Idle issues with A/C now running poorly
 

I have 1988 911 with a 3.2. The car went through a ground up restoration 3K miles ago. A few weeks ago, the engine started to stall occasionally when I pushed in the clutch while the A/C was on. Now the engine struggles to maintain a consistent idle with or without the A/C on. In addition, it has begun to run very rough. It won't pull over 5K RPM and makes little power. I've checked the plug wires to ensure that all are connected. (They are) I've read some threads that lead me to believe that it may be the idle control valve. Can anyone confirm this? Would this valve also cause these other issues? Thanks for any help/advice
WC

I don't think the ICV would affect ability to not pull past 5K rpm unless it has a massive vacuum leak at the valve or hoses. I'd check for vacuum leaks and AAV, though.

Would've suspected the clutch switch (prevents starting unless clutch depressed) but since it starts -- just runs rough -- not likely clutch switch or fuel pump.

Does this happen both hot and cold? Or just one/other? If just hot, check cylinder head temp sensor.

Otherwise, sounds more like misfire; check coil and reference/impulse sensor.

Hope this helps; keep us posted.

D

Thanks for the info. The A/C /stalling issue happened when hot. Basically as I was pulling to a stop and pressed in the clutch, the RPM went below idle and would not recover, stalling the engine. This will still happen. This new issue now does seem like a misfire as you mention. I have checked visually for leaks and cannot find any. Incidentally it seems much more pronounced under load whether hot or cold. It will rev (albeit it a bit rough) in neutral, but when driving the car bucks and misses, and will not rev. Can you tell me how to check the coil without getting killed? :-) Just replace? How can I check the impulse sensor? Thanks again

that might be your temp sensor

Fixed it for you. ;)

My '88 does not have a clutch pedal switch for starting.

Gee Milt that is what i was thinking, why isn't that what I wrote? Old age is creepy.

FYI: My temp gauge on the dash has never registered more than 130 degrees even after running in Fla heat. I assume that this is further evidence of the temp sensor being faulty? Any tips on removing it would be greatly appreciated. It looks impossible to get to.

Hope this helps. Keep us posted.

http://forums.pelicanparts.com/uploa...1288756022.jpg

You see why I inserted "head" temp? :D

Update: I tested the sensor and it was 1.7kohm. So it's not the problem. I put it back together and started it up. The car still idles lumpy, but it revved freely in neutral. It still stumbles badly under load. I also noticed moisture spitting out of the exhaust, and forming a small puddle inside the exhaust pipe. (Fuel I assume) Any other suggestions? Thanks

The idle can be poor if the idle microswitch doesn't engage. Check the throttle linkage. That is the easiest fix. Next, check your idle mixture. If you are lean you might have delevoped an intake leak.

The poor running can have many reasons. If it happens mostly under load you could have fuel starvation issues (poor filter, fuel pressure wrong, etc). You need a pressure gauge to check the pressure in the rails. The other think could be sensors (AFM, flywheel sensors, etc.) being poor. Or simply bad plugs or wires. Lot's of potential sources for problems.

I doubt that you puddle up fuel in the tail pipe. What you see is most likely condensating water from the exhaust gases and pretty comon with a cold engine idling. It will go away once the engine and exhaust are at operating temperature. Don't worry about it.

If your engine was running very rich you would smell raw fuel in the exhaust and see black smoke. The proper test is to measure CO before the catalytic converter.

Ingo