Bad stumble/hesitation on tip in

[ctgreddy]

Car in question is 03 cobra. 3.4 whipple crushed, e85, longtubes, gt500 maf, DW 95lb injectors, sct pro racer package, etc etc.

My issue is when accelerating from a stop I have to be very easy with the clutch and rev it just right otherwise the car will have a sort of dead spot. It will hesitate bad and sometimes jerk very bad. Drives me crazy and I can't figure it out. My old kb setup used to do it but now it's gotten way worse. only changes are the blower, changed from mammoth tb to crusher tb and the maf housing is larger. Any ideas what to try and change tune wise, or what to check on the car?

 

[Weather Man]

I have a 3V with 3.4 crusher and it took 2 tuners (Danny at DB Performance & LITO from MDS tuning) working together to solve it on my car, it was a very vexing issue, but it was solved with tuning.

 

[Weather Man]

I have a 3V with 3.4 crusher and it took 2 tuners (Danny at DB Performance & LITO from MDS tuning) working together to solve it on my car, it was a very vexing issue, but it was solved with tuning.

 

[ctgreddy]

Altho I'm sure my problem could be mechanical, I am fairly certain it's something in the tune that I just dont know how to fix. I'm a very amateur tuner.

 

[Weather Man]

Might pay to engage one of the reputable mustang shops in your area.

 

[SVTag]

The larger MAF housing could cause that stumbling at tip-in if it is not setup properly in the tune.

 

[ctgreddy]

The larger MAF housing could cause that stumbling at tip-in if it is not setup properly in the tune.

That's one thing I was thinking however dont really know how to change anything to make it better.

 

[cj428mach]

Might look at putting a screen on the MAF.

 

[ctgreddy]

I was considering that. Didn't know if it would help at all tho being the maf is right after the filter, i always heard the screen trick helped mainly when it was after a bend. But it is a cheap easy thing to try.

 

[cj428mach]

I was considering that. Didn't know if it would help at all tho being the maf is right after the filter, i always heard the screen trick helped mainly when it was after a bend. But it is a cheap easy thing to try.

I've read where Decipha of www.efidynotuning.com says he's seen where turbulence can be created when the throttle blades are opened. I respect what he says so I'd give it a try, like you've said its a cheap mod to try.

I have a screen on my JLT RAI between the maf and the air filter, I didn't think I'd need it but I figured it couldn't hurt.

 

[Philitup]

If you went from lets say 110mm maf housing to 123mm maf housing you absolutely have to update the tune for it or it will run improperly. Same as when a stock car goes from a factory airbox to a tuned required intake, need the updated tune for the bigger housing or it runs terribly

 

[SVTag]

That's one thing I was thinking however dont really know how to change anything to make it better.

You need to make adjustments to your MAF table. If you download the spreadsheet in the sticky post of this sub forum, it will give you an idea how the tables shift with different sized housings. It will probably be a trial and error thing for you to get it right.

I can tell you I am 99% sure that is your problem. I accidentally had MAF tables loaded for a jlt high boost intake (larger MAF housing) and the car stumbled really bad at tip-in. The car would buck horribly and feel like it was going to die. I had to let off the gas and ease into the throttle with the clutch to get past it. Once we figured out the wrong tables were loaded the problem was corrected.