s50 Car sometimes Idle is not steady, but with o2 sensor disconnected.

[BingM3]

Hi guys, need your inputs:

With the o2 sensor connected the car sometimes would have an irregular idle when car is at a complete stop, sometimes it would stall.

No problems when you put load...

Upon disconnecting the o2 sensor, the idle is rock solid and does not stall.

Car has no vac leaks & ICV cleaned.

o2 sensor is brand new - could it be a defective sensor?

Car has no cat anymore/straightpipe

Thanks

Bing

[PiercedE30]

have you checked the heater relay/wiring.......it may be cooling off too much when it's idling and when you unplug it it would get put into closed (i believe) loop mode.

[tjhartge]

have you connected the speed sensor to the DME?
do you have a/c on the car?

if you didn't connect the speed sensor, the car idle will die at stops and have irregular idle lumps
if you a/c on the car, you need to connect the a/c system inputs to the DME, else you will have the same effect

after i did both, it has been a solid and stable idle

[BingM3]

The AC is disconnected due to fabrication needed in the spring. I have the lines in the bay but need to be customed for the e36 compressor. Why would it cause a possible idle problem? Fill me in.

Speed sensor connected

Pierce, on the heater relay/wiring - this was not touched during the conversion. What exactly do you mean? My heater is working

Thanks

Bing

[PiercedE30]

Well, we would need alittle info on how you went about the wiring harness adapter for your swap. With pin 6 on the C101 plug side of a plastic bumper e30, it would be the wire for the O2 heater relay, but (not sure of others) on my swap I ran it straight to the diagnostic plug since the heater relay is controlled by the DME (on my swap). The relay that controls this could possibly be dead or could not be getting a signal from the DME, and if the latter is the case then I would begin going over the wiring and possibly switch out DME's for a known good one to check and see if it is possible that you have a bad DME.

But then again it could be something else. But I don't believe that to be since you are only having these problems when you connect/disconnect the O2 sensor.

Jon

[BingM3]

Here is the update, idle problem is now good.

Changed Turner Chip in DME with stock 506 chip, O2 sensor connected.

DME is 413 silver, no problems, started, no longer stalling and smoother idle by 90%.

Also, can has better powerband with stock chip, pulls hard in mid to high rpms

Turner chip was all over the rpm range, fast low-mid but weak top end

Weird but it is what it is.

Also put in a 6 cyl coding plug in cluser, correct reading now of rpm tach

Thanks guys!