Bucking at low RPM

[bzern326]

My M60 is starting to buck at low RPMs when pulling from a higher gear (cornering in 3rd or taking a hill in 4th at 1000-2000 rpm). This is a new problem, and also intermittent. It feels like the motor is not getting fuel (my fuel pump quit last year and this is what it felt like), but I have a new fuel pump, both fuel filters are new, as is my air filter. I am not showing any idiot lights.

I am thinking that there is maybe some water in the fuel, and the motor is skipping, which is an easy fix (some isopropyl alcohol and 93 octane).

[mateo710]

or it could be a much simpler solution. like possibly that your rpms are too low and your lugging the engine. just a thought. maybe motor mounts are gettin worn?

[bzern326]

Its never done this before...I try not to downshift if I don't have to (tranny mounts are totally gone). When I came home from the gym tonight (after my post), I noticed that the motor sounded like it was skipping at low RPMs in all gears. This stopped when I hit about 2200RPM. The last time I had an issue like this, a coil pack had quit and i wasn't firing on a cylinder (stupid Buick!). I'm wondering if I haven't cracked the ceramic on one of my spark plugs. The last couple of weeks have been extremely cold (minus single digits), and the plugs are probably 2 years old.

[Meeve]

ifyou think you have craked spark plug, then maybe you should check them. It's fairly easy. Although you may miss the crack. Change them perhaps? If this fix you issue please update, lots of us have this problem.

[paperplane94]

Similar thread here recently, still unsolved.

I also had it happen and suspected some kind of fuel delivery but you say you replaced the pump, was it new?

Also this is an m20 im talking about but another guy had it happen on an m50, and you have an m60. hmmmm...

electrical maybe???

[bzern326]

I am going to replace them. I use Bosch platinum plus 2, if anyone is curious. After replacing them, I am also going to verify the function of my coils by unplugging the lead to the coil and seeing if the idle is affected. I will keep you all updated.

My car quit on feb 15 last year...I don't know what it is with this thing and valentine's day!

[bzern326]

Alright...so I replaced my plugs, and that was definitely what was causing the bucking. One of the plugs on the passenger's side was destroyed (the 2 prongs that the center part arcs to had both broken off). I am horrified to think that that crap got passed through the head, but whatever...it is running ok.

I am still getting a slight hesitation/buck at 3/4 throttle and above, but it has run like garbage for the past couple of days and I am assuming that some of the sensors are mucked up with unburned fuel.


ifyou think you have craked spark plug, then maybe you should check them. It's fairly easy. Although you may miss the crack. Change them perhaps? If this fix you issue please update, lots of us have this problem.

I use non-gapped plugs, but maybe the gap is off for other people's cars. Or possible the plugs are backing out and not in the optimal position for combustion. Mine were quite loose (although that is a problem for everyone I know with an aluminum block due to expansion and contraction because of temperature)