Forscan and fuel trim questions

[Black Dream]

Recently Forscan Lite quit connecting to my phone. It posts an error message that the OBD2 connector can't be found. Everything else I run through my ELM scanner  including Torque Pro works just fine. Any ideas why Forscan doesn't any more?

Also what fuel rail pressure should I be seeing on my '10 MKS Ecoboost? I'm seeing a range from low 200's-2130 under a variety of driving conditions. And what fuel trims should I be seeing? I'm chasing a vibration/shudder between 65-80 mph. I've replaced all plugs, coil packs, fuel control module and both upstream sensors recently and looked at suspension bushings, control arms, shocks, endinks, CV axles and the hardware seems fine. Tried each wheel for play to check hubs/bearings, none have play and the PTU fluid was changed 3k miles ago and still looks good. I'm having all 4 wheels rebalanced tomorrow and have fun Chevron Techron fuel system cleaner through to clean out the injectors.

I've attached a Torque page with the fuel trims I get regularly under a variety of driving conditions but have no clue what numbers I should be looking for. I'm aware how the trims work so that's a plus I suppose.

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[StealBlueSHO]

Recently Forscan Lite quit connecting to my phone. It posts an error message that the OBD2 connector can't be found. Everything else I run through my ELM scanner  including Torque Pro works just fine. Any ideas why Forscan doesn't any more?

Also what fuel rail pressure should I be seeing on my '10 MKS Ecoboost? I'm seeing a range from low 200's-2130 under a variety of driving conditions. And what fuel trims should I be seeing? I'm chasing a vibration/shudder between 65-80 mph. I've replaced all plugs, coil packs, fuel control module and both upstream sensors recently and looked at suspension bushings, control arms, shocks, endinks, CV axles and the hardware seems fine. Tried each wheel for play to check hubs/bearings, none have play and the PTU fluid was changed 3k miles ago and still looks good. I'm having all 4 wheels rebalanced tomorrow and have fun Chevron Techron fuel system cleaner through to clean out the injectors.

I've attached a Torque page with the fuel trims I get regularly under a variety of driving conditions but have no clue what numbers I should be looking for. I'm aware how the trims work so that's a plus I suppose.

Sent from my LM-G820 using Tapatalk

I can assist with fuel pressure and fuel trim issues..

The fuel trims you are looking at are a point in time picture for the load you are seeing at that moment. They are corrections needed to keep desired AFR's (called lambda). To get an understanding on how much correction is needed you will add the LTFT and STFT together.. so in this case you are correcting .8% on both banks on the short term based on long term trim of -2.3% for bank 1 and -1.6% on bank 2.

Overall correction would then be -1.5% on bank 1 and -.8% on bank 2 which is perfectly normal. That means its correcting for a small amount of rich condition so its removing fuel. Fuel trims go all over the place depending on temps and weather etc.. and when tuned this gets even more pronounced depending on the methodology used by the tuner. IE.. letting the widebands do the corrections or doing it in the tune.

Fuel pressure is similar as its a point in time reading on your gauge.. the min and max look normal though.

Based on this quick snap I don't see anything glaring, however, a datalog with a device would prove more valuable.

The shudder could be a lot of different issues, alignment, balancing of the wheel, issue with the drive train, etc.. those are hard to diag over the internet :-/

 

[Black Dream]

Thanks for the awesome tutorial on fuel trims.  I had a bit of knowledge about the computer adjusting the mix on the fly but you really filled in the gaps for me.  And I went and had the wheels rebalanced today to start with the basics and lo and behold the vibration is gone, woo hoo!  I just had 2 new tires installed a couple of months ago so I was going to put the rebalance on the back burner and look at other possibilities first.  The vibration started when the new wheels were installed but that was also the same time I had the misfire/smoke issue so I didn't think it would be the tires/wheels out of balance.  Live and learn I guess, all is well with the MKS now and I'm grateful for the help I've gotten here.

 

[StealBlueSHO]

Thanks for the awesome tutorial on fuel trims.  I had a bit of knowledge about the computer adjusting the mix on the fly but you really filled in the gaps for me.  And I went and had the wheels rebalanced today to start with the basics and lo and behold the vibration is gone, woo hoo!  I just had 2 new tires installed a couple of months ago so I was going to put the rebalance on the back burner and look at other possibilities first.  The vibration started when the new wheels were installed but that was also the same time I had the misfire/smoke issue so I didn't think it would be the tires/wheels out of balance.  Live and learn I guess, all is well with the MKS now and I'm grateful for the help I've gotten here.

Fantastic! Always nice when it’s an easy fix, hopefully they didn’t charge you for the rebalance?

 

[Black Dream]

Thanks for the awesome tutorial on fuel trims.  I had a bit of knowledge about the computer adjusting the mix on the fly but you really filled in the gaps for me.  And I went and had the wheels rebalanced today to start with the basics and lo and behold the vibration is gone, woo hoo!  I just had 2 new tires installed a couple of months ago so I was going to put the rebalance on the back burner and look at other possibilities first.  The vibration started when the new wheels were installed but that was also the same time I had the misfire/smoke issue so I didn't think it would be the tires/wheels out of balance.  Live and learn I guess, all is well with the MKS now and I'm grateful for the help I've gotten here.

Fantastic! Always nice when it’s an easy fix, hopefully they didn’t charge you for the rebalance?

Nope, I've used Discount Tire for years and they do free balance and rotation when you buy from them.

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