Isuzu NPR High Idle

Don Owner/Technician Snohomish, Washington Posted   Latest   Edited  
Question
Heavy Duty
2011 Isuzu NPR-HD 5.2L (6 4HK1)
High Idle

NPR came in with 1800 rpm idle when in park or n. Goes to stock idle in gear. Had codes for regen too often and over boosting. Found turbocharger bypassing oil and wastegate frozen. Installed OE turbocharger and replaced map sensor (I broke the original taking it out to clean) No vacuum leaks detected. Codes causing to default after 2 block of driving. I cannot find the source of high idle. I think this will solve my code issue since turbo is spooling at a high rate at the 1800 rpm idle. Any suggestions?

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Michael Diagnostician
Champaign, Illinois
Michael Default
 

Can you do a log file of the truck while its happening and post it please? Can you show it as a excel file?

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Ricky Technician
Wilton, Connecticut
Ricky Default
 

Just because I have to ask, does it have the rotary idle/rpm control knob on the dash? If so have you checked it to make sure it is not turned up?

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George Owner/Technician
Skagway, Alaska
George Default
 

stranger things have been known to happen! I was called for a bus that wouldn't start last summer. I asked the driver if it was in Park or neutral. Driver got a little offended with me. Showed up. Put it into park and started it up. Walked away and called bus owner. he was't happy but paid the bill. So that is a very good question. I don't work on these very often so it's a good thing to know.

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Don Owner/Technician
Snohomish, Washington
Don Default
   

I could kick myself. I completely forgot about the idle knob until your response. Thank you, Now I can finish testing.

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Joe Owner/Technician
Gilbert, Arizona
Joe Default
 

I second Rickys suggestion. I had one on Monday that the driver would hit the knob with his knee and not bother to turn it down.

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George Owner/Technician
Skagway, Alaska
George Default
 

This is really good to know, I only work on these minimally but will remember this one.

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Albert Owner/Technician
Towanda, Pennsylvania
Albert Default
 

Is there A way to lock the knob in place so it doesn't get knocked out of spec?

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