GodFather

iTrader: (10)

Scenario:
Friday, Installed EU and WB at the same time, ran fine for 5 minutes, saw some numbers on laptop, and noticed A/F is consistently at around 14.67. I didn't start tuning it because I had to leave home for the weekend, there's no time. Turned off the car, left it there for 3 days, came back Monday and cranked, sputters and dies off. Won't crank for about 3 days till I replaced the ignition coil packs and that EU is removed. I am suspecting EU to be problematic at this time. So I took it off and cranked it up no problem without it. EU wont' work with my car at this time, I dont' know what the deal is, but I am going to consult with Greddy when i get the time. (Note, I bought this EU used from a Ebay guy who's used it on a Talon)

Problem:
Put the EU aside (I returned to run the Stock ECU to seek some numbers from A/F). So I am driving the car and looking at the WB numbers. It only fluctuates around 14.50-14.81 range. No matter how I floor my Throttle, it would not see any different number outside that range. It actually constantly stays at 14.64 to 14.67 range at idle and light driving. And when I floor it hard and suddenly, it'll hit 14.61 to 14.55 and come back to 14.67 again. This number puzzles me because I was seeing redlines with this A/F ratio, and that's what worries me the most. How can I see redline with this number? Wouldn't it hurt my car badly?

Assumptions:
I am assuming that my ECU never kicked into WOT for open loop maps. I remember Friday, before i ran the car with EU, I was getting the TPS voltages: 0.13-3.76 volts. This brings me to think that stock ecu never see a need to kick in the open loop fuel maps, thus, A/F never got down to below the 14.5 range. But there's also a saying that at 40%-60% throttle, it'll bring in the open loop operation. I am confused about this. Can anyone input more wisdom on this topic?

Thanks

-Peter-

DandyMax

iTrader: (7)

Okay first off forget about the EU and get the stock ECU scenario figured out first. THen go back to the EU.

3.67 volts is close enough to full WOT that it should definitely get you into the right portion of the fuel map. The VQ is surprisingly tolerant to lean AFRs even up at high rpms, but nevertheless I wouldn't want to do that for long/too many times.

Your AFR's are fine for cruising and driving normally (closed loop) but definitely not at high rpms/WOT.

Do you have any pending codes or CEL's on? Are you still running stock 95 injectors and fuel pump? You may simply not have enough fuel flow/pressure or injector size necessary for your mass airflow rate with the 3.5/cams at WOT. Speaking of, which MAF are you using... stock 3.0?

GodFather

iTrader: (10)

I have a CEL just last week after a 2 hour drive. Came back and pulled the code, it's front left bank heated O2 sensor fault. Then I cleared it and never seen the code again. I know with these O2 sensors when they are bad, it always takes a long drive to finally get the code up. Short trips will never pull that code. (My stock O2's are in their respective locations, none removed. WB O2 is placed on the Cattman Headers right before the cat converter. I am running stock 95 injectors and fuel pump, I'm using 95 MAF, and 3.0 JWT S1 cams, not the 3.5 cams.

So, with this CEL that I cleared, does it really matter so much that the car must have been running on a regular map, or a safe map? But I thought safe map tunes are pig rich to start with. But this constant stoich A/F means that I haven't met open loop, correct?

matty

iTrader: (54)

Im very sceptical about used EU's off of ebay, or even for that fact, the NEW EU's off of ebay. I know another guy from .org that has a NEW EU unit off of ebay and pretty much had the same problem/senerio. Ran fine for a while, then the car just wouldnt start. Cranks cranks cranks, and nothing. He got multiple misfires as well. He took the EU out and the car and runs fine now on the stock ECU.

Your pump might possibly be bad/old...
What injectors are you using ?

-matt

GodFather

iTrader: (10)

Yeah, put the EU aside for now, I'm just trying to figure out why doesn't my car run on a open loop fuel map. This lean A/F really bugs the heck outta me right now.

Stock 95, 4th gen injectors, BTW.

matty

iTrader: (54)

What wideband are you using ?? Possibly needs to be re-calibrated or an open air calibration. Do you have all the settings inside the Wideband Software set correct. ie. fuel type. Wheres your wideband bung located ?

-matt

GodFather

iTrader: (10)

PLX M-300 WB O2, it's self calibrated on every start. I placed it right before the cat converter on the downstream of the Y-pipe section.

DandyMax

iTrader: (7)

Even with an O2 code, at WOT you should be rich not lean, as that's open loop - not closed loop. It might be possible that your O2 sensor needs to be replaced, however for WOT at this point I don't think the ECU is necessarily your problem. I suspect you simply don't have enough fuel flow. Do you have a fuel pressure gauge you could throw on there and test at WOT?

GodFather

iTrader: (10)

Havent' had a chace to install a Fuel pressure guage, yet.

DandyMax

iTrader: (7)

Ok well at this point that's my suggestion... you need to find out whether your fuel system is adequate (injector size, pressure, pump flow all works together etc). I suspect for your setup it's not.

GodFather

iTrader: (10)

alright dude, I'll have to find a good time to install that.

In the mean time, what can be said about my car not doing open loop at all? I mean, I did test idle fuel pressure at 43psi when I first got my swap done. My mechanics tested that for me. WOT settings are just not switching to open loop maps, what gives?

SPiG

iTrader: (7)

I think you might want to put in a Walbro Fuel pump at least for now and maybe even bump up the fuel pressure with an AFPR.

DandyMax

iTrader: (7)

I think your car is in open loop. The ECU is probably acting normally. But if your pump can't supply enough fuel at high rpms you will lean out, and the ECU will have no way of knowing that, since it IS in open loop and not monitoring O2 feedback.

Measuring fuel pressure at idle with the vacuum hose connected/disconnected doesn't tell you if the fuel supply is adequate under WOT at high rpms. It only tells you that the pump can supply enough fuel flow at 43psi for that idle rpm. Under higher rpms, and WOT the fuel flow (volume) requirement is much greater. So you need to drive the car under WOT at high rpms and then see what happens. You will probably see a much lower pressure on the gauge. In other words you've shifted the operating point on the pump curve because of the higher flow rate demanded. But at that lower pressure, you will see a leaning out becuase you're not increasing the injector size, and the ECU is not increasing the pulse width durations. If x ms of PW was adequate previously at xx psi, then now at <xx psi the PW would have to be greater to get the same fuel volume.

For example when I was installing my AFPR, just for fun I set the FP up at 52psi at idle (with full manifold pressure, not vacuum) and went for a rip down a back road at WOT. My pressure dropped to 46psi and that was the max the pump could supply. But that's on my car, a 3.0. Your 3.5 with cams and what not is undoubtedly pumping a lot more air and needs more fuel. At least that's my suspicion at this point...