7.4L MAF Issue?

[Christian Steffen]

Still looking for an answer. I cannot get the O2 sensors out. Purchased an O2 sensor socket and soaked the sensors in Kroil (penetrating fluid) to no avail. I don't want to ape on them and break them and end up in a massive world of hurt because I have no proof that these are the issue. Truck still fires up great and runs good cold. Sucks when I'm towing. I picked up my brother in law's tractor last night and towed it home (15 miles one way). Truck ran ok on the way out there empty and then slowly deteriorated on the drive home to the point I could barely get up to 50mph on the last leg of the journey. I've been reading up on anything I can find that deals with this hesitation/loss of power/crappy fuel mileage problem that seems to plague this engine and so far everyone who's solved their issue's solution is different from everyone else. What a gremlin factory.

Two new discoveries/possibilities that I am going to try tonight. My truck has had some witchcraft done to the battery cables and when the truck warms (or when the alternator has charged the battery back to full after starting) the voltage drops to below 14. I know that 13+ volts should still be plenty to run the truck but I'm going to check and improve grounding contacts, just to make sure. I'm also going to replace my Ignition coil. Its one of the few components that will deteriorate performance wise due to heat. Plus the issue has been getting progressively worse. I'm leaving on another long camping trip soon, but this time I'm pulling two mountain passes and will be driving in much hotter conditions, something this truck hates.

**** that sucks.. And the fact that you can't get above 50 pulling leads me to rethink the o2 sensor diagnosis. When the truck is in high throttle scenarios it will go into what is called power enrichment mode. It commands ~12.5 AFR and adds spark, so you should make a bunch of power. I believe the factory delay is 60 seconds for this, which is really ******. Pretty much everyone that tunes these removes that delay and makes it come in sooner.

The reason I doubt the o2 sensors are the issue now, is that they aren't used in high throttle areas.

Though looking back, I see you didn't have this issue until you replaced the thermostat?

 

[Supercharged111]

Delay really depends on the truck. At the very least flooring it will pull him out of CL which may be a moot point if a **** O2 has skewed his trims enough. Just heat it with a torch and honk on it. May require vise grips and some cuss words. Or **** it and weld in another bung next to it. It's possible you'll need to retap the threads in yours when it finally comes out anyway.

 

[Tom P]

**** that sucks.. And the fact that you can't get above 50 pulling leads me to rethink the o2 sensor diagnosis. When the truck is in high throttle scenarios it will go into what is called power enrichment mode. It commands ~12.5 AFR and adds spark, so you should make a bunch of power. I believe the factory delay is 60 seconds for this, which is really ******. Pretty much everyone that tunes these removes that delay and makes it come in sooner.

The reason I doubt the o2 sensors are the issue now, is that they aren't used in high throttle areas.

Though looking back, I see you didn't have this issue until you replaced the thermostat?

So if its supposed to add spark and make more power then perhaps my coil failure hypothesis is a lot closer to a theory? This is true about not having an issue until I replaced the thermostat but let me add some more info to clarify.

The last time I towed before replacing the thermostat the average ambient temperature was much lower (around February or March in NW Washington State) last night the ambient temp was about 75.
The trailer towed probably only weighed about 4500 lbs
The truck also had leaky injectors and a bad fuel pressure regulator

Delay really depends on the truck. At the very least flooring it will pull him out of CL which may be a moot point if a **** O2 has skewed his trims enough. Just heat it with a torch and honk on it. May require vise grips and some cuss words. Or **** it and weld in another bung next to it. It's possible you'll need to retap the threads in yours when it finally comes out anyway.

I'm about to that point...

 

[Supercharged111]

The coil is kind of a go/no go item IMO. Altering ignition timing won't significantly change the demand on the coil.

 

[Tom P]

I suppose I should also clarify that when I first hooked up to the trailer, I had the reduced power that I expected. Enough to eventually get me up to speed. but by the time i made mile 13 out of 15 I almost couldn't get it up to 50. I had her pretty well pegged in 2nd and she stuttered around 2200 rpm and then eventually got me there.

 

[Supercharged111]

Do you have a crappy OBDII scanner or can you borrow one that displays live data? You need only observe O2 bank 1 and 2 sensor 1. You're looking for one to peg full zero or like .999V.

 

[Tom P]

I will have to check that out. I know some people who have them but not sure if they do live data.

 

[Tom P]

Do you have a crappy OBDII scanner or can you borrow one that displays live data? You need only observe O2 bank 1 and 2 sensor 1. You're looking for one to peg full zero or like .999V.

Something like this?
https://www.amazon.com/ANCEL-AD310-...rd_wg=dxsJY&psc=1&refRID=W1AZH5PWRQ1YQGJ8DGH5

 

[Christian Steffen]

Yeah I'd really doubt it to be the coil. I hadn't really considered the effects of the trims. Did you try running with the o2s unplugged? That should throw it into an error state and keep it open loop, correct?

 

[Supercharged111]

Again though trims apply in open loop. If he could clear his trims then run open loop that'd give us a better idea. I have a Harbor Freight scanner that displays PIDs. That's what you're after. The ability to monitor ECT, IAT and **** like that.