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'97 F350 7.3L running bad.

1373 Views 5 Replies 4 Participants Last post by  Kimber1911
Need help. Truck started missing and smoking. Have put new injectors, uvch's, cps,icp,ipr. It will run but still missing and smoking and the check engine light and codes say icp high, and high to low on cylinders 1,2,&7. What is my next step in getting this truck running good again. Thanks.
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How many miles have you driven it since you had the oil rails open? It sounds like you still have air in the system.

After that, and absent any other ideas, I would be checking the high oil pressure. You need fittings to block the oil lines to the heads, and you'll need to be able to get the ICP sensor to read the right bank only.

From the repairs you've made, it would seem the problem would be in the HPOP itself. If testing shows the HPOP to be weak, I would clean the PRV and retest. Then I would shim the PRV spring and retest.

Before I made any expensive or difficult repairs, I'd verify my scanner pressure reading with a mechanical gauge. Note that I am the only person on this forum who would EVER distrust a scanner reading :)


Ha! I'll be d****d!

I re-read the original post and see where he stated his ICP was high. I was thinking duty cycle...

I've never heard of ICP being too high. And I can't see how that would cause a miss.

If the ICP is in-fact reading high, for sure I would verify it with a gauge before proceeding.
The ICP can be biased where it REPORTS a too high number which is false. The computer respond by lowering the IPR duty cycle but the value won't come down so it throws a code. It runs bad because the IC pressure is actually lower than required as the PCM has dropped the duty cycle.
Thanks, that makes perfect sense.

Is "biased" another word for "defective"? :smile2:

If the ICP sensor is defective, (in theory) the op could unplug the ICP and should have a smooth-running engine - at least up to the (rpm) limit that 750 psi will support. Is that correct?
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