iddle surg+/-50 rpm and stalls w/ coolent >70f
03-20-2019, 12:28 PM
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iddle surg+/-50 rpm and stalls w/ coolent >70f
I'm working on a 2005 Freightliner mt-45 Medium Duty truck 5.9ISB,EGR Allison (not a Dodge yes it is a 5.9 EGR) 377k Mi
everything works perfect, except the idle surges +/- 50 rpm (750-850) similar to a lopey cam on a gasser bump the throttle +50 to full and all is smooth . The drivers would be fine with this surg as an idiosyncrasy of the uint, but the motor will stall when the coolant temp is less than 70f stalling only lasts 3-5 start/stall cycles before coolant reaches 70f and runs fine (with surg )making troubleshooting difficult as TX is a fair weather state.
when cold:
surg is as low as 300 rpm 3000 rail psi and high side is 850 w/ 6500 psi, command and actual rail psi are bouncing all over the place in time with the surg
commanded Vs measured fuel rail psi code pops when the rpm/ psi drops too far it locks out the throttle pedal stop engine light and motor stops surging but putters at 300-350 rpm ~2500-3000 psi rail (temp dependent). under 2500 psi will stall motor if it does not stall you can leave it in this puttering mode till coolant reaches 70f restart the motor and all is well( still surging). you can also fire it up hit the throttle and hold a high idle ~1200 rpm till the Coolant reaches 70f to keep it from popping a code
Warm
idle surge as described above +/-50 rail pressure all over the place stays below 10,000 psi
troubleshooting done
disconnect pressure sensor on back of IP psi spile and steddy 28k = psi control solenoid pass
homemade( none on market as light duty 5.9 has none) EGR delete temporarily installed to rule out a faulty valve (parts only not computer this set the expected 3 egr related codes) valve is not causing the surge. = egr pass
has new LP w/ 35-50 psi verried by the computer ( 50-200%duty cycle).
last night
I turned up the idle speed from 800 to 850 with a Cando Pro II followed the prompts . This solved the surge rocksteady +/-10 rpm rocksteady rail pressure but then the idle resets on restart = fail
I tried 825 rpm surge still present but minimized
.
.
other than giving the local Cummins shop $500 to set the idle to 850 rpm what are my options?
what is the root cause ? I'd rather fix the problem than put a bandaid on by turning up the idle.
Dream Big Chisel Down To Reality
everything works perfect, except the idle surges +/- 50 rpm (750-850) similar to a lopey cam on a gasser bump the throttle +50 to full and all is smooth . The drivers would be fine with this surg as an idiosyncrasy of the uint, but the motor will stall when the coolant temp is less than 70f stalling only lasts 3-5 start/stall cycles before coolant reaches 70f and runs fine (with surg )making troubleshooting difficult as TX is a fair weather state.
when cold:
surg is as low as 300 rpm 3000 rail psi and high side is 850 w/ 6500 psi, command and actual rail psi are bouncing all over the place in time with the surg
commanded Vs measured fuel rail psi code pops when the rpm/ psi drops too far it locks out the throttle pedal stop engine light and motor stops surging but putters at 300-350 rpm ~2500-3000 psi rail (temp dependent). under 2500 psi will stall motor if it does not stall you can leave it in this puttering mode till coolant reaches 70f restart the motor and all is well( still surging). you can also fire it up hit the throttle and hold a high idle ~1200 rpm till the Coolant reaches 70f to keep it from popping a code
Warm
idle surge as described above +/-50 rail pressure all over the place stays below 10,000 psi
troubleshooting done
disconnect pressure sensor on back of IP psi spile and steddy 28k = psi control solenoid pass
homemade( none on market as light duty 5.9 has none) EGR delete temporarily installed to rule out a faulty valve (parts only not computer this set the expected 3 egr related codes) valve is not causing the surge. = egr pass
has new LP w/ 35-50 psi verried by the computer ( 50-200%duty cycle).
last night
I turned up the idle speed from 800 to 850 with a Cando Pro II followed the prompts . This solved the surge rocksteady +/-10 rpm rocksteady rail pressure but then the idle resets on restart = fail
I tried 825 rpm surge still present but minimized
.
.
other than giving the local Cummins shop $500 to set the idle to 850 rpm what are my options?
what is the root cause ? I'd rather fix the problem than put a bandaid on by turning up the idle.
Dream Big Chisel Down To Reality
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