After the short test ride I mentioned above, I commuted to the office with her. Not good. The sputtering was back.
It seems like the behavior manifests itself after warming up a bit. At a constant speed, its enough to rock me back and forth a bit. During acceleration, its much more noticeable. When coming to a stop, and letting her idle, the RPMs will bounce around a bit for a few seconds before becoming constant.
Since I last posted, I:
1) replaced the fuel injectors with some refurbished Bosch 4-hole injectors
2) replaced the spark plugs with Bosch XR7LDC
None of those made a huge difference, albeit my old plugs were in pretty rough shape.
3) replaced the spark plug wires with a new set from BBY
The initial short test ride had me filled with a great deal of hope. I rode her on the long commute this morning though, and it is STILL there.
I think all I've done at this point is lessen the symptoms of the underlying cause.
As I ride along at 80+ MPH I will, about every 10 mins or so, get a brief moment of what feels like FULL POWER. Its enough to tease me and let me know what she's capable of.
At this point, my guesses are:
- fuel pressure regulator on the fuel rail
- distributor or electrical connection thereto
- fuel pump or electrical connection thereto
- rail on the back side of the throttle valve that comes from the crankcase breather (EGR)
I'm thinking that that cracked rail could potentially create inconsistent pressure in the intake, which might manifest itself in this sputtering behavior. Given a blind guess, that will probably be my next move.
Any tips for common failures or diagnostics?