Chevy & GMC Vans

Well, i gritted my teeth and parted ways with $275 and had a new cat installed. This one is a hi-flow cat. Granted, cats are supposed to last the life of the vehicle, assuming nothing goes wrong with the beastie. Unfortunately, the O2 sensor that the dealer installed was a low-quality sensor and failed relatively early, resulting in a very rich mixture which, in turn, plugged the cat.

My fuel consumption went from approximately 18.5 mpg down to a low of about 10 mpg. It rebounded to almost 14mpg after I replaced the sensor, but it has gone back down to around 12.5mpg. After the new cat was installed, one immediate result was that the van idled much smoother. It did idle like a Hog for a while. We'll see in about a month when I refill the tank just how much better Klementine operates.

I think I have the same problem. Did you have any of these symptoms?

It was running rich, found vacuum leaks that seamed to fix the rich symptom but it still idles rough

Runs good when its movin, but wants to die when I put it in Park or Neutral.

Changed out all 3 02 sensors/ Plugs n wires / Cap-rotor/ IAC valve/ERG valve/ Fuel filter and it still doesnt want to idle right. Im thinking I either need to replace the Cat, or Injector assembly.

Supersport wrote:
...Changed out all 3 02 sensors/ Plugs n wires / Cap-rotor/ IAC valve/ERG valve/ Fuel filter and it still doesnt want to idle right. Im thinking I either need to replace the Cat, or Injector assembly.

I went through incredibly similar hair-pulling troubleshooting on my 89, only to find that it seems my air intake preheat flapper was staying in the closed position. It would only breathe through the preheat hose coming off the hot exhaust manifold.

After spending a couple of hundred dead presidents on all that same stuff you list, it seems that adjusting that little spring thingie made my 89 idle nicely.

Lump

Lumpy wrote:

Supersport wrote:
...Changed out all 3 02 sensors/ Plugs n wires / Cap-rotor/ IAC valve/ERG valve/ Fuel filter and it still doesnt want to idle right. Im thinking I either need to replace the Cat, or Injector assembly.

I went through incredibly similar hair-pulling troubleshooting on my 89, only to find that it seems my air intake preheat flapper was staying in the closed position. It would only breathe through the preheat hose coming off the hot exhaust manifold.

After spending a couple of hundred dead presidents on all that same stuff you list, it seems that adjusting that little spring thingie made my 89 idle nicely.

Lump

fortunately, I live a very warm climate, so I just removed the preheat flapper since it was frozen at about half mast anyway.
During the summer I remove the preheat hose. In the winter I keep it on. the intake duct work breaths pretty good now.

kings-x59 wrote:

fortunately, I live a very warm climate, so I just removed the preheat flapper since it was frozen at about half mast anyway.
During the summer I remove the preheat hose. In the winter I keep it on. the intake duct work breaths pretty good now.

I'm in Phoenix. It's 102 on my back portch as I type this at 2009 hrs local..

I wanted to keep the preheat intact for the smog inspection.
But I'm happy to hear that wasn't your problem. Well, actually,
it would have been simpler if that WAS your problem. Oh well.
Back to the drawing board.

Stay cool

Lumpy

You played on "The Love Boat"?
Yes. White tux, huge sideburns.

http://www.LumpyMusic.com

A stock cat is actually designed to last 10 years. You can get more out of them depending on mileage and the type of driving you do. If you are mostly highway miles you will get more if you are short trips around town so it doesn't get hot and stay hot to clean itself out you will get less. Most aftermarket cats are rated at a 5 year life. Once again it all depends on use. Glad to hear your van is running better now.

Supersport wrote:I think I have the same problem. Did you have any of these symptoms?

It was running rich, found vacuum leaks that seamed to fix the rich symptom but it still idles rough

Runs good when its movin, but wants to die when I put it in Park or Neutral.

Changed out all 3 02 sensors/ Plugs n wires / Cap-rotor/ IAC valve/ERG valve/ Fuel filter and it still doesnt want to idle right. Im thinking I either need to replace the Cat, or Injector assembly.

Have you done a compression check on the cylinders to see if the valves are sealing?

This Friday is payday. I think I'll make a trip to the Little Big Horn Battlefield or Pompey's Pillar to blow out the crud and get the kitty warmed up. It's all highway driving.

Well, didn't do what I said last time. but after this morning's fill, my fuel consumption went from 12 mpg to 15.3 mpg.

i believe this may be the problem with mine. My cat has 165k and 22 years on it. thank goodness here in FL no inspections. The cat is scrap metal as far as im concerned.