if you throw a CEL by putting in a test pipe and dont fix it but instead drive around with the CEL on from the lower o2 sensor, does this affect the performance of the car or is it just an annoyance?

 

i have the same problem, and im gettin bad gas mileage, running really rich


is this bad for the car? i ordered the 02 sim.

 

You could just drive around with the CEL lite on, but one problem comes to mind. The lite is on with just the one code, or you could have multiple codes and not know it.

Do your car a favor, fix that damn lite!! It can be fixed for $5! (or$100) its up to you.

-Vince

 

I think that I am getting bad Gas milage too. Can anyone confirm this.........Cuz this qeustions has seem to come up alot lately

 

i have the ultimate racing test pipe and when my friends dad installed it he didnt put in the 02 fix, i have been just driving around with it but i cant tell if my gad mileage is bad cuz it seems like i go through more gas in this heat anyway. ive been told it makes no difference in performance, just the annoyance of the light always being on

 

Read this...............

http://auto.howstuffworks.com/question257.htm

The two 02 sensors basically relay information back to the ECU which then adjusts the AFR accordingly. If you install a test pipe or high-flow cat and trigger a CEL then I would guess your AFR is outside the optimum limits. This could undoubtedly affect your gas mileage and possibly the overall performance. I would view this warning light as more than a simple annoyance.

 

Yea my car felt worse with the CEL...get it fix..make your own mechanical 02 fix....Its in the Installation/How to forumn....

 

Only the O2 sensor in the O2 housing has any effect on A/F ratio's. The O2 sensor behind the cat is there to check if the cat is doing it's job. That is it. For example, you have a test pipe on and your rear o2 sensor senses high exhaust flow due to the test pipe. It throws a CEL code and does nothing to the ECU as far as tuning goes. Even if it did, what would either adding fuel or removing fuel do for a catalyst inefficiency? Exhaust gas still flows quickly either rich or lean, it doesn't matter. The front one on the other hand does have control over A/F ratio's. My O2 cents... Get it?? lol

 

That's good to know about the 2nd O2 sensor.

With regards to your question about adding or removing fuel......if you are running excessively rich you can irreversibly damage a cat and I'm sure that would throw a cat inefficiency CEL.

 

annoyance

 

Also, if the 2nd O2 sensor did nothing but monitor air-flow through the cat, then why do some HFCs operate OK for several thousands of miles and then suddenly throw a cat-inefficiency CEL?

 

Hi,

I believe the p0420 cat inefficiency code does not affect performance, based on other threads, but no concrete proof one way or the other.

Regarding how a HF cat can throw the cel after awhile. WIth my RT cat and 1 anti-fouler mech fix, I may get the code if I let the car idle for a long time. Also, I got the code when I first re-installed my silencer. My theory is that the exhaust doesn't flow through fast enough in an idle situation, or if there is more backpressure with the silencer, so the 2nd o2 senses too much exhaust and triggers the cel. After a few cycles of driving, turning the car off, and turning it back on, the cel will go away, even if I don't clear it by pulling the fuse. I think this indicates it's an "acute" condition, not "chronic" to borrow a medical analogy...

FB

 

Correct!