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Low ICP when Hot

1K views 7 replies 3 participants last post by  NYC F-350 
#1 ·
Not sure where to go with this problem anymore. The truck runs after starting wither its a cold start or hot start but will not always start when warm. I have recently replaced the IPR, Oil Cooler, FICM, and did an EGR delete. When the engine is cold it will fire right up and makes great power. ICP actual and ICP desired are within a couple psi of each other through all RPM ranges but when hot the ICP actual is only about 320 psi and slowly builds while cranking but never enough to start. I have run out of ideas and don't want to keep throwing any more money into it. There are no misses found in a contribution test when running warm and the truck doesn't have standpipes or dummy plugs. Any advice will be appreciated
 
#2 ·
I went up and ran the truck today. Previously had a misfire on cylinder 3 when doing a contribution test but now 3 is running fine and the miss has moved to cylinders 4 and 6 when first started. the truck ran with very little power on a street tune and still had a slight miss on the stock tune. When restarted again the miss completely disappeared. With engine warmed up the EOT was 180*F, ICP actual and desired were identical at 612 psi and the IPR duty cycle was at 24% at idle. We commanded the IPR to 45% closed and were getting 1500psi actual ICP at idle. The HPO system is strong just as predicted and we are ruling out a HPO leak also
 
#4 ·
FICM has 0 to do with HPO psi...but could be contributing to the "miss"

Typically when someone has just got done with an oil cooler swap, and was not as clean as they should have, they start having problems like this.
First check is easy (and unrelated to the above), and that is to check the pigtail on the ICP sensor. You do not state whether or not it is on the passenger side valve cover or on the HPOP cover...but anyway, the typical ICP problem with the pigtail is that when the ICP sensor fails, sometimes oil makes its way up into the pigtail. That will add resistance and skew the readings that the PCM receives. If that is the case, replace the ICP sensor and the pigtail back far enough into the harness to be sure that there is zeroo oil present.
Next, remove the IPR valve from the HPOP cover. Check that the screen is still attached to the IPR, the screen is intact, and that the screen is clean. When cleaning the reservoir under the oil cleaner, if you left anything in there and it got under that screen, it got sucked up by the HPOP and was shot right into the face of the IPR.
If you still have problems with the truck running properly when hot, you will have to air-test the HPO system.
 
#8 ·
Not nearly enough background info to nail that down. How long ago did he finish this oil cooler replacement? Did he immediately get those codes? Those could be that he still had air in the hpo system. Could be a bad FICM harness, the plugs aren't fully seated, what you said...etc etc
 
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