By on March 19, 2014

Well that looks cool... (photo courtesy:

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 [email protected]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. 

Get the latest TTAC e-Newsletter!

29 Comments on “Piston Slap: If Only We Knew Ye, Trooper!...”

  • avatar

    Engine mounts, tranny mounts causing a loose wire to kick off CEL?
    More data please, std in/std out.. or rather, garbage in/ garbage out :)

    Help us help you!

  • avatar

    Depends on the age of the Trooper, which we don’t know, but could this be a physical problem like a vibration or shunting that trips an unrelated sensor?

    It reminds me of things I’ve read about dozens of makes and models over the years.
    There’s a gearbox/engine mount that wears out and allows just enough movement to fray a cable that monitors the cat/lambda/O2 sensor. That causes a cat/lambda/o2 error. People were replacing the cats or whatever and finding that the new cat ‘failed’ very quickly. Lots of forums have big threads like this for different makes and models.

  • avatar

    Wait a minute… you’re telling me that Izuzu made a Trooper that freakin levitated? Why am I only seeing this now?

  • avatar

    What you wanna do is drop a 5 speed in there. No more trans problems. In all seriousness, I want one of these Troopers.

  • avatar

    I owned a 99 Trooper for 10 years. You may want to check out your alternator and battery first. Troopers are very prone to what appears to be transmission problems caused by a weak battery or alternator not functioning correctly. Have you noticed the illuminated gear selection display in the dash flickering when going from drive to park or reverse? If so you need to inspect the Transmission Range Switch which is located on the drivers side of the transmission right behind a heat shield.
    The switch looks like a metal box that has a lever that moves when you move the gear selector. The inside of this box contains a circuit board with contacts and a arm that moves across the contacts in response to the movement of the gear selector. You can clean the circuit board and the contacts and apply some di-electric grease to the contacts and the arm and close up the box and reinstall the box.
    MAKE SURE you mark the position of the switch as it is installed on the transmission before you remove so as to put it back in the same place as it is adjustable. Hope this helps.

  • avatar

    If it’s the 2ng gen there is an electronic box attached to the transmission where the shift cable connects to. It is the electronic indicator for the computer for what gear you are in. Sometimes if the nut slips a little or it twist on the shaft a little the transmission will physically be in D but the computer is getting mixed signals. With the rodeos (less ground clearance than troopers) eventually the dialectic grease in this box gets so dirty and filthy the contacts aren’t good and it causes this clunky shifting. You can pull it off pretty easily and clean it out and clean the contacts. The hard part is getting it back on and aligned correctly. Make sure to put aligning marks on the bolts and body before removing it. I accidentally cleaned my alignment marks off the body so putting it back on was a PIA and took a lot of trial and error getting adjusted. It could also be caused by stretched or damaged shift cable with some slack in it not triggering the switch in the right position. Best resource is There are a few threads some with pictures. My rodeo had the same issue and it saved me a lot of money that wouldn’t have fixed the problem.

    Use this link for some pictures and explanation

    Lost1 beat me to it but I would be 99% sure what he and I are describing is your shifting problem.

    As for O2 sensors. I am betting it’s blockage in the EGR tube that runs through the intake manifold. Pull off the throttle body and there is about a 1/4″ tube that runs from EGR valve in the back of the engine through the manifold and ends in front of the Throttle body. It’s bad about getting clocgged at the end. Use a screw driver to break up the junk in the tube and a brush and some deep creep spayed in the tube from EGR and TB to clean it out.

  • avatar

    I always have liked the Trooper, especially in Limited or SLX (lol) trim. But with all the “transmission will asplode” and the “fourth owner don’t give a sh*t” maintenance histories, there’s not a good way to own one.

    Also, I think it was a big mistake to not put 7 seats in them like they did overseas. And more two-door model years. And keep the little Volvo wipers on the headlamps.

    Oh and finally, this is one of the BEST looking vehicles for 90s two-tone paint.

    • 0 avatar

      You mean you weren’t fooled by the “Acura” clever disguise?

      • 0 avatar

        Better than the “Honda” disguise of the Passport.

