Manifold bolts, fuel pump and catalytic converter (vehicle, exhaust, engine)

[mmorris8211]

I have a 20 year old suburban that I have kept in good shape. Recently, I had to have two manifold bolts replaced, the fuel filter and the fuel pump. Now I am getting a check engine light for my catalytic converter. It appears to be the only code showing. I don't have the money to repair it.. Should I get a second opinion? What will happen if I just ignore it?

Thanks,

Mike

[need4speed2012]

1. Get a second opinion.

2. You may have other items causing this as long as its running correctly.

3. A bad catalytic converter can clog up and create excess back pressure in your exhaust which can make your vehicle run badly and consume more gas.

[Labonte18]

Manifold bolts? I presume we're talking exhaust manifold?

That's probably your issue.. "Cat system below efficiency"?

you likely have a leaking exhaust manifold, which is triggering the cat below efficiency code.

[HarborRat]

Most cars use a second O2 sensor behind the cat just to monitor the cat's efficiency. A bad O2 sensor there will throw the code, and they are more likely to go bad than the cat itself. If it's running fine and the exhaust smells normal a bad after-cat O2 sensor won't cause ANY drivability problems, just the check engine light. If all seems fine other than the light go ahead and keep running it, won't hurt a thing.

[UpstateJohn]

Its 20 years old, stuff is going to wear out! ITs at least a 95, so its not going to be a touchy about stuff as a newer engine. Whats the code?

[Labonte18]

Originally Posted by HarborRat

Most cars use a second O2 sensor behind the cat just to monitor the cat's efficiency. A bad O2 sensor there will throw the code, and they are more likely to go bad than the cat itself. If it's running fine and the exhaust smells normal a bad after-cat O2 sensor won't cause ANY drivability problems, just the check engine light. If all seems fine other than the light go ahead and keep running it, won't hurt a thing.

That would actually throw.. If I recall properly.. O2 Bank 1 sensor 3 code.. P0142-ish

vs the "Cat Below Efficiency" of P0420

BUT.. You caught something on post (I think) that I didn't.. OP says it's a 20 year old vehicle, which would put it pre-OBD II.

So.. I'm confused here.. I didn't think OBD1 monitored the cat.. If it's truly a 1995, it should be OBD1, which has no cat codes.

[HarborRat]

Originally Posted by Labonte18

That would actually throw.. If I recall properly.. O2 Bank 1 sensor 3 code.. P0142-ish

vs the "Cat Below Efficiency" of P0420....

It would actually probably throw both eventually on OBD2 cars. It uses that O2 to know when to throw the P0420 so it will throw that first, and then if the output voltage of that O2 is out of whack too long (and only once drive cycle parameters are met) it will throw the P0142 (actually the P0144 is more likely).

Originally Posted by Labonte18

....
BUT.. You caught something on post (I think) that I didn't.. OP says it's a 20 year old vehicle, which would put it pre-OBD II.

So.. I'm confused here.. I didn't think OBD1 monitored the cat.. If it's truly a 1995, it should be OBD1, which has no cat codes.

Yes, 95 was the last year of OBD1 for most GMs, although a couple models did adopt OBD2 that year. Without knowing the code I guess we will never know . Not all OBD1 cars even had downstream O2 sensors to monitor the cat.

[Labonte18]

Originally Posted by HarborRat

It would actually probably throw both eventually on OBD2 cars. It uses that O2 to know when to throw the P0420 so it will throw that first, and then if the output voltage of that O2 is out of whack too long (and only once drive cycle parameters are met) it will throw the P0142 (actually the P0144 is more likely).




Yes, 95 was the last year of OBD1 for most GMs, although a couple models did adopt OBD2 that year. Without knowing the code I guess we will never know . Not all OBD1 cars even had downstream O2 sensors to monitor the cat.

True.. The 420 is such a generic code.. I wish I knew the parameters for setting that on some vehicles. I've had that code set when there was an exhaust manifold leak (Actually, there was a hairline crack on the exhaust manifold at the first 'manifold' cat on a vehicle with multiple cats) and when the catalyst has come loose in the housing and many other times.. It rarely actually points to a problem with the cat itself.