Engine ticking, rough idle, low rpm bucking - solved

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G03rt2
Posts: 62
Joined: Sun Nov 05, 2017 11:48 am
Location: Wisconsin

Engine ticking, rough idle, low rpm bucking - solved

Post by G03rt2 »

Just looking to post my issues/experience in hopes that it helps someone someday in the future. Look at the bottom for a quick summary.

I had a rough idle issue with my M30B35, along with a bucking/surging between a 1500-2700 at any speed. For instance the street near my house is a 25MPH. I leave it in 3rd gear and do 30Mph and you could feel it almost chugging. If I reved it through the range I would have no issues and it seemed to pull just fine.

I also had a very audible tick all through the RPM range. So I decided to do valve adjustment. I did it 3 times. It didn't sound any quieter after the first time. I did it again and it got more quiet but not really. So I finally did it on the cam side and it seemed more quiet.. at first.. then it eventually got loud again.

Something I noticed when I took the plugs out was a grey watery film on the threads. I figured it was just anti-sieze since all the plugs seemed to have some on them. After thinking about it more I realized that cylinder #5 had it on there each time, and the other plugs only had it on there after the first removal.

After counting the number of 1/4 turns it took for me to get one plug out I realized that the #5 plug wasn't threading all the way in. So I bought a "powerbuilt" back tap to chase the threads (it doesn't work that great, the hole for the plug is too deep and tough to expand once it's through). I then bought a 14mm thread chaser from the local automotive store and coated it in grease and chased it with that a few times until I could turn the plug with a extension and socket and no ratchet. I replaced the plugs with NGK's. Gapped them to .032 and now I have a smooth (smoother) idle, no bucking/surging, and no ticking.

Summary: Spark plugs not seated all the way, most likely causing loss of compression, running lean, or whatever else might happen.
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