Help!! wont pull uphill

[stalecracker]

1999 expy 5.4.I live near vegas,my expy wont go over 70mph pulling empty 14ft railer and only 45 ish with load.It runs ok just wont accelerate...I am mechanic but been out business fir while..ANY IDEAS?? NEW PLUGS,NEW DUEL FILTER ,AIR CLEANER GOOD

 

[ExplorerTom]

What gears does it have?

 

[Russell Lewis]

Is your trans slipping or converter not locking up ? Lived in CA for 19years not to many really bad grade hills at all. Motor RPM but no output?

If motor just is not doing it then Yes. Plugs, air and fuel filter, clean mass air flow.

Use Sea Foam in gas tank and threw throttle body. Sold in store and online few bucks more in store.

 

[Russell Lewis]

What gears does it have?

3.31 and 3.55 both should have no problems. On the rear diff metal tag it will show or call dealer give vin will tell you gearing.

Or check the door piller/door sticker will tell you.

 

[ExplorerTom]

Depending on the hills and altitude, 3.55 gears may struggle. And weight of the trailer.

Check your throttle cable stretch. Remove the air intake tube and have an assistant (or a jack stand) push the gas pedal all the way. Look at how far the throttle plate is open. It should be "flat".