mrmoots

Hi

I recently had the gearbox only taken out of the car to have some leaks sorted on it following an unsatisfactory rebuild by a supposed specialist last year.

Anyway, enough of that….. I now have a slight rocking/vibration at idle, it goes completely as you increase the engine revs. I know the rear mounts were sagging, so changed these at the weekend for new 993 mounts, they have lifted the engine back into the bay, but not got rid of the vibration/rocking motion.

There is no noise like anything is touching, just a rocking sensation, any other thoughts? I have checked the torque on the gearbox cross member and both the gearbox nose and tie mounts look in OK condition.

Engine rpm is about right, not too low.

Very puzzled!

Ross

mrmoots

Sorry, should add I am running an RS flywheel, but thats been on the car since may last year.

Thanks

Ross

911Jetta

Recently another thread questioned this kind of shaking; people stared diagnosing various cylinder firing problems? Are the 993 motor mounts Porsche OEM or ebay specials?

My car rocks/shakes at idle, I love it. Reminds me of my high school hot rod days.
I have Wevo motor mounts. With these mounts the whole car feels much more solid and direct.

crg53

Isolate the 2 ignition systems (top & bottom) by disconnecting the igniters by the coils. Run the engine on one and then the other to see if you have a faulty plug/wire, that could cause your engine imbalance.

911Jetta

This is the thread I mentioned above:
Body shimmy at idle?
https://rennlist.com/forums/showthre...ferrerid=19642

Hope it helps?

mrmoots

Thanks for the link jetta, I had not yet found as I was searching for, rocking, vibration, idle, not shimmy.

Right, pulled both caps and they are OK inside, you cannot move the secondary rotor arm, so the belt’s not broken. Isolated primary dizzy so its running on secondary dizzy and car runs OK with s slight shimmy. Isolated secondary so its running on primary and it is VERY lumpy, knocking also from banks 4 to 6. So from this is it safe to assume that there is a fault with the lower spark plugs or wires, maybe on cylinders 4 to 6?

I have not driven the car hard since I noticed this shimmy, so hopefully internally everything is OK.

Do the primary and secondary dizzies fire simultaneously or is there a slight delay? Just puzzled why I detected a slight shimmy when just the primary was isolated, but maybe this is a combined result of the new engine mounts, lightweight flywheel and stiffened engine carrier.

I don’t know how old the leads are, but the plugs were new when I finished the rebuild last year. I will try the plugs, but if not it looks like more expense on the leads, great!!!

Ross

mrmoots

Just a quick update for anyone that has a similar problem in the future.

I pulled off the lower heat shields and saw that number 4 lower plug lead was spilt where it entered the boot. Ended up replacing all leads including the king leads, everything working, as it should.

It’s a bit disheartening really. I got a local independent to do the valve adjustment after my first thousand miles following my rebuild. I found a third of the tin wear and heat shield bots missing and the plug lead was at a very contorted angle, no wonder it spilt!

Thanks for your help.