simons2k

Anyone experience this:

You're in 1st gear. You start to take off but you don't give it enough throttle and the engine stutters, almost cuts out but it doesn't. It does however make this noise that is definitely not normal. Sounds like a slap or something like that in the engine.

What is that noise, and is it bad for the engine?

Squeezer

its the engine almost dying because the RPMS are dipping to around 200-400 rpm...cams on our engine weren't designed to run so slowly and have trouble getting air/fuel into the engine.

simons2k

I kinda figured that it's not suppose to run that low of rpms.

This happens sometimes when I'm being a little lazy and don't release the clutch properly.

The question is will it damage/wear the engine when this occurs?

Sideways

Lugging the engine that much could cause pinging (knock.)

Wesmaster

I believe that when a motor spins at a very "low" rate it becomes off balance. That's why the car starts to shake etc. So, the question would be, does a motor being able to shake around cause any damage over time?

Sideways

My take on it is as follows: When the rpms get very low (200-400 rpm) the oil pressure can drop. At the same time, the extra forces from pre-ignition cause the crank rod journal and the rod bearing interface (where the oil prevents contact) to narrow while needing more oil pressure to prevent metal to metal contact. A good oil prevents us from destroying that bearing. If the viscosity (and several other factors) are not adequate then stressing the engine with low rpms and knock can ultimately damage the engine. One form of damage may be done directly to the combustion chamber (piston, head, valves, seats, or sparkplugs) by knocking. The other form of damage happens to the bearings when they are damaged by inadequate oil pressure and metal to metal contact.
One part of the shaking is probably knock forces in opposition to the normal direction of engine operation while at low rpms.
I've seen engines actually spin backward in the end while shutting off while running on because of pinging.
The intake manifold contents are forced back up through the intake (carburetor or throttle body.)
My advice is to make sure you have adequate RPMs to avoid knocking and it's problems.

simons2k

last couple of replies was what I was looking for. Thanks.

I will be more careful with giving it enough revs to make sure it doesn't happen again. Better to replace a clutch than to have engine damage.

xviper

Sideways, that explanation was SUPERB!