SR Tech

After going into closed loop it seems like there is an increase in backpressure in the exhuast. Even going back to open loop in WOT there isn't any. could the valves be tuliped or overlaping? timing off a few degrees? Throwing a P0136 which is the 2nd O2 sensor, doesn't really help my cause though. I'm also thinking it could be the stock cat gettin a little clogged after 85k mi? Please all opinions are appriciated, i'm really tired of sounding like an iroc-z

StrikeEagle

Get the O2 sensor replaced right away, that should clear up most your issues. And reset your ECU too of course after doing that.
Doubt your cat is clogged, although a possibility, when you get a CEL, your engine stops 'learning' and goes into more of a steady state mode rather than trying to perform right. Fix it and it should work.

DTN

What does that mean?

Troubleshoot any codes you get first. Alot of the time a faulty 1st o2 sensor can cause the 2nd one to call a code. This is because it takes longer to change over and will allow the engine to go leaner or richer then it should. It may be the 2nd one too, but the 2nd one is just to monitor the efficiency of the catalytic converter. The cat cannot do it's job if too much unburned fuel is making it through though.

If your engine is sounding loud, then it may be because you have an exhaust leak.

Either way, if you have a code, get it fixed before you try to troubleshoot anything else. There's a reason they call it a dummy light. It tells you there's something wrong with the car that needs attention. It's not something you can put off. It dosn't matter if a dog takes a crap on your car hence there is no dummy light. If you have a dummy light, it's there for a reason, it's saying fix the dang problem before it becomes a much bigger problem!

SR Tech

your computer runs in open loop until it gets warm and @ WOT until it gets proper readings from the sensors mainly the 02, meaning it has a pre programmed A/F ratio, IAC count, ect. when in open loop. I'm saying after it warms up, and not at WOT, it sounds like exhuast is comming back into the head. I plan on replacing o2 sensor after getting header so i can relocate them at the same time, but an o2 sensor shouldn't really have anything to do with my backpressure unless the computer has taken over the engine more than i thought?

In NY you can't pass inspection with a CEL so i "reset" my ecu a few days prior, passed inspection and the code didn't come back for 2 weeks after that, still had the same backpressure the whole time. Thats what kinda makes me think its not the sensor. But im gonna have to replace it anyways. Thanks for the replys

Jay-M

Did your rd2 come with 2 cats (1st one attached to the exhaust mani and the 2nd at the bottom ofthe car?). Try changing the 2nd o2 and see if you have the same problem (cel)... if yes, it seems like that your cat is not that efficient anymore and needs to be replaced.

SR Tech

yes 2nd cat was taken out with replacement of the exhaust, but i plan on putting it back after the header goes in. I ordered 02 sensor today so i will find out in a few days, thanks. Does anybody know if the replace the cat with the manifold recalls?

DTN

Yes they do. Did you inspect your manifold and find a crack?

HyundaiKitCoupe

i have P0134 after relocating both my sensors for my custom exhaust. did you touch your exhaust at all or is it 100% stock? what are your mods if any?

SR Tech

well i had the recall done last year so that would kinda off eliminate the cat being the problem, yes i took the 2nd cat out put test pipe in, when i get a header im gonna put a cat there and extend 02 wiring, haven't touched o2 sensors since i got the car ...bout 3 years ago.

DTN

You're probly running rich from the o2 sensor, or have an exhaust leak. Not backpressure.

Run your car to make it sound like an iroc-Z for about 5 minutes. However you have to do it. Then immediately shut off the car and pull the spark plugs. Read them. They should be grey/tan. here is a spark plug reading guide http://www.ngksparkplugs.com/techinfo/spar...&country=US

If you are running rich, it's probly your first o2 sensor.


BTW... Our cars strictly monitor and run on o2 sensors in closed loop. In open loop, they run on the MAF, IAT, TPS and use the o2 sensors to attempt to maintain a stoichometeric ratio.