I just rebuild my t2 and I'm running into the little run issues that come with it. the car is running very lean at idle and it gets worse when driving. I replaced the fuel filter, the injectors, the pulges and reset the timing. the only thing that i would this it to be is the fuel pump but i can hear it when the car starts. at this point im stumped if u have any ideas let me know. thank you

 

how do you know your running lean

 

i put on a aem yband

 

First off, do you have an air pump hooked up? If so, it will make your AFR readings far leaner than they actually are.

If not, tee a pressure gauge into your fuel feed line and measure fuel pressure. At idle it should be around 30 psi, with the vac line removed from the FPR or FPR solenoid ~40 psi, and then increase by 1 psi per lb. of pressure applied (bike pump works).

If this is an S4 TII, are you able to richen up the idle mixture with the variable resistor? Turn it towards "R" and check the AFRs.

List out exactly what you're running too. What fuel pump, FPR, injectors, fuel controller, ECU, boost levels?

 

as of right now everything on the car is stock. the thing that worries me is that the car is running 15.1+ air fuel at idle and it only gets worse.

 

The airpump dumps air into the exhaust ports during idle. It should show very lean.

Under cruise it will lean out even more.

 

i dont have a airpump on the car and i am running an aftermarket exhust which i forgot to say before.

 

its probably an air leak

 

The car would not idle with an afr of 15.1+. Check the wideband.

 

The numbers are too high to be right. Check for exhaust leaks before the sensor. If your exhaust manifold to turbo gasket or turbo to downpipe gaskets are used, they have a good chance of leaking.

 

Ive pressure tested the motor and pulged all the leaks. the only reason y i think the wide-band is right is because i pulgged it in and was idleing at 16.1ish then i changed the fuel filter and it went down to 15.1 but when the car comes into boost it pegs over 17.1 afr and it will hold boost for a few seconds then backfire and lose all power. after that coming back to idle its rough and will usually stall. if i let it sit for a few seconds and then start it, it comes right back to life and idles with a afr of 15ish again.

 

do u have a fuel cut defender?
if not that might be why it dies at 17psi

did u buy the afr gauge used?
i know that the AEM wideband o2 sensor has a adjuster on the back of the gauge, might have been messed with

 

the AEM wideband is a piece of ****

 

I still maintain that the gauge is wrong. The engine will run very rough if you try to make it idle with anything above about a 14 AFR. But what you wrote ^ sounds like you're hitting fuel cut, which will produce a very lean reading on the gauge anyhow. You said you have an aftermarket exhaust, so what exactly does that include? Turbo-back or cat-back only? If the precat and cat have been removed, you're guaranteed to overboost and hit fuel cut, if the wastegate is stock.

 

I just changed the fuel pump and it was the problem. the gauge is working because now it is reading 12 to 13 afr when in boost.

 

glad it was just the fuel pump

 

12:1 is fine until about 4-5 PSI. 13:1 is way too lean.

 

I put in a walbro 255 and now when im in boost its at 10-11 air fuel. 13 is at the point when the motor will start to detonate.