help needed car misfiring/breaking up in 3rd

Ok guys I am new to the whole forum thing so please bare with me. I have an 08 vert GT with a 5 speed. Mods include ford racing CAI, Comp cams mutha thumpr cams, comp cams phaser limiters, MAC offroad pro chamber mid pipe with Pypes pipe bomb axle backs. Tuned by bama and currently working with Lito on a tune. The issue I am having is that the car does fine when doing a dig pull until about 3rd gear. In 3rd, at WOT, the car starts to bust up/misfire at about 80mph. It does not do it in 1st or 2nd but once in 3rd, is when it starts and will do it all the way through 3rd and into 4th. It will not do it in 3rd when it is not at WOT until it you get to about 80 and go WOT. I hope this all makes sense. The plugs have recently been changed and the fuel filter is fine. I have tried data logging with bama about 4 or 5 times with no luck. So I sent Lito a request and did a base tune with him last night and the car is doing the same thing. (I am getting a config file today to start data logging with Lito to see if he can see it in the log) Thanks in advance for your help guys.

wait for lito.

have you tried to short shift 2nd to 4th and see if it happens at 80?


what RPM is it happening at? and to clarify, no other gear at that same RPM does it happen?

Yeah I am waiting now to see if Lito can see it in the logs and let me know what is causing it. I have no doubt he will get it right for me or let me know what to change that is causing the issue if it isn't in the tune somewhere.

I have not tried to short shift it into 4th. I will try that this afternoon and let you guys know what it does. It seems to be around 3500 to 4k when it starts and when it does, it happens the rest of the way through 3rd and into 4th no matter what the rpms are. First and second gear, it will not happen no matter what the RPM's are.

Have you discussed plug gap with Lito? How old are the coil boots?
Do you already have a wideband installed?

I haven't discussed that with Lito yet. I just started tuning with him last night and have the base tune done. I now have the config file so that I can start logging and sending it to him. I have no doubt he will get it right for me. I assume the coil boots are the original ones. I have not changed them. I do not have a wideband. I think that will be my next thing to get so that he can see what all is going on with that.

My wild guess is there is a fueling issue and if it's bad enough it would show up on the wideband and/or the fuel pump duty cycle. But you are in good hands with Lito.

Thanks yall for the input on it. I will update as soon as I know more.

update is that Lito can not see any fueling or firing issues showing up in the log. He is working on something else for me to try this evening. I will post results later.

UPDATE:

I had recently installed a new set of plugs in the car when I changed out the cams less than a year ago. I went back with the motorcraft Platinum plugs. I decided the other day to just change them out again to see what happens. I go to the local auto parts store and tell them I want to see every brand they carry of the old style plug for the car. I may get blasted for this but the E3 plug was the only one that had the "shank style" plug that was one piece. I do not care for this brand at all but thought heck why not, it can't hurt to try right? I told them to give me a set of those. I installed them that night and the problem is gone. The old plugs didn't look too bad but obviously that was the problem. Thanks guys for all of your input on this and hopefully it will help someone else out in the future.

I have issues with my car from time to time. The car will break up at certain boost levels. Say 14psi will be good but when I go up to 18psi it will break up like you are describing. A lot of times in my case its spark.....I just hate chasing it down.