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Old 08-28-2004, 01:35 PM
Duke2.6 Duke2.6 is offline
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Join Date: Mar 2003
Location: Southern California
Posts: 2,270
This sounds like a typical case of the converter being too cold.

I assume you live in California?

Go to a drivethrough place with a short line after driving the car at least 15-20 minutes including a freeway hop, and drive it aggressively.

Keep the engine at 2000 revs in neutral with the AC on and the window/sunroof open to keep a load on the engine until the tech is ready to drive it onto the rollers.

Note that your 15 MPH O2 is 0.4% percent and only 0.1% at 25 MPH. This is the tipoff that the converter was too cold, and it could not use all the available oxygen to oxidize HC and CO. Likewise, a cold converter will not reduce NOx efficiently.

What were the conditions of your test? Did you just drop off the car and come back later? Did you wait, but shut off the engine?

I don't think there's anything wrong with your car. Mercs need proper "pre-conditioning" or a cold converter will bust the first test with the second test being okay because the converter heated up to proper temperature during the first loaded test. Owners need to be aware of this and properly "manage" their emissions test.

I've measured the converter inlet nipple temp on my car with an IR gun after a normal drive, and then after five minutes of idling. The measured surface temp dropped from about 600 to 300 F.

BTW is your engine a M104 twin-cam or the M103 single cam, and is it a KE fuel system or the later all electronic system with solenoid injectors. Sorry, but I can't keep all the various model/engine configurations straight.


Last edited by Duke2.6; 08-28-2004 at 01:54 PM.
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