Failed Smog Test California

[rjm65]

Took my 79 in this morning for the biannual smog check, didn't pass. Here are the results:

15mph 1500rpm CO2=13.3% 02=2.7 HC=428PPM CO=.02 NO=519

25mph 2500rpm CO2=13.8 02=2.0 HC=31PPM CO=.01 NO=396

The max HC at 15mph allowed is 201.

I'm thinking possible vacuum leak? The HC readings at 25mph are WAY lower than at idle. All the readings except the one in red are well within the passing range.

Anyone have any thoughts?

Thanks.

[SolReaver]

428 is pretty high.

Assuming that you have a fresh air cleaner, good plugs, new oil and the car was thoroughly warmed up and running on high test with no vacuum leaks and a healthy charging system.(that is a hint)..,.I am going to take a wild stab at it and ask you how old the O2 sensor is. They will give bad performance long before they go so far as to throw an error code.

Before replacing the sensor (or any other sensor) check the connectors and the wiring. This means pulling the rug on the passenger side and following the wires.

K-jet is not my specialty, but I vaguely remember a few adjustments that can be made IF you know what you are doing. I never touch them.

When in doubt... clean and secure all your grounds. (it can't hurt)

[MPDano]

Raymond has a 79, he's lucky to have a Cat on his. No O2 on his model.

[SolReaver]

Sorry, my bad. in that case...Cat?
(hey, what do I know?)

[MPDano]

Originally Posted by SolReaver

Sorry, my bad. in that case...Cat?
(hey, what do I know?)

All good bro. I was also thinking the same thing. Maybe an original Cat? He's going to try and replace all his spider Couplers first since that could be his source of vac leaks. That would be the easiest and least expensive route.

[rjm65]

Would a bad cat cause high hc readings at 1500 rpm's but normal readings at 2500 rpm's? PO replaced the CAT about 3 years ago, maybe has 8000 miles on it.

I have the spider couplers off, no tears or splits but will be replaced while I'm at it.

I did notice the tube on the side of the cold start injector adapter plate was slightly deformed-ovaled (the spot where the rubber vacuum hose mounts to it). Thinking the piece was made of metal, I applied a little pressure with my thumb and forefinger to see if it had any give, to see if I could reshape it. I just barely touched it and here are the results. Now I didn't inspect it closely for cracks before the piece broke, well it didn't actually break it just crumbled, but I'm thinking there was probably already a crack at the base and quite possibly the source of a vacuum leak. That or the fact that the inlet for the vacuum hose was oval shaped might have kept it from properly sealing.

[MPDano]

Can be used as a Prison weapon now.

[XLR8928]

Back in the early '80s when I lived in Cali, I used to get my modified 240z, 280zx and my '68 GTO to pass by adding about 10% alcohol to the fuel and retarding the timeing 4 degrees. You could probably get the same effect with 5-6 gallons of E-85 added to your normal fuel load. I'm not sure if this would have any adverse effects on your fuel system, bur it never seemed to bother my cars. At least this will give you some time to find the problem, and still drive your car.
-Kerry

[rjm65]

All my numbers are good on the smog test except for the HC's at 1500 rpm's, will adding alcohol or E-85 to the fuel have any effect on the other readings? Does the alcohol only server to lower HC's?

[johnnywishbone]

I had major previous owner mutilation of smog equipment. steve at dieters
made the problem go away. Last 3 smog checks passed no problem.

Highly recommened. Johnny

[MPDano]

Originally Posted by johnnywishbone

I had major previous owner mutilation of smog equipment. steve at dieters
made the problem go away. Last 3 smog checks passed no problem.

Highly recommened. Johnny

On a 928?

[Danglerb]

Maybe cat wasn't fully warmed up?

Maybe something related to the smog air pump?

Maybe somebody that really knows will post?

[SolReaver]

I think going through the usual suspects it the first step. A smog pump or the filter could be responsible. So could half a dozen other items. I would suggest a vac gage to check the vac. ( hey, what do I know) I would caution against the alcohol as it can degrade seals. Dang: you are correct. Expert advice WITH THIS model is needed. I can only give generalities and Moral support.

GO team GO! Wrench till it works! Yaaaaa team!

[rjm65]

Did a 15-20 minute drive at freeway speeds prior to the test for the sole purpose of getting the cat warmed up, pulled right in to the test site and never shut it down until the test was over. It did sit idle for a few minutes while the tech punched in the info, not sure if that matters.

Found this troubleshooting chart, which right now seems to confirm vacuum leak (low CO and high HC at 1500 rpm test)

Recarbco - Carburetor Smog Diagnostic Chart

[neil30076]

Do you have a MityVac ? This should quickly identify if you have a leak or not - also hooking a vacuum gauge up on the vac lines and running up to 1500 may show if there is a leak.

[Danglerb]

HF metal version of the mityvac is onsale right now for $20, and I think a coupon that knocks another $5 off is available.

I thought Dieters stopped working on 928's?

[rjm65]

I do have a vacuum gauge, anyone know what a baseline reading should be at idle on a '79?

I put the new spider couplers back on and also replaced the old cold start injector base and it's o-rings, will finish buttoning everything up tonight.

I really think the vac leak was on the engine side and not the brake booster/door locks/hvac system. After shutting it down I can come back the following day and move the AC control lever and can hear the flaps moving around inside. But just to be on the safe side I plan on taking a vacuum reading at idle with everything hooked up, then with the vac T capped to see if there's any difference. If I see a change, then I'll get a mityvac and start to further trace any additional vac leaks.

May just leave all vac capped except the brake booster for the test just to eliminate that variable, and if it is an issue worry about it after the smog retest.

[Mrmerlin]

normal vacuum on an idling engine SB from 18 to 22 in. and steady

[rjm65]

Showed a rock solid 23 inches.

Got everything back together tonight. Took it out for a quick spin. Previously I was getting some slight pinging under heavy acceleration, totally gone now. Surprised how quickly it revved to 6K in 2nd while getting on the freeway too.

Hopefully this took care of it, will find out Saturday when I retest.

[MPDano]

Originally Posted by rjm65

Showed a rock solid 23 inches.

At first, I thought this was a Spammer posting Porno replies

Good luck on the retest.