Air/Fuel Mixture - Checking Lambda System

91mercedes03

REF. NO.: MBNA 07.3/17


TO: OUR MERCEDES-BENZ PASSENGER CAR DEALERS

DATE: October 1991 (supersedes MBNA 07.3/7, October 1987)


SUBJECT: ALL MODELS WITH CIS-E IDLE MIXTURE ADJUSTMENT TOWER


In case of customer complaints regarding engine performance, the Lambda adjustment "On - Off" ratio may be checked and adjusted if necessary in cases where the readings are not within the specified value as outlined in our service literature. Caution:
According to federal regulations, it is unlawful to make adjustments when the test values are within specifications, i.e., if the "On - Off" ratio meter needle oscillates anywhere within the upper and lower tolerance range an adjustment is not permitted.

Lambda "On - Off" ratio readings before and after adjustment must be listed on the repair order. Additionally, if the "On - Off" ratio adjustment is claimed under warranty, the before and after adjustment values must be listed in the text field of the warranty claim.

Whenever a fuel injection/emission control system part is replaced and/or an engine repair is performed that includes the removal and installation of such part, the "On - Off" ratio should be checked and adjusted as necessary after the work is performed.

If a steel plug or ball is found to be missing or the tower is found to be damaged, the "On - Off" ratio must be checked. A tower should be replaced if damaged; a steel plug or ball must always be replaced.

The steel plug or ball is essential to prevent any unauthorized or unintended tampering which could lead to emission standards noncompliance, and also to keep the Emission Control System Warranty in effect.

As a reminder, please make sure that the "On - Off" ratio is checked at idle and then checked again at 2500 rpm with the purge line disconnected and plugged. The values of these two readings must be within specifications in our service literature. Refer to the following literature sources for adjustment specifications:

Engines 102, 103 (up to MY '90), Engine 103 as of MY '90 Engines 104, 119
116/117

Diagnostic Manual Volume 2. Model Year 1990 Intro. Manual Diagnostic Manual Model 129/140
Gasoline Engines Models 124.0, 126,0. 201 Engines, Volume 1
Lambda Control Test Group 07.3 Section: A CIS-E
Test & Adjustment Specifications Test & Adjustment Data