No, Im not stuck in the mud lol. Ive had my service engine light on for a while.

I reset the computer, then as soon as the light came back on I had it tested. First code showing up is the dreaded P0174 and P0171. Lean bank 1 and 2. So I get under there, and find a bad vacuum hose and replace it. Passenger side PCV hose was bad. I also replaced the hose going from the manifold to the Canister Purge Valve Solenoid, although it looked to be ok, it was old and beginning to go, so I replaced it as well.

I reset the computer again, drove it for a while and light comes back on again. I havent got the code this time yet, however, originally it was showing 4 codes. Unfortunately I threw my notes away But the guy at autozone was kind enough to print out the parts that MAY need replacing due to the codes listed, which are:

Canister Vent Valve Solenoid
Canister Purge Valve Solenoid
EGR Valve
Mass Airflow Sensor

Now, I'm pretty sure that its not the MAF, although I did take it off and clean it. So I guess my question is would any one of these things cause the others to fail? I don't want to just start throwing parts at it, yet I don't really have the money to put it in the shop for diagnostics either.

ALSO, the truck does NOT have its OEM gas cap. It is an aftermarket cap I got at autozone. One thing I've noticed (and I'm not sure if it should be this way or not) is that when, after running the engine for a while, I take the cap off, it sucks air INTO the tank really strong. The suction is so strong that its kind of like putting the palm of your hand over a vacuum cleaner hose. When it sucks this air in, the truck acts as if its going to stall and die, then it picks back up and runs fine. Would a gas cap cause all the problems listed above???

The truck does not smoke, it does not have a "miss" in it, it starts and runs great! Other than the check engine light being on its perfect! But it wont pass the stupid emissions test with the engine light on.

Its a 1998 Ford F150 with a 4.6L EFI-SOHC (according to VIN)
All vacuum hoses under the hood are now good with no breaks or leaks.
PCV valves seem to work fine.
Clean air filter
Clean MAF

Any suggestions???

-Josh

 

Aftermarket gas caps usually are too loose for emissions tests, and you get a P0455 or P0442

You really need to get your codes run again before even thinking about throwing parts at it

 

Ok, I took your advice. I went to the dealer and got a gas cap made for my model truck. Then I rest the computer again, and drove it for about an hour, mostly around 40 mph, but I did go out on the interstate and got up to 65 mph for about 10 minutes. After using up an eighth of a tank of gas, the light came back on again. I then took it to Advanced Auto Parts and pulled the codes.

Looks like changing the vacuum lines and gas cap fixed all the codes but one, P0401.
So, does this mean I need to remove my intake and clean out the EGR flow tube in it?

Also, is there a way to check an EGR valve without having a hand pump???

Thanks for the help!

-Josh

 

EGR valves very rarely fail on their own

 

Thats what I thought... so looks like I'm taking off the manifold tomorrow huh?

 

No, you don't have to pull the manifold. The most common reason for that on a 4.6 is plugged EGR passages in the throttle body elbow. You only have to pull the throttle body and elbow to clean them out.

You can test the EGR valve with a piece of vacuum line, just suck on it with your mouth. The idle will get rough and possibly even stall. If it doesn't, the passages I mentioned are most likely clogged.

If my 16 year old grandson can do it, so can you.

 

Thanks for that info!!! After inspecting, you are correct. I took off the throttle body, cleaned out the passages to the EGR (wich were completely clogged up) reset the computer and drove it for about a week, then took it down for inspection and it passed.

The check engine light still has not come back on! Thanks for all you guys support!!!

 

Great!

I bet your gas mileage will increase at least 2 mpg now.