Well, on my way to Orlando this past weekend, my check engine light came on again. I get error code 72 and 31. The resistor trick that I did does not seem to work correctly. However, the car does drive noticly better now. I am beginning to think that the CEL #31 is causing some problem. I would think that if I removed my CAT I would only get CEL code 72. Every time I reset my ECU, the car will pull code 72 AND 31. To make things worse, my egr value is not moving when I rev the engine from under the hood. I used to see it move open when the car would rev down, but now it does not. It also takes a very long time for my car to rev down. If I rev to 5000rpm, it will take forever to idle.

I am beginning to think that the resistor trick is working because of how much better the car drives, but it is not taking care of my CEL. I think the CEL is being lit up due to another emmision problem. What kind problems do these EVAP and EGR actuators cause if they go bad? I am beginning to think that my car has a vacuum leak somewhere in these emmision devices. Like the EGR is always open, or the EVAP canistor is always open purging constantly into the engine. When I fill up my gas tank, I do not get that rush of air or decompression sound when I remove my gas cap. My girlfriends car does and I think mine used too, but I cannot remember. I think its time to buy a vacuum gauge and a hand pump.

-Jared
96 GS
Melbourne, FL

Iceman CAI | RS*R Cat-Back | AFX Pully | Milled Head 10:1 CR | MP 60mm TB

I have been catless for about 2-3 months and I still have no CEL.

Dave
05 Ford F150 SuperCrew FX4

I know, I read it every time someone posts about removing the CAT. I however do get a CEL code, and my car will run 100% different when it happens. I have to reset my ECU once a week to get the car to run ok, only to get code 72 and 31, then the car runs all wierd. I will eventually figure this out. You wouldn't happen to have removed any emmision devices from your car have you? Also do you get that decompression sound when you remove your gas cap to fill you tank? I need to take a poll on this.


I like that starion front mount by the way... I plan to go that route soon after I get my stage 1.

-Jared
96 GS
Melbourne, FL

Iceman CAI | RS*R Cat-Back | AFX Pully | Milled Head 10:1 CR | MP 60mm TB

This is what I think about that, the downstream 02 sensor must be lower than the upstream by at least 30% according to the techinical manual, well what about just taking the output wire from the upstream sensor tapping into it(leaving its signal the same) and then adding a small resistor to lower the voltage at least the 30% and sending that voltage to where the downstream output hooks to. That way whenever the upstream changes the downstream would also and it would always be at least 30% diff. to fool ecu into thinking the cat is still there and functioning.

So if the upstream is sending 1vdc to the ecu the downstream should be sending at the most .66vdc in order to NOT trip the CEL. Only a small resistor is needed to change the 1 vdc to .66vdc and so on.

did I make any sense??

1998 dodge avenger 4 cyl AT
Mods are:
Not enough

You make perfect sense. But I am trying to figure out if the ECU looks for more than just a voltage drop from the rear O2. Perhaps it also looks for a different frequency or waveform from the rear O2 as it should be delayed from the front one. The idea behind the 1 Mega Ohm resistor is to fool the ECU into thinking that the CAT is super efficient. A 1 Mega Ohm resistor almost acts like a ground for the amount of signal the O2 sensor puts out. You would probably think that if the ECU did not get any signal from the rear O2 that it would pull CEL code 21 (O2 sensor failure). But it does not, it just keeps giving me code 72 and 31. I am waiting for my pocketlogger to arrive before I continue troublshooting this one. The guys at the shop next to me are tired of me bothering them for a datalogger.

-Jared
96 GS
Melbourne, FL

Iceman CAI | RS*R Cat-Back | AFX Pully | Milled Head 10:1 CR | MP 60mm TB