964 C4 Cruise control and intermitent transmision warning

Fordartur · 01-12-2006, 12:22 AM

Good morning to everybody

I've a 89 C4 since a year ago, it had a minor malfunctions, but due to lack or time, I didn't attempt to fix it... till two week ago.
Thanks to older posts here I have a clear idea about my sudden loss of power and rough idle till stall in my little beast, guess is the airflow meter unit (anyway, I changed the DME relay and now gonna change the motor temperature sensor located in the 3rd head)... anyway, I'll let it clear here when I solve it for future fellas requesting.
Now I have two "minor" problems:
My cruise control don't function and I don't have ANY idea due to my lack of knowledge about it, I was looking in internet but no luck, so if somebody could help me with some advise about what to check or test... it would be simply great.
The other problem is that the blocking diff warning light is switching on and off without sense... I don't know if somebody suffered the same and could help me a bit about that...
Any idea or advise will be really welcome!
Many thanks to everybody who care to read this.

Artur

colo964 · 01-12-2006, 09:32 AM

Your engine symptoms can also be a bad O2 sensor (among other things). Try unplugging it and see if it smooths out.

The diff light may be a bad sensor (located on the drive tube just below the spoiler and locking diff switches). One of them (I think the one mounted closer to the shift knob) makes that light go on when bad, while the other one makes the both diff and ABS lights go on. These sensors are about $300 each. I've flip flopped mine and made my warning lights less prone to flicker. Also cracked them open to try to center the sliding mechanism, kinda works too.

My cruise control has also been acting up (or not acting) lately - it works only 1 in 5 times. Might be a bad clutch switch or dirty/worn multi switch. I pulled open my control unit (under the passenger seat) and didn't see burnt parts or bad solder, so probably is not that.

Fordartur · 01-13-2006, 01:48 AM

Well... then I'll try to check the O2 unplugging it, although unfortunately the car isn't suffering that always (is curious but it passed when I was in the snow, from minus 10 degrees to 5 degree Celsius, not in the city or in more warm places). Before to find this wonderful site I dismount the airflow from the car (it seem completely new and clean), so now I'll mount it again and test what you advised me.
Before to contact here I asked to porsche dealer and they told me to change the heat sensor in the head, that maybe that could fail when hot, but I guess that isn't the problem (well, to be sincere, they told me to begin changing that, and after that the complete airflow system... imagine! real pro people!)
About the cruise control I'll follow what you said and take a look the control unit under the passenger seat and check the switch (guess is under the clutch pedal?) too.
For the diff light warning... well, I'll try to locate it and check it (I didn't understand what you mean with with "flip flopped".

colo964 · 01-13-2006, 07:01 AM

On the airflow, you might have to open the black plastic part. There is a copper contact - mine broke so I soldered a wire in its place. Also check for loose intake hoses and the six rubber couplings at the manifold. (I'm guessing the 89 doesn't have a check engine light - so it makes it a little harder to troubleshoot a sensor vs non-sensor faults).

Flip flop means to switch places.

Fordartur · 01-13-2006, 07:31 AM

Thanks for the information, I'll do it and I'll tell you about. Hope it will be like you suggest... anyway, I've read a way to jump the o2 sensor quite simple.
About to open the black plastic, it is clear to see that copper? It is sealed with silicone, so I'm a bit afraid to crack something (I don't know if it is delicate or not) anyway I know that bosch repair the airflow meters for less than 250 USD, so shouldn't be too much complicate inside (that part new here costs around 1000USD so is interesting to try...
And yes, the auto checking is from '91 on models... bad luck.
By the way, do you know a cheaper substitute of the hammer? (for my audi I just need a cable OBDII and the VAG program and a portable)
Really, many thanks for your advises, they are really welcome.

Fordartur · 01-16-2006, 01:50 AM

I've done what you suggest, I've checked the afm and seemed pretty ok inside, I opened it and all looks good (I didn't looked under the electronics). As you said me, I disconnect the o2 while the car was idling and no changes, I cleaned deeply the intakes and all the electric plugs.
I test the car in the road raining and didn't misfire, but I felt some light stalls... I've runned 50 km with this short stalls (do you think that it could be due to some cleaner rests on the intakes?)
did you ever changed the head temperature sensor? It is difficult?
About the diff light... incredible... I refill till max level the oil reserve (wasn't empty but I did anyway) and the warning dissapeared! no alarms in the 50 km... crazy because I didn't seen no sensor in the bottle!