Missing.but ONLY at highway speeds!?!?

[Jiggyfly]

2000 astro, 98k.....runs great. New plugs, wires....At highway speeds.....65+, there's a miss....a hesitation. No specific time....ie- under load, or not. No engine light, no codes. Ideas?

Usually, if it's doing it, if I give it a bunch of throttle, it goes away, until I let off.
It's not constant.

[Splendid]

Mine did that, it was the hall effect switch underneath the distributor, cheap and easy to replace!

[Jasen]

Is it worse on wet day's ?

[Jiggyfly]

No. Same, wet or dry

[Phantom]

2000 astro, 98k.....runs great. New plugs, wires....At highway speeds.....65+, there's a miss....a hesitation. No specific time....ie- under load, or not. No engine light, no codes. Ideas?

Usually, if it's doing it, if I give it a bunch of throttle, it goes away, until I let off.
It's not constant.

ONLY at Highway speeds but yet whether or not there is a load???

anytime it is in gear there is a load ,, no load means it is not in gear ,, bit of a contradiction there

you could have a defective spark plug wire , or a plug is not gaped properly ,,, a leaking injection system or a partially plugged fuel filter
or
Could be camshaft sensor , distributor cap / rotor . or screens plugged up in distributor base

I would look at dist cap and cam sensor first , and screens while your at it ,,, crank sensor could be going bad as well

[Jiggyfly]

Ok, since you want to be literal.....

Do you think an engine is under more, or less load going up a long, steep hill......or being put in drive in a parking lot.....since their both technically under load..........?????????

So, really......when you think about it......there was no contradiction of terms.

Otherwise- thanks for the advice.

[chevymaher]

I am with you.I use the term under load and coasting.Slang but effective.Hard to convey what you mean if it is always under load if it in gear.
Check for vacuum leaks.PCV stuck open,cracked or broken hoses.Throws the fuel mixture in the intake out of balance near the leaks.cylinders getting a lean mixture miss.