03 CLK 200K A209 High CO

GadgetBoy

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I have the above car which very nearly failed its MOT on high CO. There's no CE light and the car runs as you would it expect. The exhaust is sooty which would suggest there's an issue somewhere and the car can smell petrolly when cold. Mileage is 46K.

The car is serviced by a very good Indy here in Belfast (Creevy Autos) but they don't have an emissions testing rig.

Is there anything obvious I can look for?
 

glenavy-drongo

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You could try Terry McEvoy in Carryduff. Very knowledgeable guy, although I'm unsure if he has a resting rig.

D
 

PobodY

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Have you given it an Italian tune? - Good run with some high revs to blast all the soot out and get the catalytic converter properly hot.

It does sound like it's running rich, but that could just be the cold start portion of the map. - If the Italian Tune doesn't fix it, I'd be checking for air leaks between the MAF and the inlet manifold (on the basis that it's fuelling for metered air that isn't reaching the cylinders).
 
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GadgetBoy

GadgetBoy

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Yes it's had an "Italian tune" or a good hoke as we would day here! LOL
 

Joesoap17

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stick a can of BG44K in the tank, get it from Kwik Fit £20, the only thing I would buy from them, and follow the instructions on tin.
Only other things to cause rich problems are blocked air filter, fecked O2 sensor or MAF? BG44K is cheapest and works.
 

DSM10000

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stick a can of BG44K in the tank, get it from Kwik Fit £20, the only thing I would buy from them, and follow the instructions on tin.
Only other things to cause rich problems are blocked air filter, fecked O2 sensor or MAF? BG44K is cheapest and works.

If the lamda (O2) sensor was out of range that should have showed up on the emissions test data, what were the lamda values?.

Have you checked the condition of the spark plugs? Also, try unplugging the MAF, if it runs the same then the MAF is a likely culprit, bear in mind that doing thi may cause a CEL.
 

PobodY

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What type of MAF is it? - Can it be cleaned with some throttle body cleaner, or is it the type that's best left undisturbed?

If all else fails, sometimes disconnecting and reconnecting hoses can work. - You'll never know what you did, but the problem may go away.
 

Joesoap17

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BG44K? it does work.
It passed so shouldn't be spending any money until it needs it?
 
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GadgetBoy

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Yes it's had fuel treatment through it. Yes it passed but it's doing about 3 mpg. If you want to pay my fuel bill I'll be happy to accept. :)
 
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GadgetBoy

GadgetBoy

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In the event anyone else has similar problems here is a more comprehensive description of the symptoms.

The engine runs smoothly but has always smelt rich. The MOT CO figures as above confirm this. If you just pootle around it would go for weeks with no apparent issue, as soon as you accelerated hard on the kick down the car would bounce on the limiter at the red line for a few seconds at the 1st upshift. At the 2nd upshift it would throw a <Check Engine> light and very occasionally enter limp mode. I discovered this with experimentation after the original post. Sometimes the CE code would be P0300 (misfire detected), sometimes it would be P0170 (fuel trim bank 1). Even on STAR the MAF was never mentioned.

Last week I had a long chat with my Indie at Creevy Autos and we decided to fit and new set of plugs and a 2nd hand MAF. The car is transformed. Much more responsive and definitely more power (mind you a 200K is never gonna win any races!). It doesn't smell rich anymore and (fanfare) no CE lights even under very hard acceleration. The other thing which threw me all along is the upshift is now normal, it's accelerates to just around the red line and upshifts quickly and smoothly - no bouncing off the limiter. How the MAF affected that I have no idea. Where the reported MPG was mid to high teens for pootling about it's now mid to high twenties. All in all I'm a very happy bunny.
 

markjay

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Good news.

The issue may have been a compound one caused by both the MAF and the plugs.

What was the condition of the plugs removed from the engine, how old were they, and were they the right spec for the engine?

On your engine the plugs should be replaced every 4 years or 40,000 miles.
 
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GadgetBoy

GadgetBoy

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I don't know what the plugs were like but they were about a year old and the correct spec as fitted by Creevy Autos.
 
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GadgetBoy

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Going back to this old thread .....

It turned out things weren't fully sorted. On a long run, upwards of 50 miles or more, the CE light was still coming on. There was no apparent effect on performance so I have to admit to just resetting it and forgetting about it. I eventually did get it checked and it was the downstream O2 sensor. While the car had been running like crap this had got very sooty and when the soot burned off it left the sensor covered in a hard ash. Changed and the car is now 100%. It's better than it's ever been in the 3 years I've owned it. The fuel consumption is superb as well. Low 30s easily attainable which for a 200K is very pleasing.
 
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GadgetBoy

GadgetBoy

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Emissions before repairs ..

CO 3.480%
HC 359ppm

Emissions after repairs ..

CO 0.010%
HC 19ppm

Just a slight difference! ;-)
 

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