2003 5.4 with about 135,000 miles.

About a week ago it had a P0171 or P0174, not sure which one. A few years ago I replaced the vacuum hose and PCV valve assembly so I started there. It ended up the PCV valve wasn't all the way in. I cleaned it and pushed it back in, and erased the code. The truck was missing at that time too, but wasn't giving a misfire code. Previously I've replaced half the coils, when the code for that cylinder came up, so I just wait for the code. A day later it gave a misfire on cylinder 3, so I ordered the coil but didn't change it yet.

This morning my wife was driving it and said it stalled while driving at about 30mph. She pulled over and restarted it, and drove it home. She said it was shifting hard.

This afternoon I changed the cylinder 3 coil and erased the code. The truck still runs rough and felt like it would stall when I dropped to low RPMs when I drove it 500' down the road.

It isn't throwing any code, and there is no pending code.

I've changed the air filter, cleaned the MAF sensors, and checked the vacuum hoses from the PCV valve to the rear of the engine. I checked the TPS and it has a good ground and 5v supply I unhooked the battery to reset the fuel trim values after all this. Here is what I ended up with:

At idle:
ABSLT TBS % 19.6
ENG Speed RPM 682
CALC Load % 25%
MAF Flow g/sec 5.92
IAT F 91
IGN Advance 13.5
ST FTRM1 % -1.0
LT FTRM1 % -14.7
ST FTRM2 % -2.2
LT FTRM2 % 23.4

At 2500 RPM
ABSLT TBS % 23.5
ENG Speed RPM 2577
CALC Load % 24.7%
MAF Flow g/sec 21.98
IAT F 91
IGN Advance 39.0
ST FTRM1 % -1.0
LT FTRM1 % -4.9
ST FTRM2 % 3.1
LT FTRM2 % 3.9

I'm stuck... what do I look at next? Is it still showing as running lean? It's odd to me that it is showing a lower load value at 2500 rpm than at idle.

Thanks for any help!

 

When was the last time the fuel filter was changed? Did you check your fuel pressure at the fuel rail? Should be 35 psi ( +/- 5 psi ...) .


-Mike

 

I thought I had replaced it a few years ago until I looked up how to do it just now... and I have never done it. I confused it with another vehicle. That will be the first thing I do in the morning, and then i'll check the fuel pressure.

Thanks
Dave

 

Replaced fuel filter and checked pressure, at 47-48 psi.

Took it around the block, has power, but surges at low RPM. Feels like it will stall starting from a stop sign.

 

I took the rubber intake off and cleaned the throttle body, with no improvement.

Here are some updated data:

At idle:
MAF Flow g/sec 5.82
IAT F 82
IGN Advance 15.0
ST FTRM1 % 0.7
LT FTRM1 % -18.6
ST FTRM2 % 0.8
LT FTRM2 % 21
O2S11 V 0.480
ST FTRM11 % -2.2
O2S12 V 0.720
O2S21 V 0.755
ST FTRM21 % 0.8
O2S22 V 0.670

At 2500 RPM
MAF Flow g/sec 22.81
IAT F 84
IGN Advance 39.0
ST FTRM1 % -5.1
LT FTRM1 % -0.0
ST FTRM2 % 7.0
LT FTRM2 % 0.0
O2S11 V 0.840
ST FTRM11 % -2.2
O2S12 V 0.745
O2S21 V 0.875
ST FTRM21 % -3.4
O2S22 V 0.445

I'm thinking something is up with lean/rich, with the long term fuel trim values going from high positive/negative to zero at the higher RPM. Which makes me think vacuum hose? I've checked the hose at the PCV valve and the elbow at the back, and they are ok. Are there other lines that I should check that are relevant? Or with one bank lean and one bank rich, o2 sensors?

 

Updated data at idle, which leads me to think rich on bank 2, but no codes at all today.

 

I ended up taking it into a shop for diagnostics. Feedback was to change the oil (it was past due) and add seafoam. They said the potential problems are either a variable timing issue (due to oil/sludge) or catalytic converters.

