Date registered: Aug 2005
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this seems to be a common issue with M112(V6)and M113(V8) engines. I have a similar issue with my S500, as well as my family's S430 and ML 350. I have also had a few customer's come in with similar complaints. So far, I havent fully tackled my own vehicles, but the customer's ones were usually plugs, wires, fuel filter(fpr part) bad coil(s), MAF, throttle actuator, shrunk fuel injector o-rings, and most commonly, evap and other vaccum leaks. there are a few vacuum connections on the intake manifold that will develop a leak, even on lower mileage vehicles, like mine. the vacuum leaks I encountered most frequently were the breather hoses coming off of the valve covers and goint into a union at the back of the manifold. another common leak is at the MAF boot seals, and also the brake booster quick connect line at the back of the manifold. another culprit I encountered was a leaking upper manifold seal, the factory applied silicone.
so far, the items I listed are fairly easy to diagnose and replace. but there is one more possible cause. there is a sinlge, tiny vacuum line on the bottom front of the intake manifold, buried behind and under the AIR pump, this vacuum line is impossible to remove without taking off the entire manifold, and is replaced from the inside of the manifold. whats funny, is that the EPC does not even list this part/location properly.
for those of you who did or think of getting fuel injector cleaning service done, I would advise against it. the solvents used in injector cleaning machines are usually cheap and highly corrosive, and will eat away the injector coil coating, resulting in possible injector damage/failure. if you do opt-in for this service, make sure the shop uses quality brand solvents.
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Last edited by nenad16; 11-17-2010 at 10:43 PM.
Reason: extra info