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It's not so much valve duration but valve overlap. A 'hotter' cam is designed to work better higher up the rev range but is less efficient down low due to a bigger overlap. You'll be getting some of the inlet mixture going out the exhaust valve at idle.
I was out with the flu for bloody week. Anyway, I just picked my P38 up and I noticed that the engine will simply stall when I come up to a crossing (for which I need to stop). Getting the engine going again is very difficult, flat out floor the gas during cranking and it will very cautiously stumble back to life. So now I drive around left foot braking to keep the revs up.
I just can't bloody understand where this sh... is coming from?! I bought this engine new from RPI last year, it never ran perfectly at idle but I was warned for that due to the cam. It passed the MOT last year with a new set of cats (the old ones having been burnt out by the old rubbish motor). This year has been a whole set of problems ... again. lamba sensors, spindle seals, etc. I finally got it to pass the MOT just barely and now the engine won't run properly at idle. :soapbox:
The missus is beginning to doubt my sanity for keeping such a car around and I am beginning to loose my mind over all these little snags. I am hoping the ECU will learn itself in over time to compensate for all this but if not, I am at a loss what to do next.
Oh the joys of owning an english car :)
-P
Sounds to me like a vacuum leak.
No leaks in the intake system after the throttle body?? Or even something as basic as a spark plug/injector (or multiple) not seated properly?? A vacuum hose from the PCV valve?
Cheers
Keithy
I have redone all the PVC hoses and clamps, replaced the intake pipe clamps etc. I used a fog machine and a compressor to put overpressure on the entire intake system and checked to see where smoke would escape and fixed all those spots one at a time. I now have less then 1% of o2 in my exhaust gas. I am hoping that the auto learn function of the ECU will take care of the idle problem else I will have to take things further apart :(
I am planning on installing a pvc catch can since WAY to much oil (vapour) ends up in the intake. I allready got myself one of those MANN thingy-me-bobs that are widely used on diesels. But first, I'll sort this out :)
Cheers,
-P