WS6 Canada

I removed my cat back and now only have spiral flow mufflers and then dumps. My car is a dragcar with some street driving. The problem is my FAST wideband is showing 18.9 A/F. By removing my exhaust would this cause this problem??? yet it smells like unburnt fuel in my shop??

Please give me your thoughts

WeathermanShawn

iTrader: (1)

Where is your wideband 'bung' located?

You might try the 'free air calibration' of your wideband O2 sensor. I had the reading once, and that turned out to be the problem.

Hard to believe you could effect the injector pulse width and make it leaner by just dumping cats and going to sumps. I would try to reset your wideband O2, and try it again. Sounds like a 'false' reading.

WS6 Canada

the wideband is in the collector's (dual system) both sides read lean. when I lay under the car and put my feet against the mufflers, i can drop it to 16.5???

WeathermanShawn

iTrader: (1)

Well, the only other thing I can think of is an exhaust leak. Something would have to be mixing in additional O2 to have the sensor read that lean.

Again, its hard to imagine the actual PCM has recalculated the IPW to go that lean, but I could be wrong. Usually that is controlled by your VE Table and/or MAF. If that did not change, then it is either the sensor or an exhaust leak..

Thats my educated guess..

WS6 Canada

I have new NTK sensors in..... All worked fine untill I removed my y pipe and catback??
Is it possible that with little back preasure the 02 sensors for the car just don't have time to read the A/F??? I trust my wideband is right, most drag racers have them in the collector with no mufflers or dumps.

WeathermanShawn

iTrader: (1)

Its possible.

Need to figure out a way to get reliable readings. But, your theory has some validity.

Now, for the solution???

joecar

If it is misfiring, then the fuel is not being burnt, and the wideband will read lean (since there is excess oxygen).

01Z28M6

As little as I know, this is something a lot of people miss. An exhaust full of unburned fuel also has a lot of unspent oxygen in it.