VQ35deMax

iTrader: (6)

This is not the typical stupid question that all the newbs have.

Utec is installed on a turbocharged vehicle. Map sensor is also installed. Car has 600cc dw injectors and an adj. fpr with a return fuel system. Base fuel pressure set to 50 psi. Maf sensor is in a 3 inch housing. Utec also has the latest firmware flashed.

Base map that is uploaded to the utec is from TurboXS is the APS 550cc map as well as the parameters. With the values unchanged in the 0% column the vehicle starts right up and idles. According to my wideband a/f ratio reads a consistent 11.1 which is rich.

Now the problem arrises with the 0% column. No matter how much more fuel is subtracted it has no effect on the a/f ratio at idle. If you input a new value all the way across the board, save the changes, the idle bumps down and then back up and the a/f returns back to 11.1. If too much fuel is subtracted, the car dies and has a hard time starting back up. MIL comes on for p300 (multiple cylinder misfire). If the code is cleared, add a little more fuel onto the map and the car starts back up again and returns to the same a/f ratio.

Also Dave bumped to base idle to 900 rpm and that made the car idle a little better but with the same a/f ratio. He tried to lower the base fuel pressure as well and that had little effect as well.

Any ideas what is causing this issue? I had the car towed to Function Tuned and Dave had this issue. I never tried to get the a/f at idle to a normal value while the car was in my garage due to the reason that it was getting tuned anyway. But Dave spent a couple of hours on the car and at the end of the day I ended up leaving with the vehicle in the same state as I got it there.

thanks...

mx594

iTrader: (4)

This might be a silly question, but are you positive that the map selector switch is on the same position as the map which you are making changes to? In other words, if you are working on map #1, make sure the switch is set to #1. It also shows which position the switch is on if you look at the UTEC dashboard.

Other than that, your 0% column should be somewhere between -10 and -20 throughout. Even if you just get it close, the stock computer's A/F compensations should get it close to 14.7.

VQ35deMax

iTrader: (6)

I am pretty sure that I have the map switch on the utec set to the same map slot. But I will verify that to be sure.

Other suggestions welcomed...

athenG

iTrader: (2)

So what value are you putting on the 0% column? did you try to reset the ECU before you made the changes? I find disconnecting the battery for 10 mins better than doing the pedal reset.

djamps

iTrader: (1)

Problem goes away when you remove the UTEC or not?

Is your factory ECU recalibrate for the new MAF housing?

Try puttin OEM MAF housing back in and try again.

VQ35deMax

iTrader: (6)

I have Not tried to reset the ecu. However the values that are in the 0% column are -15 all the way down. I'll take a snap shot of the screen.

Could it be a maf issue because after a certain point the car would enter limp mode and not rev past 2400rpm.

VQ35deMax

iTrader: (6)

I have not tried setting the map switch to 0 to see what happens.

By calibrating do you mean doing the Idle relearn position?

that is my next step is to install the maf back into the original housing to see what happens.

mx594

iTrader: (4)

It sounds like the changes aren't taking effect until the car is restarted (and the UTEC is re-booted). If I recall, every time I saved changes on my UTEC the engine would die and I would have to re-start it. In the process of doing so I would turn the key off and then back on so the UTEC would re-boot. Maybe try that?

It's also possible that your wideband is giving false readings. What type of wideband are you using?

mx594

iTrader: (4)

Didn't see the part about the 3" MAF housing. I would agree with everyone else - put the stock MAF housing back in.

djamps

iTrader: (1)

No by calibrate I mean you have to reflash the stock ECU for the new MAF profile...unless you plan on doing uprev tune (instead of UTEC) I would recommend leaving the stock maf and housing in there.

VQ35deMax

iTrader: (6)

Seems like everybody is suggesting to put the stock maf housing back in. Guess I will do that first and see what happens then.

BTW my wideband is dead accurate with the device that was used to measure the a/f on the dyno.

And the stock ecu was not reflashed in any form. I assumed that it would be able to compensate for the added difference in diameter (2.70 inches stock vs 3.0 inches) for the airflow.

qqqqball

iTrader: (10)

i had a similar problem, i had a/f 10.6 constant, turned out to be a bad maf wire, got shorted out, if you have MAF CEL thats the case. Otherwise a vacuum leak post MAF is suspect

djamps

iTrader: (1)

The larger MAF housing probably wouldn't cause a rich condition though, the more I think out it I think it would actually push things more lean....gotta be something else, check wiring, CEL, ect.

athenG

iTrader: (2)

if your idle rpm is low or below 1K then yes the car will die when you save in Utec. One quick work around is just press the gas pedal a little and hold your RPM to about 1rpm and the car should not die. I think as long as your RPM is below 1600rpm then you'll be able to save your changes.

athenG

iTrader: (2)

keep it simple.. put back the stock MAF housing and troubleshoot from there. Once fully warmed up the car should be in close loop so the 02 sensor should correct it. Since he has a big injector, the ECU is probably going crazy trying to correct it.

VQ35deMax

iTrader: (6)

That was the impression I was under. I will check my wiring. However like I stated the dashboard does show the iat and the maf voltage.
And there is no cel until the car gets in normal operating temp. After that the car enters limp mode and wont rev past 2400rpm. As soon as the p300 code is cleared, the car runs fine but still rich.
You are correct. The primary o2 sensors are reading rich.

VQ35deMax

iTrader: (6)

Before putting in the stock maf housing I decided to give the 0% column some adjustments. So I imputed -19 all the way down. A/f stayed at 10.9-11.1. Car ran and then shut off. I started it up and the code for IAT sensor came on.

mx594

iTrader: (4)

IAT sensor? Maybe your MAF is busted and the IAT is reading lower than actual and causing the computer to dump in extra fuel?

VQ35deMax

iTrader: (6)

Looking through the fsm, this is what I found

“Short term fuel trim” is the short-term fuel compensation used to maintain the mixture ratio at its theoretical value. The signal from heated oxygen sensor 1 indicates whether the mixture ratio is RICH or LEAN compared to the theoretical value. The signal then triggers a reduction in fuel volume if the mixture ratio is rich, and an increase in fuel volume if it is lean.

So technically it also can be the primary o2 sensors besides the maf?
I have a spare maf that I will use today to see if that does the trick.

mx594

iTrader: (4)

The fact that you threw a code for the IAT sensor is what leads me to believe that it is the MAF. The IAT sensor is built into the MAF. Be careful when handling the MAF, and only use special MAF cleaner if you are going to clean it.