Ive got a big extended van, and the engine "runs good" (always starts right up, doesnt sputter or anything). But when it gets up in the higher RPMs with a load, it seems weak. For instance, when in neutral it seems fine and when giving it some throttle it revs up and hits the rev limiter no problem. But when it's in Drive and you take off from a dead stop with the gas pedal to the floor, it can't get going fast enough to hit the rev limiter in 1st. It doesn't shift out of 1st until about 40mph (pretty normal as far as I know). But the engine stops accelerating the van at around 20mph (acceleration doesn"t stop completly, but it drops drastically). Same thing happens in 2nd... it doesn't shift out of 2nd until around 60mph, but stops accelerating around 40mph...

So when I take off fast and put the pedal to the floor, I have to let up a little around 20mph so it will shift and keep accelerating, and same thing around 40mph. After in 3rd it seems ok though.

I thought the plugs looked pretty bad so I replaced them but no change.. Same things with the cap/ rotor and the wires.... I checked the firing order too because I accidently swapped two plug wires (6 and 8) and it didn't seem to run any better or worse (at an idle).

So I don't know what to check or replace next...... Maybe the fuel filter?

Maybe I should check the compression on each cylinder? (especially 6 and 8)

Thanks for any help, Spenser

 

My next thought would be low compression due to worn rings or leaking valves. You'd more than likely have some sputtering or skipping if the fuel pressure is low. So yes, a compression test is next on the list of things to do.