Code 59 and AFR issues

[68steiny]

Hey guys,
I picked up a 91 Sy that is pretty much stock with a 3" exhaust and no cat, other than that it is stock. I removed the solenoid and went to a Forge Motorsports wastegate setup. I also changed out the ignition parts to verify no problem there.

Mods:
3" exhaust no cat
EGR delete
AC delete
3 bar map
Stock Code 59
Zeitronix ZT2 setup with WB


Anyway, I uploaded the stock Code 59 bin and the truck actually starts a lot better but starts with an AFR of 14 and drops to 10.0 and just sits there idling. Vacuum holds at -20. I pulled logs and when I put boost to it the AFR leans out to 21! Scary..of course it knocks and cuts out. The one thing I did notice is that the fuel pressure is very volatile and gets much larger swings...I see readings as low as 18 under boost.

Any input on this would be great...new fuel filter and AFPR are on order. I pulled the boost from the FPR and it is still very volatile.

I believe it is the fuel system that is the issue, but any other input on things to check would be great....it's just that the drop to 10 AFR at idle is strange to me.

Thanks!

Jon

 

[dgoodhue]

Re: Code 59 and AFR issues

If your fuel pressure is 18psi under boost you need a new fuel pump.

 

[Throws]

Re: Code 59 and AFR issues

If your fuel pressure is 18psi under boost you need a new fuel pump.

X2. A single Walbro is considered the bare minimum for fueling upgrades when you're going for more power.

-P

 

[68steiny]

Re: Code 59 and AFR issues

Got it, thanks. I have the pump already...guess the bed is coming off!

Any explanation for the drop in AFR at idle? Maybe the computer is adjusting for the volatile FP readings?

Thanks,

Jon

 

[dgoodhue]

Re: Code 59 and AFR issues

You often have to adjust the idle afr by either fuel pressure or through code 59. Install a new fuel pump first.

 

[68steiny]

Re: Code 59 and AFR issues

Will do, thank you.