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rpmdiag, Tech and Instructor
Category: Chevy
Satisfied Customers: 6721
Experience:  Since 1975
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It looses power on the high end. was wondering if it could

Customer Question

it looses power on the high end. was wondering if it could be vacuum hose leak or something. I replaced the wires distrubitor cap and rotor. even the mogulator and coil because they were all orginal or very old parts.
JA: How old are the hoses? And what driving conditions do you most often encounter?
Customer: At least 15 years and i drive the truck every day. Got 4 hundred 18 thousand on it
JA: What is the model/year of your Chevy?
Customer: 91 silverado with a 305 in it
JA: What year is your Chevy?
Customer: 1991
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: I replaced the distributor cap, rotor, coil, wires and spark plugs. I even replaced the fuel pump and fuel filter because i felt it was a fuel problem. It loses power after 45 miles an hour. It just wont go. Dont think it the trans because it seams to shift fine
JA: Anything else you think the mechanic should know?
Customer: dont think so
Submitted: 2 months ago.
Category: Chevy
Expert:  rpmdiag replied 2 months ago.

Hi, welcome to Just Answer. I’m Ron and I’ll be helping you
Before we get started though, Please understand that I don't know
your skill level or tools you have to assist us. Also understand that
I can't see, smell, hear, or touch the vehicle either, so patience is
appreciated. JA is a great Q/A site, but it does NOT replace a
repair shop.
My goal is to make you happy and get a great rating in return for
my time. Sometimes I have to give you bad news that I know you
didn’t want to hear, so please don’t shoot the messenger.

This actually sounds like the catalytic converter may be getting plugged up. You did many other things to it already, so this may be your issue.

Thanks, Ron

Customer: replied 2 months ago.
hey thanks for your help! I took the converter off the truck some time back. may be 8 years ago. also i did not say this before, it back fires or cough trrough the throddle body when it starts to loose power.
Customer: replied 2 months ago.
did my reply go through?
Expert:  rpmdiag replied 2 months ago.

Okay, check your ignition timing and valve timing with a compression test.

Thanks again, and please don't forget to rate me and keep this link in case you need me again later on.