By on January 18, 2012

TTAC Commentator Tree Trunk writes:

Hello Sajeev,

I comment on TTAC as Tree Trunk from the frozen tundra in interior Alaska and am looking for advice on how to deal with an out of control repair of an old beater. I have a ’95 Isuzu Rodeo with 130K that until recently had been a pretty low maintenance, reliable ride.

Out of the blue the check engine light came on and the engine stalled.  A handy friend checked all obvious things to get it running again without success.  It would start up run for a few min before reving wildly and then die.  Luckily I thought, it broke down close to a reputable shop (NAPA certified) so we towed it there.

Seven weeks and two thousand dollars, not to mention the rental car cost I am back at square one. First they diagnosed bad PCM, a rebuild unit was in five weeks later, two weeks behind schedule.  I made it half a mile down the road before it stalled again.

This time around it was supposedly a slack timing belt hitting the crankshaft sensor causing the engine to stall. Week and another thousand dollars later, after first ordering the wrong parts and then not all the needed parts the engine started up, but wouldn’t you know it stalled again.

In hindsight, I should have scrapped it the moment it broke down.  But short of finding a time machine that is not an option.

Now I am waiting the next call from the shop and need advice from you and the best and brightest. It seems obvious that the one or both of the diagnostics were faulty and some third thing is causing the stalling.

What do I do, keep paying with a smile, demand a full repair free of charge or something in-between?

Sajeev answers:

First off, this is NOT the Isuzu’s problem. Sometimes I treat Piston Slap like a child psychologist, blaming the parents for the bad behavior of a little kiddo.

That said, I am sure you are a wonderful “parent” and I’d never think otherwise. I blame your shop: my first indication was their first suggestion, a bad ECU.

Folks, the computer is rarely the culprit in a poorly-performing electronic fuel injection (EFI) system. Yes they are wear items, other more actively engaged EFI gizmos are far more fragile as time goes by. Many times a problem like this comes from a bad TPS (throttle position sensor) or the electronic idle/choke system, normally called an idle control valve.  The only way to know for sure is to scan for engine codes, write them down, and look up the diagnostic tree associated with that problem via searchable database. Any decent mechanic should do this. Thanks to Google, anyone reading this website can do it, too. I am not sure if your rig is OBD-I or OBD-II, and the latter is universal and rather easy to diagnose.

You need to know the codes generated from the Isuzu’s self-diagnostic test. Do you know them? If none are present, the EFI sensors themselves need to be tested to see if their electronic guts are to spec. In this case, I suspect the Idle Control system is at fault…but that’s just a wild-ass guess.

So what should you do? Demand answers.  Demand engine codes.  If the shop stutters and sputters in their answer, demand a full refund for your lost time/wages/money.

From what little I see, it really, really sounds like they didn’t diagnose the problem. And threw your money at the problem instead. Not good.

Send your queries to sajeev@thetruthaboutcars.com . Spare no details and ask for a speedy resolution if you’re in a hurry.

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16 Comments on “Piston Slap: Bad ECU, Cowboy? This Ain’t my First Rodeo!...”


  • avatar

    You go Sajeev!

  • avatar
    dejal1

    1995 Isuzu Rodeo

    KBB value: $2,375 – $2,850

    You’ve spent what the thing is worth.

    You’ve been taken. In good faith you let them do the first repair as we all would. When that didn’t work, doubling down probably wasn’t a good idea, but we have all have faith in others and presume that they will do good by us.

    They put the parts in. You pick it up and it dies a half mile later? WTF? No road test by the shop?

    At this point, I’d also demand the old PCM back. As their “Fix” didn’t work, they will probably sell the old one.

    Could the injectors themselves be clogged?

    You also might want to try this yourself
    http://www.justanswer.com/car/38nb7-diagnostic-connector-95-isuzu-rodeo-v6.html

  • avatar
    Halftruth

    IAC will absolutely do what you describe. You may want to pull it yourself and clean it the best you can and see if there any changes. It is quick and easy to do. Let us know what happens. Good luck!

  • avatar
    wstarvingteacher

    Seems like the shop owes you something. As contractors they are not paid for effort but for results. Think I might stand on someone’s desk.

  • avatar
    JCraig

    I had a similar situation with the Grand Cherokee I had a few cars ago. It started hesitating then just quit. I could get it started after a while but it wouldn’t drive more than a few blocks before shutting down. The shop didn’t seem to know what the cause was and I paid for a couple unnecessary repairs (luckily they were only $100-200). Then they checked the gas and said it was the color of coffee. I worked with them on the cost of flushing the fuel system and they took care of it a a very low cost since I’d already paid for the pointless repairs. They need to cut you a break on the ‘real’ fix once it is determined.

  • avatar
    acme66

    Oh crap my identical Rodeo just hit 125,000…

    • 0 avatar
      Tree Trunk

      Well the clock is always ticking when you have a car with experience.

