XE pinking - cause and cure ??

[dogsy]

recently replaced the head gasket on my c20xe and since then its started pinking (rattling when under load). its definately top end (sounds like exhaust cam). ive checked the timing and its spot on. also checked exhaust system - no leaks at all. all gaskets were replaced with new. didnt unplug any sensors from the block or the inlet manifold / fuel rail when the head gasket was changed. no carbon on the piston crowns. im using the same optimax fuel as before i did the HG. the head had the inlet ports opened up a small amount, and the exhaust ports cleaned and smoothed, and the valves were lapped in, apart from that no other work done to the head. ive covered about 200 miles since the HG and the noise is still the same so i doubt its tappets. the ecu light isnt coming on to tell me there are any faults. also its got a dizzy if that makes any difference ??

what causes pinking ?? i know its pre-ignition but what could cause it in the xe ??

what is the cure ??

cheers, Mark

 

[Dave GSiT]

Your pinking could be caused by a problem in the fuel pressure regulator. Did you remember to bleed the fuel rail when it was removed/re-installed?

Did you have the head skimmed when it was off? Too brutal a skimm can cause pinking.

Also, is your oil breathing heavily into the air mixture? (under the SFi box). Oil vapour lowers fuel octane points dramatically and if its breathing hard after the gasket change, this could also be a problem.

Have a check and let me know.

Dave BBT

 

[dogsy]

dont think i removed the fuel rail from the inlet manifold, i took the whole inlet manifold off as 1. i could be wrong tho. how do you bleed them ??

the head had a very minor skim, more to make sure it was flat than to actually skim it. looking at it they only took a very tiny amount off.

i do need a new sfi gasket where it joins to the throttle body (i think thats what its called). cant see any signs of oil around it tho ??

i also noticed i had a few holes in the exhaust manifold and was told this could cause a noise very similar to pinking, or could maybe cause pinking (due to lambda sensor getting wrong reading ??) so gonna get a new manifold in the next few weeks.

 

[Dave GSiT]

If the manifold is damaged it will make pinking noises. Its the carbon build up on the manifold going "ping" when it heats up. Thats the pinking noise you hear when you razz your N/A car then pull up on your drive and switch off.

Zetec Fords make a hell of a racket! Seem to remember my XE tinkled for a little bit as well when Id been hammering that.