Chrysler 300 3.5l V6 High LTFT at idle.

[George7941]

A friend of mine just bought a 2006 Chrysler 300 and, when I hooked up my Equus 3130 scanner to it, I noticed LTFT Bank1 at around 10 and Bank2 at around 18. Under load the LTFT values drop to between 5 and 7.

I did a quick check for intake leaks by introducing propane (from an unlit torch) around the outside of the intake ducting and manifold and did not notice any change in the STFT values. I will do a detailed check of the intake sometime.

Anything else I should be checking?

 

[gathermewool]

Just stabbing in the dark here - could it be slightly dirty or faulty injectors? If the IDC expects that a certain amount of fuel will be injected, but, due to them being either faulty or dirty, less is, then the O2 sensor will read lean and add fuel, right?

I would say the same about the MAF sensor possibly reading low, but, you've got two 02 sensors providing much-different feedback, so that might be able to be ruled out.

I just started learning about all of this a month or so ago, tryin to track down a high (+10% LTFT) in my turbo Subie. After a treatment of Redline SI-1 last tankfull it went back down to around +3%; however, it was back up to +7% cruising around yesterday. If you figure anything out, please post back. I'm going to clean my MAF today, and will let you know if that helps at all.

 

[CourierDriver]

MMO to the rescue,,,,its a thought.

 

[George7941]

Clogged injectors could lead to high LTFT but, with this car, they decrease under load, which is why I am checking out the intake.

CoutierDriver. I too use TCW3 oil as a fuel additive in a Cummins. I have the VP44 pump and you gotta keep the pump lubed.

 

[mechtech2]

Injectors are probably dirty.
This causes uneven flow to the cyls.
At WOT or under load, there is not as much % difference as at low flow/loads. This explains the readings.
What to do? A tank or two of good injector cleaner is a good first choice. Cheap, and will help all sorts of stuff, no matter what.

 

[George7941]

Thanks, I will try the injector cleaner.

 

[gathermewool]

FWIW, the bottle of SI-1 I ran in my car didn't help for squat - I only have
What is strange is that my LTFT dropped on the same tank of gas over three days from >+7% to right around 0%. These were constant values over many miles, not sporadic or max values. The difference. I experienced the high LTFT when the temp was in the mid 70s F and the near-zero LTFT on the last day of my trip when the temp was steady at 50F. Common sense would say that More air = more fuel needed, but I experienced the opposite.

What does this mean to me? It COULD mean that I've got an after-MAF leak some where that contracted enough with the colder temps to minimize the leak.

I did clean the MAF w/out resettting the ECM a couple of days prior to logging for that tank of fuel, so it could be that the dirty MAF was reading low and took a while to set the new LTFT, but watching STFT over the couple of days before it dropped didn't show a lot of -STFT that might indicate such.

You and I have completely different machines we're dealing with, but please let me know if you figure this out. Try a bottle of SI-1, Techron or Regane and clean the MAF to see if that helps.

 

[George7941]

Originally Posted By: gathermewool


What is strange is that my LTFT dropped on the same tank of gas over three days from >+7% to right around 0%. These were constant values over many miles, not sporadic or max values. The difference. I experienced the high LTFT when the temp was in the mid 70s F and the near-zero LTFT on the last day of my trip when the temp was steady at 50F. Common sense would say that More air = more fuel needed, but I experienced the opposite.




Since the ECM measures intake air temp and adjusts fuel delivery accordingly, I cannot agree with your reasoning.

With my friend's car, he reports a 3 point drop in LTFT after running a tank of injector cleaner. We will monitor the situation a bit longer and then perhaps do a injector flush.