Smog

[Rooster's 67]

I was a Texas certified emission repair technician here in and I am a Master certified ASE Tech with an L1 engine performance cert. I would be hesitant of replacing a cat just yet. is there a station that has emission test equipment Not necessarily an inspection station but that has a four gas analyzer that is closer? just for the ability to tune and test, without the long trip and paying for the gas, time, and test?

If you could post up the emission results And at what rpms they were tested at I will see if I can give you some pointers to avoid anymore parts to replace.
Is the test a dyno type road speed/load test or just rpm in a stall test?

You stated earlier that it had passed the sniff test but failed because of the puff of smoke correct? Then subsequently failed a sniff test at a later time?

Also what was the ambient temp at the time of the different tests?
was the truck allowed to idle or did it cool while waiting?
the key as how to tune the engine for passing the test lies in being able to interpret the readings.

PM me to get my number or send me yours if I can help, it can be much quicker over the phone to work up a plan of attack for ya, can be a lot of questions to get a good idea of whats causing the failures. Besides the fact that its California for ya.

Spencer

[oldspowered67C10]

What gas(s) did it fail for?

[AirSpeed]

Originally Posted by Rooster's 67

I was a Texas certified emission repair technician here in and I am a Master certified ASE Tech with an L1 engine performance cert. I would be hesitant of replacing a cat just yet. is there a station that has emission test equipment Not necessarily an inspection station but that has a four gas analyzer that is closer? just for the ability to tune and test, without the long trip and paying for the gas, time, and test?

If you could post up the emission results And at what rpms they were tested at I will see if I can give you some pointers to avoid anymore parts to replace.
Is the test a dyno type road speed/load test or just rpm in a stall test?

You stated earlier that it had passed the sniff test but failed because of the puff of smoke correct? Then subsequently failed a sniff test at a later time?

Also what was the ambient temp at the time of the different tests?
was the truck allowed to idle or did it cool while waiting?
the key as how to tune the engine for passing the test lies in being able to interpret the readings.

PM me to get my number or send me yours if I can help, it can be much quicker over the phone to work up a plan of attack for ya, can be a lot of questions to get a good idea of whats causing the failures. Besides the fact that its California for ya.

Spencer

Thanks! I will get the reports from him and post them, as for temps all the tests were done under very similar conditions, even the same time of day. I appreciate the help!
Posted via Mobile Device

[Rochlow]

Makes me glad we don't have smog testing here.. Just obdII.
Posted via Mobile Device

[AirSpeed]

Originally Posted by Rochlow

Makes me glad we don't have smog testing here.. Just obdII.
Posted via Mobile Device

In the county the kid lives he only has to smog it once, when the truck is bought or sold. Two miles away in my county we have to smog every other year for newer vehicles. I'm glad I only have one new car, my wifes car. I never have to smog my trucks thank goodness!
Posted via Mobile Device

[AirSpeed]

He can only remember the last two of the reports, he's at work (fireman) so here's what he had.
Before we changed the valve seals and EGR the hydrocarbons measured at idle 149, @2500 rpm it measured 66.

After the seals and EGR it measured 359 and 112 but no visible smoke.
He told me this from memory as he is at work today and didnt have the reports in front of him. I will verify these numbers and any other info when he gets off. Thanks! Aaron.
Posted via Mobile Device

[Rooster's 67]

So it failed on HC, yeah post all the gasses they are testing, and the rpm when tested.

[AirSpeed]

Originally Posted by Rooster's 67

So it failed on HC, yeah post all the gasses they are testing, and the rpm when tested.

Thanks, I will post the actual printouts as soon as the kid gets back to town, on shift he works/lives at a firehouse about twenty miles away. I'm hoping they have a scanner there so he can send them to me today.
Thanks again! Aaron.
Posted via Mobile Device

[AirSpeed]

Originally Posted by Rooster's 67

So it failed on HC, yeah post all the gasses they are testing, and the rpm when tested.

Here's the reports,




Posted via Mobile Device
Posted via Mobile Device

[AirSpeed]

After the one that mentions failure for visible smoke we put on new valve seals and a new EGR valve, after that it failed emissions. I just noticed I posted these out of order but the dates are on them. The smog guy now says a new cat will fix the problem but he also said new valve seals would do it so I don't have a lot of faith in the smog guy. Thanks for the help! Aaron
Posted via Mobile Device

[Lee H]

So it was the HC at 2500, way higher than the first test, interesting. High HC is usually caused by 1) timing to far advanced. 2) warn out ignition components (cap, rotor, plug wires, plugs) 3) Lean mixture usually caused by a vacuum leak (unhooked vac hose, base gasket, booster?), 4) bad cat.

I could rule out 2 and 4 above be caused it passed the first test. California allows + or - 3 degrees on the timing check, what is your timing?

I would start by looking at what changed between the first and second test. Timing, carb gasket, vac hose routing, plugs and or wires damaged, etc?

