Tunning help please

carltalon · 09-22-2005

basic mods
built motor, ported head 272's
PTE SCM61
Fuel: walbro 255 fic 850's aromotive FPR
safc
Maft 3 inch blow through
lightninggsx eprom chip for injector corection etc
better mod list here if you want it http://www.cardomain.com/ride/582719

Ive been running this settup for the whole summer and never had a problem untill about a month ago when I ran out of gas. The wires to my fuel pump melted and I thought I killed the pump. I rewired the pump and reinstalled it.

from then on Ive never been able to get my o2 voltage above .80 volts with around 20 counts of knock. I bought another 255 from Nash and figured that would do the trick. No luck. I have good fuel preshure up to red line and can try to richen it up with the afc all I want with no luck. Ive run my injector pulsewidth over 100% and it still runs lean.

I've already checked
fuel pump
fuel filter
boost leaks
injector conections
clogs in the fuel rail
maft and safc conections and settings

anybody got any other ideas? Any help would be greatly apreciated.

EclipseGST · 09-22-2005

Are your injectors clogged up? I'd see if you could find another O2 sensor to check that. Something doesnt add up. I dont trust the stock O2 sensor and I dont see anywhere in your mod list a wideband. But it is knocking which isnt good. Have you tried running race gas?

carltalon · 09-22-2005

I was thinking dirty injectors too. is there anywhere in the area that can clean and flow test them. I know I really need a wideband but its just not in the budget yet. I've run race gas a few times. The knock goes down but doesnt go away.

EclipseGST · 09-22-2005

I'm not sure on a place close by. You might see if a deisel place could do it. I know there is a place in Rochester that cleans deisel injectors, dont know if they can do regular injectors or not, wouldnt hurt to give them a call.

Edit: I can find a name and number for you tomorrow if you need it.

desolate · 09-22-2005

Even though you said you have good fuel pressure to redline. Have you logged to see if there is any voltage drop at the fuel pump? Voltage drop would be my best guess.

LightningGSX · 09-24-2005

Did you figure this out?

carltalon · 09-24-2005

havent figured it out got any ideas Eric

**Shane@DBPerformance** · 09-24-2005

What exactly does your fuel pressure do? Under WOT you should get base fuel pressure + boost level for a pressure reading and it shouldn't drop at all. If it drops at all and the boost isn't dropping with it, then you have a fuel pump/fuel line/fuel filter problem.

Another possibility is that you are hitting the injector pulse width cap with your 850s and modded ECU. Did Eric take out the cap limit in the EPROM that he made for you?

Also, if it's a 90, then tend to get lower O2 readings than the 91-94 cars for some reason. But if it read higher before and it's knocking then it's probably not just that.

What gas and how boost are you running?

carltalon · 09-24-2005

The fuel pressure is doing exsactly what you said. It is rising with the boost and never drops off. I dont know if Eric took out the cap on the ecu I know we talked about it when we did the chip. But he might have forgot. Ive been running holiday 93 or BP 92 with 20-22 psi I have a little boost creep.

LightningGSX · 09-25-2005

I save the code for every chip I burn, and I just checked, the PW cap is gone.

Did you replace all of the fuel pump wiring? It's not very likely, but maybe the contacts on the relay are damaged from the excessive current of running the pump dry.

**Shane@DBPerformance** · 09-25-2005

If the fuel pressure isn't dropping, then it shouldn't be fuel pump related.

LightningGSX · 09-25-2005

Quote:

Originally Posted by ecoli

If the fuel pressure isn't dropping, then it shouldn't be fuel pump related.

I agree, but I doesn't seem like this happening after he over heated the pump/melted wiring is coincidence.I always check the obvious whether it makes sense or not.