I have a 1990 accord that has a vibration problem when the AC compressor engages along with the cooling fans.. It seems like there is such a load on the engine that it just shakes like crap whether I am in Park or in Drive or Reverse.. It is worse when I am in gear however..

I am pretty sure that the IACV is working because the idle does compensate and doesn't drop when the AC comes on.

I have replaced all of the motor mounts within the last 60 days and am pretty sure that the rear one is operating properly when the idle drops below 900. At least I am sure that the piston in the mount is moving when the idle gets to a certain point. Whether I have a bad rear mount in general is impossible to tell. In any case, putting the mounts aside for a minute these are the other things I have done and changed recently.

I have also just replaced the distributor and the alternator and the alternator belt and the power steering belt. CLeaned the throttle body and replaced the EGR canister with one from the junk yard because one of the nipples was broken off.

I have set the idle and the timing exactly as the shop manual says and it is idling at about 800-850 with the AC on. 750-800 with it off. So I don't think that the idle or the timing are the culprits here.

I also replaced the AC condenser fan, the one with 4 blades because it was making a screaming noise.. I thought that was putting an excess load on the system also and causing the vibrations. but the vibrations are still there.

My thoughts now are toward the belts being too tight or too loose.. Could this be a cause of the vibration? or Possibly a bent AC pulley? Or maybe I need to have my timing belt and balancer belt replaced?? (with water pump, of course)

Or maybe this is an EGR problem because of that canister I put in??

Any thoughts? Anyone??

Thanks,

Mac

 

It could be balance shaft related. I've seen the shafts break in the motor before, simply due to age and use at this point in the cars life.

 

Also, check the iacv screen for cloggedness. If so, gently spray it with enough carb cleaner to make it shiny again.