To start off, my car has full bolt ons, TRex cam, and a 12 bolt with 4.30's, and Ford 30lb injectors. I was running a worn out pair of Nittos, they dont hook very good any more, but I was just going to see what kinds of trap speeds I could get. The car has a basic tune and it idles and drives good. I went to the track 2 weeks ago and only trapped about 116mph. I figured the car was running really rich, plus I was running a bit low on coolant so the engine temps were above normal, so I wasnt to worried. Last night I went to the track again, with the same tune but the coolant thing was fixed and temps were good. The only other thing I changed was my shift light was bumped up to 7000 rpms and I sealed my FTRA to the air lid. During my first pass the car felt like it was running smoothly, but at the end of the track as I put the car in neutral and started getting on the brakes the car shut off. I had to get pushed off the track. The car wouldnt start. I had to pump the gas a little bit to get it started, but it didnt want to idle so I had to keep feathering the gas to keep it from clonking out. That pass I only trapped 113. I took it back to the pits and looked for any problems. I didnt find anything. Every time I went to start the car it would barely idle and I had to give it a little throttle just to keep it running. Once it was running a while it seemed to idle fine. I left the track and drove around a while and it felt like it was running good, so I went back to the track and made another pass. This time the car felt like it was ruuning smooth but down on power, and sure enough it only trapped 112. I dont know what the problem could be. My guesses are that the stock pump could be shot, or filter. Or maybe a vacume leak some where. Every time I start the car it wants to clonk out until I give it a little throttle. Does anybody have any guesses what could be wrong. Sorry about the length.

 

personally you shouldnt of did what you did, you should of let it in gear and not neutral. you could of confused the computer slightly

 

has the car been fully tuned on the dyno?

 

What does your basic tune consist of? What A/F ratio are you running? What was the density altitude when you made your passes?

If it seems to run well in most conditions, I would look deeper into the tune. If you are having all around driveability problems, you will need to be more specific with them.

As for "confusing the computer" how do you figure? Not saying it's right or wrong, just wondering if you can elaborate.

 

It's a M6, totally irrelevant to "confuse the computer."

 

I have been doing it that way for a long time without any problems. Ive heard that its not good for the motor to keep it in gear at the end of the track to help slow it down with the rpms that high for so long. Plus I reflashed my tune before the second pass and it still runs crappy.

 

the tune is just a custom tune from rwtd for the predator based on my moddifications, I have yet to send them the readings they asked for to tweak the tune if needed, but I havent put it on the dyno yet, I think I am going to make an appointment for a few pulls on the dyno just to see what A/F im at. The car drives great overall especially for a big cam. Just not making the power. It idled fine before this incident.

 

TRex is a big cam, and I'm not certain that a handheld tune will address all the driveability problems that go with it. You would be best off to get a custom tune by someone who can check the IAC functions and the throttle cracker to get the car to act like it should. That could have a lot to do with your stalling problems.

Good Luck!

 

you need a dyno tune for a cam like that.

if the car won't start easily, check fuel issues, and spark. also double check all of your sensors that might affect that stuff.

 

How many miles are on your valvesprings?

 

This may sound stupid - but I was having similar issues. It turned out to be that the battery cable had worked its way loose. The car barely would idle - had to keep it running by feathering the throttle. Also, it would not start every once and a while. You might want to check it just to be sure.

I am sure it is probably in the tune as others have suggested though!

 

Thanks for all the help guys. I will check the battery terminals when I get home. That would be funny if it was that. I realize the most obvious thing wrong would be the tune, but I have been driving the car now for about 3 weeks on this setup and the car drove and idled great. I had friends ride in my car that have big cam LS1's and they were blown away at how well my car idled and drove. It seems strange that the tune would just go out of wack after a 1/4 mile pass. I was thinking that maybe I had a vacume leak somewhere or a bad fuel pump. I am going to check these things out tonight and hopefully I figure something out. Any other suggestions are extremely helpfull. Thanks again.