Piston Slap: If Only We Knew Ye, Trooper!
TTAC Commentator Dave M writes:
Hey Sajeev!
A question for you and B/B. Especially during cold weather my Trooper gets a ’clunk’ shifting from 1-2 (it’s a 4 speed automatic) and then back down. This coincides with a CEL. It doesn’t happen all the time. There are other times (even during cold) where the truck runs normally – no clunk, no CEL. Checking the CEL code and it indicates all four oxygen sensors (replaced last year); when no CEL no code to read.
My first thoughts were it might be time for ANOTHER transmission. But my brother says no, it has to be electrical since it’s intermittent. Any ideas where to start?
Sajeev answers:
Welllllllll…for starters you could write us with more info: stuff like the year/mileage/service history/CEL code totally wouldn’t hurt.
Perhaps it is time for “another” transmission, if we knew why you said it like that. Like maybe knowing the condition (look and smell) and age of the transmission fluid. Or perhaps the CEL isn’t fixed because Oxygen Sensors aren’t usually the problem: they are the messenger of a problem upstream. Maybe $10 in new vacuum line fixes the CEL, eliminate a leak that’s messing up both the engine and transmission’s parameters.
Or maybe you need a whole new transmission.
It’s kinda impossible to tell.
Come on son, us armchair analysts can’t judge a problem this complex with such half-baked info! That said, have at it, Best and Brightest.
Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.
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I'm just impressed someone has a 12 year old Trooper on the road. Joke. Sort of. The Trooper was a good car new. Unlike the Land Cruiser, say, it's not a good car old.
Hey thanks for picking ME!!! Sorry I was short on details. It's a 2001 2WD (poser!) LS model; the original transmission (the infamous GM 4L30E) was replaced at 60k (under warranty), and that one was rebuilt at 165k (and a transmission cooler added per suggestion by transmission shop - highly reputable local firm). It is now at 220k miles and reduced to vacation car status up north. Regarding the CEL, last summer before it hit the road the CEL came on and my mechanic mentioned all four oxygen sensors needed replacing (I didn't catch the CEL code). A day later the light went off and did not reappear until I drove it recently on vacation. As I said the CEL and clunking are intermittant. Kericf - thanks for the in-depth explanation. That will be checked out in the future. I didn't realize planetisuzu was still alive!