ok so i have an 04 with aem ems, regular bolt ons (exhaust, intercooler bov etc) evo 9 turbo, stock fuel system except fuel pump...running 26 psi...car was running fine and all of the sudden at wot it would go to almost 13.0 and drop to 11.8 and i would let off...had some boost leaks and i fixed it and now itll go to 12 ish and drop to 11.4 ish...what can it be? car drives fine and gets into boost fine etc no problem...nothing has changed in driveability...i thought maybe tune or fuel pump...my tuner said tunes dont change...the iat compensates for the change in weather etc...i thought fuel pump either works or doesnt...what should i check? where should i start?

 

If those numbers around 12 are the AFR, you're going rich, not lean (more combustible into the mixture, remember the fuel is more expensive than air, so you're being a rich guy, lol)... Anyway, I understand that's not that wrong.

When you're running high boost, you have more air (and hotter) on the combustion chamber, which may lead to knock inside the chamber before the spark plugs go off (highly undesirable). One of the means to avoid that knock is tune the ECU to pump more fuel when achieving high boosts, which is whats happening in your case.

Personally, I'm running numbers very similar to yours, with around 28 psi.

Anyway, what was the AFR before? It was always like this? If you talked to your tuner, I'd think he'd say it was programed to work that way if I was right, so that may not be the point. But it wouldn't hurt for you to ask him again.

 

The higher the number the leaner the lower is richer... you want to target mid 11s under wot

 

the higher the number the leaner the mixture as stated above...running 12 - 13 afr at wot is crazy...my afr at wot would always be 11.2 ish...it was tuned on the rich side and I'm ok with that... It is not normal for it to go leaner on it's own...I did speak to my tuner and he as well agreed it shouldn't be doing this...to him it's a fuel issue of some sort but unless I hook up a fuel gauge to my windshield to check fuel pressure we won't know...my fuel rail is stock so there's no ports for me to do that...I want to know if there's anything else I can do...

 

Check the duty cycle on your injectors. Are they maxed out? If they are above 90% I would upgrade them.

 

what fuel pump are you using? chances are is that it is starting to fail. but it would be easier to diagnose if you have a fuel pressure gauge.

 

I have a walbro 255...I bought the car with it about a year ago...I have in the closet an aem fuel rail and a fuel pressure regulator which I forgot the brand but I can install the fuel rail and it has a fitting to install a gauge on...I can take the gauge from the fpr and put it on the rail to see pressure...what do you guys think?

 

just install the gauge and don't install the adjustable fpr since fpr's will need to get their base pressure set. while you are there check the relays that are beside the abs module one of those relays is for the high voltage for the fp.

 

I will install the fuel rail with the gauge...relay for fp? As in fuel pump right? I figure that if fuel pump relay was out car wouldnt even start...

 

It could be your WB sensor, too. Maybe an exhaust leak before the WB.

 

I thought about this and tried to tighten everything before the wb...the sensor is placed about 2 ft from the o2 housing on the turbo so the only thing before it is that and the gaskets on it are only like 7 mo old or so...let me ask you guys this...I lost the injector o rings that come with the aem fuel rail...can I just go to autozone and buy universal o rings? Can I just reuse the ones on the injectors now?

 

probably no leak then. as long as the exh. mani, O2, etc are all sealed up. does the car read normal during cruise?

you can reuse the o-rings as long as they are still soft and in good shape.

 

yeah all other readings seem normal as always but wot changed...now car was tuned during the cold...tuner said iat sensor should compensate and tune shouldn't change...can maybe iat be bad or something?

 

Honestly, could be lots of things. Just have to work down the list.
If it's cruising at 14.7ish, then prob not the sensor.

 

gotcha I'll get on it...will start by installing fuel rail so I can put a gauge and go from there...thx guys...