99 blazer wont go over 60mph

[broke blazer]

my blazer started acting funny today while driving. it would shift fine at slower speeds and everything but once it got warmed up it wouldnt go over 50 mph. i know its not transmission. i was told it could be ignition coil truck will go to 60 then act like it is loosing power and will start dropping back in rpms and mph. what could it be please help.

[old skool luvr]

it sounds like your cat is finished.

if your truck is cold (like sitting over night cold), will it maintain highway speeds right away (while still "cold"), and hold them steady? and then once it has warmed up it gets really sluggish with no power?

drill a small hole right in front of your cat (3/8 is fine), and see how your truck drives then. you can also check what the temp of the cat is to see if it's plugged, but that isn't alway a sure fire way to tell.

as an example of that........the cat on my '98 was finished, but the temp was ok across it. when i pulled the cat, i found the front row of material had become clogged, then broke up into pieces, clogging against the second row, and was slowly choking off the exhaust.

[broke blazer]

i kjnow my converter was supose to be hollow out had trouble with it last year but i know there is a big converter before the muffler and like a smaller converter looking thing before that. yes it does maintain high way speeds after it sits all day but once it is warmed up it doesnt it will go to like 55 60 mph then wont go any farther