I'm new to this forum so please let me know if this topic has already been covered - I looked and couldn't find one. A friend, who is not mechanically inclinded, dropped his 1978 930 Euro off with a bad idle problem. He stated that the first cold North Carolina day a few weeks ago the idle went high and never came down. So instead of dropping if off then he started adjusting the Idle screw on the injection unit - which did drop the idle but now it will barely run, hard to start, and back fires. So I have a few questions:
1. Which part should I check first - WUR, Thermo Time valve, Aux air valve, pressure regulator or none of the above.
2. Depending what you say to test first what is the best way to test it?
3. Once the initial problem is fixed what should the idle adjustment base line be (number of turns out from all the way in)?

The car is all original 80k with a new K27, 1bar spring and exhaust. The owner did install a 02 monitor in the dash but it is not a wideband.

Please help guide me. Also, he has been trying to adjust the Mixture screw by what the low band O2 is telling him. Is there a tuning procedure for non-O2 equip'ed car? I just moved and my CO monitor is still in a box somewhere. I found the articles for the new system but not the older ones.

Thanks
Lou
nd4speed@aol.com

 

One more thing - the air pump belt is missing all of the ribs which I don't think should effect the idle but just wanted to give you all of the facts(not sure when the belt gave up). I have gone through and checked all of the vacuum lines which all seem ok.


Thanks

 

Sounds like the Aux Air Reg not the valve. The regulator has a heating element strip in it. As it warms up the door closes up and causes the idle to drop. If the heating element goes bad, and they do then it will have to rely on the warmth of the engine to bring the strip over and close the door down. One quick way to check this is while it is idling high clamp off the line coming from the intercooler to the AAR. If the idle drops then you have it licked. Check to make sure that the AAR is getting 12 volts thought before you call it bad. If it does replace it, if not then trace the lack of 12 volts down and you will have a normal car again.

 

All,
I just changed the aux air reg and the WUR and the motor still won't idle. I checked all of the vacuum lines and they all looked good. While I was in there I replaced the plugs (came out very black), wires, cap and rotor. The motor will only run if you keep it above 2k and then it pop's/backfires randomly and doesn't sound real smooth (would an overly rich or lean cause the motor to backfire?). If you take your foot off the pedal it will just stall out. If the cold start injector was stuck open would it behave like this? There isn't too much more to check out. Not sure where to go next.
Thanks

 

Sure, if the CO is way off then it will not idle. The wrong mixture is present.

However what it sounds like is an intake leak with the no idling until 2K. Enough air has be drawn around the plate to allow enough fuel to be passed through the head to idle. The popping represents more or less a lean pop. If the CSI was stuck it would flood the intake and not run at all or pour out smoke.

Pull all of your connections with O'rings and check them. Check the boots and any connection to the fuel head. It will be there somewhere.

Plugs in these cars will be black when checked at idle. The CIS does that. In order to properly read a plug it has to be done by killing the ignition under WOT and boost and pulling over to the side of the road. Pull the plug there and read it. The minute you idle it will go black. Ok, maybe not the minute but pretty soon after that.

Check for intake leaks. I would bet you have one or the CO is WAAY off.

 

It might not be the case but you have just described a plug wire to the wrong cylinder. Ask me how I know this.
Rudy

 

Or wiring the cap clockwise when it should be counter