2.3L ('83-'97) Check engine light

[craig]

My 97 b2300 has a check engine light stay on after my mechanic rodded out my cat it also has a glass pack muffler. And a 2.3L engine. Problem now is that the computer is put the engine in limp mode it is hard to drive around town with the ac on, it has uneven engine idle and I’m guessing poor mileage. Wondering if there is not a way to tweak the computer so it will perform better without the cat thanks Craig

 

[pentode]

Was the cat plugged or were you looking for more performance? I hate to say it but I think it's probably more expensive to either buy the gear to tune it or have someone tune it than to just put a cat back in it. I'm not even sure it's possible to get the computer to ignore the downstream sensor and I don't think there's much performance to be gained anyway. If you want to run it without a cat, my guess is it's going to be an ongoing project trying to get it running right. Maybe someone here knows more about tuning that particular ECU.

You should be able to megasquirt (or other aftermarket computers) it but that's an even bigger project.

 

[craig]

Yes the cat was clogged was told an engine performance improves without one

 

[pentode]

In theory, the more free-flowing your exhaust is the more power you make. In practice, these engines are finely tuned to work as designed, there's not a ton to be gained without some pretty serious mods, and the computer is in charge of everything. With no cat in it it's going to be seeing the cat isn't working, trying to protect it from melting down and freaking out when it fails and going into safe mode.

The short version is its probably easier and cheaper to make it run with a cat than without one.

 

[Curious Hound]

What are the codes? Are you positive that that is the problem or the whole problem? What happens if you unplug the downstream sensor? What happens if you remove it from the exhaust but leave it plugged in electrically?

 

[scotts90ranger]

There is no limp mode for not having a working cat, it will just complain. To be in limp mode you have an actual problem like misfire or cam sensor not lined up or something that needs actual diagnostics. Check the timing marks on all 3 pulleys, make sure the plugs and wires are good and plugged into the correct ports on the coil packs. Aside from that there could be other things going on...

 

[Curious Hound]

There is no limp mode for not having a working cat, it will just complain. To be in limp mode you have an actual problem like misfire or cam sensor not lined up or something that needs actual diagnostics. Check the timing marks on all 3 pulleys, make sure the plugs and wires are good and plugged into the correct ports on the coil packs. Aside from that there could be other things going on...

Thinking about what he^^^ said.... There is a reason why the cats got clogged up. If it were me, I'd be checking all kinds of things like timing and trying to fix what clogged the cats.

 

[craig]

P0171 will see what happens when removed (o2 sensor) from exhaust system while leaving it electronically connected

 

[scotts90ranger]

Running lean can be from many things, one is the pre cat O2 sensor, that one is needed and if it is still the original one it could be bad but I'd wait until you check some other things. First off get a can of MAF cleaner and clean the MAF sensor, if it isn't seeing enough airflow it won't be giving enough fuel to run and you could get a lean code like that. Next misfires can make the O2 sensor it is running lean since there's unused oxygen in the exhaust (the unburnt air/fuel mixture of a misfire is what takes out catalytic converters, it burns in the cat and exceeds the 900C temperature the substrate melts at).

They also run horrible if somehow the cam sensor that is on the auxiliary shaft isn't lined up, worth checking and possibly changing the timing belt if it is in bad shape.

If all that checks out I'd probably get an O2 sensor, you might luck out and it comes out easy enough like mine did with just an open end wrench...

FWIW, spark plug anti foulers help with post cat O2 sensor codes, but that's not what you are fighting

Wasn't really trying to be short or harsh earlier, just was short on time...