HELLO, I’VE BEEN UNABLE TO LOCATE A RANDOM CYLINDER MISFIRE PROBLEM ON MY 2001 MITSUBISHI MONTERO SPORT. The problem first cropped up on a long trip last May on the freeway, driving 75-80mph, and was diagnosed as misfire, replace plugs and wires. The wires had never been replaced, so at nearly 100k, I figured OK, this could be it. Well, it happened again over New Years Eve weekend (under the same freeway driving conditions) and once again, a test revealed random misfire code. Tests were run (at the dealership) with the engine both heated up and cold, and nothing else showed up. Everything tested is within manufacture specs, but after BRIEFLY READIING OVER THE AA1CAR.COM WEBSITE, could a possible culprit be the Exhaust Gas Recirculation (EGR) valve? Regarding the valve, the site talks about a possible problem that may not appear until the engine warms up. Well, driving approx. 50 miles between 75-80 would fall into this category. Would dealership tests be able to detect a weak spring inside the EGR valve, leading to the hesitation or misfiring when accelerating I have experienced? One other thing to note here: The wildcard issue, and I hope it?s not a direct cause of this, is the fact that when I had the timing belt replaced in April 2006 by my local mechanic (instead of the dealership, ARGH!), a ?dry start? was done. Is that the correct term for it? Anyhow, they tore the engine down to expose the damaged parts, replaced bent push rods, etc. with OEM parts, and sent me on my way. Suggestions?
This one may be tough to figure. I would suggest getting the codes pulled by AutoZone, Checkers, etc. and posting the results back here for further discussion. They will do this service for you free and it only takes a few minutes.
With a random misfire I would be inclined to think the problem would more likely to be related to the crank position sensor or an ignition coil getting hot and breaking down rather than an EGR fault. Actually, even a failing fuel pump could cause this.
As to the wildcard issue, your engine does not have pushrods. It uses valve lash adjusters which are basically a small valve lifter. Sometimes these adjusters have been prone to failure. Here is the part we do not know.
These adjusters should be very carefully inspected when the cylinder head was off and they should be marked to make sure they go back into the same position they were in before removal. So, the adjuster can fail because the ends are disentegrating or basically a hydraulic leak. There should be some faint tapping or clicking if this is the case.
(For what it’s worth, the same adjuster is used on some Chryslers, Mitsubishis, Eagles, Hyundais, etc.)
Probably what happened is that during the dry-start you mention the intake valves in the cylinder head were bent from piston contact. Hopefully, valve replacement, etc. was done properly. One would assume (bad word) that it was correct if the vehicle went for a long time with no problems.
That’s also one thing that really grates on me. Why any mechanic/shop will not simply rotate the engine through a few times by hand and triple check this stuff before hitting the starter motor. If for some reason the cam timing is off it will be apparent when the engine stops; however, no damage will be done and it can then be corrected.
Thanks for the info. I will have the codes by Autozone and see what they find. My next question would be how do they check the codes when the CHECK ENGINE LIGHT button has been reset? Hope that isn’t a silly question. Getting back to my trip over New Years, the light only came on after the second instance of hesitation occured (yes, it happened twice, once each way, both times after about 50 miles at 75-80mph. I guess the second time the hesitation/misfire continued long enough to trigger it.
Changing the spark plugs and wires stopped the misfire, before; so, change the spark plugs again. When the spark plugs are taken out, the mechanic should examine them closely. The connection of wires to plugs, and ignition coils, should be positively confirmed. Poor connections can allow misfire.
Some car makers have found that, on some of their engines, a certain spark plug yields the best performance.
The engine may be getting a little too hot for some sensors (particularly, the crankshaft position sensor (cps). Check the engine coolant level in the radiator. Don’t just check the overflow bottle. You can consider using a thermostat 5F degrees cooler for a slightly cooler engine.
When the trouble codes were set, there should, also, be freeze frame data stored in the engine computer. This freeze frame data (data from certain sensors when the misfire occurred) could be useful in finding the cause. If you have the trouble codes, and the freeze frame data, bring it here for advice.
I went back through your email again, and this point made by you stuck out; “So, the adjuster can fail because the ends are disentegrating or basically a hydraulic leak. There should be some faint tapping or clicking if this is the case.” Well, after the work was done (period of 6 months maybe), there was a faint tapping or clicking noise that would occur when first starting the vehicle. Not all of the time though, and this has not happened for quite some time. I guess it’s a damned if you do and damned if you don’t scenario. I suppose I can show my mechanic your response and see what he thinks. I also called Autozone, and they told me they could not help out, since the check engine light was reset by the dealership. Next time it happens, I will have them check it out.