ICV buzzing with ignition off

[Sidebp]

Hi,

Hoping this one will be a little last escapade which resulted in an ECU refurb.

My 1988 3.2 Carrera has just developed a fault whereby with the ignition off the ICV continues to buzz thus I assume receiving power and control signals. To my awareness, none of the other electrics are powered on when the ignition is off.

Could this be the symptoms of a faulty DME relay? If not, any other troubleshooting advice? 

Thanks.

[SurlySurdi]

Where are you based, maybe swap your relay for another to test? What happens after you disconnect the battery, wait a minute then reconnect, is it energised then?

SS

[Sidebp]

Based near Bishop’s Stortford.

I haven’t got a spare relay (rookie mistake I know), will try disconnecting battery and then perhaps order a DME (don’t know anyone locally with one).

[SurlySurdi]

Does the car run OK otherwise? 

SS

[Sidebp]

Generally running well once warm. I started looking into it when trying to resolve a different issue whereby the car would stall when cold unless throttle added to bring revs up.

Initially the ICV was dead (not buzzing) and wide open hence the stalling at idle. After putting everything back together having tested the ICV I reconnected it and noticed it had come to life but now wouldn’t stop buzzing. With the valve installed it now starts and idles perfectly just won’t switch off when ignition goes off.

[SurlySurdi]

Does it carry on with the key out? Or when the car is off and locked?

How long does it keep buzzing for?

SS

[Sidebp]

Runs all the time.

Plot thickens, I went out to the car tonight, turned off alarm, dash lights on, fuel pump whirrs but no crank at all, completely dead

[SurlySurdi]

Hmmmm DME relay is the first thing, there is a method ive used to bypass the relay entirely (it's well documented on the forum just search for DME)  but you say the fuel pump is whirring. I'd bypass and then try cranking.

SS

In fact , here you go, a full DME primer and diagrams to show how to bypass:

https://dorkiphus.net/porsche/showthread.php?t=16859

SS

[Sidebp]

…and went out to fit the new DME and the battery is flat. So something is a parasitic draw, potentially the ECU if the DME is faulty.

[SurlySurdi]

Interesting, have you a booster or jump pack? You need to sort out the power source then it's a process of elimination to work out where the draw is coming from. My bet is it won't be the ECU but with all the random behaviour you need to get to a position of stability and/or have a situation where something is repeatable even if it is going wrong. Might be worth looking up an auto electrician to do some basic diagnostics.

SS

[Sidebp]

It’s on the trickle charger so will give it some juice and go from there 

[SurlySurdi]

Once it's charged, before you connect the battery again check the voltage with a multimeter, then connect the battery to the car and check using the meter again for a drop in voltage which would indicate a draw from somewhere. If you have an alarm try and isolate it then it's a process of elimination after that if there is a draw.

SS

[Sidebp]

All sorted. Treated it to a new battery as the other was pretty old, then replaced the DME which stopped the ICV from running at ignition off.

Checked voltage with the new battery and old DME, with old DME removed and then with the new DME and the readings were 12.62v, 12.43v and 12.63v respective. 

Thanks for your input.

[SurlySurdi]

Great to hear that, well done! Always such a relief to sort out these issues especially when you've learnt something. Now make sure you drive her!

SS