It happened to throw a P1405 which led me to the EGR Pressure Feedback hoses, which had both rotted. I replaced both. But the problem still exists.

I noticed I really don't have much exhaust at idle. I can put my hand right by the tailpipe and it's a slight pulse of air. Does this sound like it might be the catalytic converters?

The truck was run for a bit with an intermittent flashing check engine light, which I read can lead to running rich and melting the cats.

 

Running it with a misfire might have very well done in your cats. Misfires on modern cars need to be dealt with asap. It's common too that the check engine light will flash if it's bad too.

 

Just realized you drive with it flashing. I'd be surprised if you didn't need cats now. The flashing is to indicate imminent damage to your cats.

 

Update:

I took it to a different shop (since the 1st didn't do exhaust), they said it was misfiring, even with no codes, and they had to start there before the cats. They replaced the spark plugs (Original w/135,000 miles), 3 coils (original), 5 coil boots (coils were newer), and some sort of fuel cleaning. They then said the cats were bad, and they wanted $2,000 for the cats. I took it to an exhaust shop, where I had them put universal cats on for much less. On the way to get the cats done, the engine felt so much better, no misfiring, but I believe the cat diagnosis was right, it felt like the exhaust couldn't leave the engine, there was absolutely no power, even with wide open throttle.

I just got the truck back from the exhaust shop and it had a code: running lean on bank 2 (P0174). Long Term Fuel Trim on bank 2 was 21-25. I cleaned the MAF sensor again, unhooked the battery to reset the computer, and took it for a 8 mile ride. When I returned the idle LTFT was 15. The truck has no codes.

STFT1: -1.0
LTFT1: -21.7
STFT2: 1.5
LTFT2: 15.6

The truck still has some hesitation, but at wide open throttle it has no problem.

Any ideas where to look now?

 

How's the fuel pressure at the fuel rail ? ( You need 35 psi +/- 5 psi ....) When was the last time the fuel filter was changed ? Hesitation and no codes could be fuel starvation.


-Mike

 

[QUOTE=daveplot;16379808]2003 5.4 with about 135,000 miles.

About a week ago it had a P0171 or P0174, not sure which one. A few years ago I replaced the vacuum hose and PCV valve assembly so I started there. It ended up the PCV valve wasn't all the way in. I cleaned it and pushed it back in, and erased the code. The truck was missing at that time too, but wasn't giving a misfire code. Previously I've replaced half the coils, when the code for that cylinder came up, so I just wait for the code. A day later it gave a misfire on cylinder 3, so I ordered the coil but didn't change it yet.

This morning my wife was driving it and said it stalled while driving at about 30mph. She pulled over and restarted it, and drove it home. She said it was shifting hard.

This afternoon I changed the cylinder 3 coil and erased the code. The truck still runs rough and felt like it would stall when I dropped to low RPMs when I drove it 500' down the road.

It isn't throwing any code, and there is no pending code.

I've changed the air filter, cleaned the MAF sensors, and checked the vacuum hoses from the PCV valve to the rear of the engine. I checked the TPS and it has a good ground and 5v supply I unhooked the battery to reset the fuel trim values after all this. Here is what I ended up with:

At idle:
ABSLT TBS % 19.6
ENG Speed RPM 682
CALC Load % 25%
MAF Flow g/sec 5.92
IAT F 91
IGN Advance 13.5
ST FTRM1 % -1.0
LT FTRM1 % -14.7
ST FTRM2 % -2.2
LT FTRM2 % 23.4

At 2500 RPM
ABSLT TBS % 23.5
ENG Speed RPM 2577
CALC Load % 24.7%
MAF Flow g/sec 21.98
IAT F 91
IGN Advance 39.0
ST FTRM1 % -1.0
LT FTRM1 % -4.9
ST FTRM2 % 3.1
LT FTRM2 % 3.9

I'm stuck... what do I look at next? Is it still showing as running lean? It's odd to me that it is showing a lower load value at 2500 rpm than at idle.
Why the hell you replace coil pack check so were at a shop say you have those readings go to tool box grab this handy dandy tool check them but your car advanced itself 39°