78 911 SC Spark Plug Wires

[opticalfuel]

Need to resolve the following running conditions:

1. Poor excelleration / Hesitation / revs up fine

2. Rough idle and poor warm start

More on #1:

IPB Autosport recommended and replaced the fuel distributor, (pricey little bastard) which they diagnosed as a fuel restriction problem. This unfortunately revealed another issue with the car, which they haven't been able to resolve: Namely an idle and startup issue. It starts fine with the WUR. (2 minutes at 2K and then drops to 800 - 900 rpm)

The other problem appearently must be that the spark plugs or wires might are faulty. The engine misses pretty bad on heavy load, but winds out fine (past 6K no problem) ... so it most likely is a bad wire or sparkplug. (low RPM/load requires better spark, which is plentiful supply at high rpm)

More on #2:

It occationally starts up very hard, like it's starving for fuel, and running on 2 cyl. then after coaxing it along for 10 seconds or more, it finally comes to proper idle.

Any thoughts on these issues?

Thanks!

Doesn't this car DESERVE to run perfect - looking so good?

[MotoSook]

Have you cleaned the fuel system? (filter?) ..hesitation and loaded running problems.

Is the CIS adjusted properly?..starting problems

[opticalfuel]

I think I discovered the problem.

DON'T USE BOSCH PLATINUMS on your 911SC.
It makes the car run like dog droppings.

For proof:

Where's the electrode? (it's not there...) Opps!

[MotoSook]

Yep...never had a use for Platinum plugs. Get some NGK plugs and go have fun!

[Andras Nagy]

Hi Souk and Opti,

I've been running the Bosch Paltinums, (from Pelican by the way), and have had no problems with the car at speed for the last 22 years, but there is a lot of backfiring at deceleration, but only when cold. This d8id not occur before my recent rebuild.

Could this be a reuslt of using platinums?

[MotoSook]

Andras, I see no advantage to using the Platinum plugs. The small electrode fouls easily and they cost more than a regular copper plug. An NGK plug is about $1.89 each. I can't say that your back fire on deceleration is caused by bad plugs, but I would just pull the Boash P's out and get some NGK. Then go from there.

I'm guessing your problem (esp. when cold) is more of a CIS tuning issue. Are you running more rich than you did before the rebuild? (Just a guess)

[Andras Nagy]

Hi Souk,

It's possible that I am, though I didn't mess with the CIS when I rebuilt. I had just taken it off, cleaned it "while I was in there", and put it all back together. Am using new OEM braided wires with the platinums, but many have told me to get the NGK's, so probably I will. Just hate to throw away what seem like perfectly good platinums.

It is possible that I'm running rich, for many years ago we had "tweaked" the CIS at Autothority, and the car always ran strong. I also tightened the exhaust headers, so I don't think I'm leaking there.

Strange, since the back firing goes away at 180 degrees oil temperature. Cleaned and checked my WUR, and will now go to the AAR and check it for blockage. Perhaps 22 years of use have clogged it.

[Paulporsche]

Andras,
When you say you checked the WUR do you mean you checked the cold control pressure? You might be running too lean when cold.

[Andras Nagy]

Hi Paul,

No, I meant that I had removed it, opened her up, cleaned out the screen, checked everything for cleanliness, and then buttoned it all up again.

There was no difference in the running of the engine after, compared to before. However, there was a bit of black "gunk" at the screen, so I thought that it might have kept the fuel from passing thorught the small orifice and between the round disc.

By the way, the inside of the WUR housing dosn't see any fuel, does it? It was all dry as a powdered baby's behind. It looks like the only fuel "exchange" is between the large and the small diameter fuel lines, as it passed between the disc.

The other line at the top seems to be an air line, used to equalize the pressure?

I guess I'll still have to check the control pressu4ere and the electrical continuity to see if the bi-metallic element is closing off the orifice.

Strangely complicated little piece, this WUR!!!!!

[MotoSook]

If you get fuel in the cavity of the WUR you are in trouble. The WUR is not complicated at all...it's just a back pressure regulator!

[Andras Nagy]

Hi Souk,

No there was no fuel inside the cavity. It was as dry as a powdered baby's behind.

But there was a little gunk on the screen, which might have prevented fuel transfer between the two fuel lines.

[opticalfuel]

A tip from recent unfortunate experience:

Last night after installing the NGKs I went for a drive. I found out the hard way that I had not snugly repositioned the Distibutor Cap after testing the Wires. The rotor disentigrated and a rather loud backfire insued! It was pretty scary since I didn't immeditately know what had happened. I had an old rotor there so a few minutes later, I was back home, scratching my head about it. That back clamp on my DC is a tight fit.

By the way anyone know what the wires should be testing: Here is my test results:

1: 4.1Kohms

2: 3.9Kohms

3: 4.7Kohms (initial test), then reattached and tighten end toward plug,

3: retest = 4.1Kohms (could be the source of the problem with running)

4: 4.1Kohms

5. 4.1Kohms

6. 4.1Kohms


Coil Wire: 1.05Kohms

[Rick Lee]

Have you cleaned any gunk off your dist. cap and rotor? How are your injectors? Maybe try the 6 beer bottles test to check fuel spray.

[opticalfuel]

Nice shot on the motor. I will try cleaning my injectors. I recently bought this Ultrasonic cleaner which is very capbable of cleaning the injectors.



What do you suggest I use as a fluid or cleaning agent to clean them in?

I am planning to clean them out soon, as well as replacing the cap and rotor today. It already seems to run somewhat better after replacing the spark plugs with standard NGKs.

Thanks.

[opticalfuel]

I want to own your 87 Carrera. Actually my absolute favorite so far is the 1996 (last air cooled) C4S. If could own one of those someday, I'd be a happy guy.

[Rick Lee]

Are you talking about my old Carrera? I think the guy who bought it has it up for sale now. He called me two wks. ago to talk about it. Wait til you see my 993 when I get it back next week - full respray! It will look brand new.

[opticalfuel]

Solved the problem with the car...

After installing the NGKs and new Cap and Rotor, the car runs like a champ.

The only think left to do is deal with the un-even idle, which might be a matter of the injectors being cleaned.

Perhaps this weekend I will finish that and report back. For now the car runs fine.

[jerrykrug]

opticalfuel

Where was that photo taken? Looks alitle like Donner Lake..but I think its somewhere else... see mt simmilar photo

[Early_S_Man]

Is that ultrasonic cleaner heated? If not, get a fish tank heater and crank it up to 120°F or so and use Berryman's B-12 Chemtool in the tank to clean your injectors overnight ... or 12 - 14 hours.

[opticalfuel]

I was supposed to get a heated version, but they screwed up the order. I could do what your saying, with the fish tank heater ($20 - $40 bucks) and clean it over night. The only issue is that the cleaner has a time for only 30 min at a time. Kind of lame.

I guess you can't hurt anything on the injectors? No non-metalic parts? Chem-tool is okay?

As for the picture - YES it was taken on the way home from SILVER LAKE, on Hwy 88!

NICE HUH? GOOD SPOT for a Porsche moment.