Sorting my new-ish SC

[deguitars]

Earlier in the summer I purchased my first Porsche 911, a low-mileage '82 SC that has been very well maintained over its two-owner life. I have two issues which I hope someone can maybe shed a little light on, or simply point me in a direction.

Because it didn't run especially well when I first got it, I've since had the fuel pressure regulator rebuilt and the Co2 set by a local shop. That made a huge difference in starting behavior and general running performance. The shop looked over the car and pronounced it to run quite well, and I was initially happy as it did indeed run much better. No other tune-up work was done. The valves were adjusted sometime last year. However, after putting some miles on the car I still don't think it runs as well as it can, should. I've only driven about a half dozen 911s, so my basis for comparison is admittedly small, but here's what it's doing:

Starting up from cold is great. No smoke cold or hot. Idle is steady, but every so often it's as if it skips a "heartbeat". That's what it sounds like to me, a momentary pause (fractional second, actually) Driveability is good, but best when my foot is in it. At light throttle, or when I back off, the engine does what I call "trameling" or "hunting" a bit. Like it's just not happy a partial throttle. At freeway speeds it's fine, and it seems to have good power. After a good long drive, and the engine is quite warm, the idle is higher than when the car is cold or just been been driven shorter distances. Normal idle is about 900 rpm, and "hot" idle is around 1200, and it will drop down again after the car cools a bit (temp gauge never reads higher that barely the 1/2 way mark).

The issue is not pronounced, and maybe it's even typical for these motors, but it's something I notice and I can't help but think the car could still run better. By comparison, my old BMW 2002 tii (the fuel injected version) was smooth regardless of throttle position.

Since no other tune-up work was done I thought I would start with things like a new cap and rotor, but wires are quite expensive so I don't want to go there if it's not necessary yet. I'm just curious if these symptoms ring a bell with anyone.

The other issue is to do with the alignment and ride height. I'm looking for recommendations for a shop that can make adjustments and corner balance one of these cars in the So CA area (Ventura/Oxnard) preferably. One rear wheel seems to have a little more camber than the other so that needs tweaking and the whole thing needs to be aligned and balanced.

Cheers!

[Sicklyscott]

I don't have an answer for you but I can tell you my SC does the same with the hot idle. I've read that it can be either the decel valve or the aux. air valve. Both are gold disk looking things on the right side of the motor. I was thinking of blocking the vacuum lines to see if that helped any.

[SkunkWorks]

For the idle jumping up, I had the same issue and it was due to vacuum leaks in the intake. Search for the soapy water method on here and you should be able to quickly find the culprit.

[OsoMoore]

I'm no expert, but I have a 79 SC which idles smoothly at basically all temperatures and times. For the first one or two minutes from starting cold, the idle is higher. But I am informed that this is correct behavior.

It may be related to a vacuum leak of some kind. CIS experts will have more ideas.

[Paulporsche]

Vacuum leaks are quite common on cars of this vintage, and can cause start and run problems, so you should check into that.

You might as well look into the cap and rotor and also make sure there is no lateral play in the distributor and that the rotor springs back when you turn it forward and let go. Idle the engine in the dark and see if there is any arcing between ignition wires. Be careful, they can give you a nasty shock.

Make sure your decel valve is working correctly. A poorly functioning one can cause the idle to rise. There are often vac leaks at this component.

Finally, check or have the shop check your WUR (warmup regulator) for fuel and control pressures. This one component seems to be the cause of the majority of the start and run problems CIS car owners experience. You will need a fuel gauge to measure these pressures.

[Joe Bob]

Superior Alignment up in Santa Barbara. Take a drive, have a few fish tacos.

[deguitars]

Thanks for the replies! Sounds like vacuum leaks are a good place to start. I know the decel valve has previously been plugged so maybe I'll make sure that's still the case.

I think I know Superior Alignment in SB, thanks for the recommendation!

Cheers

[dyount]

Do you have an O2 sensor in your car? Typical SC exhaust? If no O2 sensor it may not act like a typical car. I have my cat removed and no O2 sensor and at different times of the year it may rich/lean and hunt a little.

