Hesitation at low RPMs

hunters2019

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New VMP tune based on following mods. 2.3 SVT Super Charge kit/68mm pulley, Stock 3in Idler pulley, Cobra Jet Dual 65mm Throttle Body, VMP 56lb injectors, Nations 270x alternator, Kenny Bell Dual Boost a Pump, Brisk GR12S plugs/gap 28. JLT 123mm CAI, M-6312-SVT harmonic balancer, AFCO PRO dual heat exchanger w/fan, Shelby heat exchange surge tank, 170 dg thermostat, Ford Racing 3.73 Gears, 2014 carbon fiber 1 piece driveshaft, Borla tour exhaust, MGW 2 shifter, Mcloud RXT clutch, Eibach Pro suspension w/ sway bars, BMR Lower/Upper Control arms, Maximum Motorsports Caster/Camber, FAYS 2 Watts, Nations 270 alt. When doing mild pulls 2/3 gear there is a definite hesitation or better put non-linear throttle response 2,000 thru 4,000 RPM. I suspect possible vacuum leak, maybe MAS, or plug gap/coil problem. I've driven the car gingerly since new tune install and have gone through three separate tank fills of different brand 93 octane fuel. Will of course call VMP for guidance, if I cant narrow potential mechanical issue. Idle is good
 

hunters2019

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Funny you asked. Yes to the laptop, reading about data logging but not comfortable about what I know at this time. Hunting locally for possible mentor. have the SCTx4, and a Ngauge (not installed yet). Work gets in the way too. I will attempt some form of data logging soon. That said a buddy said just get the car dyno tuned. Would that be a possible solution? Car is 07, and that would require additional 02 sensor down stream to get proper AFI info, correct?
 

Catmonkey

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Open a ticket with VMP and describe the issue. I don't see anything in your description that would make me think this can't be resolved via e-mail. You know your car was likely built in 2006, so maintenance items like O2 sensors, MAF sensors, etc. are going to start giving older cars issues. See if you can detect any codes with your programming tool. That can sometimes provide valuable clues to what's going on.
 

merkyworks

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See you live in Florida, heat can really affect what timing the ECU will throw at the car. If the ECU is pulling timing on the initial WOT and then slowly adding it back this would give a non-linear throttle response. You could easily verify this by data logging and seeing what IAT2 and timing is.

Getting with a tuner is never a bad option and will likely get this issue resolved.
 

Mojo88

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Sounds like a tune issue to me...... however.......

One thing I would do first is thoroughly clean the MAF (using appropriate cleaner). My MAF seems to require cleaning every year, and it takes 10 or 15 good sprays to get it working again.

And why not double check EVERYTHING else first just to make sure. Confirm no vacuum hoses disconnected. Air filter assembly clean and tight? All connectors securely fastened? Have you run any fuel injector cleaner recently??
 

hunters2019

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will do. injectors new, plugs new gapped at 28 per VMP, 123 JLT new. Plan on just taking a look at all new parts hopefully this weekend coming up. I've had two prior tunes with VMP and was not disappointed with their product. Perhaps the plugs are not right. Brisk GR12y? Its just a few hours to check it all out. Thanks for you advice.
 

RedVenom48

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What year is your Shelby? What flash tuner are you using?

Make a data log of your car with your handheld tuner:

Send to VMP and let them review. Data doesnt lie. The ECU is making decisions on the same data you're logging if something weird is going on, it should be in the data. If you have a 2011+ GT500, you may have false knock cutting your ignition timing.

If youre 07-09, no knock sensors.
 

hunters2019

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Made a list and started to address any issues. MAF was first, cleaned and then drove to see if that was the problem. Indeed it was and all is good. Thanks for the advise
 

hunters2019

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After having a remote tune put on car I later found that there was a bad coil (that unto itself never threw any codes, used volt meter to check the coils after they were replaced) . Now all ignition parts are replaced and the car runs great. Thanks to BJ
 

VNMOUS1

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After having a remote tune put on car I later found that there was a bad coil (that unto itself never threw any codes, used volt meter to check the coils after they were replaced) . Now all ignition parts are replaced and the car runs great. Thanks to BJ
Glad you're loving that car again!
@venomoustuning

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