Last July was getting hesitation with a p0172 and p0174. Looking at the vacuum lines and seemed to be good. Replaced O2 sensor and ran some cleaner on the next few tanks of gas and the problem went away. Now the problem is back, but with a rough idle. I have a 95 F150 5.0 dual tanks. The problem does not matter which tank I am using. I replaced the fuel filter about 2 years ago and about 30K miles. Over the weekend pulled code p0172 (KOEO). I have little mechanic knowledge and the Hanyes book is a joke for this model year. I am leaning to the MAF or fuel delivery... Any ideas?

 

Are there any audible exhaust leaks near the engine that you can't find?

 

Not that I have found earlier. Rough idle just started today. Will look into it.

 

Looked/listened this weekend there are no audible exhaust leaks. Could a bad gas cap affect the fuel system? I know on the newer models it can give you a CEL code. Can anyone let me know on how to test the MAF. I have a meter. Without a pressure gauge or a book, testing the gas pressure is not possible at this time.

 

Replaced gas cap and fuel filter and cleaned MAF. Still getting a 172 lean code. Does not have the rough idle, but still getting hestiation when the CEL appears after 10 plus miles of running.

 

Check that the EGR valve is operating properly and that it is fully closing, pull the vacuum line off it with the engine idling, the valve should be closed and not move(you can see the plunger through the openings in the body) and there should not be any vacuum present on the line. If there is vacuum on this line that points to a possible EVR failure. You can also apply full manifold vacuum to the valve with a piece of ruber tubing and watch for the valve to open and close smoothly.

 

The last few weeks, I have not gotten the CEL. The only thing I did was fill up the tank with Chevron vice the low budget gas station. So far so good. See how long it last.

 

And if there was a exhaust leak?

 

Then I guess I would still have an idle/accleration problem, which is not occurring. But I heard no noise from the engine area or visible areas of concern.