Quote:
Originally Posted by Matt Laube
Symptom persists after gask renewal and cat. check. Car will idle normally when air pump is on ( rich) and then lose power after a few revs in warm up phase.
If you press on the disc on the intake the engine will richen and normalize.
EHA ? Some type of potentiometer in the fuel distributor?
Ideas. ? New ignition ,chain, valve seals and gasket. Vac. ga reading was erratic as cat was suspected but verified nonissue.
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You seem to have mostly identified your own problem. Vacuum gauge is erratic and pushing down the MAF disc will richen and normalize the running.
Since you recently did a head-gasket job, go back and make sure you used a NEW manifold gasket and that the bolts are torqued to spec. Check and make sure you didn't leave a vacuum line off somewhere.
The vacuum gauge should be reading a relatively consistent reading, it shouldn't be all over the place. Mixture control is a function of manifold vacuum on a K-Jet car. Ultimate mixture is controlled by the movement of the MAF disc in the inlet plenum. If you have air ingress from somewhere else, your mixture will be off due to both the mixture control being wrong and the ultimate mixture based on airmass being wrong.
Another possible cause, although a bit more unusual would be if you got the cam timing wrong during reassembly. Cam timing being incorrect can cause erratic or low vacuum issues.
When you had the head off, did you get the valves ground and their seats lapped? Adjust the valve clearances? If you have worn valves, seats, or guides, you can get some bizarre effects as well.