WJDiag Fuel Correction Test

[bluegrommet]

Here's the overdue update - the new injector #3 totally fixed the rough idling. The tachometer needle sits firm at 750 with no jumps or surprises, and the car no longer shakes madly. Great! Driving the car feels like a dream - thanks for the advice guys.

However I still get P0190 "stalls".

When driving on the road sometimes I'll feel either one or multiple (3-4) jolts with rapid deceleration, as if the car stalls for a split second and then continues on with the MIL and P0190. It always happens after cold starting the car whilst the car has about halfway warmed up to operating temp. Won't happen again until the car has the chance to cool completely.

Not really sure what to make of this and why it always happens at the same time in the heating cycle. I was hoping the new injector would fix it, but nope.

Any ideas? I'm also sometimes getting P0340 "Camshaft Position Sensor A Circuit (Bank 1 or Single Sensor)". This seems to come on immediately when starting the car sometimes and I don't think I've noticed any side effects - maybe some unusual revving? Not sure if related to the P0190.

[bluegrommet]

I've dug a bit more into the P0190 - I think it may be something to do with the fuel sensor wiring. To test this I started and idled the WG in my driveway and watched the fuel pressure voltage and corresponding pressure using WJDiag. Here are my notes:



Basically the fuel pressure sensor seems to alternate between working and not working whilst the Jeep is warming up. Following the tests in the service manual tells me that in this case I should be checking the wiring (I've skipped pasting in Tests 1-5 here as the intermitent fault path leads to 6):

P0190-FUEL PRESS SENSOR CIRCUIT MALF SIGNAL VOLTAGE TOO LOW

POSSIBLE CAUSES
FUEL PRESSURE SENSOR
INTERMITTENT CONDITION
FUEL PRESSURE SENSOR SIGNAL CIRCUIT SHORTED TO GROUND
FUEL PRESSURE SENSOR SIGNAL CIRCUIT SHORTED TO SENSOR GROUND
ECM - FUEL PRESSURE SENSOR SIGNAL SHORTED TO GROUND

TEST 6
With the engine running and at normal operating temperature, monitor the DRB parameters related to the DTC while wiggling the wiring harness. Look for parameter values to change and/or a DTC to set.
Review the DTC When Monitored and Set Conditions. If possible, try to duplicate the conditions under which the DTC was set.
Refer to any Technical Service Bulletins (TSB) that may apply.
Visually inspect the related wiring harness. Look for any chafed, pierced, pinched, or partially broken wires.
Visually inspect the related wiring harness connectors. Look for broken, bent, pushed out, or corroded terminals.

I've inspected the harness from the ECU to the engine without pulling anything apart and can't see anything yet - I guess I need to keep digging. The next photo shows roughly the path of the wire. Does it seem like I'm on the right path, and does anyone know any likely spots where the cable might have chafed/etc?