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1994 k2500 suburban 350,000 and a 1995 k1500 200,000
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Discussion Starter #1
This problem is a little hard to describe. So to start I guess this is a 1995 K1500 6.5 egr deleted w/ chip.
Heres the rub. After the truck gets above 2000 rpms while driving. If you let off the gas pedal the rpms drop below 1900.
If you hit the gas again it jumps back to whatever rpms it was at. its almost like a dead spot but its only when you let off. The truck accelerates smoothly tho. I'm lost on this one. Any help would be greatly appreciated.
 

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Does it do the same thing if you are in a lower gear? How about if you first put your foot very lightly on the brake? Not enough to slow down just to hit the electrical switches which among other things should unlock the torque converter.
 

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Welcome to DieselPlace

Start by going through all grounds
 

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Registered
1994 k2500 suburban 350,000 and a 1995 k1500 200,000
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4 Posts
Discussion Starter #4
Its been doing this since I bought the truck back in october. Unfortunely it blew a head gasket a month ago. i put 2 new heads on when it happened cuz of a couple cracked valves. I pulled the motor all the way out to look over the lower end and check for cracks in the block . All was good. When I put it all back together I cleaned all the grounds and connections as i went. I havn't felt it in lower gears. I'll check tho by leaving in 3rd and getting it above 2000 rpms. I'll also see about touching the brake to unlock the torque converter in 4th. This one has me scratching my head.
 

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Its been doing this since I bought the truck back in october. Unfortunely it blew a head gasket a month ago. i put 2 new heads on when it happened cuz of a couple cracked valves. I pulled the motor all the way out to look over the lower end and check for cracks in the block . All was good. When I put it all back together I cleaned all the grounds and connections as i went. I havn't felt it in lower gears. I'll check tho by leaving in 3rd and getting it above 2000 rpms. I'll also see about touching the brake to unlock the torque converter in 4th. This one has me scratching my head.
Checked for any codes?
 

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1994 k2500 suburban 350,000 and a 1995 k1500 200,000
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Discussion Starter #6
The only codes I've had are egr and map codes before I installed the chip. After install there was an app code and a pmd resister calibration code. I put a new app sensor on today but did not fix the issue.
 

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Premium Member
1995 Chevrolet Silverado Z71 6.5 TD
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324 Posts
If you go to FAQs and look up 1995
Driveability, Emissions (Diesel) & Electrical Diagnosis Manual
Section 3 3-5 this explains how the three potentiometers work and talk to PCM and the optical sensor.

See what you can gleam from that.
 

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1995 GMC Suburban
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17,986 Posts
If it has EGR, have you cleaned the Intake?
From what I have read, they can get clogged with soot/carbon and caused issues.
It requires you to take it off.

The EGR may not be the cause but it may contribute to it.
 

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Premium Member
1995 Chevrolet Silverado Z71 6.5 TD
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324 Posts
EGR was deleted with a CHIP.
The only codes I've had are egr and map codes before I installed the chip. After install there was an app code and a pmd resister calibration code. I put a new app sensor on today but did not fix the issue.
EGR was deleted with a CHIP.
What DTC code pointed to replacing the Accelerator Pedal Position
Did you take dare of the PMD resistor code calibration. I'm fairly new but haven't heard or seen a DTC code for resistor calibration. Maybe you don't have a resistor or since chipping the PCM the value was erased for the pmd resistor.
 

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1994 k2500 suburban 350,000 and a 1995 k1500 200,000
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Discussion Starter #10
EGR was deleted with a CHIP.

EGR was deleted with a CHIP.
What DTC code pointed to replacing the Accelerator Pedal Position
Did you take dare of the PMD resistor code calibration. I'm fairly new but haven't heard or seen a DTC code for resistor calibration. Maybe you don't have a resistor or since chipping the PCM the value was erased for the pmd resistor.
Sorry I was looking at the wrong DTC code chart.
It was dtc 99 voltage reference code
 

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Premium Member
1995 Chevrolet Silverado Z71 6.5 TD
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324 Posts
DTC 99 - Accelerator Pedal Position 2 (5 Volt Reference Fault)
That voltage I believe originates on the PCM Pin BO2
You can measure that voltage on the APP pin G
 

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