1987 Suburban R10 emissions problem due to modified intake

[thatgermanguy]

I got this sweet Suburban last year and needed to register it in Colorado. It failed emissions on HC and CO. When I bought it I noticed some tubes that seemed like something had been removed and the owner in Idaho (where they don't have the same emissions test requirements) said it was an air filter "some crap for California emissions you don't need" that he had removed. So... what did he remove? Could it be a reason for the poor emissions test results? Are there any tips people can give me on how to get the car to burn more cleanly? Plugs? Filters? Tune up? Additives? She starts and runs well but it smells like she doesn't burn all the petrol... Love this car and really want it to pass. Thanks! Here are some pictures that might help...

I saw this schematic that seems relevant but little explanation. It seems that the removed parts were the Air Cleaner unit... here is a link. Does that seem right in explaining the poor emissions performance?
https://www.gmpartsnow.com/oem-parts/gm-air-cleaner-25042891?c=Zz1lbmdpbmUmcz1haXItaW50YWtlJmw9MSZuPUFzc2VtYmxpZXMgUGFnZSZhPWNoZXZyb2xldCZvPXN1YnVyYmFuLXIxMCZ5PTE5ODcmdD1zaWx2ZXJhZG8mZT01LTBsLXY4LWdhcw==

 

[dd1990]

Sounds like your missing the stock air filter housing and preheat tube. This would not affect emissions out the pipe but it would not pass the visual in California, don't know about CO. In terms of emissions, a tune up will help, BUT do you still have stock intake manifold, tbi, with egr and all vacuum hoses attached? Do you still have a catalytic converter that would be the biggest problem if missing.

 

[Ricko1966]

Without pics we are guessing about a lot here. Please post pics of the engine so we can see the mods and try to help you.

 

[fast 99]

Is an under hood visual part of the emissions inspection? If all the vehicle needs is being lower than the limits an air pump and cat do wonders on emissions. Here they only did under hood if the vehicle needed a waiver. If everything installed by OEM is required some of it may be difficult to locate.

 

[thatgermanguy]

Is an under hood visual part of the emissions inspection? If all the vehicle needs is being lower than the limits an air pump and cat do wonders on emissions. Here they only did under hood if the vehicle needed a waiver. If everything installed by OEM is required some of it may be difficult to locate.

Visual is not a part of it here. My HC and CO values are too high. I've attached a pic above!

 

[thatgermanguy]

Without pics we are guessing about a lot here. Please post pics of the engine so we can see the mods and try to help you.

Sorry I thought it had loaded. Here you go. You can see the cut hoses.

 

[fast 99]

Will help to know how clean the exhaust needs to be. What is the emissions limit and vehicles reading.

 

[Turbo4whl]

So... what did he remove? Could it be a reason for the poor emissions test results?

Yes, the A.I.R. pump plumbing is missing. HC would would be higher. With higher HC, the CO would also go up. This may not be all that is wrong.

 

[Ditch Wicked]

Is it a CA emission vehicle? It looks like your missing the diverter valve, and maybe the AIR check valve on the PS. Cant see the DS, but there should be an AIR check valve there too. The air filter cover looks fine, just missing the clean air intake tube and the heat riser tube. I highly recommend getting a Haynes manual 24064. There is an entire section on the emission systems. Also if the ECM has not been changed the missing smog parts will cause it to dump more fuel into the system causing higher HC and CO readings.

 

[Turbo4whl]

Will help to know how clean the exhaust needs to be. What is the emissions limit and vehicles reading.

If memory serves, the hydrocarbon limit for tailpipe analyzer was 200 PPM. Hard to find this info online now, as there has been so many changes.

Pumped air injection​

[edit]
Pumped air injection systems use a vane pump called the air pump, AIR pump, or colloquially "smog pump" turned by the engine via a belt or electric motor. The pump's air intake is filtered by a rotating screen or the vehicle air filter to exclude dirt particles large enough to damage the system. Air is delivered under light pressure to the injection point(s). A check valve prevents exhaust forcing its way back through the air injection system, which would damage the pump and other components.

Carbureted engines' exhaust raw fuel content tends to spike when the driver suddenly releases the throttle. To prevent the startling and potentially damaging effects of the explosive combustion of this raw fuel, a diverter valve is used. This valve senses the sharp increase in the intake manifold vacuum resulting from the sudden closure of the throttle, and diverts the air pump's outlet to atmosphere. Usually this diverted air is routed to the engine air cleaner or to a separate silencer to muffle objectionable pump noise.

 

[fast 99]

Hard to tell from the pictures but if TBI, with O2 sensor [not carbed], AIR system only pumps during warm up unless it has a dual bed cat. After system goes into closed loop, additional air injected into exhaust would bias the O2 causing incorrect fuel mix.

What I am saying is it might be possible to pass the emissions with a good functioning cat without air pump. All depends on what the state standards are and how this vehicle was equipped. As I stated earlier if they do an under hood inspection or state standards are strict you need a bunch of parts.

 

[Ditch Wicked]

Here in So Cal the max HC is 134(ppm).

 

[Ricko1966]

I believe O.P. has left the building.