Is this Lambda ECU Dead?

scmguru · 06-08-2009, 05:48 PM

I've been trying to track down why our 1986 930 has been acting so strangely and why I just can't seem to get it running properly.

I noticed the frequency valve stopped working and when I checked the connector, I discovered no voltage.

I searched the forums and have checked the following:

1. Engine compartment o2 sensor relay is working.
2. Pins 5 & 16 on the lambda connector have grounds, though one of them isn't great.
3. Pins 8 & 15 have 0 voltage.
4. Interior/dome light works fine (fuse is OK)
5. O2 Sensor is OK.

Is there anything else I should check before I look into sending it out somewhere for repair?

Thanks!

Mike

Gogar · 06-08-2009, 08:13 PM

Does 1986 have a relay in the lambda circuit? If it does, might want to check that, and maybe swap in a known good one to see if it helps.

john walker's workshop · 06-08-2009, 09:02 PM

the 930 has a standard round black lambda relay on the engine area electric panel. the FV has power when the engine runs and the computer modulates the ground to it. sounds like your computer is not being turned on by the relay.

scmguru · 06-08-2009, 09:34 PM

Thanks for the relay info.. I swapped relays with a known good relay and I've still got no lambda.. Could you tell me what pins on the relay should be hot and when?

The only time the relay "clicks" is when I pull the green connector off of the back of the air flow meter.

Thanks!

Mike

scmguru · 06-08-2009, 11:05 PM

Did some more digging and determined I didn't have 12V+ to Pin 30 of the Relay, I jumpered 12V+ into it and BAM! the Frequency Valve fires right up. (sounds almost like an electric razor)

I can honestly say, I've never heard it before and I've been in the engine compartment for the last couple of months trying to figure out why I couldn't get a handle on proper rich/lean tuning.

The car has been to 2 separate Porsche specialists and neither one of them checked to see if the lambda computer/FValve was even running.

Will get everything buttoned back up tomorrow and report back.

Thanks for all of your help!

Mike

john walker's workshop · 06-09-2009, 06:45 AM

be sure to reset the CO and clamp the air pump output hose before you do it. the shop probably compensated for the lean condition (FV inop) and set it to what would be normal with a functioning system. now it will be very rich with the FV working.

scmguru · 06-09-2009, 10:50 AM

She's all back together and running great.

Feels like a totally different/new car.

John's dragging a boat anchor analogy was 100% spot on.

I couldn't be happier!

Thanks everyone.