ICV Testing
 

Gents,
I am in the process of chasing down a rough/low idle on a 1991 C2 964. I have cleaned the ICV with Carb cleaner and I can hear a faint rattle in the valve. When I turn the ignition switch to the run (not crank) position, I am expecting to feel the valve vibrate, no such luck. What is the procedure to test for power at the connector of the ICV? should I be looking for amps, ohms or voltage? I would hate to buy a new valve and find out the original valve was still good. Any help would be great.
Thanks in advance,
Phatnine11

It sounds like you are asking about the connection/wiring to the ICV. Did you check the ICV itself? Check out this thread: http://forums.pelicanparts.com/porsche-911-technical-forum/360766-bench-testing-carrera-idle-control-valve.html . The 9V battery test is easy and quick.

Also, there are various methods to check the operation as you read through the thread. Good luck.

John,
Thanks for the help! I built a little test setup with a 9V battery to test the ICV. The valve tested good. I checked the Idle Microswitch, 0 ohms when the throttle is closed, open circuit when I open the throttle. I re-assembled the ICV and took the car on a test drive. As soon as the car warmed up, I lost power and the car was starting to stall. I gave the car a little gas so it wouldn't stall and I had a backfire. I limped the car home and now I have a check engine light. I have a spare CHT sensor, but I would like to test the current one before attempting to replace it. I know where the connector is in the engine compartment, do you know what ohm range I should be looking for?
Thanks for the help,
Phatnine11

You said... "I checked the Idle Microswitch, 0 ohms when the throttle is closed, open circuit when I open the throttle."

I am pretty sure 0 ohms is a open circuit. If your statement above is true, idle microswitch is bad.

The quick mechanical way to check the micro switch is to by hand - move the throttle linkage (engine off & in a quiet environment), listen for a click during the first few millimeters of movement. That’s the switch engaging. If you don’t hear the click, the switch is bad or the plunger is stuck. It’ not loud, but it’s very repeatable. Some say you can clean it with spray, some say be careful not to add anything that will attract dirt and clog the switch.

Here are the CHT resistance values: http://forums.pelicanparts.com/porsche-911-technical-forum/666453-3-6-cylinder-head-temp-sensor-resistance.html

The nice thing about these tests is that they are pretty simple and quick.

DCinVA,
What I meant to say was when the throttle is closed, I have continuity, when the throttle is opened, I have an open circuit. I am trying to fix this but I have no way of reading the codes. So far, ICV and the Idle microswitch seem to be doing their job. My next step is to remove the blower unit and check the CHT readings. Gents, any suggestions?
Phatnine11

Did you check the DME? Easy to check and a perishable part. At least read Adrian's document below.

http://www.adrianstreather.com/docs/Corrections%20Pgs%20387%20&%20388.pdf

JSny,
Thanks for the tip and the article, will check the relay ASAP!
Thanks,
Cesar

To all,
I tested the DME relay and the car runs a little better using the jumper wires, but not much. The car does run with the DME installed, but idle is very low and unstable. i believe the car is now in a 'LIMP MODE', but I do not have a Hammer or a Durametric tool to read the codes (check engine light is on). I will replace the DME, I should have an extra anyway.
Thank you all for the help,
Phatnine11

Hey Cesar, inspect the little belt inside the distributor by taking off the distributor caps. Again, easy to check and can cause a back fire if the belt is broken or has missing teeth, etc.

John

JSnu,
You read my mind. The distributor belt was replaced about 3 months ago, but I still pulled the cap and checked the belt, everything looks good.I was looking at checking the CHT but, getting to the cable inside the engine compartment looks hairy, heater blower is blocking the access. Have you ever removed the blower motor on a 964?
Pahtnine11

Removing the rear blower is very easy. Two 10 mm bolts, 3 connectors, 2 hose clamps. The air duct near the fan just pulls off. The CHT connector is on the connector tree behind the blower. Try a search if you need more detail and pictures, there are good threads on both the blower removal and the CHT resistance values. Good luck.

JSny,
Thanks for the info on the blower motor. Talking to a friend, I have decided to replace the fuel filter. A little history first. The car sat for 7 years with a broken engine. I purchased the car and had a wrench do a top end, we found 2 burnt cylinders. I had the injectors serviced, replaced the injector manifolds (at the bottom of the plenum), new belts, oil, plugs and filters. That is the key word, filters. After a few beers, I pulled the invoice from the shop, I looked for the cost of the filter, it was never changed. I spoke with the wrench and he is trying to get me to pay for a new fuel pump, the filter is cheaper. I expecting an order for a new filter in about a week. local FLAPS want $50.00, online I found them for $16.00. Needless to say, I'm a CSOB! I will let the board know my results.
Phatnine11

Cesar, your friend has a good idea. Do let us know. Thanks

John

JSny,
I read an article on the Rennlist about how to test the fuel pressure regulator. Quick test is to disconnect the vacuum line at the intake manifold that is connected to the FPR. I started the car, disconnected the vacuum line, gas started pouring out of the vacuum line. This is raw gas that was being spilled into the intake. Needless to say, the FPR needs to be be replaced.
Phatnine11

That is really good to hear. There’s nothing better than figuring it out & fixing it yourself! I have learned so much for so many here.

Deleted

Update!
Looks like the problems have been fixed. The issues were: hard starting (hot or cold), rough/hunting idle and loss of power. The FPR was the issue. It took 5 hours to do the job, but it's a totally different car. Tomorrow I plan a nice drive to road test, right it's time for a double shot of a good single malt!
Cheers!
Phatnine11