Carrera 4

I have a 1990 911 Carrera 4 that has just had a complete engine rebuild and have stalling issues:this occurs; in traffic or at a stop/red light when I take the car out of gear and step on the break the idle drops so low all the dash red lights come on and the engine dies out. I restart it right away. And the idle picks up to normal. Once in awhile all the red lights come on but it come back to life and the engine returns to normal idle.

went back to the shop where they tweaked the Idle as much as they could , but to no avail it still dies... they mentioned that due to the modified cone air intake sensor sensitivity to the cold weather (that I don’t agree with as the car used to be run winter and summer) and the fact that the engine needs time to break in that I need to wait a few weeks and with the warmer weather and some additional break in of all the new engine components it should iron itself out. What do you think?

Mr.Alex

Does your idle fluctuate? Perhaps try cleaning the ISV. On the rebuild, did you by any chance go with a lightweight flywheel?

robt964

Is the throttle idle switch 'on' with your foot off the pedal?

Derek911

I would check the condition of the battery. A new battery can fix stalls at idle. I had similar stalls at idle. New battery fixed it.

sml

We've been through this many times before .... Step 1 is a system adaptation with the Bosch Hammer.

https://rennlist.com/forums/964-foru...daptation.html

After the system adaptation, then do this ...
- new ISV
- Steve Wong chip
- new coils
- new fuel filler neck & cap
- checked for vacuum leaks
- new air filter
- cleaned AFM
- fuel injector cleaner fuel additive
- new oxygen sensor

Carrera 4

Wow, Thanks, lots of stuff to look into, "throttle idle switch" could you explain please? Battery is only 2 years old, but I will recheck the connections, the gentlemen that took care of the rebuild also race these little beasts and really know their stuff.... so I believe, this is not their first rebuild. how do you clean the ISV?

dlpalumbo

I have recently gone through a rebuild and had idle issues. I did 3 things:

1) Fuel adaptation
2) Checked codes. Turns out 02 sensor had disconnected
3) Fresh gas and gas treatment. My car sat for a loooong time. If your gas has ethanol in it, it will absorb water and the car will not run well.

Now its fine. Good luck,

Dan

Mr.Alex

The ISV can be cleaned by just hosing it down with carb cleaner and giving it a little shake to move the valve around.

To check O2 sensor, unplug the sensor in the engine bay, and then unplug your battery for a few minutes. Then connect battery and start the car, if it runs alright without the o2 installed then that is your culprit.




The idle microswitch is this little box, watch to see if that little red button is depressed at idle.

Carrera 4

Thanks once the weather gets better I have a lot of tasks to try.....Snow again when will it ever stop....

sml

No we cannot explain because you have to do system adaptation with Bosch Hammer first.

Please do system adaptation to fix problem. The other list is just for fun.

Carrera 4

Anybody know where I can get this done? I live in the Montreal area.

Earlydays

Every independent Porsche repair shop should have a Bosch "Hammer".....

Carrera 4

Almost have 400 miles on the rebuild, still having to cope with the “Stall out” situation, still occurs intermittently, but the revs still drop below 200 most of the time and climb back up after seconds…. When depressing the clutch and breaking for cars in traffic or for red lights or stops, the revs still drop to almost zero then sputter and kick back up and re level at about 950 which seems to be a normal idle, sometimes she just stalling out without kicking back up. My wife refuses to drive the car anymore….(that’s not bad for me…lol), but it does make me uncomfortable, after stalling out a few times I tend to ride the gas and clutch more and I can smell that’s not good. I am trying to cope with it by leaving the car in gear until she is almost at a stop and the revs are around 1000, then depressing the clutch and breaking, it seem to help the revs from dropping….. but I don’t think that’s the right thing to have to do.

I've tried everything but the Bosch Hammer approach, but every time I ask local mechanics they send me a new list of things to look for... this is becoming ridiculous ..... most of these Porsche guys say it will stabilize itself...

Your thoughts?

klokwerk

Don't know if this'll help you but it cured this problem for me.

In your driveway start the car up and then rev it a little to get it above idle then let off the throttle.

If the idle is really low, it could be the same problem I had.

Apply the parking break and leave the car running. Get out and open the engine cover up and take a look at the idle micro switch.

Is there any gap between the throttle plate and the switch?
Can you press that throttle plate back at all onto the switch?

If the answer is yes, the switch needs to be adjusted so that when the throttle plate comes back to the idle position, it fully contacts the switch and presses it ALL THE WAY IN.

If it's partial or off, then you'll stall out.

After adjusting this on my car, no more stalls.

Good luck!

vespam5

Check your distributor drive belt.........if the belt breaks it can cause similar issues.