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Failed CA Smog, High NOX '89 240

philski o'flood

Active member
Joined
Nov 7, 2005
Location
San Diego
ok got everything back together and running... also fixed

all 4 EGR rubber vacuum pieces were bad
cleaned every manifold and throttle body vacuum nipples
clean all plastic intake pieces
super glued Harbor freight electrical tape over accordion intake holes (because TB :)
replaced intake side O rings on injectors
scrubbed and re-oiled junkyard K&N panel filter and installed and cleaned air box
cleaned MAF with correct spray cleaner
installed a KNOWN GOOD 933 ECU in place of the original 556

drove it around for a half hour, got rolled tacos and some beers and came home
 

tbrcktch

New member
Joined
Aug 31, 2006
Location
So Cal
Nice work, the only thing I might recommend to you, is to ditch the K&N. I like them, have used, & still use on some of my vehicles (carbureted truck, motor cycles, and my K-JET 242's). I've had K&N issues with one of my LH vehicles, and also customers with driveability & / or smog problems. It doesn't take much to degrade a MAF (oil fumes, from treating the filter, contaminating the sensor), requiring replacement, and installing a stock air filter. Just my 2cents. Good luck on your smog!
 

philski o'flood

Active member
Joined
Nov 7, 2005
Location
San Diego
never had a problem with K&N filter and here is my '90 smog results with V cam, pink injectors and a K&N

index.php
 

philski o'flood

Active member
Joined
Nov 7, 2005
Location
San Diego
pulled out the Bosch plugs, they looked pretty good a little on the lean side, and installed NGKs and put in a set of pink injectors
 
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bobxyz

Board Member
Joined
Aug 29, 2014
Location
Boulder CO
Woo Hoo, Nice retest numbers! There's nothing like a failed emissions test to make you go over the engine in excruciating detail to find all the gremlins that you never knew were there.
 

philski o'flood

Active member
Joined
Nov 7, 2005
Location
San Diego
ok can any of you smart 5 gas guys explain what is going on with the extreme differences in the C02 and 02 levels between the 2 tests...
the elevated NOx was a direct result of the exhaust leak at the cat and down pipe...
but when I put these passing numbers in the Lambda calc form it says no bueno

index.php

index.php
 
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PCH

Active member
Joined
Oct 25, 2008
Location
Oxnard, SoCal
All I can tell you with certainty that on the failed test you EGR was not working and now it does. On the Pass test if the Cat had a chance to get hotter your CO2 would rise up to proper 15% and free O2 would drop because of that.
 

tbrcktch

New member
Joined
Aug 31, 2006
Location
So Cal
Congrats! Sometimes, it's just the little things, not having any leaks, (and a working EGR!) Tacos and beers time!
 

ZVOLV

<Master Tech>
Joined
Nov 19, 2002
Location
California
Your exhaust leak was the downpipe to the exhaust manifold gasket?

Is the O2 in at the cat? Or in the manifold?

I need to brush up on interpreting the CO2 and O2 readings.
 

philski o'flood

Active member
Joined
Nov 7, 2005
Location
San Diego
Your exhaust leak was the downpipe to the exhaust manifold gasket?

Is the O2 in at the cat? Or in the manifold?

I need to brush up on interpreting the CO2 and O2 readings.
The leak was between the downpipe and cat, it's the kind with the 2 flanges and a loose donut ring, no gasket. The bolts tightened all way but the donut was crooked or something and it was leaking.

The sensor is in the cat
 

bobxyz

Board Member
Joined
Aug 29, 2014
Location
Boulder CO
I didn't notice the CO2/O2 difference before. Maybe there's still a single-cylinder misfire problem, but it's within the range that the CAT can still cleanup the HC+NOx. If you're going to leave the CAT installed, then yeah, you should figure out what's going on so that it doesn't damage the CAT. Does it idle and run smoothly? While idling, if you disconnect one injector at a time, do they all cause about the same rpm response?
 

ZVOLV

<Master Tech>
Joined
Nov 19, 2002
Location
California
I'd be interested to see what a post-O2 sensor exhaust leak does to emissions vs. pre-02 sensor leak does to emissions.

Exhaust leak pre O2: I think the ECM doesn't see the fuel in the exhaust as much, thinks its lean, then dumps in extra fuel. I have seen cracked exhaust manifold cause rich black soot on the O2.

Pre cat exhaust leak....I'd imagine the cat won't light off as well as it should.
 

philski o'flood

Active member
Joined
Nov 7, 2005
Location
San Diego
I didn't notice the CO2/O2 difference before. Maybe there's still a single-cylinder misfire problem, but it's within the range that the CAT can still cleanup the HC+NOx. If you're going to leave the CAT installed, then yeah, you should figure out what's going on so that it doesn't damage the CAT. Does it idle and run smoothly? While idling, if you disconnect one injector at a time, do they all cause about the same rpm response?
PCHs explanation for the CO2/O2 differences seems spot on. On the second test there were 2 cars ahead of me and the car was off for 30-40 minutes before testing. The smog guy had it idle for 10 minutes or so and ran it on the rollers for maybe 2 minutes. I looked back over all the other test results and this is the only one that doesn't have a 15% CO2 also this is the only time where the car was off that long before testing.
All I can tell you with certainty that on the failed test you EGR was not working and now it does. On the Pass test if the Cat had a chance to get hotter your CO2 would rise up to proper 15% and free O2 would drop because of that.

The car is running the best it ever has, very noticeable improvement in off the line and freeway speed power and acceleration.
 

philski o'flood

Active member
Joined
Nov 7, 2005
Location
San Diego
I'd be interested to see what a post-O2 sensor exhaust leak does to emissions vs. pre-02 sensor leak does to emissions.

Exhaust leak pre O2: I think the ECM doesn't see the fuel in the exhaust as much, thinks its lean, then dumps in extra fuel. I have seen cracked exhaust manifold cause rich black soot on the O2.

Pre cat exhaust leak....I'd imagine the cat won't light off as well as it should.
Look at the test results again... the fail test with high NOX... the leak was BEFORE the cat and O2 sensor
 

ZVOLV

<Master Tech>
Joined
Nov 19, 2002
Location
California
Confusing post, sorry.

I am just wondering if your fail was due to the exhaust leak skewing the mixture, or the cat not working properly due to the leak. (If the sensor were in the header, would it have failed? )
 

bobxyz

Board Member
Joined
Aug 29, 2014
Location
Boulder CO
I'm not a smog tech or a mechanic, but I did read up on emissions last year when my 245 failed for high NOx. I wanted to be sure that the $800 CAT replacement would fix the problem and there was nothing going on that would damage the new CAT.

My guess at the high NOx in this thread is that the air leaks between the head and CAT were big enough and continuous enough to prevent the CAT from ever reducing the NOx. Once the leaks were fixed, the normal slight rich-lean-rich-lean cycling of the ECU gave the CAT the time needed with lack of O2 (on the rich swings) to reduce the NOx.

My concern with the high O2 on the passing test is that there should be almost no O2 in the exhaust if the engine is running right and the exhaust probe is accurately sampling the emissions. Air is ~20% oxygen and ~80% nitrogen. Complete combustion uses up all the O2 and coverts it to CO2 and water. Normal exhaust numbers should be ~15% CO2 and ~0% O2. Having ~5% O2 post-cat means either 1 cylinder is not firing (20% O2 in, divided by 4 cyls), or maybe the exhaust probe is getting some O2 from outside the exhaust.
 
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