Hello,

I have a '94 E250 with a 4.9L 6 that has a problem. After the engine warms up it knocks under hard acceleration (not while it is still cold). I wanted to retard the timing a little, but my manual says that the timing is controlled by the computer and can't be adjusted. It runs smooth enough under normal load, except that it randomly stumbles (briefly) while the throttle is held steady. I tried premium gas, and it reduced the degree of knocking, but it didn't stop the problem. It could be caused by a dozen different malfunctions. Any thoughts on the most likely culprit (or culprits)?

Tom C

 

You might try posting this on the Forum for your year of vehicle. This Forum deals mostly with the I6 engines.

 

tgcapizzi,

Welcome to the forum!

I have no experience with the later model 4.9L, but recently investigated a similar problem involving a 1984 4.9L which although it has a carburetor and distributor, is computer controlled [timing & carburetor]. It, too, pinged easily after warming up. I did retard the timing [can be done with spout disconnected] and it slightly helped, but performance and gas mileage suffered. The MAP sensor was bad and was replaced. The timing was reset to factory specifications and the truck ran like new!