I've had an M-Tune installed on my 951 track car (K27/8) for about 12 months running E85 and have had no issues (other than idle) for most of that time. In the last 3 months, the car has started cutting out/hesitating when I hit the throttle and just getting into boost. At 2-3 PSI it will hesitate for a couple of seconds, then continue boosting to 18 PSI with no issues. On the track, this hesitation is border line dangerous, so any help would be appreciated.

Here's what I have replaced: vacuum lines, fuel pump, coil, plugs, DME, cylinder head, TPS, BOV and fuel regulator, with no luck.

Thanks...

 

Contact Joshua at Rogue Tuning in regards to the M-Tune itself. There's no one else who knows more about it than he.

 

Double-check the line to the MAP sensor... if the DME thinks you are getting a bad MAP reading, it will trigger an error, causing the hesitation.

 

I get a hesitation at the transition to boost when my cap/rotor are past it, although certainly not 2-3 seconds worth. How fresh are they on your car?

 

Josh,

I've double check all my soldered connections with a volt meter and they look good. Do you think it could be the map sensor?

 

I think Josh was referring to the vacuum line that runs to the MAP sensor.

 

MAP pressure line is a t-connection off my fuel regulator and looks good with no leaks.

 

Is the FPR holding vacuum too?

 

Did the problem show up and stay consistent starting 3 months ago, or did it progressively get worse? What injectors are you running?

On a car running stock management, I have seen a bad KLR cause a hesitation like you describe. It was traced back to a bad solder joint. I see that you have a replacement DME, did you try swapping the KLR as well? Since I have no knowledge about the M-Tune, I can't comment if on how the KLR might affect it but perhaps Joshua can chime in on that.

 

Problem has always been there, but has gotten worse since I switched to E85 and started running higher boost. I am running the injectors that came with the M-Tune. KLR was swapped with DME, so that's not the issue. I've swapped out all the vacuum lines, but have not smoke tested the system yet. I will try to smoke test tomorrow to see if I have any vacuum leaks.

Thanks....

 

We use the KLR in its normal fashion... So a KLR issue could be a problem.

Double-check for vacuum boost leaks, and let me know.

 

never mind read the first post

 

Josh,

Just smoke tested the vacuum system and could not find any leaks. Thanks for shipping out a new chip for my issue. Looking forward to trying it on the track this weekend.

 

Moisture in fuel would cause hesitation.

E85 has a way of freeing fuel varnish that builds up in the tank over the years, as well as accumulating moisture if it sits in the tank too long without being run. Boats don't like it. Drain and flush tank and start fresh if yours sat for a while.

You changed the pump and FPR, and <the filter> too right? Not explicitly listed...

 

Fuel filter is new and fuel in tank is 2 weeks old. The hesitation occurs every time at the start of boost, never before and never at boost > 3 PSI. It seems too consistent to be fuel related. Thanks for the input.