I have high CO levels where do I start

[Totally 80s]

I moved from Hawaii to Colorado and I have to get an emissions test pass to register the car. Took it in today for the test and failed. Says i have high CO readings and the air/fuel mixture is probably too rich.

Is it as simple as adjusting the CO screw on top of the motor? I have a dwell meter can anyone direct me to some simple instructions for testing with the dwell. Also would i turn it to the left or right to fix my high CO readings? Car is stock with original cat and seems to be running pretty well. Starts right up etc.

Thanks for any help,
Alex

Oh, to give you an idea of how far I am off. The limit of CO% is 1.2 and mine is 5.4. The HC PPM limit is 220, mine was 493.2.

I just read that the "full throttle enrichment switch" needs to be disconnected on cars at high altitude. Guess that will help? Where is this switch located exactly, no pics in book.

[Exolis]

I would start with the Cata Converter. That's the main attribute to High CO.

[DMCMW Dave]

I moved from Hawaii to Colorado and I have to get an emissions test pass to register the car. Took it in today for the test and failed. Says i have high CO readings and the air/fuel mixture is probably too rich.

Is it as simple as adjusting the CO screw on top of the motor? I have a dwell meter can anyone direct me to some simple instructions for testing with the dwell. Also would i turn it to the left or right to fix my high CO readings? Car is stock with original cat and seems to be running pretty well. Starts right up etc.

Thanks for any help,
Alex

Oh, to give you an idea of how far I am off. The limit of CO% is 1.2 and mine is 5.4. The HC PPM limit is 220, mine was 493.2.

I just read that the "full throttle enrichment switch" needs to be disconnected on cars at high altitude. Guess that will help? Where is this switch located exactly, no pics in book.

Assuming your lambda system is working, you probably need to lean it out a bit. Yes, the CO adjustment. It's been written up on here a few dozen times I believe. Read the orange wire on the diagnostic plug, you want it centered around 45 degrees (if it is constant 45 degrees or does not respond to the adjustment, the O2 sensor is not working or not warmed up yet). Too lean and your NOx will go high.

If the lambda system is not working you will need to fix that first.

I've never heard of disconnecting the full throttle switch. This makes no sense as I've never heard of anyone doing an emission test at full throttle. If you have the usual wiring harness, it is one of the two black/white connectors on top of the W-pipe at the front of the engine. If you have an automatic the second connector is the trans kickdown, you'll have to experiment to tell which is which. If you have a manual it's the only one that is connected.

[Totally 80s]

Assuming your lambda system is working, you probably need to lean it out a bit. Yes, the CO adjustment. It's been written up on here a few dozen times I believe. Read the orange wire on the diagnostic plug, you want it centered around 45 degrees (if it is constant 45 degrees or does not respond to the adjustment, the O2 sensor is not working or not warmed up yet). Too lean and your NOx will go high.

If the lambda system is not working you will need to fix that first.

I've never heard of disconnecting the full throttle switch. This makes no sense as I've never heard of anyone doing an emission test at full throttle. If you have the usual wiring harness, it is one of the two black/white connectors on top of the W-pipe at the front of the engine. If you have an automatic the second connector is the trans kickdown, you'll have to experiment to tell which is which. If you have a manual it's the only one that is connected.

Thanks Dave, I will work on that. Pretty sure Lambda is ok, Frequency valve is buzzing, idleing well etc.

Yeah, in the main Delorean repair guide it talks about disconnecting that for high-altitude. I thought it was strange as well. Page D:04:03

[DMCMW Dave]

Thanks Dave, I will work on that. Pretty sure Lambda is ok, Frequency valve is buzzing, idleing well etc.

Yeah, in the main Delorean repair guide it talks about disconnecting that for high-altitude. I thought it was strange as well. Page D:04:03

Might make sense for operation but it won't have any impact on an emission test. Easy to play with it.

[Flicky]

Not that this will make your car run better, but most non-Denver area counties in CO do not have emissions. I like to use Summit County (Silverthorn) because they don't have home mailboxes. You can get your mail at the UPS store's PO Box type thing.

On getting it running right, you went from 0 to 5280+ elevation. It is fat (rich)...but you know that by now from what you and the others said.

If the mixture adjustment's don't get you all the way, try new spark plugs. I caution this a bit because you don't want to put new plugs in just to have them fowl. Once adjusted pull 1 and see if the base ring is black.

[Totally 80s]

One more question. Should the O2 sensor be disconnected to do the dwell adjust?

[Bitsyncmaster]

One more question. Should the O2 sensor be disconnected to do the dwell adjust?

