88 560SEL - Emissions Fail

[Jigglybus]

Hi,

I live in Ontario and emissions are required up to 25 years.... just my luck my MB is 24.5 years old.

It's been sitting a while and recently brought out of the garage. I changed all fluids, spark plugs, wires, cap and rotor, and air filter.

It passed everything at idle (although it has a strong stumble... see other post) but failed HC's at cruise. The belt for the air pump is not there, but I thought as long as the CAT was warme up, it should be ok?

Am I wrong? Should I replace the belt? I'm not sure if the pump even works.... it was disconnected when I bought it.

(ps.... you might notice I have a few new posts on here, sorry for the flood, I have quite a few gremlins... thanks for your help!)

[JamesDean]

Typically those smog pumps seize up and people remove them or the belts. Or they just remove them because they are a drag on the system and not needed in certain areas.

My 420SEL is like this, I removed the belt as Ohio doesnt test emissions and it doesn't really do anything other than introduce air into the exhaust.

As to your stumble, look around for vacuum leaks. Some of those plastic hoses tend to get brittle and develop cracks. Check at the EZL ignition module on the driver side fender, that will cause some good stumbles.

[pmckechnie]

The pump is only turned on for a few seconds during cold engine start up and then turned off. It won't come on again until the next cold engine start up. I am assuming Canadian cars are the same as US cars.
Paul

[mbdoc]

High HC readings are usually caused by incomplete combustion. (misfire)

Make sure that the O2 sensor is functioning & has control of the fuel mixture (duty cycle).

BTW, the smog pump is just a warm-up smog part and has NOTHING to do with fuel mixture once the car is warmed up.

[Jigglybus]

I'm somewhat of a rookie... how can I check if the O2 sensor is functioning correctly..... if it wasn't, wouldn't the check engine light come on at least periodically?... it doesn't.

I've given up on the air pump... the lines running from it are corroded and the adjustment/mounting bolts are seized. I probably could fight for another 2 hours to get them off, but I don't really see the point, given it's limited value.

I replaced a few vacuum lines today which were brittle.... almost like macaroni. Didn't notice any audible or visual difference afterwards but who knows....

[Hit Man X]

Under the hood is a mess of vac lines. The only one you need is the one to the EZL ign box... yes, the rest are just emissions crap. Pretty shocking how clean it is under there once you delete all of that garbage.

There are three or four connections to the throttle body, I forget. Two run to those thermal activated switch valves on the intake plenum... from there they run to EGR and the charcoal canister stuff. I removed ALL of that crap, cut off the pipe tits, and filled with epoxy. One ran back from the charcoal stuff and I think one had just a cap.

The AIR pump stuff runs down the pass side of the intake plenum, just remove it all and put in trash. The tit on the intake plenum I TIG welded shut, I suppose a vacuum plug would suffice too. I cut apart the check valve down to a threaded bolt... yup filled with epoxy and reinstalled. There is no trace of the AIR crap on my car now.

EGR... well, chances are your tube if plugged shut from 25 years of carbon build up and it has not been functioning for years. It was on my ride. Just remove it all and cap the exhaust manifold. I also TIG welded the lower intake plenum hole where the EGR tube bolted down.



What plugs did you install... those +4 crap Bosch ones?

As MBdoc stated, HC is unburned fuel...someone may have adjusted the CO screw in order to compensate for vacuum leaks. These V8s really need a complete intake manifold reseal every 8-12 years. It is not too hard, just time consuming and typically very messy. You can do this over a weekend easy.



https://www.startekinfo.com/StarTek/outside/12253/disc%202/program/Engine/107/M117_56/073-013.pdf

[Hit Man X]

Here is my modified intake: