Ok guys ive tried to search the forum for some of this stuff and didnt have too much luck. My 94 lt1 overheated due to the waterpump going out about a month ago. I got a new waterpump and decided to replace the opti while i was down there sense i was pretty sure it was bad. The car ran better than before but was still a little "off". It always jerked a little under load but now it was losing just a littlebit of coolant so i decided the head gasket was bad and i needed to rebuild the top of the engine. Ive never done any engine work besides boltons but im pretty good with my hands so i decided to go for it. I had an extra lt1 laying around so i got the heads reworked off of it and started the teardown on my car. Everything went really smoothly and i found that the lifter for the exhaust on cylinder 8 was dead, the roller wasnt round anymore. Again i took all the lifters off of my spare lt1 and swapped them into the car. After it was all back together it seemed to run great for ooo about a week and then i noticed i was leaking oil. After that i noticed it was smoking a little out of the tailpipes at high rpm. Not at startup though. Recently i went on a roadtrip and checked the oil right before i left. It was spot on. About 120 miles later it was off the bottom of the dipstick...couldnt see it at all. so...i filled it up with lucas and some 20-50 weight oil and drove it home. It didnt seem to go down very much if at all but is still smoking and dripping down the trans. I just dont even know where to start except get a new motor. So my problems are thus:


1. The engine hiccups (the tach will drop 200 rpms once or twice quickly at high rpm under WOT. Didnt do this until the rebuild)

2. Blueish smoke out the tailpipes (just started after rebuild, its never happened before)

3. The S.E.S light has been coming on intermittently for about 5 minutes at a time and then goes off. this has happened for about 3 months now. OBDI system...pain to scan

4. Oil leaking out of the external of the motor. cant figure out where its coming from but it eventually drips off the bottom of the transmission. seems like its coming from around the back passenger side. Rear main seal? again this didnt start until the rebuild.

5. The car diesels when you cut the key off about 30% of the time. This has been going on for about a year now...no idea why. Sometimes the speedometer jumps when u cut the key off also. maybe related?

6. After all this junk it probally isnt suprising that it seems to be lacking power...

P.S The only thing ive changed besides the heads and all related hardware in the last few months is that i got an lt4 knock module.

 

The SES light flashing is indicating a misfire. Did you check to make sure the cam was not damaged on the #8 cylinder with the bad roller? It could have worn off the lobe. Desieling can be caused by a couple things like carbon build up in the cylinders igniting fuel after cutting off the engine. Engine running hotter than normal. Might want to check injectors for sticking open and leaking fuel into cylinder.

Did you have the heads checked at a machine shop before doing the head gasket? Did you torque them properly during install and in right sequence? Is the oil you see leaking, coming from around the head or intake area or dripping out around the inspection plate of the tranny?

Have you double checked the plug wires to ensure you did not cross the wires and that the wires are pushed down good onto the plugs?

Also, you say coolant is leaking somewhere? Is it getting into the oil, leaking on the ground or leaking into one of your cylinders causing the miss fire?

 

The SES light isnt flashing, it stays on solid but only for a few minutes at a time.

I didnt pull the cam out but i squeezed my head in there and visually inspected it with a flashlight, it seemed fine except for a very micro scratch on one side.

When i had the heads off there was almost NO carbon buildup at all.

The engine is running nice and cool, actually cooler than operating temperature due to a hardwired fan and no thermostat.

The fuel injectors were spotless but not to say one isnt on its last leg. They have 300k miles on them.

Yes i had the heads checked, all new seals, they checked the spring strength, and also did a rock job on it.

Yes the heads were torqued correctly

I cant see where the oil is leaking out honestly...

All the wires are great, ive had that problem before, its quite distinct.

and finally, the coolant thing was when the head gasket was cracked and is no longer an issue.

Thanks for the help =) keep it coming!

 

How come you put on an LT4 knock sensor? You have a mis-match. The LT4 sensor would be for a 96 and newer (OBD-II) car. Your car is is OBD-I. The two sensors have a different impedance reading, and they need to be matched to the correct OBD system. I'd say your computer is now getting an inaccurate knock signal, or one that it can't make sense of. Try the correct knock sensor and see what happens.

 

Just to make sure im on the same page as everyone else. It's the knock module, a little chip in the pcm. Not the sensor itself. From what i understand, the factory lt1 module is very sensitive and Headers (or my headers smashing into my floorboard) is being picked up as knock and heavily retarding the timing. The lt4 knock module is just less sensitive. I wasnt able to hit the rev limiter and it bogged when the A/C was on before. The swap fixed that and the car runs 20x better.

 

have the injectors flow tested, the oil leak can only be a few things in that area. intake, oil pan valve cover or rear main. most common is the intake seal on the ends. what kind of opti did you put in? you need to have it scanned for codes.

 

Yeah, the way terms get thrown around here, it's sometimes cornfusing to tell just exactly what is being referred to. Never mind the above then!
But, back on the knock sensor, you do have the correct one in for your system?

 

yes the knock sensor itself is factory. i never touched it, nor do i even know where it is. I finally got under the car and looked around for the source of the oil. The driver side of the block is completely clean. The passenger side is oily from the number 6 cylinder back. I almost think its leaking out of the valve cover on the very back side...but i cant imagine the amount that's coming out is all originating from there.

I know im going to get chewed out for this...but due to a lack of funding at the time. Also, how do you flow test an injector? I've never heard of that before.

 

to have the injectors flow tested you take them out and send or take them to a injector place and have them cleaned and tested. i used a place called doctor injector. did you seal the opti and locktight the screws to the rotor. the msd opti is known for the rotor coming lose if you dont locktight the screws. when it overheated did the opti get wet? im gona say the oil is coming from the intake manifold seal on the rear. the valve cover gaskets are normally soft and seal quite well but if they get hot they will get hard and can leak then.

 

ok well i think the oil IS leaking out of the rear of the intake. It was clean when i re-assembled it and has wet oil around the seal now so...its a safe bet. The dieseling isnt bothering me all that much, but ill still look into it. My main concern is the bit of oil coming out of the tailpipes...and mostly the stumble. Can anyone comment on those?