Ok guys , i need to know what you guys know about fuel trims. My car is running way lean and i cant figure it out . All my fuel trims ( no matter if at idle or WOT ) are well over 100%. I have a walbro pump and the rest is stock. ALthough i do have a new fuel filter. I have switched the injectors twice now and that did nothing. The O2-R reading fluctuates between .3 to .9 all the time.

I just need some of your ideas since im not very educated on the hole tuning part yet. So just gimme some info on things to check. Oh, and ive also changed the FPR a few times also, my brother has my aeromotive on his car but i will get it back very soon.

thanks

Natedogg and NCGalant will be your best bet for explaining fuel trims from my experience.

If your O2s are cycling like they should then your O2 trim is able to pick up the slack. Are you having problems at WOT? What are you using to tune? I was thinking a SAFC but couldn't remember.

What exactly are your trim numbers? If you're injectors are stock your FPR is stock and you are running a Walbro 255 then you need to get an AFPR and bring the fuel pressure back down to stock levels. That should take care of your problem.

so if im running a stock fpr and injectors the walbro pump will cause it to run lean? I thought that it would make it run rich as hell and its definetly not that case.

Also, im not using the AFCII anymore. So i guess im not actually tuning my car but making sure everything is in decent runing order.

Most of the time, the trims are as follows:
FTRL-120% on average
FTRM-110% on average
FTRH-111% on average
FTO2-100/103% at idle then anywhere from 143-54.6% while driving

the O2-R:
at idle its usually between 0.65-0.85 then veries from 0.00 al the way to 0.00-0.75

the INJD:
usually around 1.5% but has peaked at 14% during driving conditions

Fuel trims will run anywhere from 80-139%. The O2 trim does something like 30-170%. You are not maxed out on any of your trims. I'd call all of your numbers you just mentioned good. Sounds like your part throttle is all within normal specs.

I still suggest an AFPR with the Walbro at some point. Missed the 'over' part in your original email. Reading too quickly...my bad.

I agree. Running an aftermarket AFPR is very nice with a walbro 255. You are right that it should be causing you to be rich, at idle. Is your MAF hacked at all?

i am getting my AFPR back from my brother this weekend. My Maf is completely stock.

If you want to adjust your trims back to close to stock you need to turn the MAF adjustment screw.

-Take the MAF lose of the air filter canister
-On the bottom side you will see a big round spot that is probably filled with RTV
-Scrape off the RTV
-Turn the screw IN one full turn. This will block off some of the unmetered air and get your fuel trims closer to 100%
-Check your trims to see where they end up after you have completed this and a brief drive

ok, thanks! will do and let you know what happens.