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lean running? 850 1994

RE: my other post under the thread "Hard start...checked archives 850 1994"

The spark plugs are NGK 2 prongs, not platinumm or irridium (sorry already forgot what the number is, but heat range is 6) I have confirmed they are the correct heat range.

The insulators are blistered pretty badly after 20,000 miles. After the wrong heat range, the two most common causes for blistered insulators are preignition and lean running. Since the timing is controlled by the ECU, that leaves running lean, which might also explain my hard start situation.

I've chcked for vacuum leaks by both a stethescope and spraying carb cleaner, and find none. The intake gasket is fairly new, installed when I replaced the crankcase ventilation system and all of the vacuum lines a while back.

What else would cause the car to run lean? I have no codes. I do suspect I have bad exhaust valve guides. The car uses LOTS of oil, but does not leak and has no blue smoke (except at start-up) and there is no oily residue on the plug electrodes which do not look overheated or damaged by preignition. Could the oil have fouled the O2 sensor and cause a lean condition? Fuel pressure regulator is fairly new, maybe a year and 10,000 miles.

Any ideas?







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