 4500 rpms(wouldn't go over that). At this point when it shifted, there was a rapid clicking sound and the check engine light came on. I let off the pedal for a few seconds and it started working again.

I have also been told that the transmission "clunks" when it shifts and performance is better durning warmup.

I told her to get the car scanned again to see what the code is. Hopefully that will give us a better idea of what wrong. The car has close to 190000 miles. I'm guessing transmission rebuild. Any other opinions?

The check engine light came on due to a random missfire. Now I'm not sure what to think.

Plug wires or coils, perhaps?

Ok. We have a set of W-body books here. Last night I did some digging to figure out this random missfire fault. What I found is that the engine really doesn't have a missfiring cylinder, but actually data from the wheel speed sensors got messed up. We don't have a scan tool here, so I don't think there is anything else to do. I am wondering now if this has something to do with the transmission trouble I posted earlier.

I agree with Archon, the symptoms still suggest that a plugged cat or low fuel pressure could be the problem. Neither of these will usually set a code.

Well, this past weekend she dropped the car off at the GM dealer in town to get the car scanned. Turned out the cat was plugged. So that's done now and she runs like a champ.

I understand how engine performance is effected by this, but I'm still a little confused as to why is seemed to mess up the trans.

Long story short,the tranny looks at certain things to determine its shift points,such as the load on the engine(how far your foot is down),because the engine wasnt running right,you had to put your foot down further in order to get some type of acceleration outta the thing which makes the tranny hold it in gear longer but the overall speed of the car is low,makes for a confused tranny.