        Or in other limited markets, the “Honda” Land Rover Discovery >.< aka "Crossroad"

    • 0 avatar

      I agree they should have put 7 seats in it, It really would’ve given the competitors a run for their money! Not many (I cant think of any!) midsize SUVs had a third row of seats in the 90s. Someone at my school Mom had an SLX but she traded it in for an MDX around 2007 though.

      • 0 avatar

        At that time:

        Land Cruiser (not so big at the time)
        Discovery I
        Durango (1997)

        Edit: As a sort-of inbetweener
        Mazda MPV

        • 0 avatar

          I would love an FJ60…then I go look at them. Ratty ones are a mess, nice ones are too much coin, and engine conversions are out for me.

        • 0 avatar

          Ahh- the MPV.

          Something neat about that AWD people mover.

          My uncle had one from new to over 200k miles. Held up very well.

        • 0 avatar

          I knew the Land Cruiser and Discovery had a third row, But i was not sure how much they costed in relation to the Trooper. And i never realized how small the 1989-1997 Land Cruiser was, It’s the same size as my XC90!

          • 0 avatar

            88-90 Land Cruiser was smaller than the 91-97. Neither were huge by modern standards until you tried to follow a Jeep down a tight trail.

  • avatar

    Considering it’s complaining about all four (replaced) oxygen sensors, I’d look first at the contacts at each sensor or where the computer data enters the transmission. Second, I’d check the connection of that wiring harness to the BCM/ECM computers Thirdly, I’d look at the sensors themselves–are they still intact? Finally, I’d check the BCM/ECM computers. It sounds like a solder joint has cracked.

    While not a transmission issue for me, I had a sensor that repeatedly failed on a used car I’d purchased from a dealership. Said dealership tried every time to blame me for the problem because the contact lead kept breaking off. The real cause of the problem was due to the lead WIRE to the sensor was too short to accommodate torque lift under heavy acceleration–something the techs insisted couldn’t happen despite the car being a performance model and every wire was engineered to the right length. It took them five tries before they finally lengthened that lead simply to save themselves money (It cost them $500 every time it broke because I’d purchased an extended warranty on the car. They couldn’t even charge me for labor, much less the part.)

  • avatar

    Where’s that crazy fridge to get all misty-eyed about the Trooper II?

  • avatar

    Had a new Trooper in ’88 and drove it for 10 years (well my sone drove it to college for the last 2 years) in eastern PA and it got us through very ice/snow storm which was never handled by the city, county or state in Chester county. It was rough but it always worked. In your case I suspect age is the primary cause. Just a lot of little thing that can go wrong because of time and use. Still, I laugh at today’s SUV and their supposed capabilities. The Trooper was among the very first along with the old Jeeps, that could handle most any event.

    • 0 avatar

      Agreed. I bought a new ’88 also. Mine was basic. 5MT, AC, AM/FM and that’s it. Even the interior door panels were just fabric glued to hardboard. That thing was simple, flawless and went everywhere.

  • avatar

    The internet suggests strongly that no Trooper has ever had a vacuum-modulated transmission, so that should be off the list of suspects.

  • avatar

    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.

  • avatar
    Dave M.

    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!

Read all comments

Back to TopLeave a Reply

You must be logged in to post a comment.

Recent Comments

  • EBFlex: “Omicron is more contagious. you should read about it.” Yeah and consists of the sniffles and a...
  • dal20402: Those are the classic Mercedes gauge faces, essentially unchanged (except for a subtle change from a...
  • dal20402: The only good thing about the CLK was the retro-look wheels on the 320, which this car wouldn’t have...
  • Tim Healey: Well, I am a Chicagoan, so close enough! In all seriousness, VerticalScope’s U.S.-based employees...
  • MitchConner: Had conversations during the summer of 15 for a program that would of dropped with annual earnings end...

New Car Research

Get a Free Dealer Quote

Who We Are

  • Adam Tonge
  • Bozi Tatarevic
  • Corey Lewis
  • Jo Borras
  • Mark Baruth
  • Ronnie Schreiber