Hey All, After four months of reading, working on, and learning the hell out of my 75 coupe I've just about got her Smog legal for California. I started her up last week for the first time since bringing her home from arizonia. What a feeling of accomplishment!!!! Then the Smog Test FAILED. Running too rich is the diagnosis. Its a 350, with a Quadrajet. all emission gear on and working. The Rodchester book is a bit confusing with me only having basic knowledge. Where do I start?

Thanks to all in advance, Jim

 

Take a look at the test papers and see if it was at idle or high RPM's that you failed. Or was it on the NOx? What failed and during what test?

Get LARS paper from the FAQ on tuning a Q-Jet. Get a vacuum gauge if you don't have one and adjust the idle mixture on the carb to the leanest with the highest vacuum level. If uncertain on this, is there a shop that you know that has CO and HC test equipment? Have them help adjust it out. Don't tear into it until you adjust it and see what the results are.

 

A shop maybe the way to go, but I'm determined to learn about this thing. I downloaded Lars' article from FAQ and I have started reading it. In the mean time here are the numbers from the last test: The readouts from the last test are as follows: 15mph test, 1346 rpm, CO2%- 11.0, O2%- 3.7, HC(ppm) MAX- 194, AVE- 57, MEASured- 193, CO(%) MAX- 1.26, AVE- 0.25, MEAS- 1.88, NO(ppm) MAX- 1286, AVE- 570, MEAS- 64 (FailedCO%) 25mph test, 1365 rpm, CO2%- 10.6, O2%- 4.0, HC(ppm) MAX- 161, AVE- 45, MEASured- 176, CO(%) MAX- 1.06, AVE- 0.19, MEAS- 2.21, NO(ppm) MAX- 1146, AVE- 648, MEAS- 36 (Failed HC and CO%)

 

Definetely running slightly rich. At only 1300 rpm you will still be partly on the idle circuit, so I think you can make it pass by leaning out the idle.

 

Here is some more information that may shed more light.

The readouts from the last test are as follows:
15mph test, 1346 rpm, CO2%- 11.0, O2%- 3.7, HC(ppm) MAX- 194, AVE- 57, MEASured- 193, CO(%) MAX- 1.26, AVE- 0.25, MEAS- 1.88, NO(ppm) MAX- 1286, AVE- 570, MEAS- 64 (FailedCO%)
25mph test, 1365 rpm, CO2%- 10.6, O2%- 4.0, HC(ppm) MAX- 161, AVE- 45, MEASured- 176, CO(%) MAX- 1.06, AVE- 0.19, MEAS- 2.21, NO(ppm) MAX- 1146, AVE- 648, MEAS- 36 (Failed HC and CO%)
I hope you guys can help with this. I do have that book, and the tools, I just don't have the experience yet to decypher all the lingo and part functions.

Sorry, I forgot to mention that a new high flow Cat was installed last week. The timing is set at 9 btdc at curb idle and the distributor is newer HEI, installed in December last year. The carb is a rebuild from a good carb shop locally (#7045224). Which makes it the correct carb for this year car and type It is a 49 state carb, but the car is from outside CA ( if that makes any difference?). As for the metering rods and jets, I'd have to check with the shop on Monday for any additional specs. The themostate I'm running is a 180.
This weekend I am installing a new set of Boush Plat Spark plugs. Should I replace the thermostate to a 190?
Thanks again

Jim

 

i failed------- idle wasdown at 600 rpm's---- they told me to raise idle up to 1100--1150 and retest---- i went back in and passed with less than 1/2 hydrocarbons----- then i lowered it back to 600 and thanked them-they laughed--

 

Ok, guys......leaned the mix(curb idle), new plugs, checked everything.... The numbers at cruise sky rocketed GROSS POLLUTER..
I went to my Carburator shop and the broke down the problem for me. finally came up with smaller jets, and a lean mix (set on the dyno this time),check the fuel pressure again. I went through evey system an found only that the charocoal canister was not getting a vacume. would this do anything to cause a rich mix? .....Wish me luck I Go back tomorrow

Thanks for all the help

:smash: :cry :confused: :confused: :sad:

 

Viking: is this a q-Jet? If so, it sounds like a power piston sticking. There's also an adjustment within the carb that sets the depth or the metering rods within the jets (i.e. determines how lean the mixture is at idle). There's an Aluminum plug on top of the carb that can be removed to adjust this wtihout disassembling the carb.

