My car has developed a severe stumble and sputter. Since the opti is fresh, I think possibly 02s.

I unplugged them first to see if they're the culprit. I was right. The car smoothed out and ran fine, but the SES light kicked on of course. I got a new pair and put them in. Same problem came back not 5 minutes after they were plugged in. I unplugged them again, and the car ran fine. There is no SES light either with the O2s plugged in...just a bad miss and sputter.

Anybody else experience this problem? Any advice on what to check? The car doesn't feel like it is lacking power with them unplugged, but I'm getting 9mpg I will definitely need to fix this before driving it around with gas as high as it is.

Thanks

Brad H.

 

If you just bought new O2s and it still stutters, it's not the O2 sensors. Unplugging them puts your car into limp home mode, and makes the PCM rely on preprogrammed maps. If the opti is new, what about the plugs and wires? Have you ever cleaned the MAF sensor? Just a couple of quick thoughts...

BTW, where did you get the opti? You did use an OEM unit, right?

 

The same thing happing here man. But i havnt got new 02s yet. If you can get someone to scan it and see if the 02s are reading because with the LT headers maybe you burt a wire. I was also thinking maybe the 02 exstention can go bad. I know mine would run alot worse in the rain and i would only get the o2 SES light when it was raining.

Make sure to post when you get it fixed

 

yes, I've done all of the obvious and since unplugging the O2s seems to bypass the problem, i wouldn't think it'd be related to the ignition...but the wires and plugs are 2months old.

 

Will do.

I did a search function and this seems like a fairly common prob but nobody posted their fix Anyways, I'll discount the O2 and rest of wiring on the passenger side sometime this week and take a look inside the loom. The loom seems fairly close to the primaries on the way down to the O2.

 

A good data logging scan, over a wide variety of driving conditions might indicate the problem. Poor fuel mileage is often caused by the PCM repsonding to a "false" lean condition.... it only thinks the engine is running lean, and dumps excess fuel in to correct a problem that doesn't exist.

Typical causes of false lean readings are misfires, exhaust leaks before the O2 sensors, and faulty O2 sensor wiring.

 

Thanks Injuneer. I'll look into the wiring this week. Living in a small town, i don't have access to a scan tool either ...maybe it is time I bought one.

 

Yep, 2 wires from the O2 harness melted together on passenger side. The lines run through some loom and right next to a header primary. I did a quick fix to see if it would work and sure enough it did. Now to find a way to get them away from the header

Thanks for the input guys

 

Looks like I spoke too soon. The car is still doing the same thing. Any other guesses?