Hello everyone,
I rebuilt my engine and converted from C4 to C2 last year (242whp & 227tq woo hoo!). I've only been able to get out on track twice since then and have noticed two things.
1) I need to relearn how to drive the car like a 911. Before I was so down on power & C4 that getting the car to rotate on throttle was very difficult. Much easier now and I need to get comfortable driving it like an old 911.
2) This is where I need some help. I get a stumble between 4-4,500 RPM. It doesn't happen all the time, it's not consistent with partial or full throttle application. Once I get the car above 4,500 RPM it pulls strong all the way to redline.
I have taken apart my intake to see if there is anything bent in there or any vacuum leaks (due to my bent flywheel during rebuild I may or may not have blown my intake off 3 or 4 times ) but everything looks good. I did not replace the knock sensors during the rebuild, but I think that may be the next step to look at. They're >20 years old and had a bunch of corrosion on them which I cleaned off, but could be an odd resonant frequency that's causing them to pull timing?
Any insight or thoughts y'all can provide would be more than welcome. I don't have access to a hammer to pull codes/clear codes, unfortunately. The car is 95% of the way there, but I'm gobsmacked with this random stumble.
Someone on Rennlist suggested I take a look at my AFM wipers to see if there's a worn spot, but to my eyes they look good.
