Question, 83 3.0 engine surging at idle

sixgun · 07-26-2009, 08:52 AM

Am hoping some of you fellow wrenches can help me on this. I have just gotten my engine back together and running after replacing the bottom 12 head studs with steel. When the engine is warmed up to operating temp the engine starts to surge at idle. It goes from about 700 rpm to 1200 and will on occasion stall. At other times it will peg at 900 and idle fine. I am at a loss to find the problem and am hoping one of you guys can put me on the trail of what to check. I have checked every vacuum line in the car and they are all tight. Any ideas?
Thanks in advance for any help................ George

Flat6pac · 07-26-2009, 11:28 AM

Ahubting idle is usually a sign of too rich. Un plug the ox sensor and using the 3mm allen change the enrichment. Clockwise is rich and CCW is lean. turn very little as things change quickly. Your idle should stabilize. Plug the ox sensor back.
Bruce

Henry Schmidt · Henry Schmidt's Garage

A hunting idle on an engine that was running well means that something has changed.
I would hook up an CIS fuel pressure tester to determine that fuel pressures are correct. If they are correct, check the intake for air leaks and then attempt to adjust the mixture.
Adjusting the mixture sans reasonable investigation may have the effect of masking the real problem.
Good luck

sixgun · 07-26-2009, 01:58 PM

Bruce, I am a happy camper! Did what you said and now it is a swet running little Porsche. And Henry, It was doing that searching before I tore it down for the studs as well. I had thought that the broken studs had something to do with it...... I had to drop the rear of the engine down about 6" in order to get the 3mm Pelican T allen wrench to go into the hole and if a little is a lot, as you said, it must have been off a lot as I backed it off almost a third of a turn before it smoothed out!.........
I love this site and thank you both for the info. You have made my day !....
Many thanks....... George