[AirSpeed]

Originally Posted by Lee H

So it was the HC at 2500, way higher than the first test, interesting. High HC is usually caused by 1) timing to far advanced. 2) warn out ignition components (cap, rotor, plug wires, plugs) 3) Lean mixture usually caused by a vacuum leak (unhooked vac hose, base gasket, booster?), 4) bad cat.

I could rule out 2 and 4 above be caused it passed the first test. California allows + or - 3 degrees on the timing check, what is your timing?

I would start by looking at what changed between the first and second test. Timing, carb gasket, vac hose routing, plugs and or wires damaged, etc?

All the ignition components are new, rotor, cap, wires, plugs. I did find a bad vac hose connected to the cruise control diaphragm, there are 3-4 small hoses and one was cracked, I checked where the hose connects on both ends for vacuum and there was none, we're going to put a new hose on it anyway. The only thing we changed after the test that showed smoke was to replace the valve guide seal and EGR valve, it stopped smoking completely but it failed the emissions. I hate to spend money on a new cat of its not going to help. I will check the timing again and see where it is this week. Thanks! Aaron
Posted via Mobile Device

[oldspowered67C10]

Im assuming your not actually paying the smog test station to diagnose the problem, just asking them for advise? A new cat may mask the problem enough to squeak by but it wont fix the base problem, that thing is lean! If you run all those gas readings through a Lambda calculator(a formula that give you A/F ratio using gas analyzer readings) youre fuel ratio comes in between 17-18:1. Thats too lean for complete combustion and will cause a HC problem.

Check for vacuum leaks and carb adjustment(idle mixture). Unfortunately the only way to see the results of your changes is too hook the truck to a gas analyzer.

[AirSpeed]

Originally Posted by oldspowered67C10

Im assuming your not actually paying the smog test station to diagnose the problem, just asking them for advise? A new cat may mask the problem enough to squeak by but it wont fix the base problem, that thing is lean! If you run all those gas readings through a Lambda calculator(a formula that give you A/F ratio using gas analyzer readings) youre fuel ratio comes in between 17-18:1. Thats too lean for complete combustion and will cause a HC problem.

Check for vacuum leaks and carb adjustment(idle mixture). Unfortunately the only way to see the results of your changes is too hook the truck to a gas analyzer.

Thanks. This thing has TBI, there's no adjustment on it. The injectors look like they're spraying fine. Would a vacuum leak, or many leaks make that big of a difference? I will check it again and see what I can find. Thanks!
Posted via Mobile Device

[oldspowered67C10]

Didnt realize it has EFI. Need to get a scan tool and check the fuel trim levels(GM used to call them integrator and block learn back then). If the computer isnt adding any fuel or is taking fuel away then youd look to a new oxygen sensor. If, on the other hand you look at the fuel trim and you see the computer is adding all the fuel it can and its still that lean youd look for a vacuum leak or a fuel delivery problem.

[AirSpeed]

Originally Posted by oldspowered67C10

Didnt realize it has EFI. Need to get a scan tool and check the fuel trim levels(GM used to call them integrator and block learn back then). If the computer isnt adding any fuel or is taking fuel away then youd look to a new oxygen sensor. If, on the other hand you look at the fuel trim and you see the computer is adding all the fuel it can and its still that lean youd look for a vacuum leak or a fuel delivery problem.

I guess I should have mentioned its fuel injected, it was the first year for EFI. I will see what I can do about getting a scanner, the kid has no day off for two weeks so he can't try smogging it till then, we're going to go nuts on it after work until we work out every detail. If it fails again I'm going to pull the engine, trans, axels and anything else worth anything and push it off a cliff! I can't believe how many problems it has had, I took fantastic care of it. I guess I should have drivin it around more often, it say for several years, I drove it around the block once a month to lube it up, it always ran great. The year I parked it was the last year it was sniffed and it had no problems at all passing, I guess time takes its toll even on Chevys! Im really thinking its a vacuum issue after so many saying the same thing, we are going to replace every soft vacuum line and check all the hard lines but I think I will throw on a new cat just to make sure, I found a universal cat for $50 delivered, it's supposed to work on pretty much any V8 as long as there's room to mount it and there is plenty of room. I've never replaced a cat converter so I don't know if a universal cat will do the job. I have a MIG so installing it is no problem but if anyone can tell me if its advisable to use a universal cat please let me know! Not trying to cheap out but a lot of money has gone into smogging this thing.
Thanks again for all the help! Myself and the new owner really appreciate it!
Posted via Mobile Device

[Lee H]

EFI, arg, that opens up a whole lot of other variables. Computer controlled, who's? Where is the O2 sensor?

[AirSpeed]

Originally Posted by Lee H

EFI, arg, that opens up a whole lot of other variables. Computer controlled, who's? Where is the O2 sensor?

