I was driving back to Rochester today from PA, car ran well most of the way, but once I crossed into NY I got a CEL while on the highway. This dipped my AFRs (on NGK wideband) down from about stoich to about the mid 13s during cruise. O2 sensor I think to myself, pull over, jiggle connector, restart car, no CEL, back to stoich at cruise.

This worked for about 20 miles, then it throws a code again and my AFRs fall off. This lasts a few miles, then the CEL goes off, and the car runs normally, until it goes back into "closed loop" (normally meaning anytime I was on the gas, or coasting or whatever, AFRs were the normal). However, once it switched to closed loop (20% throttle or so accord to SAFC), it would run stupid rich, like 11-10 AFRs. Occasionally the CEL would come back on at it would rise back up to 13s, then it would repeat this process. Tried stopping and wiggling the wire again, but to no avail. Is this just a dead 02 sensor, or did I lose a ground or something somewhere? Again, no CELs, but the car did hiccup a lil under throttle position change, and the wideband indicated it would spike lean then spike rich before settling into a "normal" ratio.

It was about 20F outside, which is far colder than I usually run the car in. It seemed like it had been acting weird during cruise for about a week now... the closed loop AFRs were down in the mid 13s, but with no CEL. I imagine this is just a bad O2 sensor, but after searching my symptoms don't seem to match. Will pull codes tomorrow when its light out and less cold.

Thanks for the help, sorry its so long.

 

it never hurts to check the TPS. and if it's just a bad connector you can just cut and solder them together. and btw a generic Bosch 1 wire O2 sensor is like $50 or something. I don't know what wideband you have but on the Innovate at least you can just use the 0-1V output wire and eliminate the stock O2 sensor altogether.

 

So....you check to see what the CEL is and if it's the 02 sensor, check the wire out and its connections on each end.

The symptoms do sound like a open 02 wire to me. And you know around 3700rpms the closed loop won't work anymore.

If the 02 drops out you'd expect the afr to go DOWNWARDS like you saw.

Like I was driving early this moring in fifth gear at 65mph and the afr are in the 14.7 range as the closed loop tries to keep it there. later on the way back I left it in fourth gear at 65mph. Afr are around 13.6 afr give or take a point. Not in closed loop because the rpms are up in forth at sixty five.

And in close loop at 65 the EGR is showing to be in work, the Port air Solenoid comes on IF I go up a steep slope in the road. Goes out when the road levels. The Relief solenoid is not energized, the Switching solenoid IS energized unless I go down a steep grade whereupon the Switching solenoid energizes (port air now) and then de energizes as the road becomes level once more. Just some FYI that is meaningless to this post.

 

I'll do it first thing tomorrow. Snowing right now... don't have a garage. Will it still give the O2 code even if the CEL is no longer on for it? I think the CEL was off when I turned the car off.

This was all at about 3000 rpm (65-75 mph cruise).

EDIT (for hailer's edit): 5th gear too lol. Where is the port air solenoid? I imagine it got removed with the rest of the emissions stuff but I wanna double check?

 

Intermittent wiring or maybe the 02 is getting old if the code come and goes. 02's are pretty cheap. Bosch are around twenty if the wiring looks good. Maybe wiggle the wiring while the engine is running to see if you can make the code come and go?

I don't KNOW. Seems they would have made the car where it monitored the wiring of the 02 all the time. Might be written somewhere.

 

Yeah, I think that is gonna be the plan, or else take it on a quick drive down the highway and try to get it to throw it. Thanks for the advice!

 

I'd warm up the engine, then as it idles, pull the plug off the 02 sensor. A code should be thrown. Seems it should happen like that. I'm going to do that with my 87 in a while and I'm pretty sure a 02 code will kick in.

 

Opps. Error. I tried this in the driveway and nothing happens with the 02 sensor disconnected. Only if I disconnect it and drive it will the code show up.

 

Thanks hailers, I'm gonna have to postpone my test a day or so then til this snow melts. Good info nevertheless.