Forum said my 14 sec live data video was to large to post. I did a cold start, spraying some engine cleaner around the intake.

Sort term Trim bank one ran from ........13.3,15.1,14.2, 21.4
Long term trim #1....................... ........ 9.4
Sort term #2 ............................................18,11, 14,15, 10
LT fuel trim #2 .........................................28.1

Hope this makes sense to you guys. How do the numbers look? I see that LT fuel trim #2 didn't move, while spraying the intake.

I found this online, does it sound like the correct way to find the problem?
"A long-term fuel trim of 28.1 indicates a significant lean condition, meaning the engine is adding more fuel to compensate for too much air. Since spraying the intake manifold didn't help, you may need to check for vacuum leaks, a faulty mass airflow sensor, or issues with the fuel system, such as a clogged fuel filter or weak fuel pump."

 

The 28.1 long term plus the short terms over 10 on bank 2 are probably the cause of the code. You're up over 30 trim, sometimes 40, on bank 2 most of the time.

Don't really see a clear mechanical cause. manicmechanic's post #6 is worth reading again. If the trims don't change with manifold spraying that suggests that the manifold is not leaking. Might be injectors.

Here's something though that I had thought up in the past. Been waiting for another lean code to show up on the forum to try it out.. If the manifold gaskets are leaking then pressing downward on the top of the manifold should seal the leak. If I ever had another lean code on a 4.2 that is what I would try, instead of spraying. The isolator bolt grommets are what create that downward force. If the grommets harden up they don't create the force and the manifold will have a vacuum leak. In short, pull up live data on your computer, and get up on top of the manifold. Press downward and see if they reduce. Worth a shot, easy to do. Don't get your shirt caught in the fan.



The thing you found on the internet looks like AI. The AI bots can't tell that spraying the intake manifold is done to check for vacuum leaks.

"Since spraying the intake manifold didn't help, you may need to check for vacuum leaks"

 

You need to determine why the processor is throwing fuel at it
It's to correct what it perceives is a lean condition
Generally, that is an intake gasket or cracked intake
Can be injectors not flowing

 

Can you please explain this part "You're up over 30 trim, sometimes 40, on bank 2 most of the time." I'm sorry it didn't see those numbers on the last test?? I isee 28.1 as the highest. What should the long term ft #2 be at? thanks

 

Total trim is long term plus short term. Long term is what the computer has in memory based on past conditions (that's why it doesn't change rapidly) and short term is what the computer is seeing from the O2 sensors.

So, your list shows total trims of 46.1, 39.1, 42.1, 43.1, and 38.1 for bank 2. That's a lot of extra fuel that the the computer is commanding, by opening the injectors for a longer time each cycle. It could be because of an intake system air leak or because the injectors are not squirting as much fuel as they should.

Even your bank 1 numbers are high, but bank 2 is very bad.

Any chance that you just have bad fuel? E85 or something like that? What's the history here? A new to you old truck? Maybe sitting for a long time? Has it ever run right for you?

 

Both fuel trims should be below 7 percent

 

Thanks for taking the time to explain, for me it's hard to under stand fuel trims.But I'm trying. I've had this truck for 2 years always ran great. Got this code a few months ago and it started to miss a little, I noticed the exhaust tip had a lot of carbon in it. I pulled out 2 plugs so far. Passenger side was in perfect but drivers side was carboned real bad, this seems to add up to the po174 code. I still need to pull the other 4 plugs to see how they look. With this code does it make sense to have a carboned plug just on one side and not the other, stuck injector???

 

Manicmechanic would know more but I wonder if you have an exhaust leak on the driver's side (bank 2) that is causing the O2 sensor to get erroneous data. The fact that the plugs are fouling means too much fuel, which should not be happening if there's an intake system leak.

Early in the thread it looked like the O2 sensors were working correctly. Maybe they're not. The dirty plugs on bank 2 is a new clue. The live data shows the PCM dumping a lot of fuel in to bank 2 and it does that based on what the O2 sensors tell it is happening there.

Is the exhaust system factory stock and intact?

Here's an interesting video with a nice car about it.

 

"The dirty plugs on bank 2 is a new clue". I only pulled one on that side. So should I pull the other 2 before we known more?

 

Might as well. The PCM sees all four on the bank as the same, since one O2 sensor monitors all four. So the other two should be as dirty, if it's an O2 sensor data problem.

I'm not saying it's the sensor itself, although it could be. Seems like you're getting closer though.

 

I always think of that, and it does happen
Are the O2 sensors switching or slammed stuck lean? That is what I look for to see if the truck is actually lean or if it's a sensor issue
The book would have you try to force it rich or lean to determine that
Propane enrichment or pull the brake booster vacuum hose and watch what happens quick before the processor adds or takes away fuel
I think his lean codes are injectors not flowing enough fuel and I have had to replace a bunch of them on those 4.2l engines and Taurus is way worse (more underhood heat maybe)