Most common "No code" idle issues
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Senior User
Joined: Feb 2017
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From: Shreveport, LA
Most common "No code" idle issues
In your experience, what issues have you seen that caused intermittent rough running at idle, but did not throw a code. I have monitored (with numerous scanners/gauges) this 6.0, but cannot get a code or see any of the sensors out of spec.
At Hot idle:
IPR: 24.2
ICP: 640
ICV: 0.90
MAP: 14.7
MAF Volts: 1.5
EOT/ECT Deltas within 10 and Avg ECT=192, EOT=199
EGR Valve cleaned and EGR demanded = EGR Measured
Vehicle will run rough after long runs or towing.
Cylinder Balance test showed all injectors on.
What could be the cause?
At Hot idle:
IPR: 24.2
ICP: 640
ICV: 0.90
MAP: 14.7
MAF Volts: 1.5
EOT/ECT Deltas within 10 and Avg ECT=192, EOT=199
EGR Valve cleaned and EGR demanded = EGR Measured
Vehicle will run rough after long runs or towing.
Cylinder Balance test showed all injectors on.
What could be the cause?
Laughing Gas
Joined: Feb 2016
Posts: 817
Likes: 27
YMMV.
Truck developed a surge at idle, maybe 150 rpm, most prevalent after long highway drive. Had about 4K on MC15W40. Changed oil as it was due, problem went away.
Fast forward a year, get intermittent ICP code. Truck never ran bad but only. Ran it about 10 miles before changing out sensor.
Probably could be lots of things but I think I may have had an ICP act up a bit. Who knows for sure, but I'd keep an eye on it.
Truck developed a surge at idle, maybe 150 rpm, most prevalent after long highway drive. Had about 4K on MC15W40. Changed oil as it was due, problem went away.
Fast forward a year, get intermittent ICP code. Truck never ran bad but only. Ran it about 10 miles before changing out sensor.
Probably could be lots of things but I think I may have had an ICP act up a bit. Who knows for sure, but I'd keep an eye on it.
Thread Starter
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Senior User
Joined: Feb 2017
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From: Shreveport, LA
maybe 5 psi. Pretty much lives at 642 when at hot idle. Any chance this is an inferred number instead of measured?
Thread Starter
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Senior User
Joined: Feb 2017
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From: Shreveport, LA
YMMV.
Truck developed a surge at idle, maybe 150 rpm, most prevalent after long highway drive. Had about 4K on MC15W40. Changed oil as it was due, problem went away.
Fast forward a year, get intermittent ICP code. Truck never ran bad but only. Ran it about 10 miles before changing out sensor.
Probably could be lots of things but I think I may have had an ICP act up a bit. Who knows for sure, but I'd keep an eye on it.
Truck developed a surge at idle, maybe 150 rpm, most prevalent after long highway drive. Had about 4K on MC15W40. Changed oil as it was due, problem went away.
Fast forward a year, get intermittent ICP code. Truck never ran bad but only. Ran it about 10 miles before changing out sensor.
Probably could be lots of things but I think I may have had an ICP act up a bit. Who knows for sure, but I'd keep an eye on it.
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Fleet Owner
Joined: Nov 2003
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Running rough at idle is definitely something that CAN BE caused by an ICP sensor, but it could be other things as well.
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Senior User
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From: Shreveport, LA
Thanks Bismic. I watched ICV and ICP on the way home. Based on some data I found, the two seemed to move together correctly.
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From: Shreveport, LA
Here's the data points I referenced. My volts were a little low (0.1-0.3v) compared to these numbers
Press Press Sensor
(PSI) (MPA) Voltage
0 0 .02v
200 1.5 .4v
400 3 0.73v
600 4 .96v
800 5.5 1.2v
1000 7 1.4v
1200 8 1.6v
1400 9.7 1.9v
1600 11 2.1v
1800 12.4 2.3v
2000 13.8 2.6v
2200 15.2 2.8v
2400 16.5 3v
2600 18 3.3v
2800 19.3 3.5v
3000 20.6 3.8v
Press Press Sensor
(PSI) (MPA) Voltage
0 0 .02v
200 1.5 .4v
400 3 0.73v
600 4 .96v
800 5.5 1.2v
1000 7 1.4v
1200 8 1.6v
1400 9.7 1.9v
1600 11 2.1v
1800 12.4 2.3v
2000 13.8 2.6v
2200 15.2 2.8v
2400 16.5 3v
2600 18 3.3v
2800 19.3 3.5v
3000 20.6 3.8v
Thread Starter
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Senior User
Joined: Feb 2017
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From: Shreveport, LA
I still fear you are right. But having tested the injectors and all checking out fine, what else can I do other than wait for the injector to bomb... most likely when I am 200 miles from home pulling the travel trailer.
Is servicing the injectors (rings/seals) a next logical step? Should I pour in some snake oil, I mean Archoil?
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Senior User
Joined: Feb 2017
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From: Shreveport, LA
I think I remember seeing a tiny bit of oil on that connector when I replaced the oil cooler 4 months ago. I will investigate.
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Senior User
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From: Shreveport, LA
I figured out the intermittent idle issue! Friday coming home from work, the engine was idling rough as I exited the interstate... but this time the scangauge was able to register misfires on cylinder 5. No codes, but I do have the misfire count programmed for each cylinder on the SG2. I checked the wiring harness and it looked like the coolant hose to the heater core was putting pressure on the harness above the injector. When I used a pry bar to lift the hose, the rough idle immediately disappeared. Let the hose back down and the rough idle returned.
So I chopped 3 inches off the hose so that it sits next to, not on top of, the wiring harness and no issues do far.
So I chopped 3 inches off the hose so that it sits next to, not on top of, the wiring harness and no issues do far.