635CSi - rough idle and engine stuttering issue.

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RetroNino
Posts: 4
Joined: Fri Oct 28, 2022 2:29 pm
Location: Europe

635CSi - rough idle and engine stuttering issue.

Post by RetroNino »

Hello everyone!

I've just taken my 635CSi (EU model) out of storage for the summer and noticed that the car has engine issues, notably:

- a very rough idle (more so when the engine is warmed up), that happens intermittently,
- a hesitant, stuttering engine, anywhere over 2,5-3,0k RPM (both at a standstill, as well as under load, while driving).

I'm going to try to rule out fueling issues by doing an external bypass line directly to the engine,
even though the system had been refreshed recently, but would still welcome any other suggestions.

What would be the biggest culprits that could cause the engine to act up in such a way?

I'm going to try to post a video of it happening when driving, maybe it proves helpful.

Any advice would be very appreciated.
Best regards, Nino
RetroNino
Posts: 4
Joined: Fri Oct 28, 2022 2:29 pm
Location: Europe

Re: 635CSi - rough idle and engine stuttering issue.

Post by RetroNino »

Video of the engine cutting out:
https://streamable.com/z20gel
TimU
Posts: 280
Joined: Tue Dec 14, 2021 2:16 am
Location: Sydney

Re: 635CSi - rough idle and engine stuttering issue.

Post by TimU »

Possible Causes and Corrective Actions:

1. Low Battery Voltage
a. Check battery voltage.

2. Poor Earth/Grounds
a. Inspect, clean and tighten all (5?) ground points in the engine bay

3. Distributor Cap and Rotor.
a. Inspect, clean or replace.
Damaged/Deteriorated/Wet Distributor Cap or Rotor can prevent spark.

4. Coil and/or Plug Leads
a. Damaged/Deteriorated can cause a weak or orange coloured spark. Check your battery, coil and plug leads for deterioration.

5. O2 Sensor
a. A clogged/damaged O2 (lambda) sensor can cause incorrect fuel mixture ratios, causing rich or lean conditions.
b. Inspect or Replace as needed.

6. Faulty Motronic DME Unit
a. Replace or repair
04/1986 635csi Euro spec
Australian Delivered, RHD
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