1991 300TE-24V Experiencing Intermittent Misfire

[DivineStripe]

I own a 1991 300 TE–24V M104 engine experiencing the following symptoms:

Operate the car till it warms up, it doesn't need to reach 80 degrees Celsius, sometimes only a 15-minute trip.
Allow the vehicle to sit for 30 minutes to 1 hour. Restarting the automobile immediately may cause no problems.
Intermittently, the automobile would misfire after being restarted.
Occasionally, restarting the automobile soon after turning it off might restore it to regular functioning.
At other times, the automobile may have issues such as trouble starting, persistent misfiring, lack of power, low idle rpm, and rough running. Sometimes I have to restart more than 20 times and the misfiring issue persists, requiring me to wait for an extended period before it returns to normal.

Modifications made to the automobile since my ownership:

8 Bosch non-resistance spark plugs
One of the two gasoline pumps is functioning normally, while the other is not.
Fuel accumulator
Bosch idle control valve
Airflow Variable resistor
Bosch distributor cap and rotor
Bosch ignition coil Camshaft position sensor ECU replaced with a different secondhand unit
OVP Relay moved to a different unit that was previously utilised.
MAS Relay was transferred to a different unit that was already in service.
The crankshaft position sensor cable was transferred to a different pre-owned unit.
The HT leads seem to be new, namely Beru brand.

Can someone provide guidance on where else to search? I have visited many mechanics but they struggle to reproduce the misfire problem, since it occasionally resolves itself just by restarting the vehicle.

[MBcarOWNER]

These automobiles are well-known for experiencing condensation in the distributor body, particularly in humid environments. When the engine is cold, moisture within the distributor body evaporates as the engine heats up, producing a short circuit in the cap region. To fix this issue, use a hair dryer to thoroughly dry the inside of the distributor metal body.

[DivineStripe]

I recently replaced the distributor cap and rotor using Bosch parts. Is there any other action I can take to reduce this moisture problem?

[veroguittar]

The ECU was replaced with another secondhand device.

Is ECU the same as EZL?

[DivineStripe]

ECU was swapped, specifically the one located near the battery, not the EZL ignition control module. I have not altered it.

[dontito]

Improbable, in my opinion. My experience indicates that things either function well or do not operate at all. However, it is advisable to get an extra one since they are becoming more scarce.

As mentioned in two previous instances, I had a similar issue where the injectors were leaking gasoline when the engine was warm and idle for thirty minutes. During start-up, it experienced misfiring initially but eventually resolved itself. Completed a morning's work by installing new injectors, guides, and seals, restoring the vehicle to its regular functioning. Expensive but fulfilling.

Regarding HT, these engines need top performance. In 2020, I upgraded the complete high-tension system with Mercedes-Benz genuine components, including the leads. I am now experiencing a higher level of confidence than I have in years.

Prior to the retrofit, I had a 9-month-old Bosch distributor cap (installed by inexperienced individuals in Toulouse) that was developing cracks around the central electrode, however it was still functioning. The outcome favoured the new Bosch MB model, which still seems fresh after 2 years.

Is there a significant difference between Bosch MB and Bosch aftermarket? They seem similar when fresh.

Ensure the shield located below the rotor arm is in excellent condition. If it is old or damaged, replace it with a new one.

Happy hunting.

[dontito]

This is often said, and I do not disagree. Despite the vehicle being exposed to outside conditions 24/7, including temperatures ranging from -5 to 40+ degrees Celsius, as well as heavy downpour and fog, I have never had that issue.

Consistently immediate cold starts unless the EZL was damaged.

[dontito]

I presume not. I believe he is referring to the KE controller.

[sherlockHOME]

I would look at the aforementioned. Fuel vaporisation due to leaky injectors may reduce pressure and affect hot starts. Particularly true in regions with higher temperatures.

[allcarsnew007]

Extended periods of daylight in your location......!;)