Black_Camel
New Member
Hello all,
I could really do with some advice on this problem. My 1997 s280 (w140) has a significant number of missfires in the lower rpms and poor hot start idling. According to a diagnostics check, it is cylinders 3 and 4 that are missfiring.
I have tried the following remedies, but to no avail:
1. The MAF sensor has been replaced - no resolution.
2. The spark plugs have all been changed, even though the originals were all fine - no resolution.
3. The HT leads have been replaced - no resolution.
4. Distributor coil on cyls 3 and 4 has been replaced - some improvement but problems still remain.
Whilst on my way home from Sweden, I stopped off at a merc dealership in North Germany to get them to run some diagnostics on the car.
They could only figure out that cylinders 3 and 4 were missfiring, and recommended the change of HT leads. Which I did, but it didn't solve the problem.
Cylinders 3 and 4 share the same distributor coil (using the 'wasted spark method'), so my guess was the next component to change is the distributor coil on 3 and 4. This seems to have made a slight improvement in the idle speed control, it returns to 600 rpm and remains stable. However, the engine still missfires a little under low speed acceleration, and hot starting has the same issue of missfires and lumpy idle control.
My local specialists guess was that part of wiring loom that connects into the distributor coils from the ECU has been slightly baked, and would need replacing. This slight baking of these wires could have occured several months back when the AC fans were not working due to a leak in the AC system - thus not supplying extra cooling to the radiator and causing the engine to overheat to and indicated 105 deg C. He doesn't recommend ordering a new loom from Merc; and at a cost of $600 - I am in a mind to trust him on this one.
So, my question is this:
Have any of you experienced this problem before on the 97 model year inline 6 cylinder engines - and do you agree with the specialists diagnosis? I am aware that the 'biodegradable' wiring looms were only an issue with pre 96 models.
I am sure it wouldn't hurt to replace the wires, but then it is a huge pain in the rear end to do it. Plus I will need to source some wiring that can withstand the high temperatures in the engine bay.
Any help would be hugely appreciated at this time.
Many thanks in advance.
I could really do with some advice on this problem. My 1997 s280 (w140) has a significant number of missfires in the lower rpms and poor hot start idling. According to a diagnostics check, it is cylinders 3 and 4 that are missfiring.
I have tried the following remedies, but to no avail:
1. The MAF sensor has been replaced - no resolution.
2. The spark plugs have all been changed, even though the originals were all fine - no resolution.
3. The HT leads have been replaced - no resolution.
4. Distributor coil on cyls 3 and 4 has been replaced - some improvement but problems still remain.
Whilst on my way home from Sweden, I stopped off at a merc dealership in North Germany to get them to run some diagnostics on the car.
They could only figure out that cylinders 3 and 4 were missfiring, and recommended the change of HT leads. Which I did, but it didn't solve the problem.
Cylinders 3 and 4 share the same distributor coil (using the 'wasted spark method'), so my guess was the next component to change is the distributor coil on 3 and 4. This seems to have made a slight improvement in the idle speed control, it returns to 600 rpm and remains stable. However, the engine still missfires a little under low speed acceleration, and hot starting has the same issue of missfires and lumpy idle control.
My local specialists guess was that part of wiring loom that connects into the distributor coils from the ECU has been slightly baked, and would need replacing. This slight baking of these wires could have occured several months back when the AC fans were not working due to a leak in the AC system - thus not supplying extra cooling to the radiator and causing the engine to overheat to and indicated 105 deg C. He doesn't recommend ordering a new loom from Merc; and at a cost of $600 - I am in a mind to trust him on this one.
So, my question is this:
Have any of you experienced this problem before on the 97 model year inline 6 cylinder engines - and do you agree with the specialists diagnosis? I am aware that the 'biodegradable' wiring looms were only an issue with pre 96 models.
I am sure it wouldn't hurt to replace the wires, but then it is a huge pain in the rear end to do it. Plus I will need to source some wiring that can withstand the high temperatures in the engine bay.
Any help would be hugely appreciated at this time.
Many thanks in advance.
