Pelican Parts Forums - sc miss under load between 1

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- - sc miss under load between 1 - 2 k rpm (http://forums.pelicanparts.com/porsche-911-technical-forum/543045-sc-miss-under-load-between-1-2-k-rpm.html)

Is there any change if you retard or advance initial timing?

Richard

i can ease some of it out if i advance the timing, but not totally

...but not totally. Rats!!
Gordon, I'm useless to you at this point. It appears that elec is good. It stutters initially when your initially ask for more fuel,but then cleans out & runs like a champ. Almost sounding like fuel or small airleak. I don't remember if you replaced the fuel filter or not. I'm guessing you did.

I hope someone with far more expertise chimes in. Hang in there!

Richard

How confident are you that the valves are correctly adjusted? A too-tight valve can sound like a miss or an exhaust leak under load.

Brian

brian,

we have adopted the back to basic approach the methodolgy is now leading us to go back to the valves and see where we are with them

Quote:

Originally Posted by gordoncoll (Post 5359275)

plugs are gapped spot on,

as for the low tick along every 911 i have known along with every 944 is as usable as my alfa gtv, they may not be happy about rumbling along in low gear and it is not something i intend to do long term but they will and it certainly doesnt provoke a set of missfires and exhaust/intake popping when you open the throttle and ask them to work harder. sorry i cant see that the car shouldnt run like every other motor.

My appologies, I misunderstood your initial description of the symptoms. There are as many forms of "misfire" as there are folks trying to describe one. Exhaust and intake popping are far different from a stumble, for instance, yet many will call both a "misfire".

Anyway, what would be different in a no load vs. under load state at 1,000-2,000 rpm? Throttle position would need to be different (more open when loaded). What does this affect? Air box vacuum, which affects initial advance and the mass airflow sensor. I would focus my efforts in those two areas. Things like valve adjustment won't have such a narrow range of affect.

Have you checked the vaccum advance/retard mechanism?

also my apologies for the description of the issue not being so good.

i am veering toward the vac advance on the dizzie. when i cleaned out the dizzie i removed the vac unit which didnt hold a vacuum well and if shaken made a noise like a childs rattle!!

holding my breath for monday when the new one arrives.

Gordon