View Full Version : Brand New 383 random missfires and eating plus

04-17-2012, 10:53 AM
So I bought a new 383 from texas speed and it was installed and tuned. Now it is running rich but the tuner (who is one of the best around I was told by my mechanic) thinks it might be oil in the intake because we checked the compression and all 8 cylinders are fine. I have had to replace the plugs twice. There is fuel on the plugs and in my oil. They did a leak seal check and found nothing as well So the engine itself I am told is perfectly fine. Today I am going to take out my intake and look to see if I can find any oil that may be causing this. Besides that we may think it is the o2 sensors which I bought from autozone I think they were bosch or a/c delco. So i may upgrade my o2 sensors as well to be safe. Besides these two things the mechanic and tuner cannot figure out why it is fouling plugs and is putting gas in the oil, tuner says its mechanical and mechanic keeps saying its the tune. But on the dyno he used a y band and it miss fired twice from what i remember. Not major missfires but enough for him to notice. I am not very car savvy I am trying to remember everything I have heard over the span of the last few months. If I need more info let me know i will ask right away. Thanks for the help!

04-17-2012, 12:25 PM
What kind of PCV set-up are you running? Do you have a catch can. If its sucking oil in through the PCV the catch can will help. Just make sure it's built with a baffle.

Check your o2 outputs and replace them if needed.

My car was eatting oil and gassing up the oil and my PCV was wacked out. If your running TFS heads make sure there is sealant on the rocker studs as they protrude into the runners on the cylinder heads.

Also I looked through your post, seems like you might want to look into finding a mechanic that knows LSX based cars and a good tuner.

Ask in the regional forums.

I don't like the fact that your mechanics could not tell you why your original motor failed, and now they can't decide between a tuning issue and a mechanical issue and are just pointing fingers.

04-17-2012, 01:24 PM
SLP lid into a swapped ls6 intake and throttle body. Buddy got a 102 so he gave me his stock 02 intake since my 2000 came with a ls1 intake thorttle body. And i run SLP headers to true duals.

04-17-2012, 07:06 PM
I say its in the tune what lbs injectors are you running, sounds like the fuel trims are off. find a good tuner that knows ls engines and have them look at the tune

04-17-2012, 07:53 PM
What about the PCV this sounds like what I had going on. Dirty oil with a stong gas odor.

Do you have a catch can? Sucking oil into the intake is a common problem on these engines with the stock PCV set-up.

04-17-2012, 08:35 PM
Took intake off there is a slight film of oil but no puddles. Also the pcv was dry and no i do not have a catch can but i am thinking of buying one. When i picked the car up todaythey said they replaced the wires because one or two seemed to be off. So i have iridium plugs in now and buying msds tomorrow and a catch can. So now i think im just going to run it and see if its the tune or if it was the bad wires since we did a compression teat i assume its not internal. If the plugs foul again and oil gets gas then we know its the tune

04-18-2012, 08:48 AM
As far as tune he is a very respected tuner and has over 12 years of experience he also tuned my car on the dyno with a y band and then on top of that we also tuned it on the street. The injector size shouldent matter since the tune controls the amount of fuel injected right? But my mechanic who is a carb guy wants to put the stock injectors back in and re tune it.

04-18-2012, 01:05 PM
Upload the tune file in the PCM and tuning section. Someone over there will see if something obvious jumps out at them