2000 5.9 fuel pressure fluctuates at idle, stalls, running rich
#1
2000 5.9 fuel pressure fluctuates at idle, stalls, running rich
Hey DF pals!
Still trying to diagnose this van after some time now. Runs rich, fuel trims leaning out, fumey, rough idle, misfires... I swear this one is possessed!
A new development in the caper:
Recently it has been stalling on sudden acceleration and when I just let it warm up it will stall out of nowhere at idle. I'm hoping this symptom can lead me to a solution finally.
I'm finding fuel pressure has become much shakier at idle, fluctuating between 35-55 at idle now, BUT is a steady 49 psi with throttle. (Previously it only fluctuated +/- 2psi at idle)
I'm thinking either
- a bad fuel regulator, filter, pump, or FP wiring issue
and/or
- fuel injector(s) stuck open or wiring (ground to ground).
First impressions? Thoughts? What would you test next?
Cheers y'all!
Still trying to diagnose this van after some time now. Runs rich, fuel trims leaning out, fumey, rough idle, misfires... I swear this one is possessed!
A new development in the caper:
Recently it has been stalling on sudden acceleration and when I just let it warm up it will stall out of nowhere at idle. I'm hoping this symptom can lead me to a solution finally.
I'm finding fuel pressure has become much shakier at idle, fluctuating between 35-55 at idle now, BUT is a steady 49 psi with throttle. (Previously it only fluctuated +/- 2psi at idle)
I'm thinking either
- a bad fuel regulator, filter, pump, or FP wiring issue
and/or
- fuel injector(s) stuck open or wiring (ground to ground).
First impressions? Thoughts? What would you test next?
Cheers y'all!
Last edited by JC2000; 02-26-2021 at 10:48 PM.
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I wonder how this could cause the issues I'm having. Any theories? 5v ref circuit gets shorted causing computer shutdown?
Does anyone know how to best test the sensor and circuit or what resistance should measure on a 50 degree day?
I guess I'll check it out and start w some wiggle tests for short to ground.
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#8
LTFT ends up -10 to -15
STFT +/-3 once LT steadies there
IAT gets up to 150's
ECT at 195 at idle (195 thermostat installed)
My biggest concern now, other than the stalling and rough idle and rich condition is the condition of the cat as 02's are showing me something new, likely due to running with a misfires for a while.
Upstream oscillates like you'd expect but downstream is fixed rich (0.8-0.9V) when idling at around 0.86V
Here's the thing, downstream goes to fixed lean (less than 0.1V) with throttle.
The stalling may be due to a clogged cat but I need to know if this is behavior of a clogged cat, a bad cat, or good cat.
This starts off with idle and ends with acceleration. What does the downstream behavior say about the cat?
Last edited by JC2000; 03-01-2021 at 06:18 PM.
#9
The sensor itself shows resistance and drops with temperature, though I'm unsure what kind of resistance the PCM is looking for.
Unless there's an intermittent ground issue, I don't know what else to test there.
#10
Thanks, yeah, trims are not the best. Leaning out heavy but not as bad as it once was after all sorts of improvements. I was going to bring this up in a separate thread, but here ya go:
LTFT ends up -10 to -15
STFT +/-3 once LT steadies there
IAT gets up to 150's
ECT at 195 at idle (195 thermostat installed)
My biggest concern now, other than the stalling and rough idle and rich condition is the condition of the cat as 02's are showing me something new, likely due to running with a misfires for a while.
Upstream oscillates like you'd expect but downstream is fixed rich (0.8-0.9V) when idling at around 0.86V
Here's the thing, downstream goes to fixed lean (less than 0.1V) with throttle.
The stalling may be due to a clogged cat but I need to know if this is behavior of a clogged cat, a bad cat, or good cat.
This starts off with idle and ends with acceleration. Why does the downstream behavior say about the cat?
LTFT ends up -10 to -15
STFT +/-3 once LT steadies there
IAT gets up to 150's
ECT at 195 at idle (195 thermostat installed)
My biggest concern now, other than the stalling and rough idle and rich condition is the condition of the cat as 02's are showing me something new, likely due to running with a misfires for a while.
Upstream oscillates like you'd expect but downstream is fixed rich (0.8-0.9V) when idling at around 0.86V
Here's the thing, downstream goes to fixed lean (less than 0.1V) with throttle.
The stalling may be due to a clogged cat but I need to know if this is behavior of a clogged cat, a bad cat, or good cat.
This starts off with idle and ends with acceleration. Why does the downstream behavior say about the cat?