Wrong spark plugs or what ?

[chris59]

Hello,

I've got a misfire problem on my 350I, cold or hot : swapping rotor arm, distributor cap, ignition module (the one screw to the ignition), plug wires, or coil didn't solve the problem.

All injectors work well, disconnecting the cold start injector makes no difference.

The 8 spark plugs are new NGK BPR5 ES : if I unplug one plug wire at a time, creating an electrical arch between the plug and the wire, the engine work correctly for a while.

Could the plugs model be wrong, ie too cold or too hot ?

Best,

Chris

[adam quantrill]

Last ones I used were BPR5 ES too. They seem OK, did you gap them (although usually the gap is set more or less correctly)

Maybe check the timing next?

[chris59]

Hi Adam, how are you ?

Thanks for your reply !

The plugs are correctly gapped, and the timing is good : it was working perfectly before I had some problems who, finally, were caused by the carbon contact in the middle of a (crappy) distributor cap.

[chris59]

But the wizard problem remain, so it's not the plugs neither...

[NMNeil]

Grab a spray bottle and fill it with tap water.
Wait until dark and with the engine running spray a fine of mist of water over the plug wires, distributor cap etc. Don't drown them you just need to give the high voltage a path to ground rather than through the plugs. Any 'leaks' will show up as a nice firework display.
Easy and free to check.

[chris59]

Good idea, but ALL the plug (and coil) wires are brand new, and from the best quality, no cheap repro here.

[colin mee]

The best and expensive still fail

[rev-erend]

I use accuspark spark flash testers.. they look like a red sparkplug cap but have an internal light when the engine is running.

Also another idea is just to run the engine and use a lazer temp gun on each of the exhaust headers.

The one with the misfire should be the coolest.

Edited by rev-erend on Monday 26th April 14:28

[chris59]

Good idea, I'll try this next weekend !