fats_40 Posted March 28, 2009 Share Posted March 28, 2009 advise sought please,i own a p38 with 116000 miles on clock.on pulling away you hear a knocking sound under load,it then stops when you hit 15-20mph.i changed the main bearings,decatted it,but noise still there.i have now read that it could be a detonation problem,ie,spark knock.are p38s fitted with an egr valve and if so where would i find it.oil and leads and spark plugs changed 8 weeks ago.any help !!!!ps,engine 4.6 thanks Quote Link to comment Share on other sites More sharing options...
Dave W Posted March 28, 2009 Share Posted March 28, 2009 Does it only do it when cold or at all temperatures ? A little bit of piston slap isn't unusual in both the 4.0 and the 4.6 when cold although it normally goes away when it's warm. Quote Link to comment Share on other sites More sharing options...
fats_40 Posted March 28, 2009 Author Share Posted March 28, 2009 Does it only do it when cold or at all temperatures ?A little bit of piston slap isn't unusual in both the 4.0 and the 4.6 when cold although it normally goes away when it's warm. hot or cold it doesnt matter,its only when i pullaway then dissapears Quote Link to comment Share on other sites More sharing options...
scube Posted April 4, 2009 Share Posted April 4, 2009 hot or cold it doesnt matter,its only when i pullaway then dissapears P38 engine’s have sensors which keep the ignition just off the pinking point to make it as economic as possible they are called knock sensors (dugh) the crank sensors may also be playing up. Best to pop it into a specialist to plug it into some diagnostic equipment. Quote Link to comment Share on other sites More sharing options...
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