3.2 Carrera - why is it running so rough?

[Patronus]

My ’85 Carrera shakes badly between 2000 and 4500 rpm, as if the fuel line is randomly cut off about twice per second. The problem peaks at 2800rpm. This only happens on part throttle. If I accellerate (even a little) the engine is smooth again. Also, the shaking does not occur when I decellerate.
The car pulls hard all the way to the redline and it idles smoothly.

Any ideas?

[RSW]

Can you expand on how the car "shakes" could it be plugs or leads? Its only a thought but if the plugs or leads are "breaking down under load" on one side of the car it could perhaps cause this effect.

Would you say the car miss fired or does it not appear to be that sort of problem?

is everything ok in the distributor cap? does it do this when parked and rev'd, or just on the move?

Regards
RIchard

[Don Plumley]

This is many ways sounds like the opposite of the problem I had and posted about. My problem was under hard load, and ultimately was traced to a faulty spark plug.

Since yours is under no load, I'd look at:
- O2 sensor (disconnect and see if it is better)
- Cylinder head temp sensor (check and see if you have the upgraded two wire sensor)
- DME Relay
- Idle position switch

The Bentley manual has a good debugging section and nominal sensor values.

Don