      Until this adventure I had replaced the starter twice and the clutch once in the 11 years I have had it, other than that there had not been much to worry about, minor oil leak, spark plugs and few other minor things.

      How does that compare to your experience?

  • avatar
    jimbowski

    It is the GM manufactured fuel pump mounted in-tank.

  • avatar
    GS650G

    Try new spark plugs. My friends trooper quit running because 4 of 6 plugs were basically shot; 140K on the original plugs.
    And oh yeah, they screwed you on this to the point you probably need a lawyer now.

  • avatar
    CarPerson

    Fuel System. Either electrical or mechanical, it has the symptom of an unhappy fuel system.

    Easiest thing to check is after it happens again, open the fuel cap and see if you get an in-rush of air. Get right down there because pressure and vacuum are surprisingly hard to discern. Let’s presume you are smart enough NOT to use a match to see which way the smoke goes. Driving it without a cap for a short trip will also diagnose this.

    Check the vent recovery system. The canister and the valve can be the culprits here. If it is not venting properly, gas will not flow properly.

    Ok, third and most expensive, drop the tank and see if the screen is covered with something or the pump is dying.

  • avatar

    I lean towards fuel system as well, with the exception of the “running widly” note. Typically insufficient fuel only leads to an engine dying. Unless the ECU cranks the timing or something.

    But the real point is, a real shop should’ve been able to diagnose this inside of a week, worst case. Like everyone else said, the “oh, it’s this, that’ll be $####” approach is not the correct one.

    • 0 avatar
      CarPerson

      The revving just before dieing is actually a tip it’s fuel related. As the mixture gradually leans out due to fuel starvation, the engine will rev. If the fuel pressure suddenly drops, it simply dies.

  • avatar
    mnm4ever

    That really sucks, I would expect that kind of crap here in Florida (although I would have choked at the first $1000 repair regardless). But I guess I always thought of people in Alaska as having a real camaraderie, like no one would ever screw you up there. I guess it comes from watching Northern Exposure… LOL

  • avatar
    rpn453

    My father once had an ’87 Olds Cutlass Ciera that was acting up. I don’t remember the details, but it was obviously doing unusual things because he picked up an ECU from the junkyard for $20, put it in, and it worked fine until it was rear-ended years later.

    Throwing $20 at undetermined problem = decent idea.
    Throwing $2000 at undetermined problem = horribly horrible idea.

    It may be running lean for some reason. Maybe it’s not getting enough fuel, or just too much air. It exhibits similar symptoms to my girlfriend’s lawnmower. She had given up on it a few years back, so I had a look at it and the wire to the spark plug was broken. Picked up a used wire at a small engine shop and grabbed an air filter to replace the extremely dirty one while I was there. Put new wire on and it ran, but not great. Put new air filter on and it would start if I primed it well, then rev way up before dying. The carb was certainly all gummed up from years of storage with old gas, so the new filter must have been allowing it to run lean. I put the old clogged-up filter on and added some injector/carb cleaner to the fuel and it’s slowly getting better with use.

    The shop should, at the very least, get this problem resolved without any further charges.

  • avatar
    Tree Trunk

    Thanks for the advice and the comments!

    The good news is that my Rodeo now runs like new, the bad news is that it did cost my over two thousand dollars and 7 weeks.

    So what was the root cause? Well the timing belt was very loose due to a bad hydraulic tensioner that may indeed have interfered with the crankshaft position sensor.

    Additionally there was bad corrosion in the electrical system that might have had something to do with an old hillbilly fix of a wooden block installed to help keep the battery in place. That wooden block was touching one of the battery terminals, causing slow discharge, crusting and corrosion.

    To get around the corrosion problem the shop changed out large sections of wire and installed a new ignition control module. At that time point the time and the cost of the repair was obviously getting out of hand so they did that at their expense. All in all they installed upwards of 500$ worth of parts that was not billed, plus labor, so even though I am unhappy about the overall situation I acknowledge there was a sincere effort on their part to make it right and paid the the rest of the bill.

    I still wonder though about the first diagnosing of the bad PCM, obviously that was was not complete diagnosing if it was correct at all.

    Supposedly the PCM was beyond rebuild so a different one was sent back by the rebuilder, I guess that I have to take their word for it on that one. I did not see the original one and really just looking at it would not tell me much, an old computer looks like an old computer to the untrained eye working or not.

    So now I that I have spent all this money on getting the engine in shape, I guess I must address the bad CV joints, loose bearings, weak clutch etc on a 16 year old car that has only received the minimum amount of maintenance through the years.

    It feels weird to have already spent what it is worth on a old truck and having to put more in. But really this is just a year or two of depreciation on the late model truck that I would have replaced it with. So if I get a few more years out of it I guess the expense is OK, though I still would have made a different decision if I had known the extent of the work before hand.

    Hindsight is 20/20 but at the onset spending the first 1000$ seemed like the quickest cheapest way to get back on the road, particularly since I did not have any time to do my own repairs or car shopping with an infant at home and a demanding new job with a long commute…


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