Failed compression test and misfire

[amorlv70]

Originally Posted by dikidera

These low compression numbers suggest either a worn out engine, or you have a bad gasket overall.

Btw, these engines cannot be rebored, the cylinder walls get too thin. If the gasket went bad, you need to resurface the HEAD and CYLINDER BLOCK. The cylinder block also warps as well as the head.

Those numbers are too low. The bifuel engine and possibly all of the NA engines need to have at least 180 psi. That is how much I got after I did work on mine due to a failed gasket. I then torqued it down not to 130 degrees at the last step but 150, with new bolts of course.

Hmm. Thanks. I'm pretty certain it's a valve issue again - no coolant or oil consumption whatsoever, the compression test was done on a cold engine to accentuate the readings - car sounds more balanced when it's warm. Hopefully nothing else but I'll do a leak down test etc and inspect properly when I have the head off again - haven't really got the time to pull the engine out

[dikidera]

It sounds odd to me. These engines have hardened valves exactly for LPG/CNG usage. Are you sure the initial repair was even done correctly?

[amorlv70]

It is very strange. yes strong and even compression after head was reconned. I am beginning to question the initial install - definitely not taking it back to where it was done, as when I called to discuss causes I was spoken very rudely to and told I would have to 'just bring it for a service'...
Anyway, I think it was running very lean, and although it is now running (supposedly) at the correct gas pressure etc, it is lumpy at idle and perhaps a bit down on power. It is definitely the valves again. But the car will have to keep doing work for me becasue I am moving across the country lol.

[dikidera]

I would definitely take it to a different shop. If you can, machine the block deck as well, for good measure.

[classicswede]

I suspect you have injector flow issues as the main cause. I would suggest a new set after the head work and then make sure you put cleaning fluid through them every 6 months or 10k whichever comes sooner

[amorlv70]

That is a good suggestion, thank you very much. I will order some then and make sure to clean them! Is there a chance that heavy ends have been playing bad games with the injectors causing underfuelling? Cheers.

[classicswede]

It is very likely. You can have some cylinder flowing too much or not enough. The ECU adjust to average mixture over all the cylinders

The heavy ends can also mess with the gas pressure from the vapouriser