No. With that altitude change you probably need to reset the mixture so you get back into closed loop range. Use your dwell and report back what you see.

[Totally 80s]

No. With that altitude change you probably need to reset the mixture so you get back into closed loop range. Use your dwell and report back what you see.

I plugged the dwell meter in and let the car get sorta warmed up. Held constant at about 29. Didn't pulse or anything (it's analog). Will I be turning it clock wise or counter clockwise to lean it out?

[Totally 80s]

I moved the CO screw clockwise and car started hunting pretty bad. Backed it off another 1/8 turn and dwell meter dropped to 20 and car not running strong. Frequency valve going non stop.

Ok, got car warmed all the way up. Dwell is curently bouncing between 30 and 50. Should be at a steady45? Frequency valve doesnt ever turn off but does change tone from swing to swing.

Was 30 constant at cold.

[hmcelraft]

It looks like the exhaust (oxygen) sensor may be dead. If the engine is warmed up at all the needle should be modulating 10 degrees or so. The goal is between 35-45 or close thereto. A functioning oxygen sensor will cause the fluxing of the dwell meter reading.

See page D:04:05 of the Workshop Manual for the specs to check the oxygen sensor.

[Totally 80s]

It looks like the exhaust (oxygen) sensor may be dead. If the engine is warmed up at all the needle should be modulating 10 degrees or so. The goal is between 35-45 or close thereto. A functioning oxygen sensor will cause the fluxing of the dwell meter reading.

See page D:04:05 of the Workshop Manual for the specs to check the oxygen sensor.

It is modulating between 30 and 50 when warmed up. Stays at 30 when cold.

[hmcelraft]

The movement seems to be with in the correct range - sort of. Is this after some adjustment? The modulation indicates that the oxygen sensor is working. The high movement or range in the dwell may mean that the Control Pressure Regulator (CPR) isn't hot enough yet or --- possibily faulty. You may want to check the CPR electrical connection. It has a heater in it to warm it up initially when the engine is cold or cool. Have you checked for vacuum leaks?

[Totally 80s]

The movement seems to be with in the correct range - sort of. Is this after some adjustment? The modulation indicates that the oxygen sensor is working. The high movement or range in the dwell may mean that the Control Pressure Regulator (CPR) isn't hot enough yet or --- possibily faulty. You may want to check the CPR electrical connection. It has a heater in it to warm it up initially when the engine is cold or cool. Have you checked for vacuum leaks?

I adjusted it clockwise a bit and now its bouncing from 10-30 with the frequency valve turning off around 10. What is going on?

It idles almost perfectly at 775. odd to have vac leaks.

[Totally 80s]

I adjusted it clockwise a bit and now its bouncing from 10-30 with the frequency valve turning off around 10. What is going on?

It idles almost perfectly at 775. odd to have vac leaks.

UPDATE now I can only get the 30-50 adjustment swing once when i unplug the CO adjust hole and plug it back in. What is going on?

[hmcelraft]

The dwell is suppose to modulate - ideally between 35-45. The oxygen sensor senses oxygen - vacuum leaks let in more oxygen and more fuel is supplied until less fuel is called for - thus vacuum leaks can cause large swings and incomplete fuel burning. The other issue I was thinking about was that the CPR could be too cool and giving low pressure and in turn allowing the fuel plate to move too much causing the large swings in dwell.

High hydrocarbons indicates too rich - incomplete fuel burn. If it has been like this very long (running too rich - incomplete fuel burn) the cat could be ineffective now. Have you inspected it? How many miles or years on the engine tune? More than 5 years on the spark plugs can be an issue - plugs do degrade.

The dwell really needs to get stabilized before you can expect decent emission readings and zero in on the cat effectiveness. Emission readings really do require some special tools to do efficiently. Otherwise you are going to be throwing some parts at the problem and doing a lot of trial and error. A fuel pressure testing tool and a smoke machine to test for vacuum leaks would be a big help. Or, of course, find a shop that knows what they are doing.

[Totally 80s]

I can't really get it to swing anymore. It stays at about 25 now and only swings once every time I adjust the CO plug. It will go up to 50 than drop down to 25. Did I break something? Or is the o2 sensor dieing? or dead?

When I unplug the CPR electrical switch nothing happens. Car doesn't die or do anything weird. I can start it with it unplugged as well. Not sure if this is a problem.

Cat doesn't glow, spark plugs are over 5 years old. Car seems to run and idle fine.

Should I unplug the O2 sensor and adjust dwell?

-alex

[Bitsyncmaster]

You should not get a constant 30 when cold. Try pressing the WOT switch and get a reading. Sounds like your meter reads backwards.

