hunting at idle? plus other stuff, help wanted.

[C-Pierce]

Hi, freshly rebuilt my 3.0 added 964 cams and SSIs. new WUR. went through the motor new everything CIS is all the way it was when I purchased the car (87K OG miles) with exception of the WUR, I added a new one becuase it had a problem warming up b4, I assumed this would help.
here is the problem now. Today I started it for the first time. after priming up the system, it wouldnt idle, I didnt do anything with the timing, left it at TDC on the one mark. I then turned up the idle screw and it would run without throttle help but it hunts up and down, looking for idle. Oh and the Tach stopped working at 3K RPM? dunno if it is related... Man- CIS......makes me crazy!

I replaced the O2 sensor with an aftermarket one- new plugs, wires and rotor.

One side of the Vacuum device on the dizzy is broken off (the retard side nearest the fan) could this be a problem?

I wonder if the aux air reg is bad? when I was into VW busses it was a similiar issue.

Any help greatly appreciated.

Chris

[boyt911sc]

Chris,

How did you prime the system? By lifting the sensor air plate? Did you check the control and system fuel pressures? How's your ignition timing set? Keep us posted.

Tony

[C-Pierce]

I didnt lift the plate, I just ran the starter in short intervals until I got a fire, then I gassed it. It has run a few minutes alone since I up-ed the idlde screw.

I did clean the injectors with a Bosch injector cleaner too ( a pressureized mechanism, shows spray pattern etc), forgot to mention that.

I have NOT checked pressures, any hints on that and what I am looking for?

thanks
Chris

[Paulporsche]

Sounds like your mixture is too rich, probably caused by the new WUR or from being set rich to compensate for the previous WUR. A hunting idle is one of the most common signs of a too rich mixture.

Certainly a bad AAR can cause a low idle speed @ warmup.

Having no vac retard shouldn't cause a problem. A lot of us have it disconnected.

[C-Pierce]

Paul, Best way to check AAR? and to lean it out what is your method?

thanks
Chris

[Paulporsche]

It all depends on how much experience you have or on how lucky you feel.

You can obviously hook it up to a gas analyzer and have the CO set. A shop can do this quickly and cheaply. Some Pelicans in you area may have one you can use.

You can search "Souk". He has a field test called the Push/Pull method in which you move the sensor plate up or down and see how the revs react.

Or you can try turning your mixture screw CCW in slight nudges, say 1/32 or 1/16 turn @ a time and see if the hunt goes away. My guess is it should after 1 or 2 of these. Be careful as one full rev is between 8 and 12% and one of the last things you want is a too lean mix.

The Bentley manual has the AAR test. I can't remember it right now, but I'm pretty sure if you search here, you will find a writeup on it.

I would try the leaning first. You can always put it right back if things don't improve.

BTW I don't know if this will help at all or not, but someone mentioned priming the system. You do this by turning on the ignition but not the engine and raise the sensor plate. You should hear the injectors start to whine. Then let the plate back down and turn off the ignition. Then try restarting the normal way. I'm curious to know if this makes any difference once the engine has already been started.

Let us know what happens.

[Gunter]

BTW I don't know if this will help at all or not, but someone mentioned priming the system. You do this by turning on the ignition but not the engine and raise the sensor plate. You should hear the injectors start to whine. Then let the plate back down and turn off the ignition. Then try restarting the normal way. I'm curious to know if this makes any difference once the engine has already been started.

I would do that first.
Broken retard nipple on the vacuum can means that you cannot properly set the timing.
Normally, the timing is set at 5deg BTDC with the 2 vac lines disconnected.
When you connect the lines, the retard will set the timing back about 6-8 deg.
Then you adjust the fast idle and the mixture.
Since you don't have retard, set the timing at 0 deg, adjust the idle and mix and see how it runs.
The AAR is easy to check:
When cold, remove the large vac line from the side of the AAR just enough so you can look inside with a mirror and light.
You should see a half-moon opening.
Put the hose back on but leave the clamp just snug.
Now start the engine and let it run for 10 minutes.
Stop the engine, remove the line again and peek inside the AAR; the opening should be closed.
If not, either the AAR is faulty or doesn't get power.

