thechief

Failed CA smog at test only facility in San Diego today. HC's were 7 PPM too high, everything else passed. My car is a '95 with 89K, just did the 90K service including plug wires and everything else required, O2 sensor is about 10K miles old. I haven't driven the car much in the last year, so after I failed the first time I put new 91 octane in plus a can of Techron and went for a nice long spirited drive and made sure it was nice and hot when I took it back for the second try. Close but no cigar, still 5PPM too high. So, the HC's are a function of engine mechanicals, catalytic converter, fuel injection, or? Car is still on original cat. Any suggestions?

jbooya

Breather tubes in the heads get clogged over time. Failed smog test @ 70K+ miles is the first indication. Design flaw. Check with an experienced 993 mechanic. The only remedy I'm aware of is a valve job.

Steve Weiner-Rennsport Systems

Hi,

High HC's are indicative of leaking valves in these situations so the first thing I'd do is perform a leakdown test for a baseline.

Techron is OK, but I've had better luck with some stronger products that I feel are more effective. I use a combination of LubroMoly Jectron and Ventil Sauber (into a near empty tank, then fill it up) and go for a 100-200 mile hard run, especially up some mountain passes to really load the engine.

After that hard run for 3-5 hours, I perform the leakdown again to see any improvements. Unless the valves were pretty leaky to begin with, this usually does the job when you are that close to passing the smog test.

If your leakdowns are above 15%, you are likely facing a valve job due to excessive guide wear that allows the valves to walk all over their seats.

g_murray

Since you are stuck for time / the pressure is on...

Try putting a can of BG44K (a *phenomenal* carbon remover) when the gas tank is half full (or less) and drive until she's almost empty (i.e. about 100->150 miles or so).

Then fill her up to 1/2-full with GOOD quality gas.

Then go for another sniff test.

Good luck!

Gerry

porsche fever

can you put a heavier oil, maybe single weight 30 or 40, and would this influence the results? I think this was the trick for tired old engines in the 40's and 50's.

thechief

A sincere thanks for all the thoughtful replies. regardless of the final outcome, I've realized that I haven't been driving the care for long enough distances on the few occasions I do drive it. For the first couple of years I owned it, it was my daily driver, then a friend of a friend's son backed his Toyota pickup into it necessitating repairs and respraying the hood, both front fenders, and headlights. Car looked so good when finished I didn't want to get any dings in the new finish. I know, stupid attitude. I'll try one of the additives suggested along with a nice long drive utilizing some 100 octane racing gas over the weekend and see what happens at the next test. Car probably needs a valve job, but with this many miles on it, theres always an argument to also do the rings, then the rod bearings, then the, you get the picture, on a 90K mile car that's only worth somewhere in the mid 20's. Still love the way it looks and drives though.

race911

At 90K, why would rings and/or rod bearings need attention?

And I'm not sure just throwing in 100 octane on an otherwise stock engine is going to do anything. But Steve can slap me silly if I've been misdirected all these years........

2Many Cars

Me too. I don't think the higher octane (over "normal" premium) will do anything other than burn your money.

Steve Weiner-Rennsport Systems

No slappin' necessary,.....

thechief

In reference to the 100 octane fuel, I think the rationale is something like, "well it doesn't cost a lot and maybe it'll help." Point taken, I'll try one of the compounds suggested if I can find one. Monday the car goes in for a diagnostic check and perhaps another try at passing smog.

As to rings, rod bearings, etc., at 90K, I don't know yet of course what condition mine are in, it just seems to be a familiar story people tell about these engines, starts out needing a valve job, but ends up with a whole lot more. I'm certainly not looking to spend money to replace parts that are still serviceable.

Slightly off topic, but I worked on 2,500 HP radial aircraft engines for years. The barrels are steel with cooling fins swedged on and the alloy heads are screwed on the barrels. The cooling fins on the head are machined. The "cylinders" are fastened to the crankcase with bolts. Pretty reliable system, occasionally a cylinder will need to be changed, usually for low compression due to a burnt valve, but by far most engines reach their overhaul high time with only routine maintenance.

g_murray

Pratt & Whitney R-2800 (D-Wasp)... Wright R-3350 Radial Engine... British Centaurus...
????

Gerry
(Private Pilot - and consumate drooler when he visits any air and space museum.)
:-)

Amfab

BK44k is Techron

thechief

That would be R2800's in Navy C-131's (Convair 440) and R3350's in SP-2H Lockheed Neptunes and EC-121 Lockheed Super Constellations, both were elegant engines. Especially the 3350's in the Lockheed planes which for all intents were identical nacelles, props, etc. There's nothing like 13,000 cubic inches at 2800 RPM's and 60 inches of manifold pressure.

tj90

Maybe, but what about the other components?

Why couldnt the problem be a faulty/old cat converter?

Here is an idea that Ive read about but never tried and therefore cant recommend. Run 87 octane for the smog test. 87 has a lower flash point and is easier to burn off. High HC is due to a rich condition. The ECU with ping sensors should compensate and avoid knock for the test.

This thought is totally counter to running 100 octane, which chould HURT HC output due to its higher flash point. The reason sports cars specify higher octane is to allow higher compression (more power) and "late" fuel detonation. You are rich or have unburnt fuel...

I cant stress enough - get that cat HOT before the test! I wouldnt test unless the oil is between 9-10 oclock.

What was you NOx numbers? These are indicitive of lean condition as well..

mongrelcat

I ordered some of the brew mentioned above from Steve and it came in no time. Cheers Steve