Hey! I have a '96 camaro SS and when i bought it i knew it had some problems. Fixed the steering, brakes and changed diff and engine oils, auxiliary belt. But except those, the engine ran really poorly. Spark plugs and wires were obviously crap so they got changed, also changed fuel filter. When i bought the car it dynoed 226 HP, right now it does 245 HP, torque is 360 Nm top.

How should i go about to figure out what else is wrong?

Symptoms: first off, the drivers side part of the engine has a metallic knocking sound which the other half doesn't have. When at over 3500 rpms this sound can be heard from inside. The rockers maybe? Second thing, the car seems to be running unevenly, while holding 2000 rpms the car vibrates, feels shakey... No idea where this is from... It seems to hold idle well at 900 rpm, but while trying to start from standstill and i don't rev it real high (2000) it falls to 500 rpm, have to clutch it to not stall the engine... Also feels powerless under 1300 rpms when i finally get it started.

I'm feeling really upset right now... hope i can fix it, the car's great, would hate to have to sell it

 

first off, the drivers side part of the engine has a metallic knocking sound which the other half doesn't have. When at over 3500 rpms this sound can be heard from inside. The rockers maybe?

that's my guess...pull the valve covers and check the valve lash. could be a faulty lifter as well. check to make sure all your valve springs are in one piece.

Second thing, the car seems to be running unevenly, while holding 2000 rpms the car vibrates, feels shakey... No idea where this is from... It seems to hold idle well at 900 rpm, but while trying to start from standstill and i don't rev it real high (2000) it falls to 500 rpm, have to clutch it to not stall the engine... Also feels powerless under 1300 rpms when i finally get it started.

some more things to check would be the coil and coil wire. problems with those tend to show up at higher rpm due to its inability to provide sufficient spark.
it is also very possible that your opti is shot. VERY possible.
this could also be stemming from a possible valvetrain problem that you listed first.

it must be showing some SES lights...its obd2 so it has alot more perameters than earlier cars.

 

Checked engine compression at a shop, they only could reach the front 2 drivers side cylinders without too much hassle, i have 9.4 compression on them both (instead of 10.5 factory...). I think it's safe to assume they all should have same. Is this bad? Good? ... car has 50k miles but has been really badly maintained up to now...

Also seems at least one of my injectors is completely dead (if not completely then close).

About the valvetrain, got to check it...

 

It would be nice to know if you have modifications. How did you determine that one injector is completely dead? Since you changed the plugs, pull them out now and see if any look 'different'. That would tell you if an injector is bad. Is that compression reading in bar or atmospheres? Either way, it is around 136-138 psi. And, yes, you want all of the cylinders to be equal.

 

Car has no modifications, it's original SS. I determined one of the injectors is dead by removing their connection and listening to the engine. While the others made the engine make bad sounds, removing #4 had no effect

I'll try the "remove the plugs" technique but they are so hard to access it could be pretty expensive to make this test

 

You could also use a noid light to see if the injector is pulsing (and would be more accurate than pulling the wires off). What happens if the plug wire for that cylinder is completely deteriorated? If it already wasn't firing, taking away the fuel isn't going to make a difference.

 

I have just replaced the plugs and wires with brand new ones!... unless it's the distributor the spark isn't gonna be the problem.

 

Ok, to make it cheaper to check, swap the injector with cylinder 1 or 3's injector. Then, verify that the injector is not pulsing (I would still suggest a noid light) and check the one you moved to cyl. 4's spot for the same. If the one you moved to cyl 4 is not pulsing, it's in the wiring. If the one you moved to cyl 3 is not pulsing, then it's probably the injector. I'm not a fan of 'just pull the wire and see if it's running bad' when checking for a bad injector. Hell, you could pull the injector off of the car and hit it with a 12V battery source (car battery and ground, and I don't believe polarity is an issue here) and hear if it pulsing or not.

 

That sounds like a good advice! Will a 12V light bulb or LED work for the "noid light" you mentioned? I don't know what it is but i guess something like that should work

 

Yeah, something like that would work. That's all a noid light is, basically. This is just to make sure that the electrical signal is pulsing. If the injector is bad, you should be able to tell with the other test.

 

They pulled out the plugs of the injectors and measured them, they give 12V stable, but they didn't remove the injectors. Also, since yesterday after a run around town when it ran very well, when i left with it again it started banging...total loss of power, makes a helicopter sound...

 

Do you have any extra injectors that you could swap in and see if those are the culprits? Too bad you have stock manifolds and not long tubes. With long tubes, you could have all of the spark plugs out in 20 min. That would tell you for sure which cylinder(s) is misfiring.

 

I was thinking of installing long tubes when i get the car to work properly. Right now it seems stupid to spend money on performance parts when the car almost doesn't drive in the first place...

I found the problem which made the car run horribly the other day, an air tube running from the throttle body to the passenger side valve cover was pulled out. But after a few hours of running a lot better, it started banging again but this time not from that hose...

My concern right now is that i am not sure which of 3 possible factors are at fault here: injector wiring, injectors themselves, opti spark. This week i'm dumping the car in a service some friends recommended, hope they can find out what's wrong and fix it... the service i've been to up to now is not good at engine diagnostics...

 

Just got it back from service. Really feels like a whole other car now...problem was dirty injectors, one didn't work at all and 2 more were spraying really badly. Car feels and runs GREAT now.

BUT

As i cruised around town for a while, without even noticing, suddenly it feels like it's banging again! I try to floor it, feels like it's lacking power. Let it idle, it was banging... WTF!!!! I finally get home, turn it off for like 15 minutes till i ate and drank something, start it up and surprise...it's working well again... After a while it started banging again... after turning the engine off for like 2 minutes and starting again runs smooth again... WHAT THE HELL IS GOING ON?!?!?

Suggestions please. thanks...