See last post for latest update/problem.




Ok listed below is a thread from the External section and since I now believe it to be a internal problem I will post up all the relevant posts from the other thread.
I am really clueless why this problem is so bad.
Basically all I did was swap intakes, take the car on the road, miss a 3-4 shift @5500+ RPMs and now I have a completely dead cylinder. You should find all the necessary info in the posts below.
Sorry for the novel and all help is greatly appreciated!


Post # 1
I did the LS6 intake swap last weekend and installed the new coolant lines but reused the LS1 intake gaskets. Now I am throwing a P0304 code and my car is not even firing on the 4th cylinder. I changed the spark plugs and wires out for new ones. TR55's went in.
That didn't help it.
I swapped coil packs from cylinder # 4 to # 2 and the missfire stayed in cylinder # 4.
I want to say that it's a vacuum leak but everyone that I've talked to seems to think that it is more of an electrical/spark problem than vauucm.
The car wants to shake really bad around 1400 rpm and there is a definite power decrease. I have searched everywhere on the forum to see if someone else has had a similar problem. No luck.

Post # 2
The injector is plugged into the harness. I haven't put a volt meter on the coil pack yet or the wires.
I've tried spraying starter fluid around the intake to see if there was a leak and the engine didn't act any differently but I can't get under the intake all that well with the spray.
I'm really starting to wonder if I didn't break a pushrod?

Post # 3

I tried the injector pulse test and yes it is still pulsing. I am really starting to think that I did not seat the intake correctly and that I need to take it off and put it back on.
Unless you guys have some other ideas I'll let you know how that works out.

Post # 4
Ok, I don't have a vacuum leak on the intake. I swapped out the injector and the problem stayed there. I put in new pushrods (the old ones on cylinder 4 were slightly bent, you couldn't tell until you rolled them) and the problem stayed.
We did a compression check on the cylinder and the highest it got was 5. Yes I typed the # 5.
So I am thinking bent valve? Or a cracked piston or ring? Anyone have these problems before?
I still need answers. ANyone got a clue or advice?

 

I'm no expert ... but you sound like one of those manual driver horror stories you hear about...

you didn't happen to do a I went into 2nd gear from the top of 3rd kind of mis-shift???

It's possible to mechanically overrev, have a piston kiss a valve and be the end of it. If you have bent pushrods, then there's a high chance you did that and you've got no choice but to pull the heads...

 

Pull the head, you either severely bent a valve or broke the piston. Could be both. Hook up an air hose to the cylinder like you are going to change the springs and you should hear air form the intake, exhaust, pressurize the crankcase or all of the above.

 

a smoked ring wouldn't read that low unless there was a huge ******* hole in the thing...there may be a hole in the piston but you DEFINATLY would have noticed that...i'm going to go with a bent valve, it explains the loss of compression but you may also consider checking your oil for flakes and fuel as these would indicate a more of a piston/ring problem

 

Bent valves in that cylinder or a hole in the piston

 

Where did the intake come from? I put an intake on my car that I pulled off of a wreck and a piece of plastic that was hiding inside of it lodged one of my valves open. I pulled the head to see where the miss was coming from and found a large chunk of plastic sitting on top of the piston. The valve did hit the piston but luckily didn't bend. So I just buttoned everything back up and it ran like a champ.

You need to pull your head and see what's going on. Hope you find something simple like I did. Good luck.

 

I got the intake from a friend of mine. Yes, I am really starting to think that I am at the least going to need new heads. I was offered a set of 98 heads for free, but why replace stock for stock when I will still have to pay $800 for the labor anyway? I was told that it would be fine to drive around easy until I was able to pull the heads adn really find out what the probelm is. I really wish it was something as simple as a piece of plastic like Jimmy says, but I used an air compresser on the intake before I installed it and blew air through all of the runners.
Damn this'll ruin a Friday!

 

IT IS NOT O.K. TO RUN THE CAR!!!! If you bent that valve, the valve is weak. The valve face can brake off, lodge itself in the head and punch a hole in the piston causing everything else to be junk. Don't start it, don't turn it over, just pull the head.

 

Whoever told you to drive it must have an engine up for sale.

 

amen to that, PLEASE dont drive that car unless you plan on a complete rebuild

 

Well the car will be parked and only driven to get me home and then to swap the heads. I have a guy willing to give me a stock set of 98 heads as long as I give him the bad one. Great guy! I just hopet that the write up on LS1howto is suficient enought to get the job done.
Has anyone done a head swap themselves without pulling the motor? If so how long did it take you to do it right? I was thinking it will take it all weekend.
Let me know!

 

OK, I put another set of heads on the car. Turns out the problm was indeed a bent intake valve. It looked like it got in a fight with a hammer. Piston had a slight half moon shaped gouge in it but not too severe. I upgraded the bolts to ARP's. The swap took about 2 days to complete. 4 hours to get the heads off and 4 to get everything back on and about 8 to clean everything the way I wanted it.
However, I am still throwing a P0300 random misfire code. Is this a spark plug or bad O2 sensor? The car doesn't like low RPM's in the higher gears and seems to buck and surge randomly while driving.
Advice needed again