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· Registered
1986 230GE
14 Posts
Discussion Starter · #1 ·

I had my G tested for Canadian Vehicle Emissions (so that I could renew my license sticker), but the G failed in one area.

Under the CO(carbon dioxide)%, the G, while running at ~ 2500 rpm, reported a figure of 3.33%, which was higher than the 2.52% that the government permits.

Meanwhile, at curb idle, the G reported a figure of 1.08%, which was below the limit of 1.50%.

I was told by a local MB service advisor, who was told by the assistant MB shop foreman that a part called the 'lambda'(which is like the throttle body) could be adjusted.. Would this help???

In order for the CO% reading at 2500 rpm to be lowered below the 2.52% level, which parts could be replaced/repaired in order for the results to be brought down to the allowable limit??

Thanks to everyone who trys to help me :)

· Registered
1980 LWB 280GE
3,505 Posts
Wow...there are a lot of things to talk about in there.

I'll tell you the easiest way to "just pass the test" is to make sure your fuel tank is less than 1/4 full when you go, and then dump in 4-5 bottles of dry-gas. This puts a lot of oxygen in the fuel being burned and brings CO emissions WAY down. (dry-gas is mainly alcohol - it's primary function as a drier is to chemically bond with water, but the alcohol's active chemical group is an OH molecule that brings lots of nice oxygen and hydrogen into the combustion chamber with the fuel to help it burn more completely.

If you have a lambda sensor (some 230GEs did, some didn't), it's not like a throttle body, and it's not adjustable. It might be bad and need to be replaced. The Lambda sensor is the one that's screwed into the side of the exhaust pipe just downstream from the manifold and senses levels of free oxygen in the exhaust stream. It provides a voltage input that a little electrical circuit uses to fine tune the amount of fuel being delivered to the cylinders in order to achieve the best burning mixture. A good mechanic familiar with the various types of Bosch K- and L- jetronic fuel injection systems should be able to test and tell you whether the lambda sensor, and it's associated fuel delivery system, is working properly.

If you had a means of checking the exhaust yourself, you could cheat the idle a little toward the lean side and that would also bring the running CO level down a little (unless a bad lambda sensor was incorrectly compensating). The factory spec at warm idle is 0.5 - 1.5. You're at 1.0 now so you could safely lean it out a little. You can do this by just turning the idle mixture screw in the fuel meter body as shown in this article: Article&sid=item&tid=17
But doing it open-loop without a way to know what your CO really is puts you in danger of running too lean which is a bad thing for the engine.

So long story short, there are a couple ways to "cheat" the test, or you could have a full diagnostic work-up done on the fuel system to see exactly what's wrong. The possibilities of which components might be malfunctioning to result in running rich at 2500 is too long to list here, and only a good mechanic with the right diagnostic tools will be able to tell you just what the truck needs. It might very well be as simple as a new lambda (oxygen) sensor, but I'd want to see some test data (output voltage) measurements compared to specs before I'd replace it.

Good luck! And let us know what you find.

-Dave G.
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