Fuel cuts durring emissions test. HELP!

[DSMmonster123]

Ok this one has me stumped. I have to take the car in for emissions and twice it has had the same problem. Because it is an AWD they can't put it on the dyno and spin the wheels so the leave it in neutral and free rev the engine to 2500rpm. For whatever reason my car cuts the fuel anywhere between 1900 and 3000 rpm on free rev. It goes up, stabalizes, and cuts fuel. Wideband goes to max lean, rpms drop below 1900 and it tries again. Therefore the test center's computer won't let them run the test. so what is it doing?

My car runs absolutly fine on the road under load. there are no emmsions solenoids that open durring this event, I've checked. I'm running speed density and have a narrowband simulation from the wideband on dsmlink. Blowoff valve it open due to lower vac but shouldn't make a diffrence due to speed density. no intake leaks i've checked. It sound electrical or some ecu setting but I have no idea what.

Any suggestions?

 

[steve]

Are you simulating the idle position switch in DSMLink? What about TPS voltage scaling?

I bet it doesn't take much throttle opening to hit 1900-3000 RPM free-reving.

 

[DSMmonster123]

I have a working idle switch and 2g tps. idle switch is off at that engine speed. i had the same thought and it does only open 2 or 3%. i'm leaning towards something to do with the fuel trims and when they activate. i've returned those values to stock but it made no diffrence.

 

[steve]

Post a log of it doing this.

 

[DSMmonster123]

i added closed loop and selected fuel trims to it. maybe it is in open loop between these engine speeds? this log does not contain above 3000 I guess I stopped it when I before tried above 3000 rpm.

 

[navyissuedsm]

That is a very strange issue to have. Are you running a performance map with the stock exhaust for Smog purposes??? If so maybe inserting the exhaust probe for the test is creating enough back presure to make the engine cut fuel because of knock.

Hopefully some log info will help track down the issue.

 

[steve]

Looking at the log your dropping out of closed loop pretty regularly.
The airflow/rev is low ranging from about 0.12 to about 0.26 g/r and it doesn't track RPM very well.

You can see the injectors being cut off but it's not due to the throttle closing or some specific RPM like coasting FC. I see that you have made changes to the OpenLoopThresholds and STFTAndO2Feedback direct maps which could have some impact here.

 

[DSMmonster123]

so I set the fuel trim selects to stock. However it didn't make a diffrence which makes sense since they run off of MAF signals. Heres a new log. What I've noticed is in order for this fuel cut event to occur the rpm's must be between 1900 and 3000 and the coolant MUST be above 200. This log shows it reving fine at 190 degrees and cutting fuel above 200. It also seems to ignore front O2 input and runs off of open loop tables above 200. Below 200 it corrects fuel mix normally. I just don't understand.
Has anyone else had trouble with emissions while running speed density??

Actually now looking deeper into the log it doesn't seem to depend on anything. there are two points towards the end where it for seemingly no reason drops into open loop and cuts fuel.