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Isuzu Trooper Engine Misfire

krowekrowe Posts: 1
I am trying to fix a problem with a '01 Trooper Limited 4WD. The vehicle has 75,000 miles and started to sound rather rough. My wife had the vehicle checked at a shop and was told the EGR valve was bad. I replaced the part as well as a new set of plugs, reset the OBD codes and the car runs a lot better. I am still getting a P0300 code (multilple engine misfire) and the check engine light blinks only when the car is moving. It does not blink when the car is not moving even if the same RPM level is reached. What is causing this misfire?


  • When changing the EGR valve make sure to clean out the carbon buildup inside. The original EGR valve on some 01's is known to go bad. The replacement EGR valve is an improved design and should not need replacing again. Both the original and replacement versions are GM parts.
    The other known occasionally >60K miles failing part on the 01 Trooper 3.5L engine is the intake manifold gaskets. These are thick composite insulating gaskets, and they can sometimes crack allowing air into the engine. Air input into the engine at a gasket leak bypasses the air filter and engine computer monitoring. This can cause damage from dirt sucked in and poor engine performance because the computer cannot adjust the fuel mix properly to account for the extra air. The replacement gaskets are supposed to also be better than original so the problem will not happen again.
  • I've been having the same stalling issues. How much does it cost to have intake manifold gaskets replaced?
  • boxtrooperboxtrooper Posts: 843
    I don't remember the cost, but the labor was a lot and the gaskets are complicated since they are a thermal barrier so they were not inexpensive either. I had mine done here: 919-872-1999
  • Alright I've searched the history and dug as far back as I can to find an answer with no luck! My Trooper has 173K on it, timing belt done at 120K and regular service done always. I was driving for a while, maybe 2 months, with an intermittent check engine light. It would only come on while driving around 50-60 mph then when it would come down to idle speed it would go off. Then one day it started misfiring and bellowing black smoke!!! I had an oil change , fuel and air filter done and she ran fine, FOR A WHILE!!! :mad: Then all the sudden it's back the bogging, the smoke. I've replaced plug wires, new Bosch platinum plus 2 spark plugs and new O2 sensor(it was black as were the plugs) and it still is missing???
    Any ideas what to check next? :confuse:
  • boxtrooperboxtrooper Posts: 843
    Black smoke means it is not burning the fuel completely, maybe loss of spark or too much fuel. Maybe the plugs are all firing, but the computer is sending too much fuel.
    Is the loss of power extreme when it smokes? That might favor the not firing scenario.
    Paison I think, had a failed catalytic converter slowing down the air flow and that caused power problems.
  • atfdmikeatfdmike Posts: 414
    Hi, did you check the ECM for codes when this started? I would hazard an EGR valve/module issue. Good luck.
  • My 92 trooper has the same problem. Have you found a solution?
  • I've had an ongoing problem with the engine having a intermittant misfire, i have cleaned the egr valve and tube, replaced 2 O2 sensors, replaced spark plugs, replaced 1 coil pack, and all tube and valve cover gaskets, but my problem persists. I'm now noticing a rusty oily material in the spark plug tubes. It appears as though the oil and water conbined and evaporated in the tube. I was thinking head gasket, but it seems to me the gasket should not be involve in the spark plug tube, so now i am at a loss. the codes read misfire # 4 cylinder and i replaced that spark plug. Any suggestion would be a good suggestion at this point
  • atfdmikeatfdmike Posts: 414
    What engine are you having this problem with? Generally, I have only heard of antifreeze in the spark plug tubes when the head is cracked. It does happen but pretty rare. More likely the spark plug wire tube seals are letting moisture in. How about spark plug old and what condition are they? They may look OK, but age and use can cause their conductance to deteriorate.
    HTH One guys opinion.
  • Your opinion for mdenman may be right on mine. My 3.2 sohc is stalling, huffing and puffing clouds of black smoke intermitenty. The wires are old. When I pulled one, the seal stayed on the plug. The tube came out though, but the plug could not be removed. Any ideas on how to get that seal off the plug would be helpful.
    The 5 plugs are still out and I haven't tried to restart it since I replaced the o2 sensor.

