nzdatman

thanks for the replies. Haven't adjusted lash at all but the car has hardly driven much in 10 years. I will adjust the clearances but I don't think they are wildly out. Plug 5 looks slightly wet, black but not too oily.

Hi all, I'm really starting to run out of ideas here, so thought it might be worth putting a post up here for help. My 280Z is running on about 4 and a half to 5 cylinders. 1,2,3 and 6 seem to be firing as normal. 5 seems to be running, but the header pipe is noticeably cooler than the others. Cyl 4's header pipe is stone cold. First I checked for spark, it seems to be OK. I have swapped plugs and leads around, and checked the cap. Second I checked the injector wiring, all seems good, have swapped plugs from 5 and 6 onto 4, makes no difference. I removed the fuel rail and injectors and turned the engine over to check that all injectors are squirting and not blocked. Third I suspected it might be a blown head gasket between 4 and 5, so compression tested it, results are #1- 125psi #2- 125psi #3- 125psi #4- 125psi #5- 95-100psi #6- 125psi So obviously it has a low cylinder, but it wasn't no. 4 as I had expected. It might however expalain why the header pipe on no. 5 is cooler than the rest. I haven't done a leakdown test as I don't have the equipment to do it. Starting to run out of ideas I removed the rocker cover to check the valvetrain. It looks to be ok. The valve clearances on no. 4 feel a little looser than some of the others but not widly out of spec and if it was I would have expected it to show in the compression test results? I intend to set them with a feeler gauge next but the way it went from running ok to not without apparant reason has left me a bit confused. I am tempted to pull the cylinder head off to see what's going on but I want to eliminate the easy stuff first. Any ideas on what it could be or what to try would be very much appreciated, thanks.