I shouldn't be surprised. This car is starting to really get under my skin. It feels like it is missing, at idle it shakes and if i put my hand on the tb I can feel it not hitting on all 8 properly. It also does it at all rpms, I can just feel it not running 100%. When decelerating it will tend to bog down and idle low once stopped. I need more ideas on stuff to check that could cause this type of constant/all rpm miss. One other thing is my valvetrain seems noisier than normal as well but this miss has been a constant thing for the last year now. Please ask if I can provide more info.

 

you may have looked at this already, but have you checked the injectors?

how about a quik rundown on what you have checked, so i know where to start from.

 

The best thing to do is use an infrared thermometer and check the temperature at each manifold connection to the head. If you find a cool one, pull the plug and check for spark. With a new plug, try swapping a plug wire with another cylinder and see if the cylinder is firing. If you see it has spark and it still misses, you may want to check compression. Only thing left is gas and you could swap injectors.

If you are not running on all 8 but fuel is being supplied to the cylinders, you run the risk of damaging the cylinder wall. FIRST, check the oil for a gas smell.

Check the basic things also, fuel pressure, spark at each cylinder, compression or leak down.

 

The above idea about temp's at the header is a good way to track a miss... Easier if you dno't have a infra momitor.. is to use a water bottle.. spray each primary.. Most will burn off quickly.. then a few "might" take longer to do so.. I'd check for plug wire's.. and also make sure you didn't accidently mix up some wires down below on the opti.. its really easy to do so...

 

If you have a sudden change in valvetrain noise, you might want to look under the valve covers. Could be a busted spring or rocker. Otherwise check plug wires and plugs.

 

The gas does smell like oil and with the cutout open makes my eyes burn.

Fuel pressure is 39psi, it has been like this ever since i did the lt1 swap a year ago. I am running a racetronix fuel setup and that did not change the fuel pressure.

I will try to borrow a heat gun and or water bottle today, pull the plugs and do compression test.

Could the fuel pressure be causing miss like this?

 

If your smelling gas and burning your eyes.. its running fat.. get that bottle and see what happens..

 

Not likely. Considering you have a miss and your oil is contaminated, you have a dead cylinder. That is potentially devistating. The cause has to be found. At this point you know it's either spark or compression. When you look at the wires, check the socket in the opti as well as both ends of the wire. If need be, swap a wire from another cylinder that is firing good.

Change the oil right away and avoid running it long.

 

Well here is an update.

Compression test showed between 150 and 160 on all cylinders except #6, which was at 127. This was the one I suspected from the valvetrain noise. All the spark plugs looked good, like they were burning perfect, even #6. So I replaced plugs, checked wires, and replaced the 02 sensors. Runs the same. The heat gun is showing near constant temps on all cylinders as well. Now we are thinking it is mechanical.

Tomorrow I will be using some extra plug wires to check again to make sure it's getting spark and then I plan on pulling the valvecovers and check for bent pushrods, broken springs, etc.

Anything else I shold look into?

 

So all the the cylinders are firing if the temps are consistant. Granted the #6 is low, it's not the source of the problem. If it's firing, you can't feel it as a miss. I feel now that your wires or something ignition related is arcing causing the miss.

As far as your lower #6 a bent push rod will not usually cause that problem. You should do a leak down test on that cylinder and the 2 surrounding cylinders. You will more than likely find the exhaust valve on #6 is leaking either due to being burned or carbon holding it open.

 

Well, after doing the test where you add a little oil to the cylinder then do a compression test it seems the rings are bad. I added a catch can to the engine found a decent amount of oil in it after a short period of driving. Guess it's time to build a stroker, unfortunetly sooner than expected. Thanks for the help guys!