Backfire (POW) in intake
The car: 1989 260E (103 engine) with over 300K on the clock
The problem: Backfire at start up (50% of the time) when it has reached normal operating temperature. If the car sits, say for 10 minutes, when I start it a loud (POW) backfire happens in the intake maniforld.
The cars has new plugs, wires, cap, rotor, ignition module, valve guides/seals, new gas filter, fuel pressure regulator, All parts replaced are OEM. Compression at 165 on all 6, burns no oil, excellent gas mileage, runs smooth, no idle problem, good power (for a 260E). Always start on the first try either cold , very cold (minus 35 last winter) or hot, no overheating. No gas smell. No play in the timing chain.
The problem was present before I had the ignition system was renewed.
When the backfire happens, the car will start with no problem afterwards.
Any idea? Thanks