1997 4.6L f150 poor running condition. HELP needed…
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1st Gear
Joined: Jun 2026
Posts: 1
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1997 4.6L f150 poor running condition. HELP needed…
Hello, I’ve been working on a 97 4.6L f150 (waste spark system). The battery sometimes stops charging from the alternator fuse in the GEM panel under the steering column being loose. The truck got to 9.3v and was spitting / sputtering, owner cut it off and it wouldn’t turn back on (dead battery). The spitting & sputtering issue first appeared when the battery voltage was low. In idle it’d rev up fine, put in drive or reverse it’d bog / sputter.
Replaced the battery, and the bog stayed. It was just bogging / sputtering when accelerating or when put in gear. But now it’s stalling upon first 1-2 startups of the day.
Scan data shows absolutely nothing out of the norm, except cylinder head temp sensor voltage being 4.3v (cold start), but reading 80F. Thought 5v ref thermistors reading 4v+ is really high / low.
No codes, except EGR flow insufficient, evap fault (fuel tank pressure sensor nonexistent) and EPC solenoid short circuit. (P1747) (P0453) (P0401).
sometimes misfire codes are thrown, random cylinders or 3 / 7.
Spark Adv Deg fluctuates only upon first start up. If you put it in gear or drive around, it retards to 6BTDC at idle and drive (sometimes).
(Start up data).
fuel pressures in spec (35psi+) bleeds off slow (15 min+).
MAF 6.11g/s
cylinder head temp sensor voltage- 4.29v
ECT - 2.71v
STFT - spikes high (40%) upon start up then comes down to 3+/-.
LTFT - -9% both banks
Throttle Position Sensor - 0.96v - 0.97v
Throttle position rate changes every now and then while driving.
Replaced -
ignition coils and wires.
Spark plugs.
fuel pump.
fuel pressure regulator.
fuel filter.
idle air control valve.
egr valve.
egr hard line.
alternator.
battery.
all fuses.
Engine Coolant Temp Sensor. (Both)
pcm.
Any help / personal experiences with a similar scenario, is greatly appreciated. This one has been a odd one for me.
Replaced the battery, and the bog stayed. It was just bogging / sputtering when accelerating or when put in gear. But now it’s stalling upon first 1-2 startups of the day.
Scan data shows absolutely nothing out of the norm, except cylinder head temp sensor voltage being 4.3v (cold start), but reading 80F. Thought 5v ref thermistors reading 4v+ is really high / low.
No codes, except EGR flow insufficient, evap fault (fuel tank pressure sensor nonexistent) and EPC solenoid short circuit. (P1747) (P0453) (P0401).
sometimes misfire codes are thrown, random cylinders or 3 / 7.
Spark Adv Deg fluctuates only upon first start up. If you put it in gear or drive around, it retards to 6BTDC at idle and drive (sometimes).
(Start up data).
fuel pressures in spec (35psi+) bleeds off slow (15 min+).
MAF 6.11g/s
cylinder head temp sensor voltage- 4.29v
ECT - 2.71v
STFT - spikes high (40%) upon start up then comes down to 3+/-.
LTFT - -9% both banks
Throttle Position Sensor - 0.96v - 0.97v
Throttle position rate changes every now and then while driving.
Replaced -
ignition coils and wires.
Spark plugs.
fuel pump.
fuel pressure regulator.
fuel filter.
idle air control valve.
egr valve.
egr hard line.
alternator.
battery.
all fuses.
Engine Coolant Temp Sensor. (Both)
pcm.
Any help / personal experiences with a similar scenario, is greatly appreciated. This one has been a odd one for me.
5th Wheeling
Joined: Feb 2019
Posts: 44
Likes: 8
Just a poke at a potential issue- the ltft is -9 which means the o2 sensors are detecting a low air to fuel ratio, rich condition. The mass air flow sensor is reading at >6 g/s Which strikes me as slightly high since I would expect the reading to be about 4.6 g/s at 800-850 rpm. If the mass air flow sensor is reading high then it could be adding more fuel than is necessary.
Fleet Mechanic
Joined: Jun 2023
Posts: 1,380
Likes: 383
From: WA
No codes except at least one that might matter. The EVAP system is connected directly to the intake manifold. A problem there can change the air-fuel ratio. You should give the actual code. Codes can have several possible causes.
Also, the live data is missing engine RPM and engine temperature. Kind of meaningless without those.
The battery dying might be a distraction. Good luck.
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