Bad Cat?

[Avolow]

So my car is giving me some lip lately. It has a bad loss of power and the gas mileage has gone downhill.

I tried doing a compression test and the gauge reads between 80 to 85 psi across all four cylinders. I haven't tried disconnecting the down pipe and taking compression readings to see if a clogged exhaust was effecting it at all.

I put a vacuum gauge on it and it reads 13 hg or so at idle with the it in gear (automatic) and 15hg in neutral. Driving down the road and on the highway the vacuum drops down to about 2-3 hg when the gas peddle is barely presses at all, sometimes as little as 1/4 inch to 1 inch of travel. Vacuum drops to 0-1 at about 3/4 travel and on to the floor.

Fuel economy has dropped from about 30mpg to about 22mpg.

Pretty sure the cat is going out. I ordered a new one off eBay since a direct fit there is half the cost of the ones at the parts store. Going to replace both the O2 sensors at the same time.

Guess really I got two questions.

1: Can anyone think of anything else I can try to verify the cat as the issue.

2: Does anyone have any advice on the eBay O2 sensors? The parts store wants $50 to $70 for the downstream. I would like to avoid the high price. eBay ones are $15-$20, but I don't know if they are decent and will last a reasonable time.

Thanks all.

Avolow.

[occasional demons]

You can pull the upstream o2 out to re do the compression test. If when pulling the ASD relay and cranking it, you get a good amount of ait blowing out the o2 hole, there may be a good amount of restriction in the exhaust.


You should really pull the ASD relay when doing a compression test, to keep the injectors from dumping fuel. Throttle should be propped open also.

As far as ebay o2 sensors, use at your own risk. I would search for Mopar ones on ebay, or NGK, Bosch brand, but that's about all I would trust.

A lot of folks rip on Bosch, but I have never had an issue.