Where to start? Ficm rebuilt by swamps. Blue spring upgrade. Egr delete. Rebuilt turbo. New oil cooler. New ipr valve. 2 new icp sensors. New altenator. Newer batteries. Voltage checks out. New stc fitting. 114,000 miles. Done more, can't remember. Wouldn't start before, thus 2nd icp sensor. Started and ran good with second. 300 miles later started surging bad. 100-1000 surges. And -100 to dying. Rocked the truck for sure. When it hit operating temp ran fine. Shut off for 1 second to 5 minutes, ran like absolute crap, surging 100-1000 for about 15 seconds and then good. Unplugged sensor and and poof, doesn't matter. Runs perfect. Hard question. What do I look for? Just the sensor? Can that really be it?!plug back in and right back to surging. Don't mind working on it, but we're talking about all but ficm in last 6 months. It's pushing me. Not a mechanic by any stretch, but mechanical.

 

Are you using a Ford ICP or one from a parts store? I have heard a lot of bad things about the parts store units. check out the wiring harness for nicks or chaffing, also make sure the ground is hooked up on the back intake bolt on drivers side behind the FICM, if that is left off or broken then stupid stuff can happen.

 

I would get a new plug and replace the old one and see if the problem goes away. If you have replaced 2 icp sensors and the problem goes away when you unplug it I would say its the plug it's self. Did you go to Ford for the ICP sensor or is it a cheap one?

 

But it is from a parts store. Ford was going to have to order it. Paid 10$ more at part store for it. It took an 1/8 larger wrench I believe than factory. Still have factory. Replaced cause I read I should. Everything but ficm and icp has a ford number. I'll check that ground. But I think I know what your talking about when I took intake off for delete/ oil cooler. And I took lots of pictures for putting back together. Deleted them, but had them to make sure I put back together right. Will put ford one back in and see what happens. Btw, plug nor old one had any oil seepage like I've read. But it did code. And I'll be going to part store unhappy.