Ok, where did we leave off? Ahh….right, an engine out tune up and subsequent trip back into the shop to sort some issues.
Post tune up I took the car for a jaunt on some back roads late in the evening. Car seemed to idle a bit high (1000-1100rpm) but after some research the internexperts seemed to feel that a little higher of an idle is ok as it aids in oil scavenging. Hmm, ok. Car pulled hard and clean, no more cutouts under boost, no more feeling like it struggles to build rpm. Sweet! There is now some lifter tic on the passenger side bank but I don't have any point of reference as to what is normal valve noise, nothing alarming however. John said most the intake valves were way too tight and one cylinder needed the exhaust valve tightened. The car does feel like it may be just a hair down on power but I am fine with it given it makes power smoothly and cleanly.
Once home I decided to take a quick peak under the car since two of the high pressure oil lines were replaced….Uh oh, underside of the motor was wet with oil. Now keep in mind that even with the leaky lines the underside of the motor has always been dry by 911 standards. I noticed that a few of the new locking nuts on both valve covers looked odd. The studs protruded on some and not on others. Against my better judgment I grabbed a wrench and sure enough the wettest areas of the cover the nuts took a full quarter turn to be tight. I went and cleaned the areas and haven't seen any leaking since. Likely just had to be heat cycled I suspect. Mildly annoyed.
I also had both heater box intake hoses replaced though I didn't notice any improvement and heat on the test drive. Apparently at some point I lost a clamp on one of the hoses. A quick dig through the parts box resolved that problem.
A few days later I look the car for a longer cruise and noticed that once the car is warm and holding steady at 2100-2600rpm the car surges. It felt like someone waving their foot over the brake. Not a misfire, more like a hesitation, the tach doesn't register any drop in rpm but your head just bobs forward and back. Get on the power, no issue. Lift completely, no issue. Hold it at a steady rpm, head bobbing ensuses. Argh.
Over the next week I did more road testing. The Issue was consistent and ever present once the car is warmed up. Around town you don't notice it as you are always accelerating and decelerating, on the highway however it was very noticeable and after about 10mins super aggravating. Back to Walker it went.
The car when I bought it had its 02 sensor disconnected, post tune up it was left unplugged. I have heard from a few different folks that this was not all that uncommon. John plugged it in to troubleshoot and found it was completely dead anyway. He tossed a used unit on and dialed in the cold and warm mixtures. After a road test the car was ready and I picked it up, no bill, sweet!
I made it about 10 blocks. The surging was 5x worse. So bad I turned around and brought the car back to the shop. I am the type of guy who wouldn't send back a box of McNuggets which had a chicken beak tossed in. So it was not good. We disconnected the 02 sensor as it was found to be bad as well then reset all the mixtures again. Car went back to its normal self, phew. I took it out later that night, the surging remained. Bummer. John related that all 930s exhibited some slight surge at cruise, and I thought perhaps the cams could be exasperating the issue. I agreed to put some more miles on it and see what happened. I put another 500 miles on the car and no change. Car was great in every scenario except stopped or going completely ballistic. Sigh.
Since the problem really only occurred when warm I began suspect the WUR. In the 930 the Warm-Up Regulator does more than it title belays. It plays a big role in fuel mixtures across the board. I found a used unit and a unit that has been modified to be adjustable. Allot of folks swear by having the adjustability. You don't want to know what a new WUR costs. I sent both out to be inspected and rebuilt to factory spec.
While all this was going on I though I would start on some of the misc projects. The seal on the sunroof was bad enough that at any moment I expected to see daylight through it. I also figured it would be nice to give all the guts a nice clean and grease. Though it was fully functional, it sounded a little….janky. Believe it or not the system is actually pretty well designed compared to all the witchcraft and voodoo the BMW and Scirocco sunroofs employ. Once I had the headliner panel pulled down I was able to fully appreciate the source of my janky feelings.
Hmm….someone had some parts left over the last time the panel was removed. I went ahead and replaced the front and two rear seals which are unfortunately of the glue in type. It was then I wished for the ease of the snap in seals that BMW and VW use….but I quickly realized it was a small annoyance to have a panel I could get out of the car in under 5mins. While not perfect the job came out decent (I don't like how low the front seal ended up and I need to add some glue to the ends where they dive into the roof). I found two fine pitch screws to secure the cable mount which I needed to cut down and after some washers everything works flawlessly. I ended up breaking one of the wind deflector clips….Pelican to the rescue, including the missing parts and some new rubber grommets for the deflector the total came to 40 bucks. Nice.
Skip to Friday, the car has been great just as long you never want to keep it at one speed. I popped the engine lid when I got from home to work to take a quick peak. I like to keep an eye on "new to me" engines and honestly I am kind of at a point where I think it's time to take a little more mechanical ownership. We had talked about replacing all the vacuum lines when the engine was out of the car but they appeared fine.
That being said, one of the lines in particular had always looked janky to me, the line running to what I believe is the advance side of the distributer vacuum canister. I reached in to snug it up on the nipple and low and behold, this is what I found.
You think this could be a vacuum leak? Frustrated that they weren't replaced while the motor was out of the car I cut the line back and put it back on the nipple with a ziptie to secure it. Why didn't I replace the whole line you ask? Well it disappears into the bowls of the engine and I figured this would do for a test drive. Drove the car and…..all the initial pre-tune up issues are right back. Cut out and struggling under boost arghh. The surging remains but feels slightly less severe.
The anxiety of knowing that the vacuum line was still not right became too much to bear. I had picked up four feet of new line on Friday….I started tearing into the motor for the first time. Something became quickly clear, there is not a single hose/bolt/nut/screw/clamp that was tight/secure. The intercooler bolts were all loose. The vacuum lines to the air box, all loose with one completely off laying on the back of the motor. Annoyed.
After the airbox was off I found a big pool of oil under one the high pressure lines that was replaced. Looks like it could be coming from the janky factory connection to the crankcase breather. Guess that's on the list as well. After cleaning up all the oil to recheck later I decided to call it a night.
So I had a new theory. The root cause of the boost cutouts, surging and struggling to build power are all ignition related. When I think of the problems in terms of advance and retard it begins to make sense. The cruise surge could certainly be someone cranking advance and alternately yanking it back out. The struggling to make power/build rpm under boost could also certainly be excessive retard. I have been researching the 930 ignition system and the vacuum diaphragm/distributer while not a common problem have been reported as suspect. Old grease can cause the weights in the distributer to mess with timing. Vacuum diaphragm can deteriorate and mess with timing etc. As new distributors are NLA and vacuum diaphragms are $240.00 most folks seem to take the opportunity to upgrade to a MSD 6AL system. This ditches the vacuum unit and CD unit which can also be trouble and big bucks to replace.
Sorry for the boring update. We are in the boring phase of new car ownership, fix a few things then fix a few more than just give up and fix everything.
Part 1 - Life with a legend, the Porsche 930.
Part 2 - Dear God, what have I done.
Part 3 - The choices we make.
Part 5 - Back in the saddle again.
Part 6 - Old dog, old tricks.