Did you plug the retard nipple at the TB?
What cam timing did you use for the 964 cams?
Has your distributor been serviced?

[Paulporsche]

Gunter,

I'm not sure if I expressed myself correctly. What I was getting @ was, if the car starts, albeit w/ several short pulls of the key (which he is already doing) will the priming procedure I mentioned actually help in any way? Sounds like you are sure it will.

Or is it just something else that may help and can't hurt?

[C-Pierce]

Gunter, thanks for that info. Cams are at 1.30 and 1.31 as close to 1.26 as I could get them. no I have not had the dizzy serviced, any instructions on that>. maybe I should get a new vac advance? I did plug the Blue line ( I assume this is the retard line) and hooked up the red. it comes out just to the left of the aircleaner-right?

thanks for all the help.

keep it coming please.

Chris

[C-Pierce]

Gunter- one more thing, is there one dedicated thermo time switch that runs the AAR? or is it for other stuff too that would indicate it was bad.

thanks
Chris

[Tallbrad]

I am very new to Porsches and have been reading this today to learn more about issues and general function of Porsche CIS.

http://www.classicsaab.net/files/cis_made.pdf

[C-Pierce]

I am looking at my Bosch book, here it shows a WUR like the one I put in my car, there is a nipple that sits on top of it, I thought that was ambient air sensor or something but according to this it is a vacuum niple. My original one didnt have htat. where should I hook this up? any suggestions? Funny thing is they had the same part #s... Hmmmm..


Chris

[Paulporsche]

You should have Bosch WUR number 0 438 140 072 for your 80. The top nipple should connect to the upper nipple on the front of the air sensor unit. See the exploded parts diagrams section of this site for a pic.

BTW did you ever check your fuel and control pressures?

[Gunter]

Paul: I suggested the standard procedure to be sure that there is no more air in the system.

Chris:
If you don't have it, you'll need to get the Bentley SC Repair Manual and study the CIS.
The Thermo Time Switch controls the Cold Start Valve.
AAR has a heater element (no time switch) AAR and WUR have the same power supply; both have heater elements.
Did you check the AAR as suggested above? Why not do that?

To service the distributor, go here:
Distributor service (Clean and lube) real easy without removing the pinion gear!

It's up to you if you want to get a vac can with retard/advance; the retard line goes in the front of the Throttle Body, the advance line goes in the rear.
Does your WUR have the correct Bosch number posted by Paul?

It's no use to go all over the place and guessing.
Why not do/check the above suggestions first and report back?
Have fun.

[C-Pierce]

I worked on the car all day today (first nice day since october of last year), I had to replace the oil thermostat that was destroyed during my backdate oil line replacement, and you know what a job that is when they are all siezed up!
I was able to determine, int eshort time I had with the motor issue, that there is .026 volts running to both the AAV and WUR with the key on. I checked all vacuum lines and they are all routed correctly. there is not a vac line for the WUR and there was not one on the OG one, but the part#s are the same.... I made a line and "T"'d it into the retard line (blue coming off the flywheel side or front of throttle body.

I will be back on saturday to see what I can do with the follow up from you and others.

Might double check the # on the WUR as well.

Also forgot to mention that the decel valve (sideways saucer type) canister behind the AAR has a big dent in it. will that make a diff?


