Engine Mechanical problem
2000 Jeep Cherokee 6 cyl Four Wheel Drive Automatic 40,640 miles
I had my Jeep into the dealer because it was not taking the gas first thing in the a.M. You had to coax it along to get it going. After five minutes, it was okay and ran fine. They had it for two days which was very inconvenient. Ran some tests on the fuel pump and decided it was bad gas, but oh by the way, your catalytic converter is coming apart and will need to be replaced to the tune of $1230. There is a vibrating, rattling noise that sounds like it comes out of the exhaust when you first start it up. After it goes for a while, it's fine. I had some trouble with the dealer because they told me my tires were fine and the next day I had a flat. I bought all 3 of my cars there and have all my work done there. I took it in January for a thorough going over, oil change, check belts and hoses, etc. No tune up was done. I had a 1988 Jeep Cherokee 6 cylinder which ran for 15-20 years with no problems with it's catalytic converter although it made the same noise out of the exhaust. I had the muffler replaced on that one, but it still did it. A new catalytic converter is on order but I am feeling like I'm being taken because I am a woman. What is your advice?
Get it check out: How can I tell if my catalytic converter is working properly?
The catalytic converter is our main line of defense against air pollution, so it's important to make sure it is functioning efficiently and passing exhaust without creating undue restrictions that might reduce performance, fuel economy or emissions. That's one of the reasons for periodic vehicle emissions testing. If the converter isn't working, you won't pass the test.
If the your converter is plugged, it will create a restriction in your exhaust system. The buildup of backpressure will cause a drastic drop in engine performance and fuel economy, and may even cause the engine to stall after it starts if the blockage is severe.
The easiest test for converter plugging is done with a vacuum gauge. Connect the gauge to a source of intake vacuum on the intake manifold, carburetor or throttle body. Note the reading at idle, then raise and hold engine speed at 2,500. The needle will drop when you first open the throttle, but should then rise and stabilize. If the vacuum reading starts to drop, pressure may be backing up in the exhaust system.
You can also try to measure backpressure directly. If your engine has air injection, disconnect the check valve from the distribution manifold, and connect a low pressure gauge. Or, remove the oxygen sensor and take your reading at its hole in the manifold or headpipe. Refer to the backpressure specs for the application. Generally speaking, more than 1.25 psi of backpressure at idle, or more than 3 psi at 2,000 rpm tells you there's an exhaust restriction.
If there appears to be an exhaust restriction, disconnect the exhaust pipe just aft of the converter to relieve pressure and recheck the readings. CAUTION: The pipes will be hot so wait awhile for things to cool down. If vacuum goes up and/or backpressure drops, the problem isn't not a plugged converter but a plugged muffler or collapsed pipe. If there's little or no change in readings, the converter is plugged.