I recently reassembled 98 LS1 Z28 after teardown, cleaning and inspection of heads, and lifters. I cranked the car last night, and it sounded and ran horrible. It sounded like it was missing, and was running rough. I pulled injectors today and cleaned them. Cranked car and ran a little better, but still idles rough and sounds like a miss all over the place. I have 28# injectors, and NGK TR6 plugs, don't know if either could be the issue. Any ideas?

 

Are there any modifications to the engine? I would check the connections on all your sensors first and foremost, and make sure they are all plugged in good. Another thing to look for would be a vacuum leak, like from the little tiny vacuum hose that goes to the MAP sensor on the back of the manifold. If it is off, that alone would cause it to run rough. Also, check your ground wires. There should be one on the block on the drivers side, and another one on the back of the drivers side head.

 

I have checked all the wires, and even broke out the Haynes book for the diagrams on the injectors and coils, and they are all correct. I know the ground wires are hooked up because I had to have my wife put the bolts in and I went right behind her and tightened them down. The engine is bone stock. The exhaust however is Pacesetter LT's, gutted Pypes cats, rear O2's deleted, x-pipe, and Dynomax bullets. I haven't looked for the vacuum line on the MAP, so I will do that right now.

 

The mods you have posted would not cause it to run rough. This is going to sound stupid, but are all of your plug wires on tight too? They should make a "click" when they seat on the coil.

Is the only thing you removed the intake and heads or was this a complete disassemble?

Did you reuse all the sensors or has anything been replaced?

 

I just checked all the hoses and they are all ok. After I put the plug wires on I always pull back slightly just to make sure not lose or too tight. I replaced the knock sensors, and the coolant temp sensor that controls the gauge. I also installed brand new NGK TR6 plugs gapped to .040. I just ran the car for @ 2 minutes and got 2 codes, 307, and 332. I removed the # 7 injector wire while idling and there was no change, so that sounds like a bad connection somewhere. The low output on the knock sensor is now a mystery to me unless the injector not feeding fuel into the cylinder has something to do with it.

 

I'd start with checking for spark on #7 and if you have it check the compression.

Re'

 

Agreed. Pull the fuel pump fuse, pull the plug, and plug it into the wire and bump the engine a few times. See what that does, and get back to us. Not that it would make any real difference, but the recommended plug for a somewhat stock LS1 is a TR55 gapped at .035.

Actually... take a look at the plug too. How does it look? Black? Wet? Brown?

 

And I'd almost bet money that you missed a ground wire on the back of the driver side head. We did that once and had simular symptoms. There are 3 ground wires that bolt to the back of the DS head and we missed just one of them. Car ran like crap when it would run at all. Throwing all sorts of codes. When we hooked up that one ground wire everything went back to normal.

TR55 gapped at .050-.055 is what people normally run in stockish LS1s.

 

the ground wires are all on the driver side head. there are 2 that were hooked to the same bolt and then 1 on another bolt. They are all hooked up and tightened like crazy, so that is not it. I did notice the plug wire on the #7 cylinder was not catually hooked to the coil, so I fixed. Made no difference. I have voltage to all cylinders, and have spark, yet still rough idle.

 

Did you hook the brake booster vacuum hose back up?

 

What about the vacuum hoses for the PCV valve? There is one on the throttle body, and one on the intake behind the TB on the pass side.

 

all hoses and wires have been checked, double checked, and checked at least another half dozen times. I have voltage at injectors, spark at plugs, and yet still rough. next step is compression test.

 

Dead cylinder caused by(drum roll please).....rings. I am screwed glued and tattooed! Cannot afford to repair, and do not want to work on this piece of junk anymore. If I didn't still owe $5000 on it I would sell it on eBay to the highest bidder just to get rid of it.

 

I don't understand... Why did you teardown the whole top end of the motor? Did you actually do a compression test or did you just say what the hell and disassemble everything? I sure hope you did not fail to do a compression test, remove and reassemble everything, THEN do the compression test

 

I guess I'm just as atupid as they come. I had my vehicle at several shops, and even had a few of my "trusty" technicians drive it and listen, yet had no testing actually done. Every last one of them said bad lifter, so off came the heads. Lesson learned the hard way. I cannot afford to rebuild the engine, nor do I, after all this, want to try.