15 mpg....?
Joined: Apr 2010
Posts: 12,601
From: Mentor, Ohio
I believe most OBD-II scan tools can also retrieve info like that. I know the Snap-On I use provides numbers like KR, Injector Pulse Width, Air/Coolant temp, and a host of other values (some of which I have NO idea what they mean).
Monte Of The Month -- August 2014
Joined: Sep 2008
Posts: 25,145
From: Southeast PA
You could have a few sensors that are going bad or are dirty that will affect your gas mileage.
The MAF (mass air flow) sensor on your throttle body could be dirty. The front bank o2 sensor (on your rear exhaust manifold) could be going bad. These 2 talk to the PCM and tell it how much fuel to dump.
You could also have a bad injector, that is just letting fuel drip out instead of getting sprayed.
Your Catalytic converter could also be clogging up, they are a very common problem with these cars, and they won't always throw a code that they are bad.
Also, your engine could just be really dirty. Perhaps you should try getting a couple cans of seafoam and doing the 3-step procedure for helping you clean out some of the carbon. Removing your TB and fully cleaning that is also pretty good to do.
The MAF (mass air flow) sensor on your throttle body could be dirty. The front bank o2 sensor (on your rear exhaust manifold) could be going bad. These 2 talk to the PCM and tell it how much fuel to dump.
You could also have a bad injector, that is just letting fuel drip out instead of getting sprayed.
Your Catalytic converter could also be clogging up, they are a very common problem with these cars, and they won't always throw a code that they are bad.
Also, your engine could just be really dirty. Perhaps you should try getting a couple cans of seafoam and doing the 3-step procedure for helping you clean out some of the carbon. Removing your TB and fully cleaning that is also pretty good to do.
Thread Starter
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Joined: Jan 2008
Posts: 181
From: Minnesota
You could have a few sensors that are going bad or are dirty that will affect your gas mileage.
The MAF (mass air flow) sensor on your throttle body could be dirty. The front bank o2 sensor (on your rear exhaust manifold) could be going bad. These 2 talk to the PCM and tell it how much fuel to dump.
You could also have a bad injector, that is just letting fuel drip out instead of getting sprayed.
Your Catalytic converter could also be clogging up, they are a very common problem with these cars, and they won't always throw a code that they are bad.
Also, your engine could just be really dirty. Perhaps you should try getting a couple cans of seafoam and doing the 3-step procedure for helping you clean out some of the carbon. Removing your TB and fully cleaning that is also pretty good to do.
The MAF (mass air flow) sensor on your throttle body could be dirty. The front bank o2 sensor (on your rear exhaust manifold) could be going bad. These 2 talk to the PCM and tell it how much fuel to dump.
You could also have a bad injector, that is just letting fuel drip out instead of getting sprayed.
Your Catalytic converter could also be clogging up, they are a very common problem with these cars, and they won't always throw a code that they are bad.
Also, your engine could just be really dirty. Perhaps you should try getting a couple cans of seafoam and doing the 3-step procedure for helping you clean out some of the carbon. Removing your TB and fully cleaning that is also pretty good to do.
Thread Starter
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Joined: Jan 2008
Posts: 181
From: Minnesota
Should I get a downpipe with cat from zzp? The 2.5 304ss with cat? New 02 sensors?
Last edited by blueSS; Dec 6, 2011 at 06:15 PM.
Joined: Apr 2010
Posts: 12,601
From: Mentor, Ohio
If you need to replace your cat and want to improve performance, a 2.5" ZZP 304ss DP with high flow cat is a nice way to go (I put one on my Monte).
I actually cut open my original DP before I sent it in for a core, and ZZP is right, the stocker is restricted.
Keep in mind, any aftermarket CAT may result in an erroneous Check Engine code. There are fixes for this (best is have the code deleted from the PCM, other method is using the spark plug anti-fouler trick to space it out of the exhaust). I had my ZZP DP in for a whole summer, no code, winterized it and due to other mods, coded deleted the following spring.
As for the O2, don't worry about the downstream (after the CAT) O2. It does not affect performance, it just measures emissions. If you decide to change your upstream one (on the rear exhaust manifold), go AC Delco (preferred) or Delphi. Each O3 reads reads a little different, GM calibrated your PCM to work best with the AC Delco one.
I actually cut open my original DP before I sent it in for a core, and ZZP is right, the stocker is restricted.
Keep in mind, any aftermarket CAT may result in an erroneous Check Engine code. There are fixes for this (best is have the code deleted from the PCM, other method is using the spark plug anti-fouler trick to space it out of the exhaust). I had my ZZP DP in for a whole summer, no code, winterized it and due to other mods, coded deleted the following spring.
As for the O2, don't worry about the downstream (after the CAT) O2. It does not affect performance, it just measures emissions. If you decide to change your upstream one (on the rear exhaust manifold), go AC Delco (preferred) or Delphi. Each O3 reads reads a little different, GM calibrated your PCM to work best with the AC Delco one.
Joined: Apr 2010
Posts: 12,601
From: Mentor, Ohio
I would not worry at all about the downstream. Just make sure that Overkill PCM has the codes deleted for the CAT (I believe that is the PO420).