I need help with a poorly-running '87 Cab.

[Shawn Stanford]

Good morning.

BLUF: This is my first 911. I'm primarily a 928 guy, with a couple of Boxsters in my past and a Cayenne for a daily. Other than building the 1/4-scale kit my wife gave me for Christmas, I have zero experience with air-cooled Porsche engines. I'll also admit that, while I can follow instructions and swing a wrench, I'm terrible at diagnosing. I often take my cars to my mechanic and have him diagnose problems that I then fix.

The car in question is an '87 Cab with a fiberglass 993 body kit that I bought running and driving for stupid cheap money. After purchase, it sat for a year while I deployed, but I started driving it last spring. It ran well at first, but over the summer it started to miss and backfire when it warmed up. Now it does so immediately on start. After a few moments of this, it quits and won't restart immediately.

At this point, I haven't done anything, since I've been focused on the 928s and my daughter's Boxster. But, other than the absolute basics (air, fuel, spark), I have no idea how to go about troubleshooting this engine, or what the likely culprits might be.

Thanks in advance for any advice.


Here's the car, with a 928 door in the back seat.

[Tea Tray]

Very first place to look is vacuum lines. The ‘87 has no shortage of vacuum lines in miserable places. Between the throttle body and firewall is a whole array that includes a venturi device and about a dozen connections including the hose that leads to the brake booster up front.
Removing the heater blower motor and air box makes life much easier.