OK I am stumped. This is a 1996 Chevy conversion van with a remanufactured Vortec 5.7 V-8. There is less than 500 miles on it since install. Once it warmes up, the engine surges (RPMS flux up and down) when in drive. Almost sounds as if it is breathing. Put it in park, and no more surging. Back into drive, and about 30-60 seconds later it surges again. Been over it with the scanner and it tells nothing. No check engine light.
I thought it may be a bad install of the intake manifold gasket (vacuum leak). I changed it again. Still no luck...
I am at wits end with this thing and do not know where else to check.
Here are some thoughts.....wrong engine application? Bad cam lobe? (I did pressurize the oil system) Intake not seating to the heads? Tranny problem??
I dunno, I have reached the end of my expertice on this one.....
Eightupman
UPDATE...check engine light on all the time now. Calling out engine misfire. Vacuum in the engine is about 20 in/Hg. Fluxes (obviously 15-20 in/Hg in Drive)
Found out that I installed the new distributor minus an "O" ring (I used a gasket that came with the crate motor). The odd angle chewed a bit into the dist gear. Have a replacement on the way. Will the missing "O" ring have caused my problem?