Check engine light

[schusdad]

just recently I changed all the timing components on my 98 explorer (4.0 sohc).everything seems to be working fine except I have a check engine light on. I pulled the codes and they are p0171, p0174 and p1506. When the engine is cold the idle is rough. I am pretty sure all the vacuum lines are attached.any suggestions where to look.

 

[jremington59]

A lot of times it will show 171 and 174 at the same time. Try cleaning your MAF sensor and see if that clears them. The 1506is an idle issue. Try cleaning the idle air control valve and see if it helps.

 

[schusdad]

I finally found the problem...when I was reassembling the engine I had the egr tube unbolted from the egr valve. Upon reassembly I missed one of the holes on the egr gasket and the gasket rotated downwards creating a nice little vacuum leak. I put the gasket in right, cleared the codes and no more check engine light...oh and it idles sooo much better when cold.

 

[jremington59]

Glad you found the problem. One of the causes for the codes is a vac leak downstream of the MAF sensor.