idle's ok under heavy load break's up

[roy c]

Hello I was wondering if anyone could help. I've been having the following
issue when starting the truck idel's fine, when i take off to keep up with traffic no power breaks up
i changed the cap rotor wires plugs when it warms up highway speed is ok
but i wouldn't attemp to pass anyone breaks up. i replaced the fuel pump years ago, i put a new eastern cat last june some one told me it might be the cat iwas wondering if it might be the fuel pump or the electronic points which are original when i bought the truck new. thanks roy

 

[Boone83K10]

It could be the cat. you can get a vacuum gauge and hook it up to manifold vacuum (pcv port on carb or brake booster port) and hold the throttle open to keep RPM's steady at 2000 or so. If the vacuum goes up but slowly goes down to ZERO, you have a clogged exhaust system.

It also can be the fuel pump. Cheapest option is to buy a new fuel pump and install. If that doesn't fix it then buy a vacuum gauge (they are cheap) and do as I said. If it does as I described you know it's the exhaust.

here is a good website to show you all the diagnostic things a vacuum gauge can do.

http://www.secondchancegarage.com/public/186.cfm

 

[Jims86]

when is the last time the fuel filter was replaced?

 

[roy c]

good question at least 4 years i'll change it today thanks

 

[Jims86]

good question at least 4 years i'll change it today thanks

Yup, TBI very finiky about fuel delivery.

 

[roy c]

that was it thanks gets up and goes no problem thanks again roy