Need help: #1 cylinder misfire problem

[Jimbo]

I own a 99 montero sport, 3.OL, 6 cylinder

Does anyone have answers to these symptoms?

1. When I'm in Drive or Reverse and stopped-- the car will, intermittently, slightly misfire, stumble, vibrate or hesitate.

2. When I'm driving the car --- everything seems fine and speed seems normal

Last diagnostic test shows #1 cylinder is misfiring.

I cleaned the carbon inside the throttle, but the symptoms remain the same. What else could be the problem?

Thanks again,

Jim

[monterocraig]

Jim,
Was wondering if you ever figured out what the problem was....I have recently experienced EXACTLY the same symptoms on my 2000 MS with 3.5L engine. I get a cylinder 3 misfire code. I replaced the EGR Control Valve Solenoid since it was a cheap and easy try at $44, but that did not solve the problem. Any help would be greatly appreciated!

[dzuwel]

try testing your ignition control module if its bad, the symptoms Jim wrote happened to my ms but it registers a random misfire not only cyl 1.......I changed the plugs and wires and still it misfires, hesitates and vibrates, the rpm also fluctuates....untill i changed the ICM and it solved the problem... hopes this helps your problem....

[monterocraig]

Wow, didn't think of that...sounds expensive. Where did you buy and how much? Is it easy to access/fix? Thanks!

[dzuwel]

its very easy to access and fix and its only 100+/- bucks i think, shop around the internet, so many in there....or on your local parts store.......but as I said test it first if its bad then go for it.

[davidtemple]

Great Idea.

[monterocraig]

ok..any suggestions how to test? Thanks.

[jonathan997]

Hey guys, i have 02 montero sport ls and i have tryed everythin, spark plugs, timming belt, water pump, head gascket i put $ 1800 bucks already and i still have the stumble when i stop, so what exatly is ICM?

[buggzyy]

Here is the procedure to check the ICM

Attachments:

[Jimbo]

Thanks all for the update. I'm still having the problem. I will now check the ICM. Thanks buggzzy for the procedure in checking the ICM.

Note: I have to admit, every time I put an injector additive in a full tank of gas, it helps with the stumbling, the cel (check engine light) will go off for a while then come back, along with the misfire cylinder #1 symptoms.

[buggzyy]

Pull cyl 1 plug wire out its pass. Side front see if it's carbon. Tracked or oil soked.

[monterocraig]

Thanks buggzyy for the ICM test info. The ICM is also called the Power Transistor Unit.

[Jimbo]

buggzyy, I pulled the #1 plug wire out. the spark plug boot does have oil on it. Is this possibly causing the misfire in cylinder #1? I know it is going to be a job in getting back into the valve covers again and replace the seals. what do you think?

thanks,

jim

[msport99]

I will just throw this out there as food for thought..I have found drivablilty problems like you describe often happen after the battery has been disconnected. If so, the computer may have "forgot" your idle settings. Help it relearn by disconnecting the battery for a few minutes and the reconnect and simply start the truck and let it idle for about 10 minutes to "relearn" settings. Its just a simple and free check in the diagnostic process. Good Luck!

[Jimbo]

Finally, after seven months of asking and experimenting with all the good advice ( i.e., cleaning throttle body, egr valve, MAF sensor; checking fuel injectors; replacing fuel filter, replacing coil packs etc. ) I've been getting with this forum, I thank Buggzyy for his last advice, which was to check the spark plug in cylinder #1. The plug was fouled with oil on it, so I changed out my spark plugs, wires, valve seals, and again replaced my valve cover gaskets (what a tedious job). My 99 MS is now runny smooth with no more idle stumbling while in gear (D or R) at a stop position. Thanks Buggzyy for your consistant help with troubleshooting my Misfire problem.

Jimbo