Montero Misfire Cylinder 6 (Full Version)

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Montero Misfire Cylinder 6

dcvee -> Montero Misfire Cylinder 6 (2/26/2007 7:49:01 AM)
Hi all. 2001 XLS 3.5 Montero 64k miles which has been rock-solid for over 3 years and 41k miles is now giving me "fits". Right front wheel bearing went out 2 weeks ago. Not a bad job to replace. But shortly thereafter the engine started to run rough and stored 2 codes. One was left bank pre cat O2 sensor and the other was a misfire on cylinder 6. The vehicle ran, just rough. I replaced the 02 sensor and took it for a test drive. It stored another p0306 code but not a O2 sensor code. I figured that it had made the engine run rich and fouled the plug in #6. So I removed the intake plenum and did plugs and wires. When I removed the plug from cylinder 6 I noted that it looked beautiful. Nice slightly lean burn. Didn't look fouled at all. So I became suspicious but finished up anyway. Sure enough upon restarting the vehicle runs exactly the same. That is, rough. I still have the P0306 code indicating cylinder 6 misfire. I checked the coil for #6 and it tested fine. I even swapped coils and it made no difference...still getting a P0306 misfire. So I pulled the injectors last night and I'm cleaning them and will replace this evening. Of course I'll swap injector 6 with 1 just to see if my code moves. One other possibility is this. On my 99 1.8T Passat I had a misfire on cylinder 2. I checked the plug which was fine. Swapped the COP and still got the same error code. I replaced the ICM and this was the fix. This makes me suspect the "ignitor" or ICM on the Montero as well but I haven't read about anyone having problems? So my question is has anyone had ignitor problems? Is there anyway to test an ignitor? Thanks! Don

tj90 -> RE: Montero Misfire Cylinder 6 (2/26/2007 5:23:57 PM)
Sounds like you are on your way to figuring this out. I would replace the plug on that cylinder. Cheap enough to remove that from the equation. Does #6 have a wire or is it on a coil? - cant remember. If it has a wire, maybe the problem as well. Did you reuse the same intake plenum gasket? Torqued properly? Mitsu recommends replacing it when its removed. I think that will cause codes to be thrown. Check the power to the coil. You tested the coil but maybe its the power to the coil thats causing issue. Check GND faults on the power line (abrasions etc). Run truck in the dark and look for arcing. Get a noid tester to test the function of the FI or stetshcope to hear the injector working properly - again, injector may be fine, but power to it might be bad (faulty harness)... Could it be emmissions related? Think about how the o2 could be related to the misfire. When your truck is maintained, I typically find problems that come up in pairs like this are related somehow... I know this is a stretch, but if you are out of ideas I would run a can of sea foam. Either entire can in 1/2 filled gas tank. Drive 20 min and let sit overnight. Or 1/3 of can in vacuum line while truck is running, let it suck up till the engine stalls, let sit for an hour and restart. Will make a bunch of white smoke dont be alarmed.

dcvee -> RE: Montero Misfire Cylinder 6 (2/27/2007 9:12:55 PM)
Thanks for the insight TJ. Tonite I checked compression on the left bank. Everything was 167psi or better. I also did a leakdown test and the valves are holding. I noted that the rockers were rockin' and the springs were springin' and the cam was liftin'[;)]. So I guess internally, I'm in good shape for the shape I'm in. Since I decided to remove the valve cover and do all the extra "stuff" tonite I didn't get it buttoned up but I'm ready for tomorrow night. We'll see if the cleaned injectors yield any benefit. TJ, under the valve cover looked like new. There wasn't any ugly gunk or dirty oil deposits. However, I did notice quite a lot of "black gunk" in the intake runners. I also shined a light down the intake ports through the intake and could see the back of the intake valves and they were filthy to say the least. Perhaps an EGR problem? I've used Seafoam before and I'll use it on this Monty as soon as I get it running. It could definetly use it. I was dissapointed with how dirty the intake was. I do periodic maintenance at called-for intervals so maybe there is something else that's wrong. I'll finish the job tomorrow night and fire her up and then go from there. I'll keep ya's posted. Don

