I know there are millions of threads like this on here but I'm at a loss. My wife's 1998 Expedition is acting strange and has been. It has 212xxz miles, and been a great car. Now it pings when it warms up and I have replaced everything except ox sensors. Now here's where it gets wierd, if you just lay into it with a load, like going up a hill, it will ping really loud then stop. And it won't do it again till you kill it then restart. Now I've tried everything. Good fuel, tune up, gas additive all of it. I just found out about the little octane plug on it. I pulled it and no ping, but I think a Prius could out pull it. Any help would be greatly appreciated. Thanks Guys.

 

Does the pinging stop or lessen when you use high octane premium fuel?

You may want to go find a shop that can do a Motorvac or BG intake cleaning job on it, you may have excessive combustion chamber deposits.

 

I've sea foamed it twice. I doesn't really matter what grade of gas I run. I'm gonna fill it up with real gas when this tank runs out. But I've been running 89 octane. It just wierd that if you stomp it it will rattle real loud then quit and it runs great. I'm gonna get a snap on scanner from a friend and check all the sensors. And I have already pulled the upper intake to clean the carbon along with the egr valve. And I've replaced the egregious pressure sensor.

 

Seafoam? You sure you don't have cooked cats, and it's the cat guts that are rattling?

 

Well, like i said it runs fine, just pings. If you have stopped up cats, it wouldnt run like it does. No low effiency codes either. And yes, Seafoam. Its what we used at the Ford dealership when i worked there. Same sytem, just cheaper to use.

 

I'm not suggesting the cats are stopped up - I'm more suggesting they may be coming apart internally. With 212k anything is possible.

However, if it is spark knock I think capturing real time data may help, maybe the knock sensor isn't working or something like that.

 

Yea I'm thinking maybe the knock sensor may be malfunctioning. I reset the KAM last night and let it relearn the fuel trim and it got worse. I have a frien with a Snap On scanner. Im gonna run the pids on it and make sure every thing is working properly. I anybody knows of anything else it might be let me know.