Another AAR thread

[stevepatfred]

Hi everyone,

I have what I suspect to be a sticking AAR. The symptoms are as follows. Cold start the car fires up first turn perfectly fine and RPM will sit around 1000. After I drive off for a few minutes, generally the first set of lights I get to the RPM rises to about 1600rpm...all normal so far? The problem then is the idle will stay at 1600 RPM for a random amount of time. Today I drove for about an hour and a half, and after a long stint on the freeway, came to a stop at the traffic light and the idle was still at 1600...grrr. Sometimes the RPM eventually settles on its own to a normal 950. Today, only after I stopped the car and it cooled a little did I fire it up and idle was normal again. Am I right in assuming this is a sticking AAR? I don’t suspect a vacuum leak as the idle does eventually return to normal. No AAV Problem as the car starts first time no problem. And no WUR Problem as the car doesn’t sputter or stall when cold. Have I missed something? I know this regulator has been extensively covered but just wanted to confirm I hadn’t missed something. Anything I can do to solve this? Thinking of opening it up to clean it. Or maybe throttle body cleaner? Thanks in advance.

[boyt911sc]

Originally Posted by stevepatfred

Hi everyone,

I have what I suspect to be a sticking AAR. The symptoms are as follows. Cold start the car fires up first turn perfectly fine and RPM will sit around 1000. After I drive off for a few minutes, generally the first set of lights I get to the RPM rises to about 1600rpm...all normal so far? The problem then is the idle will stay at 1600 RPM for a random amount of time. Today I drove for about an hour and a half, and after a long stint on the freeway, came to a stop at the traffic light and the idle was still at 1600...grrr. Sometimes the RPM eventually settles on its own to a normal 950. Today, only after I stopped the car and it cooled a little did I fire it up and idle was normal again. Am I right in assuming this is a sticking AAR? I don’t suspect a vacuum leak as the idle does eventually return to normal. No AAV Problem as the car starts first time no problem. And no WUR Problem as the car doesn’t sputter or stall when cold. Have I missed something? I know this regulator has been extensively covered but just wanted to confirm I hadn’t missed something. Anything I can do to solve this? Thinking of opening it up to clean it. Or maybe throttle body cleaner? Thanks in advance.

Steve,

Refrain from second guessing your problem. If you think the AAR is questionable, pull it out and bench test it. At room temperature, the opening of the slide valve is approximately larger than a quarter moon shape (area). Apply 12 volts to the terminals and observe how long it would take to fully closed the valve. Typically it will be closed between 3~4 mins. If you could see an opening after 5 mins., the AAR is not operating as it should. BTW, what model year and ID number on the AAR? Keep us posted.

Tony

[Paulporsche]

Besides what you and Tony have said, I'm thinking the decel valve may be another possibility. You can plug the line to it and see if the symptoms disappear.

[Coastr]

Originally Posted by Paulporsche

Besides what you and Tony have said, I'm thinking the decel valve may be another possibility. You can plug the line to it and see if the symptoms disappear.

Do this - identify the Decel valve. Pull out the vacuum hose. Put a golf tee in it. Drive again and see if problem persists.

Mine used to do that and drive me crazy. Tee'd it and a compeltely different car to drive.

[stevepatfred]

Thanks for the replies,

Should the valve be completely closed when warm? Just did the oven test and there is still a slight opening.

I already plugged the decel valve to check if that was it but no change.

power to the regulator seems normal.

model number is 0 280 140 218 which I believe is correct to an 83SC

Is it worth opening up to adjust or is it better to bin it and fork out for a new one.

[stevepatfred]

I just replaced the AAR and took the car for a drive. the engine was relatively cool and the AAR was ice cold as it had just come out of the freezer yet the engine idled at 950rpm straight away and never changed from that until operating temperature!? Am i wrong in thinking, given the AAR was freezing cold and the opening inside was visually verified, it should of idled high until warm? Now i'm even more confused. what else could be causing a random high idle that eventually corrects itself.

[SkiVT]

I would check the opening, when hot with a mirror or cell phone pic, to confirm again it is almost or entirely closed. Your cumulative testing then basically would then tell you the AAR isnt your issue. I assume your 83 CIS is lambda controlled. I think your next step is to confirm fuel pressures as I dont think observing initial cold running equals a wur with correct pressures both while cold and warm. No need to guess when the test is easy, assuming your have access to the gauges.

[stevepatfred]

Sorry to keep going on about this, I'm aware there are many threads on this topic but i can;t quite get the answers i'm looking for. I don't have access to fuel pressure gauges. I suppose I can get some if totally necessary. Took the car for a drive this morning after spraying throttle cleaner in the AAR last night while removed. Car started right up, idled straight away at 950rpm, and stayed that way. problem solved i thought....WRONG! gave the car a quick clean, started up...back to 1600rpm at operating temperature. got home and blocked off the AAR to finally verify that isn't the problem, idle started at 1000rpm and slowly crept up to 1600 with a little bit of hunting between 1.2k-1.6k. hmm.

wound the idle adjustment screw all the way in while the car was idling high and there wasn't a change in the idle. This would indicate air is getting around the throttle body wouldn't it? would a faulty WUR do this? Could it be something to do with the vacuum advance?

sorry again for the many questions but man this is annoying!! I am learning a lot about the CIS in the mean time!

[puddy]

I had a very similar problem where it would start and idle fine, then after a hot restart the idle would jump up another 1000 rpm. I spent some time trying to clean it and test it and didnt get much better results, so now i'm going EFI so I can't wait to pull the CIS stuff off and sell it.

[stevepatfred]

I would prefer to get the system working than pull it. i failed to mention the engine only has 2000 miles on it after a full split case rebuild.

