I few days ago I noticed my engine was knocking a little bit and still does, its a 5.4 with 121000 miles on it and it still runs like a champ. Yestarday the service engine soon light came on so I took it to my mechanic and he hooked it up in the computer and it was saying that both banks the fuel was too lean. He told me to put better gas and an octance booster that it would help alot. Well he cleared the problem and its been a day and it hasnt came on, but the engine still knocking a little you really have to listen to it is not that loud. What do you guys think is causing this knocking sound, should I use better gas or what?? Thanks in advance.
<!-- / message -->

 

...Welcome to Ford Truck Enthusiasts!


..See you on the boards.

 

Could be gas, try that first and see what happens. Could also be a vacuum leak. Given that both sides are lean, check the hoses around the intake and plenum for cracks or holes.

 

"Lean on both banks" is not a fuel or additive issue.

Most commonly, it is a vacuum leak. The PCV hose elbows are the most common causes, especially the one at the firewall where it connects to the intake.

Steve

 

Ok thanks for the replies, what about the knocking is it like a ping. What could be causing this thanks alot.

 

I had a similar problem with 98 4.6 Expy. Pinging or knocking sound under accelaration, a few months later check engine light came on. It was caused by a manifold exhaust leaking.

 

Im going to check for a vacuum leak then. Where should I start behind the intake those hoses back there???

 

Guys i was looking today and i couldnt find the damn pcv elbow i saw one behind the intake manifold but it has wires through it can you tell me exactly where it is im new to expeditions thanks alot.

 

PCV is on the passenger side valve cover. Basically you want to follow the hoses the come out of the intake area and see if any have cracks or holes or fitting pulled loose.

 

Ok thanks alot will check it out and also how do you take out the MAF sensor i wanna clean that out while im at it. I sprayed some contact cleaner through the intake where is at but didnt take it out.

 

I had this same problem on my '98. Last week I cleaned the MAF sensor with break cleaning spray and this solved the problem. The sensor is just past the air cleaner and there are 2 small coils that had a lot of carbon buildup on them.

 

I did clean my MAF sensor with some electric cleaner, I sprayed the living hell out of it but the pinging still there, now does that mean I need a new MAF sensor hope not because they run about $150.

 

Did it clean the coils off and make them shiney? I'm not sure electrical cleaner will work as I tried that first. You may also need to change the fuel filter.