Hello

I've been on the forums for quite some time however this is my first post, so any help I can get will be greatly appreciated.

Anyway, I have a 1989 Camaro RS originally w/ a LO3 305 TBI; that engine blew so I got a 89 305 TPI and swapped my TBI intake over and everything ran fine for 3 days. Randomly, the engine started running very rough at idle but would clear up after driving. This has been happening since Wednesday and I figured it was an ignition problem and that I would fix it on the weekend. Just yesterday on the way to work the same issue returned except it didn't clear up, and was still present on my way home 8 hours later. Still thinking it was ignition related, I checked ALL the wires, spark plugs, etc and all cylinders have spark; did a compression test and cylinder 2 barely makes 60 - 90 psi (fluctuates). With the engine running you can pull that wire off and it makes no difference on how the motor runs, so I know that cylinder is doing nothing. Also, while performing the compression test (with all other spark plugs out), on cylinder 2 you can hear air push out of the intake, so thats what leads me to believe the intake valve is not closing completely.

I'm going to pull the valve cover off today, but I figured that if I can get any input from you guys first that might help. The motor did sit for 3 months before I purchased it, so I was told. As for oil, I just put in some of the cheap conventional Walmart brand for the time being; 5w-30 I think. I haven't performed a wet compression test yet either, so I could try that to narrow this down a bit. Lastly, compression on all other 7 cylinders was 150 - 160 psi. Doesn't seem like the motor has excessive blowby, no coolant in the oil, etc so I'm really thinking its a valve.

Anyone have any ideas or any suggestions? Thanks!

 

It could be a head gasket.

 

Thanks for your suggestion, Pound. I did eliminate the possibility of a blown head gasket by doing a leak down test today, which did confirm that air is indeed leaking into the intake during the compression stroke.

I am in no good position to be able to pull the head any time soon since this is my daily driver and I really have no other way to get to work. With that being said, I'm wondering if there is possibly a "quick fix"; but I guess I still haven't narrowed down the exact problem yet that needs to be "fixed". Obviously it is valve related, but could it be a bent valve, a stuck valve, a valve not seating, or is there even any such thing as a cracked valve?

Anyone have any clues as to further narrow this down? For example, does a bent valve make a distinct noise for instance? Like I mentioned prior, I did take off the valve cover and cylinder #2's intake valve stem did appear slightly lower than the exhaust valve next to it. Can a valve get stuck with that little travel left to go, or could it just not be seating right? Maybe carbon, or corrosion of some sort from the motor sitting for months??

I'll probably pick away at this tomorrow, but in the meantime any other suggestions are welcome! As a side note... the idle did seem to greatly improve today. You can still tell there is a slight... I don't know... "miss?", but the car is still completely drivable, and actually you wouldn't even notice sometimes if you didn't know; but the lack of compression is still there, and I don't want it to turn into a bigger issue down the road (literally lol). That and it drives me nuts when I know something just isn't right!

 

Readjust the valve lash on the low cylinders.