M42club.com - Home of the BMW E30/E36 318i/iS
DISCUSSION => Engine + Driveline => Topic started by: tigit on February 03, 2010, 10:49:30 PM
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I recently aquired a 93 318i. It had been sitting for a while before i got to it. The first time I went to start it, it turned over as if there was no compression. Did a compression test and one cylinder was at about 75 psi while the rest were gine. then It started fine a few minutes later. A few days later I went to turn it on again, and it spun over like if there was no compression again for a bit. A few minutes later it started but it had a miss on the same cylinder that was low on compression. After running the car for a bit, the miss went away, and I checked the compression again and it was fine in all cylinders. Ive been driving it for a few days, and when i first start it, it has that misfire, but goes away after a few minutes of driving. The previous owner told me that the lower compression/misfire was caused by bad lifters. Is it true that bad lifters can cause these symptoms? any suggestions?
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Yes, even 1 of the 16 lifters can cause this. When the camshaft turns and the lobe touches the lifter, the valve starts opening and then closing through the duration of the lobe turn. If the lifter is not holding oil pressure and always bleeding out because of a malfunction internally, the valve will not open fully, resulting in a misfire. As far as bad compression is concerned, bad lifters could possibly be the cause as a delayed valve opening/closing function could cause poor combustion sealing. Bent valves can cause poor or no compression, misfiring all the time and poor or no starting. Bad compression can also be failing piston rings and leaking valve seats.