BMW 1-Series Forum (F20) 135i - 1Addicts.com > Second Generation 1 Series Forum > DIY Guides and Instructions > Cylinder 1 no compression - advice please
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      01-15-2025, 06:06 PM   #1
downus
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Drives: BMW M135I
Join Date: Jan 2025
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Cylinder 1 no compression - advice please

Hi,

So I bought a BMW m135i, its issue was that it was misfiring on all cylinders, the valvetronics were deactivated, and the system was running too lean.

I managed to fix most of the misfires and that was due to spark plugs and valvetronics. I fixed the valvetronics code using ista, where I recalibrated the learning positions.

I realised that there was still a code on cylinder 1 only sometimes and the car would only run on one cylinder, so I tried a compression test and the compression was showing literally 0. I checked the other cylinders they were between 120-130 which is fine.

So I decided to take off the valve cover to see if maybe there was a stuck valve open or something and they all look completly fine, just the valve gasket maybe needs replacing. The valvetronic lifters also look good there doesn’t seem to be any wiggle or anything.

Just there seems to be a little wear on the motor, and try to do a test to see if it may be a valetronic motor issue possibly. Could this cause no compression on a cylinder, if the motor is faulty?

I was going to take off the head and see the under side of the valves but I don’t have a engine crane to take it out. I have borescoped the cylinder aswell it looks okay just has a lot of carbon deposit.

I need some help on what else the issue could be before I either invest into it more or put it back together and sell it.
Appreciate 0
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