Hi all. I'm chasing a p0305 and p0300.

New Plugs
New Wires
New Coils
Cleaned and rebuilt injectors

I just did a compression test on #5 and it is really low at 50. I had all plugs removed and my foot on the accelerator whilst checking. I put a plug in #3, no difference. Put a plug in #7, no difference. Added oil to #5, no difference. So am I looking at a sticky valve? Any options other then removing the heads for a valve job?

Thanks,
Jamie

 

So pulled the valve cover and the rocker shaft. I removed the plug from 5 and used compressed air to check for leaks. There is air leaking somewhere...i can hear and feel it come up through the holes where the lifters are. If I do the same for cylinder 1, no leaks at all. I pulled the springs for cylinder 5, and they were smooth and sealed up when I blew air through the cylinder, but it is still leaking somewhere when I did this.

So now I am stuck. I'm fearing bad rings or bad head gasket - even though the hg is pretty new and i used studs instead of stretch bolts. Is there anything else that could leak in cylinder 5? PVC or something?

Would love some thoughts before I have to dig into this engine...again.

Thanks.
Jamie

 

I'm not sure the reason for low compression, so I'll spare any bad advice, but on my last D2, P0300 (random or two or more cylinders misfiring) was a bad injector o-ring. you're not much further away from checking that as well. With low compression though, I think you'll have to get much further into the engine to figure out the issue. did it overheat recently? does it burn a lot of oil? does it make a tapping noise when warm but not when cold? does it blow white smoke out the exhaust?

 

So you hear air so far nothing to panic about, did you do a dry then wet compression test. That is the 1st way you check for ring failure, but at 50 unlikely to be a ring though possible.

The most likely culprits are valves, valve seals, injector seals. You can use dishwater soap & water mix to test both - you get bubbles if you have an air leak.