Secondary air pump on w202 c280

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21vn111

New Member
Joined
Dec 18, 2018
Messages
6
Location
Armenia
Car
w202 C280 '95
Hi friends,
The secondary air pump turns on when cold starting the car, but in 1-2 seconds it turns off. Besides, the car loses rpm at ~13 sec. every time after start, sometimes the car even turns off. In a moment after rpm loss (if the car doesn't turn off) everything goes right again. Please throw me some ideas where to dig.
PS: MAF changed recently, no any changes in performance.
 
Could be lots of things on that age of car. I assume you have a version of the M104 inline 6 petrol engine. Age [ 1995] would also dictate your is in the high risk zone for engine wiring loom insulation cracking and causing electrical faults.
This refers to the W124 engine but some sections may be of assistance as they share the same engine
14 Intake Manifold, Exhaust Manifold, Emissions Control System - M104
Much of the operation of the air admittance valves in the system are vacuum operated so many faults arise from leaks in the control vacuum system [ especially the short rubber connectors for the narrow plastic vacuum pipes] that's what I would check first as your symptoms sound like an air leak.
The airpump on the W124 is solenoid operated so it might be worth checking that also?
 
Thanks for your answer. Engine wiring changed recently, engine works better now, but no any changes in the problems above. I think there are problems with EGR, but nobody knows the way of cleaning EGR system on M104 in my city. Gonna check the vacuum system at first. The air pump turns on and goes off right after a moment. How can I check the solenoid ? Thanks once again!
 
The exact position of the EGR varies from model to model and I'm not sure where it is on your model. In terms of testing- all you can do is test the vacuum function [open and close] and give it a flush out with a suitable hydrocarbon solvent- the vacuum diaphragm is not replaceable if leaking so replacement is your best option. A common source of blockage is the pipe from the EGR to th einlet manifold. Some background here. and some parts listing which might help?
INTAKE AND EXHAUST MANIFOLDS MERCEDES C-KLASSE [Car] [CHASSIS] (EUROPA)
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Solved. Secondary air pump issue + rpm loss on 13th second were caused by the OVP relay. Hope it'll help anybody else. Thanks, grober
 

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