3800 Uber lean?

[thebullfrog]

Okay. Need some advice. I'll preface this by saying that will definately be installing a new fuel filter ASAP. Now to the nity gritty. KR of over 8 Yeah. Sometimes I'll do a pull with as low as 3.5 lol. But seeing 5's or once almost 9 isn't unusual. At WOT my LTFT will sometimes read as high as +8. It generally won't go below 4 or 5 in a hard pull. As I understand a high + number means I'm way lean correct? I have a strong suspicion that my fuel filter is the primary culprit, but any other ideas if that doesn't do it? Those numbers scare me.

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[Xtant12]

Well I do know if you dont have headers that makes a difference, also the plugs you use also help.. When I got my car tuned the guy dd something with my fuel levels that brought the KR down to balance out with out headers.. ( And Alkey ) when I dropped to the 3.4 pulley I know I scanned cuz Mikes3 always told me to and I was at 6 or 8 of KR... I heard that was normal but thats why headers and exhaust were so important.. You might want to talk to Ron and see what he says, maybe he can help get your KR down...

 

[thebullfrog]

Well, like I said the fuel filter is first. I know it's shot. I'm pretty sure it's the original at 87k miles. The fuel pump is whining really bad trying to pump through it. Like I said my LTFT that should be around 0.0 or slightly negative is way way positive, so it's clearly lean. Scary. In fact now that I put the 2 together, I'm wondering if the vibration in my other thread is really a vibration at all, and not just the engine struggling at higher loads.....

 

[PANDA]

What are your mods?

 

[thebullfrog]

Bone stock. Well, a gutted intake, but beyond that- bone stock. I just ran some logs. On the one full pull I was able to do I got a peaks KR of 5.44 and my LTFT was glued at 10.9. Though I think the LTFT is wrong because it said that for all my runs even though I know it wasn't that high. Though with what I was seeing before, that isn't really out of the question since just looking out the corner of my eye I was seeing 8 plus.
Tried changing the fuel filter today. It's not original (NAPA) but it has been on long enough that it told me to go fuck myself when I tried to detatch the fuel line. Completely rounded it. Dandy. I'll have my mech. cut it off and splice in new line when I have him figure out and fix the vibration. It's definately drivetrain related somewhere.

 

[imported_Ron Vogel]

Unless you have a baseline of your actual AFR, LTFT's won't tell you if it is actually lean or not. It will tell you that the PCM is either adding or subrating fuel. If you can get your front O2 sensor voltage it would be very helpful. If you haven't already, just do basic maintanance...02 sensor, fuel filter, air filter, spark plugs, new oil and see where you are at.

 

[thebullfrog]

Plugs/ wires and oil change are fresh. Air filter too. Fuel filter, like I said, working on that lol. I'll try and make another run tonight, logging the voltage as well.

 

[thebullfrog]

Did a couple more runs. Heres the important bits: The KR will usually stay around 2.5 - 3.5 until I hit about 5100 RPM going just over 80MPH. Then it jumps into the high 5's. On these last runs the LTFT was at 11.7 with the o2 voltage at .905. When I hit 3rd gear the KR stayed in the high 4's. The voltage dipped to .895 and I hit my highest KR of 5.9 at around 3900 where I let off. Throughout the entire run the o2 never went above .935 and the LTFT stayed at 11.7. The results were pretty consistant through all my runs. Never had the real estate to do any 3rd gear runs.

 

[Turbocharged400sbc]

i'd bet that the filter is the issue your probably loosing fuel pressure as fuel demand goes up...a fuel pressure gauge would confirm this... change the filter and scan for TCC lockup during the shudder before you go looking at too many other things...

 

[thebullfrog]

I don't have anything (or access to) a scantool to check for TC lockup, but I'm really suspecting the filter.

 

[Turbocharged400sbc]

when you have your mech do the filter and line take him to lunch with a mt2500 hitched up and look at the TCC enable/disabled PID and try to get the car to shudder



most mech will do this for food

 

[thebullfrog]

lol.
I'll talk to him about it. And I wouldn't have to "try" and get the car to shudder. All I have to do is drive it.

 

[Turbocharged400sbc]

good luck.... let us know what you/him find