91 Gmc K1500 With 350 Seems Tired

[roberth]

Ok, so the title says it. I have had this truck since new and taken care of her. Oil changes every 3-4K, etc. Only upgrade I did was Gibson Exhaust system which sounds good and seems to be a good system.

 

Only complaint is why I have low power over the last few years. She has 190K miles and should have lots more power that it does now. I stopped towing with it (occasional 3500lb boat) due to how sluggish it feels. Even driving it makes me wonder what is going on. None of my other GM's over the years have lost power like this.

 

She starts, runs great otherwise. Idles good, etc. Plugs changed, O2 sensor changed, no difference.

 

A couple folks I know that keep their vehicles like I do say that when you approach 200K miles, it is time for a new Catalytic Converter as they get plugged up. Is that right? Maybe I can punch it out and try and see what the results are before investing in a new one.

 

I tried a test with the O2 sensor out and started the engine but seems not much back pressure, but folks told me that is not really a good test since it was not under a load which is where the power would be when driving. So dunno...whadda ya'll think?

[jim brock]

I have a '94 2500 with the 350 engine also. If the cat/converter is not restricted, check the engine timing. If timing chain is stretched too much, timing could be retarded enough to cause power loss. Remove the distributer cap and rotate the engine by hand one way then the other. See how much the engine turns before the rotor moves. If there is excessive play (more than a few degrees) you'll need a new timing chain assembly. Good luck.

 

Jim B.

[Silverado4x4]

Iam leaning towards the Catalytic Converter starting to plug. I have seen them plug so bad that they glow orange.

[roberth]

I think I will try to see if the exhaust pipe will still slide off the cat and try to punch it out. If too tight, might just get a new cat and hope for the best.

 

Anyone had any actual experience with this type of mileage and results of a cat fixing the power?

 

Good idea on the timing wear check. Maybe I can change the plugs and do a compression test and while plugs are out, check the play in the timing chain by turning as suggested.

 

Thanks for the ideas, anyone else, please chime in....

[twavor]

I have a '90 GMC 2wd with a 350 that I took...er, wait, I mean the Catalytic Convertor fell off of. I used the rosebud on the oxy/acetelyn torch and she came right off...a piece of mid-80's Ford driveshaft is the perfect size to replace it. Mine wasn't plugged up, but it is worth some money if there's still some good stuff in it. It did wake mine up a little bit, but I also put a $29.99 Thrush glasspack in place of the muffler and it sounds perfect...definitely not loud, but you can hear the pulses in the exhaust when you step into it.

My 2wd also has 204,000+ miles on it, and still runs good...needs valve seals at the least, it will irritate the cars behind you at the McDonald's drive thru if they are slow that day.

 

Travis