February 2013

24 February 2013

A few quick late-Winter updates.

Early this month I replaced the fuel vent hoses in the front trunk. That's where the fuel tank lives on a Porsche, and the trunk and the passenger compartment share the same air. I was hoping that the mild fuel-ish smell inside the car after sitting closed up overnight might be diminished or eliminated after replacing the 29 year old hoses.

The new hoses did not eliminate the smell, may have diminished it a little. This probably means that I will need to replace the main fuel supply and return lines that run through the center tunnel inside the car. Someday, probably not real soon.

Late last Summer I replaced the driver's side door check assembly (August 2012). At the time I only did the one side because I only had one replacement kit (which came with the car). I did the driver's side as I was pretty certain it was bad.

After comparing the new driver's side to the passenger side, it was obvious that while the passenger side was in better shape than the bad one from the driver's side, it was far from healthy itself. So I ordered a another and replaced the passenger side a couple of weeks ago.

I've also spent a bit of time this month trying to improve the drivability of the car. For one thing, getting on or off the throttle often happened with a big jerk which made me think that the engine and transmission mounts might be soft and allowing the engine to rock with torque changes. I'd also noticed that the idle was prone to hunting up and down when the engine was cold.

The first part was easy—I ordered up and installed a new set of the four engine/transmission mounts and replaced them. That was a remarkably simple project, I doubt it took me an hour for all four. The ones I removed looked OK coming out, and were not the originals so they had been replaced at least once before. But with the new ones in place, I haven't yet noticed a tendency for the abrupt engine rock, so I suspect they were due for replacement.

The idle bit takes longer, in part because there's more than a bit of trial and error involved. The two main parts of the process are to clean/check/replace the Idle Control Valve (ICV) and to adjust the car's base idle setting. The base idle is where the car will naturally idle when the engine management computer isn't actively making micro-adjustments. There is a process to bypass the computer's input, then you can adjust the base idle. Once the base idle is correct, a clean and well functioning ICV should be able to keep it idling smoothly.

The trial and error part comes in two parts. First, it is difficult to tell if an ICV is slow to respond due to being oily and gunky inside, or if it just needs to be replaced. Second, the base idle setting can be a little fussy to get just right. The "correct" base idle should be 880 RPM. The problem with that is that very few normal tachometers are accurate enough to display the RPM to that degree of accuracy. If you are off just a bit one way it can exaggerate the idle hunting effect; off a bit the other way can make the engine die when cold and you let of the throttle (as when coming to a stop).

So far this month, I've cleaned the ICV twice (the second time far more thoroughly), and have readjusted the base idle several times. I think I've got it pretty close now, the last drive when cold had no hunting, and only died one time. Another tweak or two and it should be good.

Continued in March...