afpoint

I'm new to Rennlist and I hope someone can help me with some advice on my horribly running 87 951. I've replaced the vacuum lines I've checked all things to be checked on my car and it still runs horribly!! just recently it been idling so poorly , like its an old diesel engine i.e it vibrates very bad, Also the heat shield on the exhaust manifold has come loose, it started the same time the car started running so poorly. I thought maybe it could be a motor mount, i just cant figure it out. I checked checked the spark plugs and they look good, i checked the cap and rotor... they do need to be replaced but I've seen worse on cars and they ran better then mine. Could it be the timing is out? or the balance shaft belt has jumped a tooth? Thank you for any help...

slap929

Have you checked the timing of the engine?

Clarks-garage.com is a good place for help and welcome to rennlist.

lart951

Does it sound like a diesel engine? Like heavy ticking?

Paulyy

If something needs replacing, i think you should replace it as it still could be the cause or apart of the problem.

White_951

Timing or spark plug wires mis-configured is my first guess, if in fact you show a good vacuum....

afpoint

Thank you everyone so much for your advice...No ticking at idle...just a horrible rough idle, vibrating really. plug wires are in their correct places. I have not checked the timing and have a cap & rotor on its way.

Tom M'Guinn

Does it seem to have normal power, just lots of vibration, or does it have low power and/or have a hard time rev'ing normally too?

Does it smooth out if you rev the motor to 2 or 3k rpm?

To check if all 4 cylinders are firing, pull one fuel injector or spark plug wire at a time and make sure the motor runs lumpier with each cylinder disabled. If it runs the same with one cylinder disabled, then start sorting why that cylinder isn't working.

T into the fuel pressure vacuum hose and read how much vacuum you have at idle.

Check the balance shaft and timing belt marks to see if they line up with the motor at TDC. Clarks-garage.com has the procedures for doing so....

See motor mount checking tips at Clarks-Garage.com here:

http://www.clarks-garage.com/shop-manual/eng-11.htm

afpoint

Its got normal power and lots of vibration revs easily, feels like its gonna vibrate the car apart. Ive pulled off each plug wire while running and it runs lumpy each time. Ive yet to do it by pulling an injector. It does seem to smooth out around 2-2400k but around 2800-3k its strong.

Last930

If the balance shaft belt is off it will buzz pretty badly, and can get all the various heat shields vibrating too.

cruise98

What is the idle speed ?

Tom M'Guinn

In that case, I'd focus on checking the balance shaft belt and motor mounts to start.

afpoint

Idle is at 1-1200 at this time, I set it a bit high because it idles sooooo bad at a lower speed... the (BUZZ) is realy bad. Is this a semi-common thing to happen. Also I replaced the water pump,timing belt and all other things related to the job about 1 1/2 years ago and approx 40k miles on the clock since the job.

afpoint

11-1200 rpm. not 1-1200rpm

afpoint

OK, soooo... I pulled off the balance shaft/ timing belt cover. The balance shaft belt is waaaaay loose. I can see the balance shaft can be turned just enough to, more then likely cause the (buzz) idle and the way its running. What do I need to do to fix. I cant imagine it stretched that bad in only 40k miles!

Thank you everyone for your advice and help, its much appreciated.

Tom M'Guinn

The balance shaft is pretty darn loose by design, just FYI, though no way to tell over the Internet if it's too loose. Best bet right now is to set the motor to tdc (using a 24mm socket on the main pulley bolt) and see if the shaft alignment marks are aligned as needed. It's a free and conclusive way of knowing whether the shafts are out of sync.