Randy V

WHAT!!??

Rob Edwards

Luan-

If you have a 27 mm socket, you can turn the engine (clockwise from the front) until the pointer is at O|T, then pull the air intake tubes off and shine a flashlight down the holes in the top of the TB covers on each side. You ought to be able to see the marks on the cam gears lining up with the notch in the backing plate.

If you see no notches in either hole, then rotate the crank another 360 degrees and check again.

That'll at least tell you the timing is very close if not spot on.

RED SHARK 1990

Hi ROB do i have to remove all the belts and accessories?i hope not and i know we did it last time.We should take a poll-LH or injectors?ec....i use only chevron or shell gas....

Rob Edwards

Luan-

Nope, no need. With a 27 mm socket on a 3" extension on a 1/2" drive ratchet you ought to be able to rotate the motor clockwise to O|T, which is top dead center (TDC). If you can either put the front of the car up on ramps (don't mess up your spoiler or new paint on the nose!!!!!!11!) or drive the car so the nose is overhanging a sidewalk, there ought to be enough room to reach in and do it from underneath. Or maybe you're skinier than me and can just reach in on level ground and do it....

Rich9928p

Some aftermarket "tuner" LH chips (like Autohority) use GT idle speed, i.e. the idle speed is up to 700 - 750 vs. 600 for an AT.

If you're having smog problems this faster idle speed won't make it any better.

perrys4

Luan, are taking the car to the same place every time? I only ask because Greg has told me a story similar to yours where he replaced everything and it still failed so he removed it all to start over and went to a different station and it passed. It isn't unreasonable that their equipment might be off enough to put you over the limit. Might ask when the last time their equipment was calibrated.

RED SHARK 1990

Hello PERRY well the first test at one staion,the second and third test at another location.Well i guess i will look for a third station yeah?I will ask porsche dealer to test my fuel pressure ,intake for leak,and put in on tester for a code maybe it would tell us something-could be an early sign of LH-BRAIN DAMAGE.

Rich9928p

Plug in a known good LH and see if the readings are better. Many LH failures are A/F mixture too rich, not too lean, but when they start failing anything goes.

Have you had the CO checked on each bank of the engine (tubes coming up from the cat)? If there is a leak at a fuel injector or intake gasket leak, that/those cylinders can run lean while the LH tries to richen the "overall mixture" as seen by the O2 sensor. One or two lean running injectors could also cause such a problem. I had an intake manifold gasket leak at the #1 cylinder intake, a pressure smoke test confirmed the problem.

CAShark

Sorry but I don't believe that No is high because of it being too lean. I too live in Cali and just went through this. My Co was .02 and .0, yes I was also running leaner than s#$@, but my No wasn't that high. I think it's something else. My HC was right at the max limit and I changed out the Cat and it's nice and low now.

I think those chasing the lean issue are on Crack. I think the LH is a better diagnostic. Red Shark, PM me what part of SD do you live?

jcorenman

dr bob

I want to remind everyone that we are still speculating on what the pre-cat conditions are based on the post-cat readings that Luan is sharing. All of our experience and theories really don't mean that much, since we don't get to see what the engine is doing ahead of the cats. The pre-cat gas number allow us to determine mixture and ignition issues from CO and HC, respectively. Lean mixture will make higher NOx provided the mixture is still rich enough to have a full flame. NOx goes way up in a hurry if timing is too far advanced or cam timing is advanced, since the effective compression is raised. Still, there's no way to reliably diagnose any of this by looking only at teh after-cat gas analysis.

Look for a repair/tuner shop that has a gas analyser we can attach to a sample tube ahead of the cats. That's the tubes that many take out, the ones with the blue caps under the edge of the aircleaner box. A piece of silicone hose will connect that directly with a tailpipe probe to get a good sample for analysis.

RED SHARK 1990

Hello DR.BOB mine is 1990 and there isnt one on the car under air box.I took the car to a porsche tech and he said if everything was done recently he believes the intake and the combustion chamber could have carbon build up. Therefore it makes the engine run leaner..He said to use a three step BG or BC professional kit porsche uses on every service interval?Has any members heard of this product that cleans the intake manifold,valves,injectors and also added to the gas.There are three cans for a complete job...

blown 87

I use the BG products at my shop, it will work wonders for HC's, not so much for NOX, but it will help.
We charge between 130-150, but I think our shop rates are lower here.

Bill Ball

BG's intake cleaning system works remarkably well to remove carbon build-up. I saw the backside of valves in a GTS before and after and was rather surprised at how effective it was. I can't say it will help your specific emission problem, but it is good stuff.

blown 87

We have not had to use my four gas in years, it will help when you need it though.
90% of the time when they fail on NOX and there is no EGR, it is going to cats or timing.