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Minimal Surge Every Now and Then

Brown Bandit

New member
Jan 21, 2024
1982 Red Corvette
I have an 82 Cross Fire that ive been working on for a few months. When i bought the car originally it ran decent but could tell it needed some attention. When turning on the car noticed that it would idle at around 1000 -1100rpm before it would settle at around 800rpm at idle in park but once i drove the car for a little while and put it in park its idle would be at 1000rpm again. If i shifted to reverse or drive then put it back in park it settle down to 800rpm again. Replaced the CTS and seemed to bring down to 700 rpm in park which was perfect for me but the same thing would happen when driving it. It would go back up to 1000 rpm when put in park. Is this normal? Anyways so i started to chase down some vacuum leaks. Found a few lines and replaced as needed. Replaced some just for added insurance. Got it running pretty decent, enough to take 45 minute rides to the beach and back. Ended up getting an oil leak from the valve cover gasket and a coolant leak at the back of the manifold on the drivers side. Replaced the valve cover gasket and did the 2 gaskets for the manifold ( upper and lower). Fixed both leaks. Ran good for a few days then noticed when in park the idle would surge about 200 to 300 rpm for about 1 to 2 second durations every 10 to 15 seconds then it would stop for like 10 minutes and then would come back. This didnt affect the driveability of the car just would do this at idle. So i dug around some more and found a small black vacuum hose with a white line severed. This line goes into the firewall at one end and on the other end looks like a small diaphram. Looks like a small egr valve. Anyways spliced back together and damn the car ran really well when i took it for a test drive. Came back let it idle while i was checking on other things and it did it again . Not as often, maybe 2 times in the 15 minute span that i let it idle. I also failed to mention that i blocked off the 2 ports on the manifold that go to the lights and ac functions under the hood. I know i have a smalll leak there just have not got around to rebuilding the actuators. Anyways so re-cap what ive done so far. Replaced CTS sensor, replaced O2 sensor, cleaned iac valves, replaced upper and lower manifold gaskets, replaced known vaccum line leaks, replaced pvc valve, timing is correct (6 BTDC), blocked off vacuum ports to headlights, and drove car around to reset iacs. Whats throwing me off is that it is not consistant. Most vacuum leaks are consistant. Any ideas anyone?
So i think i figured it out. Tested the tps sensor. The value is supposed to be .525 dc. Well it was set almost perfect at .527 only problem is when manually pressing the throttle the values dont change. It stays at .527, its supposed to change right? Im curious though if the values never changed wouldnt the car run like crap? Car ran pretty well other than the surge here and there
Wish I could help you with the 82 Crossfire. We have a Crossfire dedicated Forum here on the CAC called the Crossfire Injection Mine. There are several guys that are knowledgeable about the Crossfire that check in there. Many of these topics have been discussed here over the years. Do you have a GM service manual for the 82 Corvette? It can be a valuable tool for troubleshooting.


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