Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Exhaust Issue


Sept 19, 2008 167,348 miles - Cat replaced

Oct 1, 2009 175,700 miles - Cat replaced

Jan 6, 2010 181,192 miles - Cat replaced and both O2 sensors replaced

Jan 26, 2010 181,570 miles - Cat replaced and Computer reflashed

Oct 8, 2010 188,800 miles - Light has come on again with the O2 sensor malfunction code.

Anybody know what is going on with my car?

I take it that you do not have a head gasket leaking antifreeze killing the the CAT?

There are quite a few codes that refer to O2 sensors. What code(s) do you currently have? (Exact code, like P1234). What codes were there each time you had work done?

Those codes do not tell you that parts are bad.

E.g. - one common code that leads to people replacing cats and/or O2 sensors is P0420 - all that code really means is that the pre-cat and post-cat O2 sensor readings are too similar. The engine’s computer can only look at what those sensors report. It can’t tell you that the cat is bad or that either sensor is bad. And actual person with some tools and expertise has to diagnose it.

Maybe its time to have another shop look at it?

Its also the case that some cars don’t do well with generic, aftermarket cats. What was installed on yours each time?

What’s going on is that you have an incompetant…or lazy… mechanic.

No mechanic is his right mind would change that many cat converters, or even two in 8,500 miles, without it tripping a “what the…” flag in his mind. Cat converters can only be damaged by having their insides coated with something in the exhaust stream…or phsical damage to the ceramic honeycomb, which ain’t gonna happen 4 times in a row without some other disasterous symptom showing up.

A competant dude would have checked and compared the O2 signals on a scope, and the second time around he would have looked further to see what was poisoning the catalyst. Your guy is just a parts-changer. Severe oil burning and coolant burning (bad headgasket) would be good first thing sto look for, but in all honesty I cannot imagine either killing a cat that fast unless it was really, really extreme, and that would cause other symptoms as well.

You need a diagnostician, someone that will check for evidence of those things that might be cat-killers. And checking for thing sthat might be causing bogus signals to the ECU.

Sorry, but someone has to look-see the engine and put a scope on the sensors to see what’s going on.

I hope he didn’t keep charging you over and over.

No, These idiots only charged me once for the initial cat and the o2 sensors. Guess what?! When I took it back to Aamco I found that the entire crew(including the manager) had been changed out. The new guy believes it needs a new timing chain but they are waiting for some diagnostic work to come back before they make a final decision on that. They had better replace the cat and 02 sensors for free after this work is done as well.

You took the car to AAMCO?
And, “they are waiting for some diagnostic work to come back”???

Now the situation is beginning to become much more clear.

This chain is known for bad diagnostic work, “overselling”, bad workmanship, high prices, and failure to stand behind their work.

Before you give these charlatans any money for timing chain replacement, you need to have the engine examined by a competent mechanic (i.e.–NOT a chain operation like AAMCO, Sears, Pep Boys, Midas, Meineke, Monro, etc).

Ask friends, relatives, neighbors, and co-workers for recommendations on a well-reputed independent mechanic in your area. You might also want to use the Mechanics Files on this site for possible independent mechanics in your area. Those chain operations should be avoided like the plague!

 [b]  I took it back to Aamco[/b]


 It is not a good idea to take your car to any of those chain places including the fast oil change places.  They tend to sell services not needed and often do inferrer work. 

 Dealers are generally OK, but they are almost certain to be expensive.  

 Your best bet is a local independent mechanic that has been recommended by a friend, neighbor or co-worker.

Guess what! When the results came back AAMCO said yes it was the timing chain!
I did not let them touch my car after that! I took it to an independent mechanic that was recommended on this website. He said timing chains hardly ever go bad on these cars and that it would have probably thrown another code or I would hear loud noise if it really was the chain. As soon as he put it up in the air he noticed the spotty welding that was done on the car after they cut and replaced 4 cats. I paid him to re-weld the pipe. He had to weld new pieces of the pipe on to fix it. It rattles now when I accelerate but at least AAMCO didn’t get to charge me for a timing chain. I would like to take these AAMCO guys to court badly!

The rattle is probably easily fixed.

Do report back if this solves the entire error code (check engine light) issue.