loss of power at 45mph

[Delonte]

Hey Everybody! I have a 92 Jimmy 4.3L , it starts well , idles well, takes off and runs a little sluggish but smooth up till 45mph then I feel it dropping out- loss of power and it feels like the axle is jerking back (feels like its running over rocks) It will stay this way while I'm running between 48 and 55 mph. My guess is something to do with the drivetrain anybody have a similar experience?

[amac209]

replace your fuel filter first it's located in the drivers side frame rail i think you need a 16mm and a 13/16 wrench. if the problem still exists check for a plugged cat convertor

[hollyanne]

You are a little luckier than me. I have a Jimmy and one day (after alot of bs problems) I was driving my son to school, driving down the road at about 45mph, my car just died. We have tried just about everything fuel system related and we CANNOT get the f***ing thing to start again. From dropping the tank to change the fuel filter to wiring in the engine. Also, the dist., cap, wires, plugs, Im running out of things to try. I'd like to see what they have to say to you

[Delonte]

Thanks for the suggestion, you were right about the cataylic converter , it was blowing carbon out the tailpipe a couple of months back. I fixed that problem but too late it seems. after crawling under i noticed where the weld was cracking at the front of the cat. when i chipped a piece away it had carbon deposits all over it .... im convinced its clogged so I have to get my buddy to undo his weld job so I can gut out the cat. Im sure it will run much better. Also the squeaking I heard on acceleration was nothing more than the rubber bushing on the bracket of the cat it had fell off somewhere - When I grabbed hold of the pipe and started tugging on it I heard the exact same squeak that's been bothering me all this time. I put another piece of rubber between the the bracket and it rides quietly now. Whew !! I thought it was something major.

[Hearts88]

Originally Posted by Delonte

Thanks for the suggestion, you were right about the cataylic converter , it was blowing carbon out the tailpipe a couple of months back. I fixed that problem but too late it seems. after crawling under i noticed where the weld was cracking at the front of the cat. when i chipped a piece away it had carbon deposits all over it .... im convinced its clogged so I have to get my buddy to undo his weld job so I can gut out the cat. Im sure it will run much better. Also the squeaking I heard on acceleration was nothing more than the rubber bushing on the bracket of the cat it had fell off somewhere - When I grabbed hold of the pipe and started tugging on it I heard the exact same squeak that's been bothering me all this time. I put another piece of rubber between the the bracket and it rides quietly now. Whew !! I thought it was something major.

Is there a way to check the CAT to see if it is clogged? I've been having acceleration problems. The truck runs fine untill it starts to get warm, (5min of driving) and then the truck has no power. If it was an old carb engine I would think that the timing was off or the mixture was wrong. Could the CAT be causing this problem? Would the CAT be worse as the exhaust heats up?

I've got a 93 with the 4.3L HP engine. I've already checked and cleaned the EGR, new fuel, air filter, pcv valve, plugs, wires, cap and rotor. Am kinda at a stand still as to what to check.
Any help would be great.
Thanks.