Hesitation at low rpm 2010 GT500

XP900

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I seem to have a studder or stumble at around 1500 rpm. It's more noticeable in lower gear ranges and doesn't seem to be an issue at highway driving speeds in 5th and 6th gears. If I hit the pedal while in that range in a low gear the power is not instantaneous and seems to stumble for a split second before revving up - a symptom I don't notice at slightly higher rpms like 2K or above.

Even without a load on the engine I feel a slight miss or issue around that rpm range. Car mods are the VMP BAP along with the VMP Gen2R Budget kit which was the Gen2R with JLT 123mm CAI, VMP 67mm throttle body, and DeatschWerks 95lb (1000cc) fuel injectors. I also have the VMP triple pass HE, IR plugs, 2012 exhaust system installed and a few other options that should really be irrelevant. The plugs, MAF sensor and throttle body were swapped out and made no difference. Mechanically the only engine component replaced was the crankcase sensor a few years ago due to oil leakage.

I have a Cobalt vacuum / boost gauge installed and have the correct vacuum and boost readings at idle and max rpm with no unusual gauge readings when passing the 1500 mark. Tuner said he didn't notice any issues but he isn't driving it all the time. Of course there are no errors logging.

Any ideas or tips on the most likely issue? Tuning issue still? Swap injectors?? Injectors are clean and only have 5K - 10K on them. Fuel shouldn’t be an issue, 93 Shell used all the time.
 

1 Alibi 2

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" Tuner said he didn't notice any issues but he isn't driving it all the time. "
.
................Canned tune ??
 

Vinnie_B

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I seem to have a studder or stumble at around 1500 rpm. It's more noticeable in lower gear ranges and doesn't seem to be an issue at highway driving speeds in 5th and 6th gears. If I hit the pedal while in that range in a low gear the power is not instantaneous and seems to stumble for a split second before revving up - a symptom I don't notice at slightly higher rpms like 2K or above.

Even without a load on the engine I feel a slight miss or issue around that rpm range. Car mods are the VMP BAP along with the VMP Gen2R Budget kit which was the Gen2R with JLT 123mm CAI, VMP 67mm throttle body, and DeatschWerks 95lb (1000cc) fuel injectors. I also have the VMP triple pass HE, IR plugs, 2012 exhaust system installed and a few other options that should really be irrelevant. The plugs, MAF sensor and throttle body were swapped out and made no difference. Mechanically the only engine component replaced was the crankcase sensor a few years ago due to oil leakage.

I have a Cobalt vacuum / boost gauge installed and have the correct vacuum and boost readings at idle and max rpm with no unusual gauge readings when passing the 1500 mark. Tuner said he didn't notice any issues but he isn't driving it all the time. Of course there are no errors logging.

Any ideas or tips on the most likely issue? Tuning issue still? Swap injectors?? Injectors are clean and only have 5K - 10K on them. Fuel shouldn’t be an issue, 93 Shell used all the time
I suggest you start your troubleshooting in this order:

  • Check the following (PIDs)
    • DPFEGR (if equipped) (hot idle value within 0.15 volt of the ignition ON, engine OFF value)
    • LONGFT1/LONGFT2 (Rich/Lean conditions)
    • VPWR (value between 10.5 and 17.0 volts, and within 0.5 volt of battery voltage)
    • If VPWR not between 10.5 and 17.0 volts: Check charging system
      • If VPWR between 10.5 and 17.0 volts, but not within 0.5 volt of battery voltage:
      • CHECK the B+ voltage to the powertrain control module (PCM) power relay. CHECK the VPWR circuit between the PCM and the PCM power relay. CHECK the PWR GND circuits.
    • Secondary Ignition System (Wiring, Coils ect...)
    • Fuel Delivery System
    • Exhaust System
    • Positive Crankcase Ventilation (PCV) System
    • EVAP System
    • Charging System
    • Intake Air System
    • If you exhausted thru these options you might want to consider taking your car to the dealership and/or garage who has access to ford IDS to run some test on the above. Experienced tech will resolve your issue in 3 hours. Good luck!
 

tampasnake

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I had a very similar issue with my 2010. I was never able to figure it out. I replaced a lot of parts, had my tuner "data log it" I'm not sure he actually did anything but said he didn't see anything. It was most prominent when it was cold. When it was warm it was normally fine. After troubleshooting it for almost a year I threw in the towel on it.
 

XP900

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I suggest you start your troubleshooting in this order:

  • Check the following (PIDs)
    • DPFEGR (if equipped) (hot idle value within 0.15 volt of the ignition ON, engine OFF value)
    • LONGFT1/LONGFT2 (Rich/Lean conditions)
    • VPWR (value between 10.5 and 17.0 volts, and within 0.5 volt of battery voltage)
    • If VPWR not between 10.5 and 17.0 volts: Check charging system
      • If VPWR between 10.5 and 17.0 volts, but not within 0.5 volt of battery voltage:
      • CHECK the B+ voltage to the powertrain control module (PCM) power relay. CHECK the VPWR circuit between the PCM and the PCM power relay. CHECK the PWR GND circuits.
    • Secondary Ignition System (Wiring, Coils ect...)
    • Fuel Delivery System
    • Exhaust System
    • Positive Crankcase Ventilation (PCV) System
    • EVAP System
    • Charging System
    • Intake Air System
    • If you exhausted thru these options you might want to consider taking your car to the dealership and/or garage who has access to ford IDS to run some test on the above. Experienced tech will resolve your issue in 3 hours. Good luck!
Thanks,,, I think I am going to start looking at voltages to see anything is out of wack. I'm also thinking of putting in a Nations alternator for piece of mine since car is going on 12 years with 52K and I have more power draw than stock....2014 engine fan, VMP BAP and VMP HE using a larger pump. Always have the AC fan on too.
 

XP900

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Bad 02s maybe


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I actually bought a set of spares a while back just to have during my exhaust work. I may give that a try when I have car up.
 

Vinnie_B

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Thanks,,, I think I am going to start looking at voltages to see anything is out of wack. I'm also thinking of putting in a Nations alternator for piece of mine since car is going on 12 years with 52K and I have more power draw than stock....2014 engine fan, VMP BAP and VMP HE using a larger pump. Always have the AC fan on too.
I suggest you start your car and (*turn everything on) and put a clamp on ampmeter to check your total amp draw. Than get the correct alternator, cables and fuses to support your current electrical system.
 
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Catmonkey

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Ask your tuner if he changed any DBW settings. The car will run with that throttle body without any changes, but it will run a lot better with revised data for the 24% increase in throttle area. Those changes will benefit off idle and low throttle operation. If he didn't, he may not know how and you're probably better off finding a tuner that knows what they're doing for this type of change, because it can always be made worse.
 

XP900

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Thanks.... I may look for another tuner but probably next year now since the season is closing fast in NY as temps drop. I have a bigger issue now too to worry about.
 

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