car died... then came back to life

[JeffW]

My car died on me the other day and wouldn't start. It had been running really rough and started hesatating in certain rpm bands. I suspect ignition components (coil or ignition module) but I don't want to buy to many expensive parts if I don't need them. After I let it sit a while it started but still ran a little rough. Any Ideas?

[Targa77]

My car had the same symptoms. Run great for two weeks then no start. Ended up being the CDS box. I purchased a new one from Permatune. Permatune always recommends that you replace the coil as well. I think the whole bill was around $325 for both. Try this link http://www.permatune.com/Technical%20Support/Porsche/911.htm

[JeffW]

Is that an aftermarket box or just like the factory one?

[widebody911]

Permatunes suck so hard it will make your ears pop. Mine pulled 30inhg @ sea level...

[Targa77]

Ha, everybody has their opinions. Permatunes are aftermarket but they plug right into the original wiring harness. Takes all of ten minutes to install both the Permatune and coil. They also come with a two year warranty. If you can afford it, purchase an original Bosch CDS box for around $1000. I've seen where you can purchase rebuilt units for cheaper than that in certain catalogs.

[Targa77]

I forgot to mention the points. You have checked these? Don't just check the gap, check the rubbing block too. Make sure you put some Bosch grease on this or friction will eat it away and your timing will change, etc. I had a Porsche "expert" put new points on my car after I bought it last year, but the expert forgot to apply the grease to the rubbing block on the points and needless to say, after a few weeks, back to bad running.

[subdewd]

Had replaced my cd box with perma tune only to have it
go out after a little over a year. Luckily the good folks
here at Pelican took care of it for me, at the time there was
a one year warr.
In the mean time I also sent the origonal to somewhere
in Texas can't remember their name, who repaired it for
$90? . Still using it and have the peratune as a spare.
I think what happens is you get high voltage leak from
wires feeding back to the box. Check your wires at night
and look for arcing to be sure you don't ruin your new part.

[Targa77]

Very possible. From their website, they tend to blame the coil for the most part. I guess that's why they recommend purchasing one of their new coils as well. My original coil was definitely shot since all of the oil had leaked out of the bottom of it. I do like their troubleshooting guide though.

[9XI]

If it was hot, could have been a bad ground.

I had that problem in my P-car 10 years ago driving up to Chico. Electricity doesn't flow as well in the hot weather, so you have to make sure the grounds are as good as they can be.

Similarly, last year I changed the battery and didn't get the wing nut tight enough holding the battery ground cable to the body. As it got looser it started running like garbage, until it was so gutless that it barely got me to a safe pulloff spot. Suspecting electrical, I checked connections and found the problem. Fixed the ground and it roared like a champ.

Just a reminder, bad grounds can sound like misses, etc.

[Targa77]

That's a good point. I, too, discovered a bad ground on my car. One of the leads off of the distributor for the points was all corroded up. Removed the distributor so I could get to it and cleaned it up. Also put some electrical grease on it.