engine stumbles accelerating at higher speeds?

[skate1968]

The engine stumbles and/or sputters at higher speeds. The acceleration is nice and smooth from zero to 40. But somewhere after 50mph it gets bad. It doesn't make any bad noises but the acceleration feels very choppy -- jerky -- almost as if the accelerator pedal is rapidly being depressed on and off.

Does anyone know what's causing this?

Is the timing off? Might some oil be leaking past the spark plug/O rings?

Background:

I have a 91 1.5 dpfi, 210k miles, worn rings w/ a good amount of blowby, i'm just riding this engine till it dies. A trusted mechanic told me there's too much rust on the body to merit an engine swap.

At the moment, I'm due for an oil change. But i'm first going to the yard and getting a new oil pan as it's needed.

thanks for reading

 

[Steve S]

Auto trans or a manual?

 

[Jim 5]

I had what I thought was some missing at high RPM's and heavy load (transmission kick-down to pass, throttle wide open on highway).

Someone recommended fuel injector cleaner and it actually solved the problem. I'm not really sure if you are having the same symptoms. Mine was just a roughness and loss of power at high load.

 

[tom slick]

How old are the spark plugs and fuel filter?

 

[Jim 5]

Good point,

I'd check the fuel filter first.

 

[mechtech2]

If it is good to 40, do you mean that in low gears there is no problem when revving up through them? No one starts in high gear.
Right now it sounds like a fuel problem - maybe a filter or a pump that can't handle high flow.

 

[skate1968]

Doh!! Stupid me!

I discovered that i had a slow leak in the front passenger side.

The front tire low on air was probably the main culprit. I've also since gotten a needed oil change and radiator flush.

It seems to be running very well now.

Thanks to those that read and offered suggestions.

 

[HyperJinx]

A miss or stumble at high speed is usually a spark related problem. Could be a coil pack or ignition module issue.