Pinking....AGAIN.

[gaz666]

Timing is good, plugs and gaps ok, good fuel pressure, clean air filter, new fuel filter, vac advance working etc. My 350i idles and runs good,pulls well, but when engine gets around 90 degrees it starts to pink around 250-300 rpm when i burry my foot in the axminster! To me this seems like i need to duct some cold air into the air filter. Any ideas, or am i barking up the wrong tree?

[gwilson]

Gaz,
Could be a multitude of things. This time of year with the cooler damper air it should be better than the summer if the problem is intake air temperature dependant. If the probelm occurs after a hot soak (long idle, time in traffic, etc) and not at other times then it could be the issue you outline. If high mileage and you've not changed the cam this may be the culprit! It's cheap and easy to try the cool air route first but take care with where you duct it from - spray and water whilst cool tend to have a detrimental effect on the engine - Bang!!
Cheers,
GB

[shpub]

Could also be a car with a higher then normal CR, coked up a bit, wrong ignition timing for the car or wrong weights in the dizzy for the advance and so on.

[gaz666]

Engine has done 70 thousand, took out a plug and looked at piston crown with mag light and fibre optic at TDC. Looks very black. This must be running to rich, so if i reset mixture and check CO hopefully pinking will go. Ive used a colourtune on other engines before and had good results, anyone tried it on a V8? Any tips, etc.

[shpub]

If it is that black, it may need a decoke and the engine tend to run a bit rich anyway to get the performance.

Your suggestion is worth a try first.

[gaz666]

Can you confirm if clockwise at the mixture screw on the flapper is to richen and to aim for around 1.5%-2% on c/o, and plug gaps .08mm. Thanks.

[tcpc]

hi,
i have a 1987 350i and run 8 BTDC my plugs are .09mm and clockwise to rich up (1.5% TO 2% on C/o ) on the airflow meter and use optamx shell and have'nt any pinking problems

hope this helps


TONY

[Katanarog]

I would have thought any engine would pink on full throttle at 350 rpm exept a tractor!

[keithTVR350i]

I have had similar experiences with my 22,000 mile 350i, pinking under load, plus additional pinking in the upper rev band (4000 plus). The cure for me was fancy Bosch plugs (the four electrode babies) plus a reduction to 5 degrees BTDC. Any additional advance induces pinking. Although I guess I might get away with another degree or two in the cold weather.