Oh and best way to check pressures? are there tried and true places?

thanks
Chris

[Alan L]

I don't think you get power to the AAR until the sensor plate switch allows the fuel pumps to run. You need to get the car running, unplug the AAR and measure for 12+ V. If you dont get that your WUR and AAR won't work. Another way to check the AAR is to hook a 12 V battery to the terminal on the plug - either way is OK - it just needs 12v. Watch the disc in the throat - if it does not shut off after 5-10 mins, you have an electrical problem with the AAR. (broken wire). Can test by measuring resistance across the two terminals. Infinite = broken circuit.
If I want to check my mixture to get approx right, I turn the screw 1/4 turn each way and see which improves the problem. If you are too rich, 1/4 clockwise will near kill the motor,1/4 anti C will improve things sweetly.
I think the nipple on the WUR is to improve fuel load at acceleration (vacuum assist on diaphragm).
Alan

[C-Pierce]

[QUOTE=Paulporsche;3862099] The top nipple should connect to the upper nipple on the front of the air sensor unit. See the exploded parts diagrams section of this site for a pic.
[QUOTE]

Where / how do I find that?

thanks
Chris

[Paulporsche]

http://www.pelicanparts.com/911/911_Parts/parts_index.htm

[boyt911sc]

Originally Posted by C-Pierce

I worked on the car all day today (first nice day since october of last year), I had to replace the oil thermostat that was destroyed during my backdate oil line replacement, and you know what a job that is when they are all siezed up!
I was able to determine, int eshort time I had with the motor issue, that there is .026 volts running to both the AAV and WUR with the key on. I checked all vacuum lines and they are all routed correctly. there is not a vac line for the WUR and there was not one on the OG one, but the part#s are the same.... I made a line and "T"'d it into the retard line (blue coming off the flywheel side or front of throttle body.

I will be back on saturday to see what I can do with the follow up from you and others.

Might double check the # on the WUR as well.

Also forgot to mention that the decel valve (sideways saucer type) canister behind the AAR has a big dent in it. will that make a diff?


Oh and best way to check pressures? are there tried and true places?

thanks
Chris

Chris,

The voltage going to WUR and AAR should be the same voltage going to your FP. All three (3) CIS components are connected to the same terminal for power. Check terminal #30 (FP relay) in your wiring diagram.

You need a fuel injection pressure gauge kit to measure the fuel pressures plus a basic knowledge of running the FP using a jumper wire (with fuse). A Bentley manual is highly recomended reference reading material.

If I could remember correctly, WUR (0-438-140-072) does not have a vacuum line. The first seven (7) digits on the Bosch WUR bodies are the same (casted) and identified by the stamped numbers. You don't need the motor to be running to check the power to both AAR and AAR. Read the SC Bentley manual for details. HTH.

Tony

[Gunter]

Originally Posted by C-Pierce

I worked on the car all day today (first nice day since october of last year), I had to replace the oil thermostat that was destroyed during my backdate oil line replacement, and you know what a job that is when they are all siezed up!
I was able to determine, int eshort time I had with the motor issue, that there is .026 volts running to both the AAV and WUR with the key on. I checked all vacuum lines and they are all routed correctly. there is not a vac line for the WUR and there was not one on the OG one, but the part#s are the same.... I made a line and "T"'d it into the retard line (blue coming off the flywheel side or front of throttle body.
I will be back on saturday to see what I can do with the follow up from you and others.
Might double check the # on the WUR as well.

Also forgot to mention that the decel valve (sideways saucer type) canister behind the AAR has a big dent in it. will that make a diff?
Oh and best way to check pressures? are there tried and true places?
thanks
Chris

Chris:
Alan is correct that the engine has to run to get power to the WUR/AAR.

Before you test for Voltage on the AAR and WUR, do the simple test cold/hot for the AAR that I described before.
Because even if you have power to the AAR, it doesn't mean that the AAR works; look inside the AAR cold and then when hot.

BTW: The front of the engine is the pulley-side, NOT the flywheel-side.
The WUR has a vacuum line going to the front of the TB right next to the other vacuum line that normally goes to the retard on the distributor.

Trouble-shooting is done in steps; you check, or change, one thing and observe the results.
If you go all over the place, you won't find the culprit.