LS1 missing under load, neg fuel trims..help!!!
07-20-2014, 12:48 PM
#1
LS1 missing under load, neg fuel trims..help!!! My car is missing under load, appears to idle fine.
I noticed it has negative fuel trims...this doesnt seem good that its compensating that much.
New 02 sensors...no change
New Plugs...no change
New Plug wires...no change
New True Dual Exhaust...no change
Cleaned 1 year old MAF...no change
Its a 98 LS1, with 224/224/112 tuned by ion. I know the tune isn't spot on but anytime its under load it misses and shakes.
I have verified with temp gun that all header primaries are within 10-15 degrees of each other so I know that its firing on all 8.
What next?
I noticed it has negative fuel trims...this doesnt seem good that its compensating that much.
New 02 sensors...no change
New Plugs...no change
New Plug wires...no change
New True Dual Exhaust...no change
Cleaned 1 year old MAF...no change
Its a 98 LS1, with 224/224/112 tuned by ion. I know the tune isn't spot on but anytime its under load it misses and shakes.
I have verified with temp gun that all header primaries are within 10-15 degrees of each other so I know that its firing on all 8.
What next?
07-21-2014, 03:20 PM
#3
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What do you know about fuel pressure? What if anything can
you make out from the NBO2 numbers, regarding the AFR
at the problem condition?
Fuel trims from the low end don't necessarily tell you anything
about the big end; lots of things that mess with the low load
actual fueling and sensed EQ position have nothing to do with
WOT.
Other than, say, if your WOT tune originally was done against
some positive trims, later fueling drift and retrimming to the
more negative might put you lean.
you make out from the NBO2 numbers, regarding the AFR
at the problem condition?
Fuel trims from the low end don't necessarily tell you anything
about the big end; lots of things that mess with the low load
actual fueling and sensed EQ position have nothing to do with
WOT.
Other than, say, if your WOT tune originally was done against
some positive trims, later fueling drift and retrimming to the
more negative might put you lean.
07-22-2014, 06:25 PM
#5
At this point I have narrowed it down to cylinder 7. its running 140 temp when the others are 21x.
New fuel filter, racetronix pump thats giving 60+ PSI, starts happening as soon as it gets under load.
Ford 36 lb injectors, swapped #7 and #1, no change. So I am wondering if its a coil pack, spring, or pushrod.
New fuel filter, racetronix pump thats giving 60+ PSI, starts happening as soon as it gets under load.
Ford 36 lb injectors, swapped #7 and #1, no change. So I am wondering if its a coil pack, spring, or pushrod.
08-01-2014, 11:25 AM
#7
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I would continue the component swappage, on the
ignition side (coil, plug, wire) until the misfiring moves.
Can you say whether "under load" means torque only,
or high RPM as well? Any chance of valvetrain issues
(lost rock,er needles, bad springs, etc.) and early
float or late opening, not visible at lower RPM where
valve window is not the limiter for air intake?
ignition side (coil, plug, wire) until the misfiring moves.
Can you say whether "under load" means torque only,
or high RPM as well? Any chance of valvetrain issues
(lost rock,er needles, bad springs, etc.) and early
float or late opening, not visible at lower RPM where
valve window is not the limiter for air intake?
Trending Topics
08-01-2014, 02:23 PM
#9
To update the thread. Car runs on 7 cyl from start up to shut down.
Tested all coils, swapped all coils
Tested all injectors, swapped all injectors
Tested injector wiring with noid tester
New Plugs
New Wires
New O2 sensors
New Coolant Temp Sensor
New IAC
New TPS
New PCV system
HP Tuners confirms no vac leaks
HP Tuners confirms bank 2 running fine
Confirmed push rods are not bent
Confirmed springs are not broken
Can see rockers working correctly - assuming lifters are fine
Basically its bank 1 related, #7 primary is at 90 ish degrees while others are at 140 via infrared heat gun.
What am I missing?
Tested all coils, swapped all coils
Tested all injectors, swapped all injectors
Tested injector wiring with noid tester
New Plugs
New Wires
New O2 sensors
New Coolant Temp Sensor
New IAC
New TPS
New PCV system
HP Tuners confirms no vac leaks
HP Tuners confirms bank 2 running fine
Confirmed push rods are not bent
Confirmed springs are not broken
Can see rockers working correctly - assuming lifters are fine
Basically its bank 1 related, #7 primary is at 90 ish degrees while others are at 140 via infrared heat gun.
What am I missing?
Last edited by nascarnate326; 08-01-2014 at 02:29 PM.
08-01-2014, 09:07 PM
#13
Checked those, even tried a new intake.
Took intake off and realized that cyl 7 was dry, others were wet/oily. I don't think its getting fuel like it should. Noid light says its working correct but the primary doesnt get hot like the others.
Took intake off and realized that cyl 7 was dry, others were wet/oily. I don't think its getting fuel like it should. Noid light says its working correct but the primary doesnt get hot like the others.
08-02-2014, 02:12 PM
#14
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I guess you might want to check the fuel rail just
in case #7 has accumulated enough silt / flakes to
occlude the passage to the injector. If you find any
crud there then check #8 too. I have had other cars
that silted up end positions, and simply ran a little
rough / flaky (back in the days before scan tools
or OBD-II).
Can you hear that the injector is actuating, with a
stethoscope? Noid light may tell some things about
intention, but has nothing for action.
in case #7 has accumulated enough silt / flakes to
occlude the passage to the injector. If you find any
crud there then check #8 too. I have had other cars
that silted up end positions, and simply ran a little
rough / flaky (back in the days before scan tools
or OBD-II).
Can you hear that the injector is actuating, with a
stethoscope? Noid light may tell some things about
intention, but has nothing for action.
