Clogged Cat- will boring it out cause driveability issues?

[Dude]

My son has a 2003 Vice AWD 1.8L automatic. It has nearly 300,000 miles on it, and up until a recent road trip, it ran great. He called me from Idaho to say it would not go more than 7mph. I trailered him back to my place, and we took it to a local mechanic to look over. He diagnosed it as having a clogged upstream cat. They wanted $4350 to fix it. I trailered it back to my place. I have removed the exhaust from the manifold back, and a shop vac pulling in either direction exhibited no change in flow or sound, so I think this section, and the second cat. are clear of obstructions. Looking up from the bottom of the manifold, it looks like the upper cat is, in fact, quite clogged. I can get a replacement via Rock Auto for about $600 shipped.

Given the age and projected lifespan of a 300K 1.8L AWD Vibe, I am not keen on spending that much money to fix it.

My question is for those who have eliminated the cats on your car, do you have any drivability issues? Does anyone know if by leaving the second cat intact and in place if the CEL will be activated? His tags are good for another year, so even if it won't pass an emissions test, if it will run well and it buys him a year, free is a very good price. But if it won't run worth a (removed), then I will spend the money, replace the cat, and hope the rest of the car holds up for a few more years.

[joatmon]

welcome to genvibe

Theoretically, should not cause any drivabilty issues. The first O2 sensor is upstream of the first cat, it's used to monitor fuel/air mixture, so anything downstream from that O2 sensor shouldn't affect the mix. The second O2 is after the second cat, it's used to compare to the first O2, and if the readings aren't different enough it sets a CEL (usually P0420) to indicate the cats aren't converting enough.

You said "a shop vac pulling in either direction exhibited no change in flow or sound", so just to be clear, do you mean that the shop vac sounded the same when pulling from both sides of the exhaust, or that the shop vac sounded the same whether it was connected to the exhaust or not?

Would be loud as hell, but might be worth a quick test drive with the exhaust disconnected from the manifold, just to confirm no improvement

I'd say go for it, if for no other reason than as a diagnostic, to verify that's why the car can only go 7 mph.

Curious that it ran great and then suddenly became so clogged it was undriveable. If gutting the cat restores engine power, then be sure to frequently check oil and coolant levels. It may have been clogging for some time, but something happened on the road trip to clog it fully. Of course, its always a good idea to check oil and coolant levels

Hope you get it back on the road, please follow up and let us know how it goes.

[andrewclaus]

Is a non-CARB cat possible to buy/ship where you live? Those are less expensive.

[Dude]

I can get a non-CARB compliant one shipped here, but landed it is still over $500 plus gaskets. And time. I should have time after work tonight to ream that puppy out and see what happens. I'll pull the O2 sensor out, put the shop vac under it and start digging. Once done, I'll start it with the open pipe to make sure everything is blown out of the manifold before I hook the rest of the exhaust back up. The mechanic that diagnosed the issue took the upstream O2 sensor out so the exhaust could blow through there, and it revved like it should. Eliminating any clogging in the system from there back narrows me down to this upstream cat. At this point, what have I got to lose?

[Dude]

Update- I cleaned the cat from the manifold. I chose to do this with the manifold on the car to eliminate any issues with stuck bolts, trouble getting gaskets, etc. So I used a screwdriver to punch through it, and started breaking it apart to remove the chunks. I would guess it was at least 85% clogged- like, I had about a quarter of it come out in one big chunk, and I could not blow any air through it. I used my scope to make sure I got it all. I heated the handle of a wire brush to bend it to the right angle to reach the wall of the manifold, and made sure to get all of residue I could so nothing would come loose and clog the second CAT. I ran it without the exhaust hooked up for a little bit to blow any dust out, and put it all back together. It runs great. No unstable idle, no CEL, nothing to indicate there is a piece missing. I was out a few bucks for a replacement exhaust seal, and a new dipstick (don't know where the old one went). Interestingly, finding one for a Pontiac Vibe was not possible, but one for a Toyota 1ZZ-FE was readily available. Cheapest CAT fix I have ever dealt with.

Thank you for helping a Vibe owner's dad get his car on the road for the least amount possible. I have always liked these cars, and was happy when he bought one. After playing around with his, I may just have to find a cheap 5-speed version for a track/autocrosser. If that happens, I'll be back here for advice and help.

[joatmon]

Glad to hear its running again

I may just have to find a cheap 5-speed version for a track/autocrosser. If that happens, I'll be back here for advice and help.

The 5 speeds haven't had a good reliability record. Some last well, but more failed than should be expected. The six speed in the 1st gen GTs seems much more bulletproof