1999 isuzu rodeo will not stop misfiring, changed alot on it and now i need help

Asked by May 14, 2015 at 12:25 PM

Question type: Maintenance & Repair

i have a 1999 isuzu rodeo and i have changed all that i know to stop this misfire.  it will
miss under a load and just driving highway speeds, it also backfires sometimes.  i
have changed the timing belt tensioner pully all 4 o2 sensors egr valve and cleaned it,
replaced the injector o rings, fuel pressure regulator, all spark plugs and all coil packs,
fuel filter and fuel pump. we also just did a compression test on it and the psi was all
pretty similar, the lowest was 110 and highest was 150.  i just need help on what to do
next because i cant handle it anymore.  thanks

7 Answers

100,495

Try doing a wet compression test and see if the lower compression cylinders come up, it maybe rings. I am assuming you have the V6 in this rig. Do some of the lifters click when it is running?

what would it sound like if the lifters were clicking. i do hear something when accelerating but i dont know what it is.. we did the wet compression test after the dry. and the numbers did come up but not considerably. 1. 140 2. 130 3. 140 4. 140 5. 110 6.150 and that was the dry numbers. number 5 went up to 130 when doing the wet test

100,495

Just a loud click click click. try dropping the oil a quart and put in a quart of Marvel Mystery Oil and put in a can of Seafoam in the fuel tank, drive it around for 5 too 700 miles and then drain out the engine oil and change the filter. Then add another quart of MMO and refill the crankcase to specs and drive as you normally do, keep an eye on the color of the engine oil, if it starts to look dirty sooner than normal change it again, if it doesn't your as clean as you can get and hopefully it will cure your problem. It did in my Acura SLX and it has the same engine.

Best Answer Mark helpful
100,495

The Seafoam will clean out the injectors internally.

but would the lifters cause a misfire randomly that doesnt throw any codes.and i will try the marvel mystery oil and seafoam this weekend

100,495

Did on my Acura. After the MMO treatment the random misfire code went away, as did my lifter noise.

ok i will try and let you know.. thanks, if you think of anything else to try let me know

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