m42 misfire and smoking
 

Hello everyone, i have a 95ti with 275k mile. It has been running well for the past few months that i have owned it, every now and then the idle would stumble at a stop but overall okay. I left for work a few days back and had to hold the revs up to keep it running, but there was a noticeable misfire at all rpms. At this point i turned around and took the bike to work until I could mess with it over the weekend. So this weekend I started poking around, when started the idle is still very poor and this time i noticed smoke from the tailpipe, and a smell of raw fuel. I checked for signs of head gasket failure, now water in the oil, or oil in the water. At this point i pulled the plugs knowing i had a fresh set and they needed replacing anyway. Pulled all the plugs and all were dark black and smelled of fuel, also had 3 of 4 tubes saturated with oil. i replaced the plugs and reassembled, with that done i restarted the can and it is still running very poorly and smoking, but not quite stalling. If anyone has any ideas id love to hear them. thank you for reading

You need to replace your valve cover gasket. The oil is getting into your cylinders causing it to burn (hence the smoking exhaust) as well as your wet plugs/wires making it misfire.


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Thanks for the input, I was planning on ordering a valve cover set along with a new pcv valve. Figure that's as good a place to start as any. I'll keep you posted on the progress.

Pretty common replacement, mine is starting to seep into the cylinders too, good luck.


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I doubt it is the valve cover gasket. I would be more looking at valve stem seals or a piston ring problem. Leaking injectors will cause rich running. Check all the vacuum hoses too. Excess crankcase pressure would force oil where you don't need it
If the fuel filter is old it could restrict pressure or allow dirt to jam the injectors open.
Hope some of the ideas strike a chord

Sorry it taken me so long to get back to this, but haven't had a chance to work on it in a while. So I've put the new pcv in, it had come apart. I cleaned out the intake and the pcv passages, and cleaned out the spark plug tubes. Then when for a test drive and found no improvement, in fact it is now backfiring along with the miss, but the smoke is reduced but not gone. At this point I think I'll search checking compression and leak down.


Just finished my compression check. Looks like I hurt cylinder 1, it is at 145 psi while other cylinders are in the 180 psi ballpark. Also have new plugs very black after about 5 miles but that could just be the oil I was burning with the broken pcv.

Spent another day looking at her today, inspected and replaced all questionable vacuum lines. I removed the spark plugs again and found them dripping with fuel and with the injectors out I could see a pool of fuel on top of the intake valve for cylinder 1. So possibly failed injectors, or bad o2 sensor.

Well good news I guess..... found MAF full of water and stuck open. That makes sense to me for running very rich, so I guess it is time to source one of those.


Verified maf as cause of problem. Poured water out and freed up flapper door, and she fired up and ran perfectly. Still going to replace with a new one but happy to say I found the problem. Thanks to everyone that offered advice.