[Totally 80s]

You should not get a constant 30 when cold. Try pressing the WOT switch and get a reading. Sounds like your meter reads backwards.

It may be backwards. I adjusted the CO plug again and it is now going between 10 and 20 which would be between 40 and 50 if backwards and when it dips into 10 area the Frequency valve turns off for a second. Before it was running non stop. I wonder also if the check station didn't have the car hot enough for the emissions stuff to kick on.

When I hit the WOT it goes up to 50 then drops down to 10-20 range. I assume WOT switch is supposed to make it drop if the dwell meter is reading correctly? (mine goes up to 50)

I'd still like to know which direction leans it and which direction rich's it. I would guess clockwise leans it but I don't know.

[David T]

It may be backwards. I adjusted the CO plug again and it is now going between 10 and 20 which would be between 40 and 50 if backwards and when it dips into 10 area the Frequency valve turns off for a second. Before it was running non stop. I wonder also if the check station didn't have the car hot enough for the emissions stuff to kick on.

When I hit the WOT it goes up to 50 then drops down to 10-20 range. I assume WOT switch is supposed to make it drop if the dwell meter is reading correctly? (mine goes up to 50)

I'd still like to know which direction leans it and which direction rich's it. I would guess clockwise leans it but I don't know.

Before you try adjusting your way out of this you have to make sure everything else is in good condition. This includes:
Air filter
Spark plugs
Ignition wires
O2 sensor
All of the injectors have a good pattern and are squirting equally.
No vacuum leaks.
All of the intake and exhaust valves are adjusted.
Just one cylinder misfiring can mess up your emissions. The mixture screw is a "global" adjustment affecting ALL of the cylinders. When was the last tune-up done on the car? If it has been a while you should start there.

[DMCMW Dave]

Normal behavior:
Dwell meter set to 4 cylinder/4 cycle. Connect across frequency valve or to the orange wire on the diagnostic connector and ground. Some meters work better with one connection than the other.

When first started or with the O2 sensor disconnected = 45 degrees.
VERY cold (coolant below 40F) or full throttle microswitch depressed = 55 degrees

If you get the opposite your meter is hooked up backwards.

Once the O2 sensor wakes up:
Too rich - 30-20 degrees or so. Turn counterclockwise to bring the reading up.
Too lean - 70-80 degrees or so. Turn clockwise to bring the reading down.
Just right - bouncing 35-50 or so.

NOTE there is some delay when you make the adjustment, and for final settings the hole must be plugged (it is an unmetered air leak and will make it leaner than it will be with the hole plugged).

There is a very basic writeup in the service manual that explains how to test the whole system without running the engine, using only a jumper wire and a 1.5 volt battery. Nobody ever seems to read it.

[Totally 80s]

Before you try adjusting your way out of this you have to make sure everything else is in good condition. This includes:
Air filter
Spark plugs
Ignition wires
O2 sensor
All of the injectors have a good pattern and are squirting equally.
No vacuum leaks.
All of the intake and exhaust valves are adjusted.
Just one cylinder misfiring can mess up your emissions. The mixture screw is a "global" adjustment affecting ALL of the cylinders. When was the last tune-up done on the car? If it has been a while you should start there.

I absolutely think you are right, however I am just doing this because of the state emissions thing. I don't wanna drop $500+ on parts when the car is running, idling and starting great. Plus I have another business I am getting ready to start and don't have the time or the extra money right now. Any Colorado guys wanna help me out with emissions advice, I'm all ears.

-alex

[Totally 80s]

Normal behavior:
Dwell meter set to 4 cylinder/4 cycle. Connect across frequency valve or to the orange wire on the diagnostic connector and ground. Some meters work better with one connection than the other.

When first started or with the O2 sensor disconnected = 45 degrees.
VERY cold (coolant below 40F) or full throttle microswitch depressed = 55 degrees

If you get the opposite your meter is hooked up backwards.

Once the O2 sensor wakes up:
Too rich - 30-20 degrees or so. Turn counterclockwise to bring the reading up.
Too lean - 70-80 degrees or so. Turn clockwise to bring the reading down.
Just right - bouncing 35-50 or so.

NOTE there is some delay when you make the adjustment, and for final settings the hole must be plugged (it is an unmetered air leak and will make it leaner than it will be with the hole plugged).

There is a very basic writeup in the service manual that explains how to test the whole system without running the engine, using only a jumper wire and a 1.5 volt battery. Nobody ever seems to read it.

If the service center tested my car BEFORE the o2 sensor woke up do you think that would cause me to fail? Cause I definitely don't think the O2sensor was awake when they did the test.

