Odd situation

[FirstFord]

For about a month or so i've been getting a check engine light, the codes i've been getting are 336, 337, so i changed the EGR valve, still no change, ok i can live with it, but for the last 2 weeks whenever the check engine light has gone off, i have been getting alot of detonation, constant and varying with speed and load, but once the light is back on it runs like new. I have reset the computer also. Any ideas??

 

[MrShorty]

EGR codes on these engines are usually a bad DPFE sensor rather than the EGR valve itself.
1st question: Are they KOEO, KOER, or CM codes?
From there I would check out the DPFE sensor/circuit.

 

[FirstFord]

im not sure about the codes they were done at a shop, i think the were hard faults tho, and i think the dpfe was also replaced., This was all done at a shop.

 

[MrShorty]

In that case, the next thing I would do is pull the codes again and see what codes are coming up now. It's entirely possible that the EGR codes are still there, or maybe something else, but it would be a good idea to see what codes are coming up now. See tests at www.dalidesign.com/hbook/eectest.html if you want to pull the codes yourself.