If your not familiar with my engine, I recently built it up this last spring and ever since I got it in the car i've had the damn thing running rough and its been missing. The car vibrates pretty badly at idle, the exhaust isn't hitting the frame or anything, its from the engine.

It gets progressively worse as the engine warms up and the rings havn't seated properly due to this. I pulled it out of the car about a week ago with the help of a friend and we fixed one problem which was the crank hitting the oil pan. That helped a little but the car still vibrates and hesistates when I give it gas and wants to fall on its face under load. Timing chain is okay, we replaced the entire opti and the wires, triple checked the opti being on right, triple checked the wiring order and checked again to see if there was a burnt wire, everything is negative.

There is sufficient spark and every wire is recieving spark. The plugs have some oil on them but I suspect its because the engine is still new and the rings have not properly seated due to this misfire (I believe its 2 cylinders). Injectors are good.. The valves are properly adjusted. The only thing I havn't done yet is mess with the O2 sensors, simply because it does this when its cold also, it only gets worse when it warms up. Its my understanding the car runs off pre-determined tables when in open loop and then it runs off the o2 sensor readings when its warmed up and reaches closed loop.

It feels like the car is getting too much fuel or something. Blue smoke comes out of the tail pipe and occasionally some black puffs (unburnt fuel) if I get on it and it hesitates. Could someone please give me a hand with this?

Its a 95 383 LT1 w/ a m6, running 11.5:1 CR, CC306 cam, 1.6 Roller tip rockers.

Thanks.

 

Also, it doesn't backfire out the intake or anything, not sure if it backfires out the back when it hesistates, if it does, its not a POP like the ones im used to. Like I said, its like its dumping too much fuel at times.

 

Did you see if all the primaries are hot? I would try a new set of wires.Just a thought.

 

Do you have an SES light on? Also, get a datamaster log goin and see if your having any knock retard or something....could be the issue....Also, just for giggles, how's your fuel system? Put a gauge on that shrader valve, tape the thing to ur window nd drive around, see what the psi is, should be around the low 40's.

 

Yea, I do need to test the fuel pressure regulator, the pump is a brand new walbro 255lph, that ain't the problem, nor is the fuel filter. Wires are not the problem... Any other possiblities?

 

Valve adjustment? Ya got Comp lifters?
Do a compression and leak down test and see if it has internal problems.

 

OEM lifters, brand new. Compression was normal.

 

Vacuum leak,fuel pressure to high,O2's,injector pulse width,leaking valves,leaking FPR. A leak down will tell ya about the valves.

 

Did you install your rings? If not, do you trust the person that did? I dont think your plugs should be oily even on a new motor. Put a new set of plugs in and see if it runs better. Is your opti used? You could try a new autozone one. They are way cheaper than GMs and have a lifetime warranty.

 

Are you sure your coolant temp sensor on the water pump is good? I've seen bad ones cause similar symptoms.

 

Good point...don't forget there are two....one in the driver side head and one up front below the Water pump.
http://shbox.com/1/temp_sensor2.jpg
http://shbox.com/1/temp_sensor1.jpg

If you can get data logged the temp on the car should read -40 if the front sensor is bad.

Edit: Pasky points out (further don't the thread) that the front sensor is the only one that effects the PCM... my bad forgot about that.

 

How's your vacuum?? Have your heads been milled, and was the intake milled to match?? Reason I ask is that if you're getting a leak between the heads/manifold that will cause you to burn oil (leaking in from lifter valley), have low vacuum and subsequent high fuel pressure, and stumble and surge.

 

My guess is that your rings are boogered. You apparently are burning oil. I would think that it would not take that long to seat rings if they are the right ones, in the right places. I would think that with that much CR that inproper rings that you are either going to get oil in the fuel or fuel in the oil, or both. JMHO

 

Just a heads up what you said about the fuel pump. Don't make the mistake of thinking that just because something is new its functioning properly or manufactured correctly. I've had more than one ocassion where a new part was the problem, never just dismiss anything because the one time you do that'll be it.

 

I thought this as well when we pulled it out of the car because there was some oil on the intake gasket where it squeezes together. I didn't torque the intake down in a circular order. That has since been remedied and thats not the problem. The side coolant temperature sensor on the head is only for the gauge cluster, the one on the front of the water pump is operating normal because it shows up on datamaster as thats the one the pcm gets its information from.

If the rings are "boogered" what needs to be done? Re-ringed? I ringed the pistons myself and triple checked each to check the gaps and used shoebox's site on placing the gaps. Only other thing I can think of is valve seals as far as the oil goes but I think their okay, not really sure how to test those. But that would be rather odd that every single valve seal is leaking.

Heads and intake were not milled, the block was decked however.