2005 f 150 4.6 has -20% LTFT'S on both banks

Maf: 0.01 lb/s instead of 0.1 lb/s? Please confirm.

Maf reading at idle

Sorry I don't know why pics are flipped

Yes . maf reading at idle is 0.01lb/s, and with a WOT snap it maxed at .32 lb/s

Flex fuel?

0.01 lb/s x 60 sec = 0.6 lb/min.

This is a low number for me. I would expect at idle about 4 lb/min.

I was thinking that too, but am not sure about the g/s conversion, so that number might be ok?

Nissan Technician

coolant range for ford 4.6 is 190 to 225. that is the thermostat opens at 190. is the upper coolant hose hot to the touch? might want to test that coolant temp manually.

the .01lb/s comes out to 4.5g/s for the MAF as it should be.

I still think the coolant temp is too low causing the engine to run rich. Maybe someone else can comment on this to confirm... fuel pressure is controlled by the speed of the pump motor.

Tutti,

1lb = 453,6 gr

So, 0.01lb/s = 4,536 gr/s

Scannerjohn,

You're right about low temp. I would expect at idle negative trims and o2 sensors cycling as they should.

What to expect at wot? I think anyway it has to rise o2 voltage, ignoring o2 sensor and enriching the mixture.

Is this engine getting flooded at wot?

Patrick,

Is the o2 voltage steady above 0.8v at wot and at that dead aceleration you described?

You said trims are responding when you spray extra fuel. Does it mean trims become even more negative?

You replaced the MAF already. How is the wire integrity there? Are you able to scope the signal wire and compare to a known good?

I'm not dismissing that ECT, just thinking out loud a little on other options.

Nissan Technician

1lb/s to g/s = 453.592

453.6 x .01 = 4.5

.0022046 lb/s in 1 g/s x 4.6 = .01014 lb/s

at WOT the 02 no longer oscillate they go default rich. the fuel pump is working at full speed at all ranges, supplying too much fuel... pcm sees this and is compensating by taking away fuel. my theory anyway...

fuel pump would be at high rpm at WOT to keep up with fuel demand so it should not be flooding

Thanks for the reply , and no it's not flex fuel, and i understand your thought process, that ecu can miscalculate the alcohol content on flex fuel vehicles.

And I believe you are right scannerjohn, from my research the pump is pulse width modulated, and controlled by duty cycle from the fuel pump driver module. it has 12 volts with key on and the module supplies a ground, during cranking i believe the duty cycle command is to give it a full ground and not limit pump speed, after it starts up duty cycle changes to vary pump speed.( Im not sure what all imputes effect the duty cycle) I think you are suggesting to check the duty cycle during cranking, and compare it to engine running to see if it changes, you think its not changing duty cycle after it starts running, or that the temp being low is commanding a longer on time of the duty cycle? but if this were the case , wouldn't my fuel pressure be higher? Im not sure on that, far from an expert.

One piece of info I forgot to mention is smoke coming out of my exaust. To me it looks white almost like a head gasket failure, but I assure you I drive it 150 miles a day on the interstate and it never overheats and I never need to add coolant. Below I'll post a video of the exhaust smoke after it idles for a few minutes and then having the throttle pushed .

Ok, it wouldn't let me share a 6 second video, so here are some pictures of the exhaust smoke on a snap throttle after it's idled a few minutes

the -20% on LTFT's stays the same at all increments of rpm, (1000, 1500, 2000, 2500, 3000 rpms) and at 70 mph they are still around -20% . i just added propane into a vac line and the STFT's immediately go negative, so yes it can take even more fuel away, And if i pull a vacuum line the STFT's go positive immediately.
Yes, during WOT while driving down the road, the upstream 02's flatline at 0.8 volts
Yes i have changed the MAF 3 different times with junk yard parts (same truck and engine).The MAF voltage is around 0.8 volts at idle and increase to 3.6 volts on a WOT snap. I will go and check the signal voltage with my vantage pro now to see if it is the same as scan tool voltage ( I believe thats what you were suggesting?)

Does it smell like fuel out the tailpipe?

No, the exhaust smoke does not smell like raw fuel to me, comparing it to a V8 engine with no cats on a cold start up, its no where near as strong of a scent .but i could be wrong, and I am getting good gas mileage (15-18 mpg)
I changed the plugs (motercraft platinums) last year, and last week pulled all the plugs to see how they looked and they were all in great condition still new looking after 30,000 miles. (no black soot, or oil fouling) which i was very surprised to see, due to the exhaust smoke. I can pull them again and post pictures, but there was no signs of any excessive burning of anything.

fuel pressure will not be higher, but high all the time same as startup duty cycle of 50%. Should drop to about 25%. If coolant temp is low, it would be signaling pcm that engine is not at operating temp and to stay at 50%... bad temp sensor would do the same.

scantool fuel pressure readings will only show as high as 70... put a pressure gauge on it, should be around 90psi

that white exhaust has to be addressed first... transparent white smoke is usually coolant, opaque white transmission fluid... blue is oil and black is fuel. what ever it is, if its getting on the 02's your going to have wonky readings.