Rev 318 in park, slows down and stalls..case study.
Hey guys:
I thought I would post this as a "case study", since it's not technically on an A-body, but my '87 Plymouth Gran Fury. The backstory is that this is a very original car with 98K. When I bought it late last year, it had a terrible mid-range stumble that was predictable and consistent. Hold your foot in one spot and the car bucked and surged. It started easily and ran much better with the choke engaged. I rebuilt and installed a regular Holley 2280 carb which worked well in the past and built an HEI system to eliminate the ESC.
Fast forward to now: Starts easily, idles great, but has a part throttle flat spot severe enough to turn into a stall. I discovered that it's able to be duplicated in Park.
What I've done:
1. Removed the carb and replaced the linkage and baseplate with the factory items instead of the 6280 stuff and made sure the accelerator pump is working fully and the mechanical power piston is working fully and verified float height. No change.
2. Rechecked the timing. 10 degrees initial, mechanical and vacuum advances functional. No change.
3. Pulled the fuel pump inlet line and ran it off a bottle to eliminate the tank and lines. No change.
4. Pulled the fuel filter. Not clogged. No change.
That's where I'm at so far. Next up is put a clear filter in temporarily and observe fuel flow while prompting it to starve for fuel. There are always lots of could be's while diagnosing fuel problems, so maybe this will help.