So my (stock engine 5.0) 90 Coupe has had a bucking issue for a long, long time now. I've tested and/or replaced many/most of the sensors, swapped EEC's after replacing caps, checked charging system and grounds, fuel filter, etc. I've been searching forums forever but this doesn't seem to match any other issues. Most are no start or cutting off type issues.
The last thing I've done is taken apart and cleaned the 10 pin connectors and separated the pins for a more snug fit. After doing this, the idle is amazing, but the car still bucks and jerks while driving. Which kinda led me down the electrical rabbit hole even further - not my strong suit.
Background:
-Car starts, runs, and idles fine (the 10-pin connector work ironed out the little bit of a surge it had), and has yet to cut-off while driving or stopped.
-Pump primes (Obviously, but seems kinda loud IMO - subjective, I know)
-Fuel pressure is 41psi at idle with vacuum off. I am waiting on a gauge extension, so I can actually check while driving and the issues occur to see if pressure is cutting out.
Issue:
The car runs strong up to about 3.5-4K @ 3/4 to WOT with no electrical load, then will buck and jerk moderately through that range, then smooth the rest of the way to redline. RPMs go spastic when it happens.
BUT - when I have an electrical load on it - headlights, fan, wipers - it is much, much, worse (severe bucking at random RPM ranges) and doesn't like me to give it much throttle at all. If I let off the gas it calms down and will stay running still.
That is what leads me to an electrical issue. Like, perhaps there is resistance somewhere in the circuit that becomes too great when accessories are on or fuel demand is greater, and the pump can't keep up? Where should I check first in this circuit? I've read that EFI primer, but it's difficult for me to figure where to start since the symptoms are strange and I'm not very experienced with electrical.
Thanks!!
The last thing I've done is taken apart and cleaned the 10 pin connectors and separated the pins for a more snug fit. After doing this, the idle is amazing, but the car still bucks and jerks while driving. Which kinda led me down the electrical rabbit hole even further - not my strong suit.
Background:
-Car starts, runs, and idles fine (the 10-pin connector work ironed out the little bit of a surge it had), and has yet to cut-off while driving or stopped.
-Pump primes (Obviously, but seems kinda loud IMO - subjective, I know)
-Fuel pressure is 41psi at idle with vacuum off. I am waiting on a gauge extension, so I can actually check while driving and the issues occur to see if pressure is cutting out.
Issue:
The car runs strong up to about 3.5-4K @ 3/4 to WOT with no electrical load, then will buck and jerk moderately through that range, then smooth the rest of the way to redline. RPMs go spastic when it happens.
BUT - when I have an electrical load on it - headlights, fan, wipers - it is much, much, worse (severe bucking at random RPM ranges) and doesn't like me to give it much throttle at all. If I let off the gas it calms down and will stay running still.
That is what leads me to an electrical issue. Like, perhaps there is resistance somewhere in the circuit that becomes too great when accessories are on or fuel demand is greater, and the pump can't keep up? Where should I check first in this circuit? I've read that EFI primer, but it's difficult for me to figure where to start since the symptoms are strange and I'm not very experienced with electrical.
Thanks!!