My 93 F150 in-line 300 six experiences momentary lag, or hesitation, while accelerating.

Does anybody have ideas, or knowledge of what may cause such?

Aside from this lag, the engine runs very smooth and well....has good acceleration!

Any ideas why?.............S

 

Easy to change the plugs, wires, cap, rotor, fuel filter, and run a bottle of injector cleaner. 10 to one that fixes the stumble and gets it runnin in top shape.

Adrianspeeder

 

my suggestion - change the airfilter or make sure there is no blockage. in my old 88 f 150 i had a piece of something actually get sucked in the intake (cardboard it looked like) and it was blocking the air intake, and giving me hesitation on acceleration. removed the blockage and replaced the filter, truck never ran better!

 

Your engine (and mine ) are notorious for having problems with the injectors getting dirty. The two most common symptoms of dirty injectors are an off the line stumble, like when the light turns green, and a slight stumble or miss when cruising in 4th gear at around 35-40 mph, barely touching the gas.

The easiest and cheapest way to determine if your injectors are dirty is to let one of your tanks get almost empty, and then add two large bottles of injector cleaner, and about 3 or 4 gallons of gas. Drive around on that tank for 30 minutes or so, and then park the truck overnight. The following day, take it for a test drive, and if you notice an improvement, your injectors need attention.

More often than not, doing the procedure exactly the way I described will clean out the injectors sufficiently, and they won't require any further work, but not always. In any case, it's an inexpensive way to find out, and it might save you a lot of time and money trying to figure it out. Besides, with a 4.9L engine, it's never a bad idea to try and clean the injectors.

Take care,
~Chris

 

This is common. Assuming that all other items mentioned are corrected and the lag still exist, the problem is with the EGR design. The ports and rate of opening with the initial throttle are too great causing a momentary "lean" condition. Purchase a piece of stainless steel (14 - 18 gauge) and build a restrictor plate inbetween the EGR & the manifold (yes insert an extra gasket). Your port sizes should be about 3/8" diameter, but I would suggest starting off with 1/4" ports and increase by trial. You will find the right spot and it will still pass smog.

 

This is true, although you might want to disconnect and plug the vacuum line going to the EGR valve first, and see if it makes any difference, before you go to the trouble of building a restrictor plate. If you notice a marked improvement, then follow this gentleman's instructions to the T, and your problem will be solved.