Haven't looked for it yet (o2 sensor) I haven't priced it yet either but I'm sure it will be at least $100. The pushing it over a cliff idea is getting more tempting!
Posted via Mobile Device

[leddzepp]

Originally Posted by AirSpeed

The pushing it over a cliff idea is getting more tempting!
Posted via Mobile Device

Give the kid his money back and part it out, or sell it to someone out of state where smog is not an issue. Get rid of it! It is, and will continue to be a money vacuum for the rest of it's life in California. The state wants these vehicles off the road, and smog repair stations have dollar signs rolling in their eyes when they see an 80's domestic vehicle come in. Whoever owns this truck will go through the same crap you are going through now again in the future.

[Rooster's 67]

All above are good and valid ideas and comments. I would look for the small vac leaks and scan data to look at the integrator and block learn for idle and 2500rpms and see whether the computer is adding or taking fuel away. A new O2 should be fairly inexpensive for that year. and the universal cat should work fine as long as it is designed for 350ci or better. both would get you by the sniffer.

check base timing with the timing connector disconnected too.

[Rooster's 67]

most expensive O2 sensor was like $17 on rockauto.com

[AirSpeed]

Well last night we put a new catalytic converter on the blazer, replaced a couple bad vacuume lines and the thing failed smog again. This time the smog guy did a pre test so he didnt charge him. Now mr Smog says the valves need adjustment, I adjusted them very carefully when we put in the new valve seals, I guess I will try again. I begged the kid to let me give him his money back but he loves the truck and has big plans for it, I would rather never see the thing again!
I can't think of anything else to try!
Posted via Mobile Device

[406 Q-ship]

Originally Posted by AirSpeed

Smog tests suck! We changed the valve seals, EGR valve, changed the oil, all the things the smog guy told us to do, things he said would cure the issues. This morning the kid took it back and it failed again, this is the fourth time, the first test locally and three "gold star" tests, now the smog guy says a new cat converter will fix it! This sucks, each trip to the gold star smog shop cost over $100 with gas and the cost of the test. We've spent at least $200 on parts and now have to spend another $100 for a new catalytic converter and another $100 for gas and another test. It's going to end up costing $1000 by the time it's all over and we don't even know if a new catalytic converter will fix the problem! I'm thinking he should sell the damn thing or part it out at this point!
Do I have to buy a specific converter or can I get one out of a similar sized, low mile wrecked truck at the junk yard? I have found a few universal converters for around $50, will one of these work or should we just go for the specific model made for the truck? Any suggestions or recomendations would be GREATLY appreciated! Maybe I should compress the exhaust out of my wife's car, it had zero emmisions it's last test, put it in a bottle and pipe it to the K5s exhaust, heck I could make some fake pipes and pump the bottled exhaust into it! I am so glad my trucks never need smog! Another reason to drive old trucks! Thanks all! Again, any suggestions, no matter how ridiculous will be considered at this point!
Posted via Mobile Device

I got bad news for ya, wrecking yards will not and cannot sell cats off a used vehicle (it is federal not a cali thing either). If it passed the sniffer before then it was either the cat is on its last legs (the old prints old can tell you that (it will be close to the standards). A trick is to throw some alcohol in the tank before the test, it will lean the mixture out and get it throw without needing a catalytic. Valve adjustment is probably closer to right, it is the only thing messed with since it last passed. What is it failing? HC CO, or NOX

[AirSpeed]

Originally Posted by 406 Q-ship

I got bad news for ya, wrecking yards will not and cannot sell cats off a used vehicle (it is federal not a cali thing either). If it passed the sniffer before then it was either the cat is on its last legs (the old prints old can tell you that (it will be close to the standards). A trick is to throw some alcohol in the tank before the test, it will lean the mixture out and get it throw without needing a catalytic. Valve adjustment is probably closer to right, it is the only thing messed with since it last passed. What is it failing? HC CO, or NOX

I bought a new cat and installed it last night, he took it in this morning and it didn't help a bit. Mr Smog guy is now telling the kid the valves need to be adjusted again. Haven't heard about the alcohol trick, might have to try that next time. Some one else suggested acetone in the gas, havent tried that one either. Smog guy did a pre test, said too many hydrocarbons. Thanks.
Posted via Mobile Device

[406 Q-ship]

Sorry I just found the reports.....

With the HC jumping around that much it has got an issue somewhere. Check the valve adjustment (still the only thing you messed with since it passed the sniffer). Set the timing 2° retarded from the factory settings, it will be within tolerance for Cali and it will help but not fix the bigger problem. Throw an O2 sensor at it if you have not already, they get funky with a lot of miles on them and if you didn't change it out who knows how old it is. Alcohol is oxygen bearing (the reason they like it for emission in gas) and will help, and do not put acetone in fuel EVER it will cause detonation and kill the engien like now! Acetone works as a starting fluid but it is still a bad idea.