QuestionI just acquired a Mercedes Benz Petrol 1983 Model 126 (280SE) Automatic. After using it for a few months, I sent it for servicing and engine tuning including a CO check.
Ever since the day I got it back, I experienced a small problem. It starts easily enough in the morning but the idling speed is too low (around 6000 - 7000 rpm)when the engine is still cold, and even dies off when reversing. It becomes OK (around 7500 - 8000 rpm) when the engine gets warm.
The mechanic has renewed the cold start solenoid but the problem persisted.
Could it be that a vacuum hose has got disconnected accidentally during the servicing, and not detected.
Can you suggest a solution please.
AnswerThe symptoms suggest a vacuum leak.
A bit of judicious investigation under the bonnet with a bright torch may locate the issue.
Tubes, hoses, injector seals may have hardened and/or fractured from age.
This test takes a bit of time.
* I carefully use a hand pump water spray bottle
#1. Set to light mist.
#2. With engine running.
#3. Begin at the front of your engine.
#4. Mist an area Not larger than two hands beside each other.
#5. Listen for any engine sound/RPM change.
#6. Listen for sucking sounds.
#7. At ninety seconds move to the next section and repeat step 4 - 5 and 6.
If you have found the vacuum leak that is good, however if it is still not found, change step #1 to a heavy mist, and repeat the entire test.
If the second test with heavy mist fails to locate the vacuum leak, I suggest you take it to your local Mercedes Benz dealer.
Have a great day.