    Also, where is the connector for the code reader ( i looked )and the location of the crank sensor?
  • I'm sorry my trooper is a 1999, there are no plug wires and each cyclinder has a coil pack, the liquid is water/oil mixture and maybe condensation could be part of the problem, i have bought a new coil pack and replaced the old one but still have the problem. Also can anyone tell me how to change my email address? I just switched to comcast and my address has changed
  • Stever@EdmundsStever@Edmunds YooperlandPosts: 38,916
    If you go to Forum Profile on the upper right, there's a tab for Change Email/Password.
  • atfdmikeatfdmike Posts: 414
    A trick that works when you have a sticky boot is to take an air nozzle and blow air into the be while pulling on the boot with a twisting motion. When reinstalling, apply a dielectric grease to the boot end where it fits over the plug. That will insure it does not stick again. Most parts stores have the grease.
    Early Troopers had the plug tucked behind console where it meets the dash. Carpet may be over it. Later Troopers had it in the LH kick panel behind the trim. Try a search, may help on both questions. Include your year, model and trans when posting, makes it easier to be specific good luck.
  • atfdmikeatfdmike Posts: 414
    The new pack pretty much rules out the coil or wire being the problem. Have you had the codes read.....there are codes that set that don't trigger the CEL to come on. Even a momentary code will generally be stored for a period of time. I am not too familiar with the ignitions setup on the newer trooprs. Try having the codes scanned at a parts store that does it for free to make sure no surprises. If none, check compression on that cylinder and a couple others to see if low compression is problem. Good luck.
  • The problem continues, last night i swapped out the coil pack again, and had the cel codes re checked at autozone i had three codes; 1171 (lean mixture during acceleration), 0157 (O2 sensor bank 2 sensor 2) and 0304 (misfire #4 cyclinder) I'm beginning to think i may have a problem with my fuel injector on cyclinder 4. Does anyone have any thoughts, I've no heard of any problems with that part. It doesn't seem that difficult to take off and check, or replace for that matter. The first two codes are a result of a cyclinder misfire, but in my mind the last (0304) could be the root problem and it seems the injector is the only item i haven't replaced yet.
  • atfdmikeatfdmike Posts: 414
    I believe that you can have the fuel injectors tested and cleaned by some auto service places. My only question would be if you are not familiar with them or don't know their reputation, then you may end up with a new set of injectors based on their evaluation when you may only need one. Regardless, injectors do wear out or are damaged and need replacement, so that is definitely a possiblity. Have you done a fuel pressure test to verify that adequate fuel pressure is available? Assuming there is, then a good shop should be able to fix or recommend replacement of the injector. I know they don't come cheap, but you seem to have eliminated most of the common causes. HTH Good luck.
  • dravin21dravin21 Posts: 4
    if you like offroad asmuch as i do check for bent/dented fuel lines.... i get that alot
  • I'm having a similar misfire problem with my '98 Trooper. For a few weeks it had an emissions problem which we finally found to be a broken air line above the gas tank. I don't drive it much, since I use a company truck daily, so the battery keeps running down. One day I jumped it with a charger and may have left it too long on "start". The battery was really dead. I had to do the same thing the next day. Then took it into Autozone and they replaced the battery saying it wouldn't hold a charge. They checked the codes then.. Could leaving the charger on start too long have burned out something? Never got the P0300 code until then. After the emissions problem it ran fine until the new battery died and I tried to charge it. It will run, but I used $30.00 of gas in two days just going 26 miles round trip on the weekend. It ran really rough both days, trying to stall all the time. Help, PLEASE!!!???
  • RE: msg. 19, Any response to this?????
  • Stever@EdmundsStever@Edmunds YooperlandPosts: 38,916
    I had a P0300 on my Nissan a couple of weeks ago and that's a random or multiple misfire. In my case, the knock sensor and some injectors went bad. MPG was poor and it ran real rough too.

    Could be a coincidence that your battery went bad too. I'm not enough of a mechanic to begin to tell you where to start troubleshooting. Plugs and wires or the coil maybe?
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