[psalt]

Your 82 911SC has CIS lambda injection and my first advice would be to see if the system is working properly. You can check it with a dwell meter hooked up to the test port, everything you need to know is on this site. Even if the O2 sensor is disconnected, the ECU must be pulsing in the correct range to get anywhere near the correct fuel curve. Iv'e been driving SC's (and 2002's) for over 30 years and a properly set up 82 SC does not have a creeping higher hot idle. This shouts vacuum leak and the first suspect is the injector sleeve O rings. If they are original, they are certainly leaking. You can test for this with an unlite propane torch while wiggling the injectors with the engine running. The problem is that Porsche chose to seal the plastic injector sleeves with O rings instead of threads like other OEMs. They are staked in and the procedure to change them is in the archives. Also test for leaks around the rubber sleeves on the runners and the throttle shaft. While checking the throttle, have your lovely assistant Tabitha floor the pedal and see if you can manually open it further. Many new 911 owners are surprised that the most effective performance mod is adjusting the throttle linkage. Once you get the vacuum leaks corrected, the optimum tune for an 82 SC is to disconnect and plug the vacuum retard, adjust the timing to the high end of the factory spec, fit Bosch normal plugs, working O2 sensor, and adjust the FV duty cycle to 30-40 dwell. Good Luck.

[aoncurly]

My '81SC had a hunting idle/high idle problem and was fixed by replacing the O2 sensor. I'm no expert, but my understanding is that a quick way to check for vacuum leaks is to remove the oil filler cap while the engine is running. If there are no changes in idle, you might have a leak.

Good luck.

[Paulporsche]

I think you can also quickly see if your O2 sensor is working by checking if your interior ceiling lights are working. I don't have lambda on my engine but I understand the dome lights and lambda control are on the same circuit, so if the lights don't work that may be why.

Psalt or others please correct if this is wrong.

[psalt]

please correct if this is wrong.

Paul,

No, if the interior lights work , all you know is the fuse is good. At least your can rule that out quickly.

The Lambda relay, the switches and sensors, ECU , FV or O2 sensor could still be bad.

[deguitars]

Thanks for the continued advice! Here's what I know.

1.) Car has 84K miles on it and (presumably) every service record since new in a 2" thick folder. Nothing in there about injectors or sealing rings, etc. I noticed that one of the metal pipes can be pulled up and down maybe 3/32" but when I did this with the engine running it had no effect.

2.) Totally stock/original exhaust, Oxygen sensor is hooked up and interior lamps functional (for what that's worth). Car passed a recent CA smog even before the fuel pressure regulator was rebuilt.

3.) I will search the archives for setting the dwell. Isn't it a good idea to start with a fresh cap & rotor for that?

cheers

[na2ub]

New car to you? Time to put on a new cap rotor install new plugs and replace the fuel filter. All easy and inexpensive. Change the oil while you are at it. Then worry about if its running perfectly. Youll need to do this "regular maintenance" anyway. But the plugs cap and rotor can easily give you a "miss"

[tirwin]

You said that you had a shop adjust mixture based on exhaust gas, right? So unless you find and fix some other issues (like vac leaks) that affect the mixture, you shouldn't need to mess with dwell at this point.

There are probably no less than a half dozen things that could be an issue. If we were all standing around the car it would be easier to rule in or out likely causes. But since we're doing this by exchanging messages it is a little harder.

So you need to come up with a methodical plan. You got some great advice on looking for vac leaks. Do as psalt suggested and look for leaks around where the fuel injectors fit into the intake runners.

The rubber on the braided vac lines tends to get brittle and crack. If you have enough slack, trim like 1/4" or so off the ends and reattach.

Tony (boyt911sc) has posted many times the procedure to check the air box for cracks or leaks. Someone also mentioned the boots on the intake runners. If they are hard and brittle you might think about replacing them. Using a screwdriver and just trying to snug up the hose clamps is not hard. Some may be hard to get to with the engine and all the CIS in the car.

Point is those are all common problem areas that you can check with very little money investment (just your time).

If you verify those things and still have a problem then you can move on to checking things like the ignition and fuel delivery stuff. But I'd advise starting with the low hanging fruit first.