993 Question

[Tom]

@CarBot, we have a new member @REJ that asked the question below. He may not be aware of you -- our 24/7 answer machine -- so thought I'd share his question here and see what you think. REJ later clarified that the motor has 130k on it, but here is the original question:


Hello Forum,
I’m helping a freind evaluate what to do with the 97 993. He’s owned it since new, blue convertible roof, light gray. The Interior is close to excellent. Will need tires. It’s been sitting in the garage for the last 4 years.

Problem is it won’t smog. He was told there are some kind of tubes in the engine that get clogged and prior to him parking it he was told it will be harder and harder to pass smog.

Any thoughts on the cost to get it back on the road. What are the tubes that get clogged. I’m a V8 guy, don’t know flat 6’s.

[CarBot]

, we have a new member REJ that asked the question below. He may not be aware of you -- our 24/7 answer machine -- so thought I'd share his question here and see what you think. REJ later clarified that the motor has 130k on it, but here is the original question:


Hello Forum,
I’m helping a freind evaluate what to do with the 97 993. He’s owned it since new, blue convertible roof, light gray. The Interior is close to excellent. Will need tires. It’s been sitting in the garage for the last 4 years.

Problem is it won’t smog. He was told there are some kind of tubes in the engine that get clogged and prior to him parking it he was told it will be harder and harder to pass smog.

Any thoughts on the cost to get it back on the road. What are the tubes that get clogged. I’m a V8 guy, don’t know flat 6’s.

On a 1997 993 the “tubes that get clogged” is almost certainly the secondary air injection system. The 993 uses an electric secondary air pump and a set of small passages/ports in the cylinder heads that feed air into the exhaust on cold start to help the cats light off. Over time those ports can carbon up, and then the car fails smog because the secondary air system isn’t flowing as expected (often it’ll also set a check engine light related to secondary air flow).

Before assuming it needs the big “head port cleaning” job, it’s worth doing basic diagnosis because a lot of 993 secondary air failures are simpler: cracked/brittle vacuum lines, a bad combination valve (check valve), a weak/dead secondary air pump, bad relay/fuse, or a vacuum control issue that prevents the valves from opening. A good Porsche-friendly shop can smoke-test the vacuum side and verify the pump actually moves air and that the valves open on cold start.

If the head ports are truly clogged, the proper fix is cleaning those passages, and that’s where cost can jump because it’s labor-heavy (often discussed as an engine drop/top-end level job on a 993). I don’t want to throw out a number because it varies wildly by region and how deep the shop goes once they’re in there, but it’s the difference between “a few parts and some hours” versus “serious labor.”

Since it’s been sitting 4 years, I’d also budget for the normal recommissioning items regardless of smog: tires, battery, fresh fuel (and possibly fuel filter), oil change, brake fluid flush, and a careful brake inspection (calipers can stick after long storage). On a 993, old distributor belt/vent kit condition is also something a shop will usually check because it’s a known maintenance item.

Practical next step: have him scan for codes (even if the CEL isn’t on, check readiness/monitors), then do a cold-start test of the secondary air pump operation and vacuum actuation. That will tell you quickly whether you’re dealing with a pump/valve/line issue or the dreaded clogged head ports.

If you want, have REJ share any fault codes and whether the secondary air pump audibly runs for the first minute or so on a cold start, and we can narrow it down.