Weird fuel trims

[matt98eclipse]

My datalogger reads 81.2 % for the low so i lean it out as much as possible to were it shows only .06 volts on the datalogger and it wont even read on my narrowband its so lean and my fuel trims only move up to around 90.4 % .

What would cause this issue?

 

[spyderturbo007]

Normally, fuel trims will max low when the front O2 sensor dies. When it fails, it reports a false rich condition to the ECU. In an attempt to correct the problem, the ECU begins to pull fuel which results in low trims.

I'm guessing the 0.06v is what you're seeing on the datalogger for the front O2 sensor? Also, you should have a P0170 CEL for a fuel trim malfunction.

 

[matt98eclipse]

The O2 sensor is almost new it has probly only 200 miles on it. The 0.06 volts is what i was seeing on the datalogger when i leaned it out that much i didnt see any check engine light.

When i do a boost leak i get a good amount of air leaking into my crankcase due to i have a leaking head gasket.

 

[matt98eclipse]

Anyone have any idea's? I really need help with this guys.

 

[1gDSM4g63]

Anyone have any idea's? I really need help with this guys.

Is this based on what just datalogger says or do you feel a mechanical problem when you drive the car.

 

[matt98eclipse]

The car pulls hard and feels great. The reason i was checking it is cus i have to go to emission. I was trying to get the low fuel trim as close as possible. Its wierd cus at idle i can get my o2 volts to bounce like crazy and doesnt smell to lean or to rich but for some reason the datalogger shows extremely rich for some reason.

 

[->PrOjEcTGS<-]

Did you reset your battery once you put that new O2 sensor in? That will reset your fuel trims. Then any adjustments it makes from there you can tune accordingly.

 

[matt98eclipse]

I have tried resesting my battery but i shouldnt need to thanks to the stage 3 keydiver chip.

 

[->PrOjEcTGS<-]

I don't believe the chip has anything to do with resetting your fuel trims. Correct me if I am wrong but I think it only resets your octane values stored in the ECU at every start. Tell me this... When you do reset your ecu, do all of your fuel trims go back to 100%? Don't even start it up. Just connect your logger turn the key on so the ECU will turn on and log your fuel trims. If you just reset your battery they should be @ 100%. BTW, leave it disconnected for about 10-15 minutes.

 

[matt98eclipse]

Every time i start the car up the fuel trims change right back to 100% then the low changes slowly down to around 81 to 82%.

 

[matt98eclipse]

The octane value is what resets the ecu everytime on startup.

 

[50trimmed1g]

What size injectors. Are you running a 255 walbro. If so do you have a afpr? Maybe no matter how much airflow correction you are performing it still isn't able to lean out you fuel trims enough? Just a guess.

 

[matt98eclipse]

I have PTE 680's with a walbro 255 and i do have a afpr. Jeff set the chip up to run 43.5 base fuel pressure. Thats what i have it set at.

 

[srumel]

The only two things that I can think of are either A) a faulty fuel pressure gauge or B) i'm fairly certain that the TPS and the throttle stop switch can have an effect on fuel trims, make sure both of those are adjusted properly.

Are the other two trims giving you problems also?

 

[matt98eclipse]

If i had a faulty afpr should try and lower the fuel pressure and see what happens. I also have a brand new tps sensor. Were is the throttle stop switch located?

 

[->PrOjEcTGS<-]

Did you adjust your TPS when you installed it to read 10%? I reread your oringinal post and saw you have a leaky head gasket. Why don't you replace that first and then try to tune it? Fix the known problems first, then go from there. It's not hard, I'm sure you've done one before? Have you done a compression test?

 

[matt98eclipse]

Yea i have a compression test. Right now my tps showes 7.6 % so i do need to adjust it to around 10%. Do you think its possible this problems related to my leaking head gasket issue im haveing?

 

[->PrOjEcTGS<-]

Yes. get your tps to read 10% with the throttle fully closed. See if that fixes it. And yes, your problem could be related to the head gasket also. You never want a head gasket to leak.

 

[srumel]

The throttle stop switch is located on the back of the throttle body. When the throttle plate is fully closed, the lever arm of the throttle plate will make contact with the switch which lets the computer know that the engine is idling, or to cut the injectors upon deceleration. The connector should show continuity when the throttle plate is closed, if not the throttle cable could be binding/ not properly adjusted, or the switch itself may need to be adjusted (this is done with a 14mm wrench.)

I wasn't trying to say that the AFPR itself is faulty, just that the gauge may be.

And are you sure that the boost leak issue is the headgasket and not the valve stem seals, pcv valve, or turbo oil seals?