New chip very lean

[98sst]

I just installed 60# injectors, 255lph fuel pump, 3-bar MAP, adjustable fuel pressure regulator, and 91 octane TT chip set up for the mods on my ‘93 Ty. I also have an AEM wideband that I installed prior to these modifications which would read fairly normal numbers.

After the modifications, the truck is starting at about 14.7 and then immediately shoots up off the charts lean. I know that it needs to learn the chip, so I stayed out of boost and drove slowly around town for about 15-20 minutes and then let it idle another 20. At no point did I get an AFR reading- it stayed completely leaned out.

I don’t have my wideband connected to F14 yet but plan on doing so. I turned up my idle fuel to max on the chip and still did not get a reading.

Any ideas as to what is going on?

 

[EricM]

You still have the stock O2 sensor installed? What does it read at idle?

 

[98sst]

You still have the stock O2 sensor installed? What does it read at idle?

I do. Letting it idle last night I saw 899-903.

 

[EricM]

Ok, so your stock O2 shows its on the rich side. I would suspect the wideband reading is wrong. Maybe a bad sensor?

 

[98sst]

Ok, so your stock O2 shows its on the rich side. I would suspect the wideband reading is wrong. Maybe a bad sensor?

Weird, Ok. For reference, assuming it’s a bad sensor, what should I be looking for on the stock O2 in the interim?
Thanks!

 

[EricM]

Once warmed up, it will switch to closed loop, and the stock O2 will normal cycle up and down from .000 to .900. You will see this during idle, and cruising around. Once you get up into boost, it will stop cycling and read up around .900 or so.
If it's stuck around .900 at idle, and in closed loop, then its possible the BLM (fuel trim) is bottomed out because it's rich and the computer tried to pull fuel, but it hit the limit. I normally set the lower limit to 118. It will be "bL" on the scanmaster. If you increased the idle fuel dial to max, then it could be so rich that the BLM bottomed out.

 

[98sst]

Once warmed up, it will switch to closed loop, and the stock O2 will normal cycle up and down from .000 to .900. You will see this during idle, and cruising around. Once you get up into boost, it will stop cycling and read up around .900 or so.
If it's stuck around .900 at idle, and in closed loop, then its possible the BLM (fuel trim) is bottomed out because it's rich and the computer tried to pull fuel, but it hit the limit. I normally set the lower limit to 118. It will be "bL" on the scanmaster. If you increased the idle fuel dial to max, then it could be so rich that the BLM bottomed out.

I replaced my wideband and it eventually went completely lean, which leads me to believe we are actually lean.

My IACV counts are floating around pretty high. I don't know if that has anything to do with it or not. I was really hoping it was just a defective sensor!

 

[EricM]

Your stock O2 reads full rich, and the wideband is full lean, so one of them is wrong. We need to figure that out first.

The ECM bases the fueling on the stock O2. If it see's rich, its likely pulling out a bunch of fuel. What is your BLM at idle?

Is the stock O2 in the stock location, and the wiring has not been altered?
Where is the wideband sensor located? Are there any exhaust leaks near the sensor, or any cut-out?

 

[EricM]

I suppose the stock O2 could be bad, but I don’t typically see them go bad reading rich, but you never know.

 

[98sst]

The BLM shows 120 currently, showed 118 the other night completely warm.

I’m assuming the stock location is just after the turbo. If that’s the case, the stock O2 is there and the wiring is connected.

The wideband is about 18 inches down from the stock O2. No exhaust leaks.

Everything read normal until the injectors, 3-bar, AFPR and new chip were installed. All parts were brand new as well. Mind you, “normal” was relative. I did these modifications to be able to add fuel as needed as I’ve been chasing some knock issues.

if I haven’t said it prior, I’m noticing that it’s stumbling at the first press of the throttle coming off idle. It didn’t do that before the new modifications.

 

[EricM]

Unfortunately I don't know why you are seeing full lean on your wideband. In general, an engine won't even run if its that lean.

I would say for now, lets tune using the stock O2 reading, which says it's rich.

You say the IAC is on the high side. If the IAC is high, then the throttle blade needs to be open a little. Turn the throttle stop screw clockwise, say 1/2 turn, then start the engine and drive around a bit. We are shooting for around 25-35, warmed up, in park. The more you open the throttle blade, the more the IAC will drop.

Once you get it into the 25-35 range, then lets see where the idle BLM ends up.

 

[98sst]

Rec

Unfortunately I don't know why you are seeing full lean on your wideband. In general, an engine won't even run if its that lean.

I would say for now, lets tune using the stock O2 reading, which says it's rich.

You say the IAC is on the high side. If the IAC is high, then the throttle blade needs to be open a little. Turn the throttle stop screw clockwise, say 1/2 turn, then start the engine and drive around a bit. We are shooting for around 25-35, warmed up, in park. The more you open the throttle blade, the more the IAC will drop.

Once you get it into the 25-35 range, then lets see where the idle BLM ends

Received, thanks for the continued help Eric. I’ll advise when I get around to it in the coming days.