 

What Kingt says is true. You can check it out easily. Get a flashinght and look down (engine off!) the vent pipe closest to the fuel inlet side of the carb. Take a long thin screwdriver and lightly poke down there and you should be able to move the power piston up and down. If not get some carb cleaner and give it a squirt and then try again.

The adjustment he is referring to is the "APT" which mainly affects the off idle and cruise A/F mixture. The book by Doug Roe gives you the procedure to adjust this if necessary.

I'd like to suggest that you find a shop that specializes in older engines and will test your car using the CO and HC sniffers. Then any adjustments made for idle etc. can be verifyied. This will save you just tearing into something that does not need it. Unless this is a replacement carb, you are a little rich. Could be float level, stuck power piston, idle mixture etc. Maybe a dumb one - but is the air filter, PCV valve and breather filter clean or new? Good luck.

 

Another thing, make sure you have fresh oil. Remember, the PCV system is recirculating blow-by into the intake. BigVette hit on a good point; get a good book on Q-Jets and study it. And be sure the air pump is working if so equiped.

 

Ok, Guys I got back from the test and I passed with flying colors. The new additions were
.073 jets replaced by .071
Rods stayed the same at .046
Leaned the mix to bearly running at idle , fine when warm
same 180 temp thermostate ( the TVS's work @ 165)
Linked the canister vacumn into the PCV (vacumn for sure)
All systems checked and rechecked to assure working properly

Here are the first results (Failed)

The readouts from the last test are as follows: 15mph test, 1346 rpm, CO2%- 11.0, O2%- 3.7, HC(ppm) MAX- 194, AVE- 57, MEASured- 193, CO(%) MAX- 1.26, AVE- 0.25, MEAS- 1.88, NO(ppm) MAX- 1286, AVE- 570, MEAS- 64 (FailedCO%) 25mph test, 1365 rpm, CO2%- 10.6, O2%- 4.0, HC(ppm) MAX- 161, AVE- 45, MEASured- 176, CO(%) MAX- 1.06, AVE- 0.19, MEAS- 2.21, NO(ppm) MAX- 1146, AVE- 648, MEAS- 36 (Failed HC and CO%)

Here are the final results:

15mph test, 1694 rpm, CO2%- 10.2, O2%- 6.5, HC(ppm) MAX- 194, AVE- 57, MEASured- 49, CO(%) MAX- 1.26, AVE- 0.25, MEAS- 0.00, NO(ppm) MAX- 1286, AVE- 570, MEAS- 570
25mph test, 1672 rpm, CO2%- 10.0, O2%- 6.8, HC(ppm) MAX- 161, AVE- 45, MEASured- 29, CO(%) MAX- 1.06, AVE- 0.19, MEAS- 0.00, NO(ppm) MAX- 1146, AVE- 648, MEAS- 648

As you can see CO@ at 0.00 HC, down considerably, and NO wet up to just below the average.....I learned way more than I wanted to about Emissions than I wanted but it's done and I can move on to the Fun Stuff.....Front End rebuild next Thanks again for all the help hopefully this thread will help others get through the dreaded CA emissions.


:cheers: :cool: :flag

 

Congrats. What do you think made the most improvement? Or was it a combo of all you did?

 

It was definently the jets. But the power drops off a bit. not to bad for a daily driver but I need to figure out why the .073 jets created the rich state before going back to them. If it ain't broke fix it til it is broke. I'm going to concentrate on the front end for now. I needed to get the DMV off my backso that I could be a bit more leisurly about working on her. ( no Due Date got enough of that at work)

 

Glad you fixed your problem and got certified. I have trouble understanding how going from 73's to 71's was the fix. Think this plus turning in the idle screws very lean did it. Changing the jets is a very small change. I looked up 1975's w/350 and they seem to all have 72 mains and 46 rods. I would suspect that you freed up the metering rods with the power piston that was partially stuck when you changed jets. Going to 71's and adjusting the idle mixture should make the throttle response crisp but pretty lean at WOT or higher RPM"s Check your plugs periodically to make sure you are not too lean. Good luck on the rest of the projects.

 

hey viking, Lori says she hears your car all the time. If you remember I live across the street in the condos. I know someone who can set you up for emissions. It will probably run around 50 bucks. The once you pass he will make it run like it should. So just let me know.

 

Thanks for the heads up. Bigvette1, Jim Send me the name. I'd like to talk to someone who can walk me through the Idle setups. I'm kind of guessing at this point and I'm getting tired of the trial and error approach.

Car won't be out for a couple of days I think. Just stated body mount replacement and it's a slow process. :smash: :rolleyes: