Hi, I recently took my truck to a mechanic shop because the check engine light was on and I needed to get my truck inspected. The light went off after the one sensor was changed and the others were good. The light came back on a day later and even with the light off it said no flow but gave no code like before and it would have failed the test to get inspected. Do anyone know what could cause that because I am at a lost and my inspection goes out tonight. Please help a Ford truck enthusiast who wants to keep his truck running great.

 

Not knowing what the exact code rec'd was, one of the causes for no flow could be the DPFE sensor or even maybe a blocked EGR passage. Better to know exactly what you are after before throwing money at replacing good parts.

 

Was there a DTC listed on the service/repair doc. What year F150 and engine?

 

I was told I have alot of carbon build up under the intake maifold and that may be the culprit. It's a 1999 4.6L Romeo

 

Ah, the old PFE system. If this is the old system where all the EGR is crammed at the back of the engine, then take off the throttle body and adaptor and clean up all the carbon underneath the adaptor in the EGR ports. Possibly add a new PFE sensor if you haven't, and that solves about 95% of the EGR problems.

 

Well after the carbon was clean out and everything put back together, the light went out but only to come back on after I picked it up. I was told I needed to get a sensor for it and as I drove the truck for the weekend the light went off and I went and had it inspected and it passed and not even a week later the light is back on.....Can someone please help me because I have spent way too much money on this problem but I love my truck.

 

1999 f150 4.6 Romeo