JCF

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Hi,
I have a problem with a '84 3.2 Carrera, and in order to solve it, I would like to know the resistance (Kohms) between the pin 5 and the pin 34 of the Motronic (under the driver seat). Look at the pictures to locate the pins.


Thanks.

Lorenfb

Pin 34 is the idle valve driver. Pin 5 is the DME ground. The resistance S/B > 5K ohms
between the pins, assuming pin 34 is positive of the meter.

JCF

Thank you.
I have 5,44 KOhm between this pins, so the negative connexion of the idle actuator seems to be good.

I explain my problem : after starting the motor (cold), the idle slowy grows, about to 1500 rpm and then, return to the normal value.
After approximatly 30 seconds, the idle is good, even if the engine doesn't turn good (backfires).

I thought about the idle stabilizer, so I remove it.

Unplugged, and when I open it fully, the engine runs like my problem (accelerate, up, down...).
When I plug it and I watch inside the flap, ignition on, the flap is middle-opened, and move very fastly each 3 seconds.
The temperature sensor of the cylinder head doesn't seem to change anything.

So on my 968, the plug for this air valve is the same than the 3.2. I try to plug the 3.2 Valve on the 968, then the flap close fully.

The valve works good when the DME wants to close it, but maybe not at middle stroke
That's why I would know how the DME control it. To my mind, it's not a "full or nothing" valve, like the 968. And how to test it ?
If you've ever seen this information...

Thanks

Lorenfb

You check by:

1. checking the resistance between the center pin & each outer pin (~20 ohms)
2. remove the valve & fully close it & re-install
a. start engine with valve disconnected, idle should be very low
b. connect valve & idle should be normal
3. remove valve & fully open it & re-install
a. start engine with valve disconnected, idle should be very high or surging
b. connect valve & idle should be normal

JCF

One more thing :

Do you know what are the two plug (unplugged in my car), leads by two brown wires, near the motronic connector ? And how must they be plugged ?
I think it's for altitude compensation or lambda probe. I also have plug which jump two pins of the lambda plug (instead of the plug of the probe), at the left of the engine.

I don't have wiring diagram for the 3.2... :S

Lorenfb

One is altitude & the other is timing retard for USA & Japan.

Bjm12001

@Lorenfb I'm the process of troubleshooting my 3.2 Carrera cold surging problem. I saw your post regarding the ICV test of opening/closing then checking idle with it disconnected.

Question: During cold start when the DME is adjusting the duty cycle for the ICV is it using RPMs to figure out the duty cycle or something else while it's waiting for the O2 sensor to heat up?

systemsc

It uses the engine temp as the key sensor input when cold, and engine RPM as a feedback parameter.

Bjm12001

Thanks Loren for the info......I noticed when you ground both outside pins at the same time on the ICV it goes to a half-closed position. When I reinstalled the ICV & overlay the 2 scope input waveforms I noticed the ICV is never in a fully open position. It appears the duty cycle is 30% half-closed & 70% full-closed after warm-up but I need to check at cold start. What should I see for the duty-cycle at cold? Right now the engine surges for ~22 sec at cold before it settles at 880 rpms on my 89 3.2 Carrera. No issues with the performance once the engine is at temp!

systemsc

Then you have the idle bypass screw too open.

1997hmc993

Have seen the YouTube btvHeidi and Franny. She had surging problems and checked all systems. It turned out among other things that her idle needle(?) adjustment screw was opened up almost 4 turns by someone previously.
I recommend to watch her video if you haven't yet.
Good Luck.