[PQ]

Originally Posted by HufferSS

My opinion is that you are not going to get anywhere until you get a scan tool on it and a smoke machine to find the leak assuming there is one.

You can chase Gremlins like this for a month and not find it.

Ok. I'll try and find a diagnostic shop. Mike, at Vengeance, had it all hooked up over the weekend. He is pretty thorough from what I hear. He assured me that everything is reading optimaly. Before I left Atlanta, I asked if they couls set it back to where it was before I got there or at least turn the idle up so it wouldn't die on me. Previously it wasn't. They said they would, but that it would be wrong. My car wasn't set right before. But probably to keep the car from dying. I can tell you there is noticeably less carbon funk on my exhaust tips since Vengeance tuned it.

So my decisions were to find leave the tune the same and find the problem, or set it back to a richer and wrong tuning to buy more time. I chose the first one. Car still drives great. Just will die at low idle in gear.

Originally Posted by n2oSS

really sounds like its missing a spark. This happened to me when i put my new wires on, one wire was just not all the way snug.

I have seen vacuum leaks cause cars to idle ruff but usually the idle will be so jerky that the car will die.

Another thing you can do if your thinking leak. There are mics that listen in small areas where you can follow your lines and listen for the hiss.

Vacuum leaks can be the lines or even the valley gasket.

Not gonna buy any more diagnostic tools. Except a cylinder temp gun. I want to check the cylinders as they idle to get the temp. It could tell me which one is misfiring if any. But the rest is gonna be left to a shop. I'll ask the shop if they have mics.

Originally Posted by Speedy1975

OK, plugs look fine, so I don't think there's problems with that.

I agree that a scan tool needs to get on the car and check out some parameters.

Hook the tool up and let the car idle.

Take a look at long term and short term fuel trims. If they're very positive that could indicate a vac leak somewhere.

Take a look at O2 sensors make sure they're enabled and reporting properly.

Take a look at the timing, specifically when the hesitation occurs. See if when the hesitation occurs you see a quick dip to negative timing.

Also take a look at the TPS setting when the hesitation occurs as well to see what it's doing.

Also, do you have a catch can on the car? If so, does it fill up with oil more quickly than normal? Double check the PCV valve make sure it's orientated properly. Had a friend put one in backwards once and have some weirdness.

I'd also do the smoke machine as well.

I'd also check with Jessika at Magnuson. She's a GREAT gal and loves to help. She's also very knowledgeable mechanically, and if she doesn't know she has resources to ask. They can point you to some common areas on the blower to check for this type of issue just to cover all the bases.

What type of scan tool are we talking about? Vengeance did that. Only thing he said was cylinder 8 was the only one that read a mis at all and that it wasn't hardly anything. Problem for me here in Mobile, AL is I can't find anyone who knows what they are doing as far as this stuff goes. They can hook it up, and look at it, but they don't know what to look for. And so if they see it, they don't know what to do. I've had 3 or 4 shops take a look now and none can figure it out. Everyone wants to run from the supercharged car.

Originally Posted by anthonyj9h

so i hate to be the barer of bad news but misfires happen because these reasons. plug which you have changed, coil pack, coil, or valves arnt opening and low compression, bad gas, or vac leak....i just recently had my lifters replaced and it went bad on me again because the lifter tray had wore down and the lifter had turned sideways and started beating down on the cam and wore it down and that made the cam bad....p0300 is multiple misfires not just one need to look deeper and its unfortunate....i dont know if we able to get it but gm has a new software call gme...check the injectors see if they are firing as well might want to take it to a dealer and see if they can find whats wrong

My dealer will change the oil and that's it. They won't do anytning else. Neither one. I've asked. I even explained to them that I understand there is no warranty, I just want them to do the work, and they still say no.

Originally Posted by Speedy1975

I don't think it's anything super serious, as the plugs tell the tale and they looked a OK to me.

Misfires are a problem if they occur with any regularity, but he's not reporting that as an issue any longer. That could have been (and likely was) occurring because the blower was blowing out the spark since it happened on a hard rev of the motor. Like I said on forced induction cars you wanna tighten the plug gap a hair.

I'll get started on the stuff I can try tomorrow night. Then Friday take it to a shop. Just been busy as hell. I got my catch can and breather in yesterday. I'm not sure if I should wait to install it, or do it now. The PCV thing you said is interesting. Maybe I'll just do the oil breather cap first.