'77, grumpy under low load

[bklopfer]

Howdy,

I just got a 1977 Targa, and am having an absolute blast with it. I drove it from my parents' place to my place (150 miles), and it behaved really well on the windy stretches of CA's Highway 1 (where there are a lot of 2nd gear turns, and stretches like this). Likewise, it just purred along the freeway, and was very pleasant in 5th doing anything from 55-70 without complaining.

Now, once I got to some city driving, it got a little fussy. It was a little jerky going maybe 25-30 mph, and shifting from 2nd to 3rd or vice-versa didn't help. However, if I just stepped on it, it settled down (of course, I can't always afford to be that liberal with my right foot in city driving!). FWIW, I didn't notice the jerky behavior until after the car had warmed up quite a bit, even though there was a 25mph zone at the beginning of the drive. I forgot to get the exact temp, but I think the temp gauge was reading over 170, but well under the 210 half-way marker.

As far as work that's been done on it recently: I believe the mechanic replaced the distributor, the coil, the fuel pump and the fuel regulator. He may (not sure) have cleaned out the CIS distributor as well (I know, I've heard this is not a good idea...). It does have issues cold starting -- it catches every time, but dies shortly after. 3-6 starts gets it going; for warm starts it fires right up. The car had been sitting in the lot for ~4 years prior to my getting it (but it's nearly rust-free and doesn't leak oil -- amazing!).

Oh, and the tach isn't working (though the tach itself was benched by Palo Alto Speedo, and is fine), but that's a minor problem. Any advice? Or better yet, maybe there's someone in the Palo Alto area with a garage who'll pass on some wisdom to a Porsche newbie (free beer to any such person)

[stlrj]

So your mechanic never touched your shielded ignition cables?

[ossiblue]

Symptoms may be due to several things, but ring true for a lean running condition from an out of adjustment warm up regulator (wur), or a vacuum leak.

Do a bit of reading on CIS and fuel pressures and you will feel comfortable that the symptoms are not too serious. CIS needs to have complete regulated air with no leaks, and fuel pressures within specs. Cold start problems as you describe tend to mean a too lean fuel supply caused by too high fuel pressure. The wur has the job of allowing low pressures (richer fuel mix) at start up/cold running, and higher pressures (leaner mix) at warm conditions. Jerky conditions while running warm can be attributed to lean (too high) pressures also.

My first suggestion is to get a mechanic who is an expert on CIS Porsches to check out your car. If that describes your current mechanic, have him run the pressure tests for your CIS system, and record the system pressure, cold control pressure, and warm control pressure. (You can do these yourself if you have a fuel gauge test kit--a good investment if you plan to keep your car.)

I assume your ignition components are all good, and valves adjusted. Pressues test will confirm or eliminate the fuel pressures as the problem. If pressures are in spec and the problem persists, you may have leaks in the intake system--but that's another story that can wait.

[bklopfer]

stlrj: I don't know when the ignition cables were last replaced. Mechanic did replace the spark plug cables with (rather pricey) ones. I think it was having trouble passing smog with the old ones because they couldn't get a good RPM reading off of them -- not positive, my Dad dealt with getting it smogged before I got it...

ossiblue: Thanks for the tips. Yeah, I'm trying to set up an appointment here to get it looked at by a good Porsche wrench (Modderman Porsche, referenced by other forum-goers here). Will post updates!

[stlrj]

The next thing I would do is pull the plugs and see how they look.