Bringing this thread back
SO I am revisiting this thread as I STILL cannot figure this one out on this particular car.
Still rough running, although the idle seems to have evened out quite a bit. The car sat for about 2 months and I recently dug back into it. My friend, (ex-Porsche/german car shop owner) helped me do some trouble shooting.
He said on the AFM for the L-jet system there was a little allen key that would manually adjust the lean/rich mixture AFTER the AFM and these were set at the factory and not to be changed. He pulled the plastic cover off it and adjusted it a bit to stabilize the idle.
We checked for air leaks with starting fluid/carb cleaner and there weren't any that were overly apparent. Took the car for a ride and it felt like it was running on 5 cylinders or missing. Not the free-revving, smooth engine I am used to.
Here's what I did today to try to trace down what's wrong:
1)Pulled plug wires to check/isolate bad cylinder. This garnered nothing, still rough running, some wires didn't even make that much of a difference when pulled, but nothing overly apparent.
2) Checked injectors by listening with stethoscope, all injectors are clicking normally.
3) Pull spark plugs to see if one was wet. All looked dry and fine.
4) Did compression test on all cylinders. Got the following pressures:
5) Checked valve timing for perhaps a skipped tooth on T-belt. With crank aligned and at TDC, alignment marks on cam hubs line up with 69/72.5 Deg diagram. Timing checks out.
6) Checked temp sensor. Engine was hot, got a reading of .6kOhms, engine cooled down a bit (still sitting in 80 degree weather, probably internal temp around 100-110F) and resistance rose to over 1kOhm. I believe this works, and should read between 2-3kOhm at 60F?
7) Checked wires at temp sensor plug. Intact and making good contact under rubber boot.
8) Checked Coil by replacing with known good. Made no difference.
9) Checked spark at all wires and coming from coil.
10) Checked throttle position sensor, verifying no resistance across 2-18 at closed and infinite resistance across 18-3, and vice versa at full throttle.
SO WHAT ELSE? Put it all back together and still running rough. Sounds like it's missing, mis-firing, etc.
OH YEAH: Checked fuel pressure at rail right out of supply line. Fuel pressure was 45PSI solid. My Porsche friend said this was too high for an L-jet system (he continued to pull out his Bosch service manual and show me it should be around 35PSI). Does too high fuel pressure have a terrible effect on the performance? Should it really be at 35PSI, meaning my fuel pressure regulator is bad? I checked for fuel in the vacuum line from the FPR to the plenum, and didn't find anything overwhelming. Looked dry to me.
Anyone, please point me in the right direction...!
Harrison Macris 860 514 7003