The county that I live in just implemented emissions testing. On the High Speed test the car past with 120 on hydrocarbons out of 150, on the low speed test however it had 4367 with a limit of 220. Did some checking and the idle mixture screw was out 4½ turns. So I seated it and then turned it out 1½ turns and retried the test. 2500 on the low speed test an improvement but still way to high. With the car running I screwed the idle mixture screw all the way in and it continues to run but roughly. With it turned out a quarter of a turn it runs better. When tested at this point the High speed test is at 52 of 150 but the Low speed is still over 2600 of 220. The car idles right at 750 rpm
The car runs fine but won't pass.
Any ideas of were to start?

 

Well its an older car, that may be tricky. What country are you in?

Id recommend a carb adjustment first. I'm not too familiar with carbonated engines but do you know if your test stated too much CO or NOx?

If you have a cat converter it may not be heating up enough at idle as well.

This is useful
https://www.txdps.state.tx.us/rsd/vi...aq/faq_asm.htm

 

What kind of climate has the car been in? Considering the age of the car I'd try and clean the O2 sensors and see if that helps(These can be tested as well). Check manifold and entire exhaust for leaks, any leak in the exhaust before O2 sensors would cause increased fuel rich mixture. A more precise fuel reading might lower your emission numbers

Edit: ok, apparently you don't have O2 sensor. All I can think of is replace the catalytic converter. If the carb adjustment doesn't do it and you don't want to replace the cat, consider going for a LONG drive before the test, the hotter the cat the more efficient it works.

 

Make sure PCV system is working correctly. However, high engine blowby (low compression) might prevent a solution.

good luck

 

I live in the USA, Utah state. I have tested the O2 sensor and it was faulty, I replaced it and the new one tests good.
The limit for CO is 1.2, high speed was .32 and low speed was .21
The car sees hot summers and cold winters with lots of snow.
A friend has lent me a book from his 89, seems to be the same. I started at the beginning and I have found that the Frequency Solenoid valves test good but they don't switch on and off like they are supposed to when the car is running. I followed the manuals guide and went through and tested the controller and it passed all of the tests. Checked the wires per the manual and they are good. A lot more component tests to do.
The car recently began smoking quite a bit on start up, could oil burning be the cause of super high hydrocarbon reading on the low speed test?
Thanks for your thoughts, will keep updating this.

 

Yes, oil burning can be cause of excess HC readings.

If oil smoke is noticed at startup and after a prolonged idle, then acceleration the valve stem seals are likely source of oil smoke. New seals can be installed w/o removing cylinder head. See youtube for videos on subject.

If fully warmed engine smokes heavily every time under hard acceleration, the engine oil control rings are likely worn or carbon-blocked.

good luck

 

I believe this can be verified with a vacuum gauge test too^

 

How do you perform this vacuum gauge test?

 

You can get a cheap one from harbor freight or go a bit more expensive and buy one at an auto parts store. They're very useful.

Basically you're hooking the gauge up to your intake manifold and measuring the vacuum with the engine running. Typically the car will run about (-)18-22 in/hg at idle and steady load. In the link below there are tests that will reveal what issues there may be going on that could cause the failed emissions.

Technical Articles: Engine testing with a Vacuum Gauge - at Greg's Engine & Machine

 

I have now tested a majority of the emission control devices and they all test good. I have also performed a compression test with the engine hot. #1 145 #2 140 #3 140 #4 115. The person at the emissions center for the county told me that he believes that the #4 cylinder is the cylinder that is causing me to fail the test, he said that he thinks that #4 is basically not firing or not complete combustion and that is were all of the emissions are coming from. After performing the tests and such it appears that the car is now starting to smoke (blue) all the time so it looks like maybe it is time for a rebuild or something. I did a quick check of the valve lash on #4 while it was still hot and the lash was fine, I thought maybe a valve was being held open and that might be causing the low compression.