A vacuum leak caused misfires on mine.

 

^^^When i had my lsj All my vacuum hoses were dry cracking and one was leaking and then the second time I experienced a misfire issue, I had mad carbon build up, Just a thought/Idea to help you diagnose.

 

Man, I've checked for so many possibilities for vacuum leaks I was checking my own a$$ for one!!

But for an update, I am doing a full valvetrain overhaul! I can post pics if you guys want. But I've got a question, I'm limited to just Amazon at the moment for valve springs, all I can find are the Supertech ones. I've read somewhere that peeps were having problems with them, any thoughts? And if they're good, does the head have to be machined for them?? Heard something about clearance issues...

 

Why are you just changing the valves?

Start with a compression check. If you have valve sealing issues it will show up on a compression test.

 

Well good sir because it's like this. Before I supercharged the car, I was getting misfires. This was a replacement engine I installed because the last one I had skipped a tooth and valves smacked the pistons. So since I've had this engine, I've had misfires. Believe me, I've done everything to try and correct the issue except removing the head and checking the valves. Now, yes a compression check would've been ok, but a leak down would've been better. And more or less joe, at this point it had to be it. I went through the entire process of elimination. Multiple times even...

Point is, I'm rolling the dice here. It isn't ***** nilly as it sounds. I've been at this misfire thing for months. It's gotta be it. Everyone is saying its ZZP, but like I just mentioned, it was doing it before I had the supercharger in. AND lastly, if you're wondering why did I put the S/C in if I had misfires, well the kit came with new injectors, I tried everything else prior to that so my only thing was at that point an injector problem (or obviously a leaky valve). So I put it all together and bam, misfires. I've got the head disassembled, valves are coming in today, going to lap them, and put it all back together again. Any helpful suggestions are welcome. I will definitely update everyone if the misfire problem is cured.

 

Did you check the old ones for even sealing before removing them?

I recently had to replace a couple LSJ valves due to a timing mishap that bent them, I was able to see light around the valves on the worst ones, even though they didn't look bent, they were when tested with a flashlight.

Just nice to confirm that you're actually fixing the problem while you're in there.

 

Yikes! Were the valve guides still good after that?

I am waiting on a valve spring compressor. Bought one and it was HUGE! So i sent that back. Then got a cheap-o "OEM" brand valve spring compressor for $20 bucks. It sucks! So im waiting on one to come in from amazon and hopefully it will do the job. In the meantime im going to test to see if in fact were leaky valves... apparently there is someone on youtube who uses some soapy water and a air compressor see if anything is leaking past. Just waiting...

 

Yeah the engine didn't run with the bent valves so there's no reason the guides would take damage. It happened on the initial startup, and it got torn right back down, 4 valves replaced, and put back together. Runs great now.

I have the actual Kent-Moore ecotec valve spring tools which I used, works awesome. I found, on my Tercel with the tiny valves, I had to order a motorcycle spring compressor tool to fit into the head. That would have also worked on the cobalt head I believe, but I didn't have to use it since I had the right tool.

 

Alright, got it back together and up and running. Absolutely no misfires! Which is great then it was definitely something to do with the valves or valvetrain. BUT now this....

Getting a P0016 and a P0171. The P0171 not too worried about, I think the exhaust manifold gasket is just bad. But the P0016... I made sure to set the cam shafts to the 3 o'clock on the intake, 10 o'clock on exhaust and the notch at TDC with the dot at roughly the 5 o'clock position on the crank.

It is running horrible. Normal acceleration it starts to buck like as if the clutch is giving. (Clutch is brand new and ZZP stage 1). It's a bit more than that but hard to explain. If I ease the gas then it will do fine and I can gradually get up to speed. Thoughts???