Failing 02 sensor symptoms...

[gvr4ever]

I replaced my 02 sensor once before. Maybe I don't remember all the problems that it caused, but I remember bad fuel economy and a CE light.

I'm having a problem with my car that I thought was a repeat fuel delivery problems, but now I'm not sure sure. I took the car out on an extended drive today. Got it really warmed up. Probably had it out for about 40min driving it around.

Starting out cold, the engine smells really rich and runs rough. I noticed today that my A/F gauge took way longer then normal to start register. Then when it started too, it seemed to have a delay from the time I hit the gas, till the gauge registered a richer condition. This is a very new symptom. Driving the car before the engine is all the way warm, the car sputters, has a throttle delay.

After the car was fully warmed up and I had been driving it for awhile, I noticed it ran exactly like it should. Under normal conditions anyway. I have the boost set to 7psi and I'm not touching WOT till I get this figured out. I've hit 5psi at about half throttle or more and it seemed to be acting right. Throttle response, idle, boost all act perfectly normal once the car is warmed up.

I don't have a CEL light, knock gauge never goes off, but could a failing 02 sensor cause all these problems? If not, what else could throw off air fuel ratios when cold? Their also seems to be a slight delay when warm too.

Tune has been the same for years. Keydiver chip, 550cc injectors, 3G MAF. The car ran perfectly at WOT at 18psi like 1.5 weeks ago or so. Something changed, but it wasn't parts or tune.

COP, plugs, wires, are all new. I checked the base fuel pressure again. The timing was checked not too long ago because the CAS was changed out. I can do another boost leak, but I did one not too long ago. The way the boost gauge reads, I'm pretty sure that's not it. Boost climbs normal once the car is warmed up.

Any ideals?

 

[ktmrider]

O2 or ECU coolant temp sensor.

 

[misterfixit]

Get it on a logger and look at the o2 readout. it should be cycling about the 0.5v Mark IIRC. it will do this naturally as you load and unload the engine. The reaction time should also be fast.

If it doesn't follow this then the o2 sensor is toast. They stop working after a while due to silica build up on the sensing element. This can come from the fuel.

There was a scandal in the UK about three years ago where a Petrol chain let the silica go out of spec and cars were having this issue as a result of it.

If you a log in mmcd, then put it in excel and plot the coolant temp, throttle, injector time, revs and the o2 readout. This way you should be able to see the fuel delivery increase and the o2 readings should peak in in coincidence as they signal the ecu to lean out.

If the graph doesn't show the o2 readout as reactive or achieving full scale, then its time to change it.

Have a look on the DSM technical information manual floating round the net. There is a graph of the o2 sensor characteristic with values quoted on the axis. I seem to. remeber 0v-1v, but please check.

Hope this helps,

Rich

 

[misterfixit]

Get it on a logger and look at the o2 readout. it should be cycling about the 0.5v Mark IIRC. it will do this naturally as you loaf and unload the engine. The reaction time should also be fast.

If it doesn't follow this then the o2 sensor is toast. They stop working after a while due to silica build up on the sensing element. This can come from the fuel.

There was a scandal in the UK about three years ago where a Petrol chain let the silica go out of spec and cars were having this issue as a result of it.

If you takea log in mmcd, then put it in excel and plot the coolant temp, throttle, injector time, revs and the o2 readout. This way you should be able to see the fuel delivery increase and the o2 readings should peak in in coincidence as they signal the ecu to lean out.

If the graph doesn't show the o2 readout as reactive or achieving full scale, then its time to change it.

Have a look on the DSM technical information manual floating round the net. There is a graph of the o2 sensor characteristic with values quoted on the axis. I seem to. remeber 0v-1v, but please check.

Hope this helps,

Rich

 

[gvr4ever]

Foot in mouth.

It was a boost leak. Guess that should be done every time the car is running strange. I just checked it about 6 weeks ago but still some how got a pin hole leak on weld near the BOV mounting point on the intake. I'm gonna get it fixed at Fathouse Fabrications this week.

 

[iceman69510]

(keep the car, keep the car, keep the car...)

 

[gvr4ever]

It's going to take some real coin for me to let it go. For now, maybe I can at least break in the new tires.

Oh, Dave, I'll get that extra injector to ya. I wanted to throw in some extra stuff too.

 

[gvr4ever]

Problem and solution.

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