1979-1993 & 94 Conv [Subscribe to Daily Digest] |
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This is still on my 91 900NA 190k. Got the head machined about a year ago due to a burnt exhaust valve. Car has been driving good since but sometimes when I'm cruising with very little accelerator I get a gentle surging. Also, seems to happen especially during descents or at the bottom of a steep hill. I have been trying different things such as a different AMM, new ignition hardware (rotor, cap, wires, plugs, Hall). Spark plugs looked all fine. I also had my laptop hooked up to the O2 sensor with an AD converter, while still connected to the ECU, and looked at the O2 profile during these episodes. O2 probe seems to work fine. Had already replaced all the vacuum hoses but decided to investigate the vacuum this weekend with a gauge from Harbor Freight. I have it hooked up to the inlet manifold so I can monitor while driving (feel like a ricer monitoring turbo boost but unfortunately I have a lowly NA). When the engine is warm I'm at about 18"Hg and pretty steady, which seems to be in the normal range. The needle is also pretty steady while driving but then suddenly starts to fluctuate wildly and I get the gentle surging, like I'm pulsating the accelerator. But I'm keeping the accelerator steady. So my next thing is to do a compression check but since the problem seems to be intermittent, I don't know how much that will tell me. Anything else I should do or try? Should I just bite the bullet and take the head off again? I'm sure I could do it faster than last time which was a first for me. Would the shop even be able to find the sticking/leaking valve?
posted by 167.83.10...
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