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Plugged cat?


2k2cse

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I'm having some trouble with my car.. I hit a bad pothole the other day, and ever since, its been hesitating while i try accelerating. When I accelerate from a light, if i push the throttle more that 1/4-1/2, the revs will drop and it'll accelerate much slower than it should.

 

When I'm driving at normal speed, 50km/h, and I accelerate WOT, it'll bog down for a second, then start accelerating, but it'll keep revving higher than it should and not shift until I let off the gas. When this happens, I can hear a hissing sound coming from either directly under me, or from the engine bay..its hard to tell.

 

I've also noticed that at highway speeds, when I try to pass another vehicle, o/d will cut in like it should, but it'll rev up, and not accelerate much, until I let off the gas, and it shifts back up a gear..

 

I'm thinking that the cat might be plugged. Does that make sense? I'm gonna try to bring it to an exhaust shop tomorrow to get their opinion on it, and take further action from there.

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Wouldn't that cause a coolant leak somewhere? There's no coolant in the oil, no visible leaks on the outside of the motor, and its not overheating bad. It just runs a little hotter than it used to, but still nowhere near the red zone.

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Wouldn't that cause a coolant leak somewhere? There's no coolant in the oil, no visible leaks on the outside of the motor, and its not overheating bad. It just runs a little hotter than it used to, but still nowhere near the red zone.
Nope.
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Pretty much the same symptoms I had with my TrailBlazer a few weeks ago--although as it got worse, I could barely go 30 mph. Stranded in South Dakota until they could weld in another converter--mine was plugged.

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I would check for vacuum leaks before I started blaming the cat, since they're usually cheaper and easier to fix.

 

First off, check your vacuum lines and hoses. If they're melted, or rotted, or broken, replace. When in doubt, swap it out. Vacuum hose is cheap, and if it's original hose in the car it's well past due for a change (IMO at least.)

 

Another point to check is the check valve on the brake booster. I have heard that can seize up and cause issues. That and the diaphragm on the booster itself can fail over time. A way to test that is to pull the vac hose off the booster and plug it (the hose.) Start the car and see if the issue persists. Don't drive the car like this unless you have stuper-strong legs, as you will have NO brake assist. It's not fun, believe me, I did it once.

 

After that, then it's time to start looking into your intake manifold(s). I'm not familiar with the 3800, but I know the 3100 UIM comes off fairly easy, and the gasket from the upper to the lower intake isn't expensive IIRC. Fairly easy job, scrape off old crap, stick new win on, reinstall.

 

If all this fails, then it's time to either look at your LIM gaskets (although you said it's not losing coolant or oil, so I'm not 100% if that could be the issue) or your cat.

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Thanks for the input guys. I did check over all the vac hoses when this problem started, and I couldn't find anything wrong. I'm bringing it to a shop today to get the ses codes read..that might tell the problem, or at least give me a better idea of where to look. I'll mention the booster thing to them then. I really hope it isn't the intake manifold..I'm going to school about 4 hours from home and have no tools at all :mad:

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