tj90 -> RE: Montero Misfire Cylinder 6 (2/28/2007 12:43:40 PM)
I think the carbon deposits in the runners are normal. I typically use throttle body cleaner and clean all the stuff out when the intake was out on my truck. I did mine at 60k service and it was black inside. I would replace the plenum gasket as well - simple and cheap. Mine looked brand new at 60k but I replaced it anyway, just taking another thing out of the equation. I hear a leaky one will throw codes - just dont know which one... Im thinking its an electrical fault. You need to really test the function of the injector and spark plug while its in the car and running to eliminate power problems due to bad grounding or bad harness. I would also replace the upstream (precat) O2 sensor on the right side as well if you have not done it. If you have more than 100k miles - it should be changed. If anything, you might bump up your fuel economy.

dcvee -> RE: Montero Misfire Cylinder 6 (3/5/2007 8:44:38 AM)
Well I'm off to the dealer. I'm thinking bad PCM at this point. Maybe they can reflash? Dunno. I do not have an O-scope so I can't check injector timing or coil fire signals. But the problem must be in either one of these two area's. Appointment is for tomorrow morning....I'll post back with the diagnosis. Don

tj90 -> RE: Montero Misfire Cylinder 6 (3/5/2007 2:15:13 PM)
Let us know. Hopefully its simple....

wrexed03 -> RE: Montero Misfire Cylinder 6 (3/5/2007 9:55:12 PM)
Check for vacume leaks on the rear. I spent the last 4 days on mine chasing a miss on no.6. Dont know if it stored codes or not but it had me baffled. I went as far as spliting the manifold and replacing all the inlet gaskets lower and upper. Plugs leads etc you name it i swapped it thank god i had spares. The vacume leak was an o ring on injector no.6. I ended up replacing them all and just to be sure i sealed all my gaskets with some 02 safe silicone and tested for leaks again. No issues runs smooth as silk now. I must admit it was a stresfull 4 days but i wasnt going to let it beat me. It 's great knowing you fixed it yourself. Dealership advised to change the o rings on the injectors they sell heaps of them. Good luck with it..

dcvee -> RE: Montero Misfire Cylinder 6 (3/6/2007 8:28:57 AM)
....been there done that[:)] But thanks for the suggestion just the same. I replaced ALL of the injector Orings...top and bottom. I also removed the clutch fan and engulfed the area in MAPP gas to check for vacuum leaks. ZZZZIP! Nada. This has me baffled. Only thing I couldn't test was the EGR motor....and I don't see how that would give a missfire on cylinder 6 code. Especially since the code stores(after it was cleared)within 1 minute of starting a cold engine. Gotta be something electrical. Either injector signal, power transistor that feeds the coil or the PCM. Everything that could be checked with a DVM was checked and is OK(least to best of my ability). On the Mitz, like many other cars, the code P030X(x=a particular cylinder)is determined by the PCM when acceleration maps within the PCM are less than or greater than a specifed RPM increase (100) that the crank must achieve before the next cylinder fires. So the cylinder timing could be off. Either the injector or coil is firing before/after when it is supposed to. When you get to that level of diagnosis you are OUT of my realm. I haven't the time, tools or experience/training to be effective. I'll pay the 70 bucks an hour.[:'(] I dropped her off this morning. The techs were eating donuts and consuming gallons of coffee.....preparing for battle[;)]

wrexed03 -> RE: Montero Misfire Cylinder 6 (3/6/2007 9:03:30 AM)
I envy your persistance as well as mine lol.. If the egr isnt working correctly it could cause a miss cause it relies on engine vacume as well. Might be partially open due to carbon build up. Only other thing i can think off is timming belt slipped by one tooth. T his engines are a pig to work on but when they are sorted quite smooth. I am hopefull i dont have to remove the manifold again for 100 thousand kilometers. I am so over it. My hands are full of cuts and scratches and a nice 3rd degree burn on my wrist. Hope you get it sorted. I will follow this thread and see how you get on. Regards wrexed03

Winshawn -> RE: Montero Misfire Cylinder 6 (3/6/2007 12:19:18 PM)
I will be interested to hear what happens. My engine has idled a bit rough since new. Now at 40k it seems a little worse. No codes or anything. I wonder if it could be the injector O-rings. I checked for vacuum leaks with a propane torch and could not find anything.

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