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Early '99 rough idle, no codes.

7K views 5 replies 4 participants last post by  RT 
#1 ·
Fresh oil change, fuel filter, and air filter change was done before digging deeper...

Checked ICP(oil in connector)
Replaced ICP with a Dorman from Oriellys(Ford parts manager said Dorman has come a long ways with their parts in the past few years)
Checked EBPS and tube(clogged)
Replaced both parts from Amazon
Checked IPR(seemed to be clean)
Rebuild kit installed after taking it apart and cleaning it.
Installed new CPS(Bourg Warner) it was a black one, have a new One from Ford but it’s grey.

Takes a sec to start but idles rough at low RPMs and sluggish(just drove it around the block.

I’ve read not to use the butt connectors that you crimp when splicing the new ICP pig tail. So I’m curious if this might be my problem. I have everything on standy in case I need to solder and heat shrink.
 
#2 ·
You could tell if the ICP sensor circuit is affecting anything by just pulling the harness while the truck is running - if it smooths out, there's a pretty good chance the problem is in the high-pressure oil circuit. I would also suggest a cylinder contribution test and maybe someday a compression test might lead to a cylinder that isn't pulling its weight. Might be something as simple as a misbehaving injector.



Or a bad ICP (dorman)


Most here recommend Motocraft only for this part.
 
#4 ·
I have a similar problem on my completely stock 2000 F350, but mine sometimes throws ICP code P1280 low oil pressure right after starting for a minute or so. I replaced the ICP with the Ford part and I replaced the IPR. My idle is rough most of the time and oil pressure is in the 600s.
 
#6 ·
Set it up to graph the IC pressure and the IPR duty cycle at the same time. Then compare the graph. The P1280 is pressure lower than expected. That would imply that the IPR duty cycle was high and the IC pressure wasn't responding appropriately. Could be torn injector o-rings or some other problem in the high pressure circuit.
 
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