Emissions

[arlbrl]

What can be done to lower the Hydrocarbons and the CO levels in my exghaust fumes?  My truck did not pass my state required emissions test.  THe engine is a 1990 fuel injected chevy 350 out of a Suburban in a 1985 C10.  The engine runs fine with the exception of the foul fumes.  Any assistance :will be greatly appreciated.  

[Blazin]

Don't know for sure. I have heard dry gas will help. Also fresh plugs, wires, fule, air filter etc.

[VileZambonie]

If your CO & HC's are hi that is a rich condition. Make sure your air filter is clean, your ignition timing is correct and your O2 sensor is switching to start with.

[arlbrl]

If the "Check Engine" light is not on can the o2 sensor still be bad?  How is the EGR Valve supposed to opened since the vac. line is ran through the EGR valve first?  Is it supposed to open in a pulse like fashion?  Please advise.  Thanks in advance.

[VileZambonie]

It's not the EGR valve. The EGR Solenoid is pulse width modulated ny the ecm to open the bleed port.

If the O2 voltage is low your injector pulse will go up. Look at your fuel integrator and block learn on your scan tool. The check engine light doesn't have to come on for a sensor to sway a rich or lean condition.

As i said earlier if your CO is hi you are rich and if you have hi HC's then you also have incomplete combustion.

[arlbrl]

Can this be checked without a scantool?  Unfortunately I do not have one. "Look at your fuel integrator and block learn on your scan tool."  Where is the fuel integrator?  I'm used to working on the 4B carb.  Any help is appreciated.  Thanks

[VileZambonie]

Fuel integrator and block learn can be viewed on a scan tool. For some reason I thought you had one. It is the early version of long term short term fuel trim. Your computer has what's called adaptive strategy or adaptive learning. It helps change the base air fuel ratio essentially based on many factors.

Since you do not have access to a scan tool do you have access to a digital volt meter?

[arlbrl]

Yes I do have a volt meter.  Please advise.  Just to let you know.....I changed the plugs, Pcv valve, EGR valve, EGR Vac. valve, Fuel Filter, Thermostat, and I reset the timing to 0 degrees disconnecting the timing connector.  Thanks in advance.

[VileZambonie]

Ok, backprobe the O2 sensor at the sensor wire terminal with your positive meter lead and the negative lead to a good ground. Set your meter to the 2v DC scale. With the engine hot and run at about 2000 rpm for 2 minutes, check your voltages while it is running. It should range from about .100 - .900 V and cross the .450 mark just to verify if the O2 is good and is switching. Post your results here and I'll guide you to your next easy step

[78ScottsdaleK20]

I would have to agree with the above mentioned about it running rich. Do the test with the voltmeter on your O2 sensor. I had excellent luck doing this on my carbureted motor. I installed O2 sensors on both header collectors and took volt readings to tune the carb. It works. Your ideal setting according to the volt meter will be between .4-.5 volts. This is a 14.7-15.0:1 air fuel ratio. The lower the reading the leaner, the higher the reading the richer A/F. If you lean it out a little, more than likely you will have less emission readings. Good luck!

Mike

[arlbrl]

Just to let you know I did change the O2 sensor since it was cheap to do. I'll go ahead and still take the readings.  I'll get back to you.  Thanks

[arlbrl]

First my meter does not have a setting for 2dcv, the lowest it has is 20dcv.  I took the readings using the 20dcv setting and either I did it wrong or nothing happened.  I took the readings before the terminal where the O2 sensor connects in actually two different places and nothing happened.  I did notice however that the wire from the harness to the O2 connector was rather spongy.  Could this be the problem? Or could it be that my meter not having a 2dcv setting is the problem?  Sorry for so many questions it's just that I have until this Saturday 11/25 to retest the truck for emmissions.  Please advise.  Again thanks in advance.

[arlbrl]

Ok check this.  I had the truck scanned with a Snap On scanner the intgrager was at 128, the O2 was switching like it was supposed to.  All the sensors were where they should be with besides the Idle Air Control Valve.  For some reason it was not dropping back down to where I was told it should be dropping.  It would stay reading at about 84 to 90.  I was told it should be down to about 20 to 70.  The scanner showed that this engine has a Mat sensor but everything I checked and look in says it did not have a Mat snesor.  The scanner was showing 300 - 400 degrees for the MAT sensor then it would drop to 0.  The idle is staying at about 1000rpm and told it should be at about 750 to 800 rmp.  My next step would be to change the IAC and the MAP sensor unless you have another suggestion.  Also the engine light comes on when driving on the freeyway then goes off once I turn the truck off and stays off until I get back on the freeway.  It is showing a code 32 EGR failure, I changed the EGR valve with a new one and still get this code. Please advise.  

[roundedline]

I would check for vacuum leaks or holes in all the hoses for the EGR system and then everything else.

Chris Lucas
www.73-87chevytrucks.com
www.captkaoscustoms.com
Project Su
Jimmy 2WD Project

[VileZambonie]

It sounds like the base gasket on the TBI is leaking. The reason your IAC steps are hi is because it is compensating for the increased engine speed from the leak. As far as the EGR is concerned, make sure you have vacuum to the EGR solenoid with the engine running. There should be no vacuum coming out of the solenoid until it is energized. You can energize it to make it come on to test the solenoid.

Your O2 sensor swiches Rich lean constantly to maintain Stoichiometry but also to allow oxygen to get downstream. If you don't fee the Catalytic converter oxygen then it cannot oxidize. So fix your vacuum leak, check your EGR circuit (but that is not why you failed your emissions test) and then get it retested.

Also you said your fuel integrator was 128 but what was Block learn?