Author Topic: Under what conditions will the DME shut off the injectors? (Read 7161 times)

DesktopDave · « **Reply #15 on:** March 01, 2011, 09:40:00 PM »

+1 on the DME switching off the injectors on throttle over-run. I'd guess parameters would include: if she's warmed up running closed-loop with the O2 sensor & senses TPS closed, CPS reports RPM and the AFM senses some airflow. It's a cheap way for Bosch to get a MPG or so.

That might explain your symptoms, say if the AFM door was off a little or one of the temp sensors (air, coolant or the O2 heater) was out of range. If the DME then guesses it's on throttle overrun, it kills the injectors, but then the O2 sensor reports too lean. The injectors fire back up & the cycle repeats itself.

I don't think our DME (1.7?) has a limp-home or emergency mode.

fiftytakedowns · « **Reply #16 on:** March 01, 2011, 11:58:10 PM »

How would you suggest that I could start trouble shooting using those tools?

DesktopDave · « **Reply #17 on:** March 02, 2011, 06:36:52 AM »

I'm just guessing at what the system might be doing. There isn't a test I was thinking about, other than the AFM resistance tests you've already done.

MLM · « **Reply #18 on:** March 02, 2011, 03:28:32 PM »

I dont think the ECU is that intelegent TBH. I think it would look at TPS + RPM (maybe AFM) to determine over run. It will kick in again when it passes a low rpm threshold and wont look at o2 at all. Im guessing also but this is what my Link ecu looks at for fuel cut.

Are both throttle plate completly closed? If it is over run cut it must be bypassing air somewhere? ICV to far open?

fiftytakedowns · « **Reply #19 on:** March 05, 2011, 07:34:00 PM »

Swapped in my good spare ICV, still didnt fix the massive backfiring. It sounds like the engine is running on one cyl. does the Cam position sensor have anyhting to do with it?