Hello all,

My first post on this site was about 9 years ago when I had a major problem and since then.... My 02 Monte Carlo has served me well at 240K miles, knock on wood. I love this car. Recently, my alternator finally gave out on me for the first time ever on the car and I was able to replace that on the road, however, a new problem literally developed later day that I haven't been able to pinpoint.

At sustained speeds, mostly on the highway, I feel a slight vibration, almost a misfire, a "chuggle or fishbite" describes it very well. A technical service bulletin I found online described it that way, and it says to replace the Throttle Position sensor, which I did. Before I did that, I could feel this "fishbite" at low speeds around 30, but now I don't feel it anywhere but in the 65-75mph range, and not as bad as it was before I changed out the TPS. It's almost like a little stumble for a second or so. Could there be some kind of calibration I need to do with the TPS? Or could it maybe be something else? Again, it's not as bad and it doesn't occur as much as it did before I switched out the TPS, but it is still very noticeable. It never happens on acceleration, even when I accelerate at highway speed, or deceleration, but always only at sustained highway speed.

This car has the 3.4L engine and is throwing no codes.

I'll switch out the PCV just for giggles, and I don't believe there are any vacuum leaks, as the car idles smoothly (as smooth as it can with bad front motor mounts anyway, which will be replaced soon). Any help or ideas would be appreciated.

Thanks,
Buz

 

Throw your gear shift into 3 when you are experiencing the issue. I'm wondering if it's the torque converter lockup getting funky.

 

I did throw it into 3 when I was feeling this and it does seem as though I feel it less.

Alongside this issue, I have noticed very hard shifting. It used to only happen when the engine was warmed up and I've been driving for a while, but now it happens quite often. Would these two issues be related, and what's the fix?

Thanks,
Buz

 

It's possible that these issues are related. You can do a fluid/filter change and see if that helps. How's the level on your transmission fluid and what color is it?

 

I did do a filter and Max Life fluid change about 3 months ago after not doing it in forever. I did it sort of "just because I hadn't" in 9 years. I know that's bad. I also added Lucas transmission fix when I changed the fluid. The fluid is kind of dark pinkish and the level is normal. It doesn't appear burned or smell burned or anything. There's no slippage or delay in shifting, tho. I was thinking about adding more of the lucas stuff because I don't think I used the entire bottle.

 

You say no slippage or delay, but are mentioning hard shifts. This is telling me that you either have an electrical issue with a solenoid and it's failing and causing a problem (unlikely to me, because it's only when warmed up), or you have an issue with the transmission that you can't feel until the car pushes a harder shift pressure.

My gut is telling me this is transmission related, and you can try to get it diagnosed now before it's too bad and get it fixed, or just run it until it's broken.

 

Thanks. I think I might have to take the car to a shop for this one. I've been able to diagnose and repair so many other smaller things on this car, I reckon this time it's worth taking it to a real mechanic. I've learned a lot on this car and my other two much older cars over the last 9 years of doing my own work, but transmissions are a bit out of my understanding and willingness to risk working on it myself. Hopefully, I can get it in soon and maybe come back with an update.

Thanks,
Buz

 

Just wanted to mention one more thing: This "chuggle or fishbite" does tend to happen way more frequently when it's raining or driving on wet roads. I don't know if that makes any difference.

Thanks,
Buz

 

May be way off but you stated you changed alternator at first . I'm wondering if this fluttering isn't a plug wire . Maybe you pushed against one and damaged it. You claim that moisture makes it happen. Not sure of age of plug wires so try this. Get a spray bottle with water and spray all of the plug wires with a little water. If you hear the wires crackle it might be the issue. Actually easier to see in a dark garage. I'm probably way off , but it's a free test. Good luck