Update: I pulled the O2 sensor and the idle is normal. perfectly fine. so the system is compensating for something, or the O2 sensor is faulty. I don't suspect a vacuum leak because the idle will return to normal after a random amount of time and stay that way. If it was a vacuum leak wouldn't the idle always be high?

[boyt911sc]

Originally Posted by stevepatfred

Sorry to keep going on about this, I'm aware there are many threads on this topic but i can;t quite get the answers i'm looking for. I don't have access to fuel pressure gauges. I suppose I can get some if totally necessary. Took the car for a drive this morning after spraying throttle cleaner in the AAR last night while removed. Car started right up, idled straight away at 950rpm, and stayed that way. problem solved i thought....WRONG! gave the car a quick clean, started up...back to 1600rpm at operating temperature. got home and blocked off the AAR to finally verify that isn't the problem, idle started at 1000rpm and slowly crept up to 1600 with a little bit of hunting between 1.2k-1.6k. hmm.

wound the idle adjustment screw all the way in while the car was idling high and there wasn't a change in the idle. This would indicate air is getting around the throttle body wouldn't it? would a faulty WUR do this? Could it be something to do with the vacuum advance?

sorry again for the many questions but man this is annoying!! I am learning a lot about the CIS in the mean time!

Steve,

You will never be able to diagnose your problem without knowing your fuel pressures. A fuel pressure gauge kit is a mandatory tool for troubleshooting whether you have a CIS, EFI, etc. without one, you will rely on luck. Looking at your information, I strongly believe you have unmetered air (vacuum leaks) and your fuel mixture has been tweaked to compensate for the massive air leak.

Performed a pressure test to locate this hard to find air leaks. A smoke machine or EVAP smoke detector will do a good job locating them. Or pressurized air with soapy water. These are just the basic tests you need to do. If you can not do these tests yourself, pay someone to do it for you including checking the control and system fuel pressures.

A lot of people are ditching their CIS because of their lack of knowledge about how a CIS works. Unfortunately, the younger generation of auto mechanics are not familiar anymore with this old and antiquated technology.

Tony

[stevepatfred]

Hi Tony,

I’m still trying to understand the CIS system...learning a lot in the process. I’m almost certain my mixture hasn’t been tweaked as the engine was only rebuilt in July. And a vacuum leak would not fix itself randomly would it? Also when I remove my oil cap there is a noticeable drop in RPM. Anyway, next step is to test fuel pressure and see if there are any vacuum leaks. Thanks again for the help.

Steve

[stevepatfred]

Tony,

Sorry to keep bothering you with this one but you seem to be the expert in the field. I have done a vacuum test with soapy water around the usual suspects and all seems well...I also removed the oil cap while the engine was revving at 1600rpm and got a significant RPM drop down to around 11-1200RPM. So I don't suspect a vacuum leak. While I sit here doing my head in trying to get my head around the CIS system can you confirm something for me (I know the fuel pressure test will confirm or deny if the WUR is operating properly but I can't do it until at least tomorrow and my brain hurts now!!):

If the WUR were to fail generally it'd fail in the cold control pressure position? Meaning a richer mixture? So when the O2 sensor begins operating when the 15 degree switch has reached temperature the o2 sensor would sense a rich mixture and adjust the throttle plate accordingly? which would result in a high idle and explain why when the o2 sensor is disconnected the idle returns to normal? If the fuel pressure is abnormal this would all fit perfectly...fingers crossed this is it...then I can finally think about something else...

[gazzerr]

Hi Steve,

There are at least a dozen things to check on the CIS system. Everything has aged past its use by date. You just have to remove each one, test and verify independently that they are in spec and then put it all back together, test that it's still holding a vacuum and adjust as needed. The fuel pressures are the place to start so you can get a good baseline. Have you read Tirwin's thread? It's the go to for CIS on here.

CIS Troubleshooting for Dummies

G.

[boyt911sc]

Originally Posted by stevepatfred

Tony,

Sorry to keep bothering you with this one but you seem to be the expert in the field. I have done a vacuum test with soapy water around the usual suspects and all seems well...I also removed the oil cap while the engine was revving at 1600rpm and got a significant RPM drop down to around 11-1200RPM. So I don't suspect a vacuum leak. While I sit here doing my head in trying to get my head around the CIS system can you confirm something for me (I know the fuel pressure test will confirm or deny if the WUR is operating properly but I can't do it until at least tomorrow and my brain hurts now!!):

If the WUR were to fail generally it'd fail in the cold control pressure position? Meaning a richer mixture? So when the O2 sensor begins operating when the 15 degree switch has reached temperature the o2 sensor would sense a rich mixture and adjust the throttle plate accordingly? which would result in a high idle and explain why when the o2 sensor is disconnected the idle returns to normal? If the fuel pressure is abnormal this would all fit perfectly...fingers crossed this is it...then I can finally think about something else...

Steve,

You may not like to hear it or know about it. You are in total denial about facts. Your CIS has unmetered air going into the system. At typical CIS in good working condition would only have a slight idle speed drop between 150~200 rpm from 900 rpm idle speed. And the fact that idle screw did nothing when you adjusted it min./max. was a good indicator of a massive air leak.

Tony

[stevepatfred]

Tony,

I’m not in denial, I’m trying to understand the CIS system. This being my first Porsche and having mainly worked on old British cars it’s a fair bit to get ones head around. Anyway. Thanks for the kind words...I note you’ve been a great help to many in the past, and I’ve appreciated the many informative posts you’ve made. A little more tact in the future however might not go too far amiss...especially people who are new to the Porsche community and just trying to understand these cars and how they work. Turns out you’re right by the way...but I don’t see a problem in asking questions while collecting tools and learning testing procedures.

Steve