[DMCMW Dave]

If the service center tested my car BEFORE the o2 sensor woke up do you think that would cause me to fail? Cause I definitely don't think the O2sensor was awake when they did the test.

If you drove the car to the test place, it should have come up within 30 seconds. If the car was dead cold it might take a minute, and if you let the car idle long sometimes it will go back open (especially if its old). New cars use heated O2 sensors, but this one is heated by the exhaust and can take a short while to wake up.

If they didn't let it get warm it won't pass. The ideal is that they run the engine at a fast idle (2000 rpm) until the cooling fans come on, then do the test.

[hmcelraft]

10-20 is too lean but, you don't know if an adjustment will get you past the test or if you are just masking over problems with the adjustment that will cause more problems or poor performance. You might adjust it enough to pass the test but I'm guessing you can't. There are most likely some other issues and, like most emission problems, they have all developed silently over time to give you poor emissions even though is seems to run fine.

Possibilities/fixes that might help:
It needs a tune up - wires and plugs, dist cap and rotor. check timing and vacuum advance functions
Valve adjustment
new exhaust sensor
new injector seals
Check for vacuum leaks - especially at the idle motor and all vacuum hoses
Inspect cat - if it is not coming apart and/or melted inside it might be ok
check all fuel system components for proper function
Do a fuel system pressure check
use a quality fuel system cleaner or run some Marvel Mystery oil in fuel for a while
Check CO adjustment.

Other D owners will tell you, when the engine is tuned and running properly the emissions are nil - The B28F can be a very clean burning engine.

[Flicky]

I do believe you have another option...at least to get plates. You have an 81 right? ( Vin 2848 ) . In Colorado you can license this with a 5 year collector plate, car is 32 years or more old, and then sign the affidavit DR2839 to say you will not drive more than 4,500 miles a year, and the test is waived.

[Totally 80s]

10-20 is too lean but, you don't know if an adjustment will get you past the test or if you are just masking over problems with the adjustment that will cause more problems or poor performance. You might adjust it enough to pass the test but I'm guessing you can't. There are most likely some other issues and, like most emission problems, they have all developed silently over time to give you poor emissions even though is seems to run fine.

Possibilities/fixes that might help:
It needs a tune up - wires and plugs, dist cap and rotor. check timing and vacuum advance functions
Valve adjustment
new exhaust sensor
new injector seals
Check for vacuum leaks - especially at the idle motor and all vacuum hoses
Inspect cat - if it is not coming apart and/or melted inside it might be ok
check all fuel system components for proper function
Do a fuel system pressure check
use a quality fuel system cleaner or run some Marvel Mystery oil in fuel for a while
Check CO adjustment.



Other D owners will tell you, when the engine is tuned and running properly the emissions are nil - The B28F can be a very clean burning engine.

I think my dwell was running backwards. So 10-20 would be 40-50 normally. It is running like it was in Hawaii now. Where the Frequency valve will shut up momentarily than come back on as it goes back and forth on the dwell. If it was lean I don't think it would do that. I appreciate your list of things to look at. I think sometime later this year or next I will tear it down to the valley and replace most those things you listed. Salt air is a bitch on injector wires. Bought my car in Huntington Beach than it was in Maui for 7 years so replacement is needed. I'm gonna try to get it tested again next week.

But on a side rant the whole emissions test thing is ridiculous. The car gets driven maybe once a week. Meanwhile these huge diesel trucks spew so much smoke you can see it 1/4 mile away. And they are worried about my little Delorean driving 25 miles a week.

[Totally 80s]

Just an update. Gave the car a complete tune up (rotor, cap, wires, oil change) with new vac hoses and it passed emissions today. I also adjusted the dwell as well. I can't believe how much quieter and smoother the car runs.

[Flash66]

Awesome! I just moved to Vegas and I have to have emissions now. I was totally worried about this. Luckily I just tuned it up as well!



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[Chris4099]

People tend to forget that as long as your car is running fine, you should have no problems with emissions testing. It's only when something is actually wrong with your car in the first place will you fail (assuming no illegal modifications have been made). The only time my D failed was when the O2 sensor went bad and was causing the engine to run rich. I'm up for testing again in 3 months and have no worries about getting through it.

[mburshtain]

People tend to forget that as long as your car is running fine, you should have no problems with emissions testing. It's only when something is actually wrong with your car in the first place will you fail (assuming no illegal modifications have been made). The only time my D failed was when the O2 sensor went bad and was causing the engine to run rich. I'm up for testing again in 3 months and have no worries about getting through it.

I had the same exact issue and after replacing the O2 sensor I passed the emission testing without a problem!