Running Lean - stumped as to why

[CrUZida]

Car runs about 16:1 cruising on the freeway. This isn't normal is it ? Didn't think so.

Things to note.

• Stock standard Celsior ecu/loom/injectors/afm/etc.
• Fuel pressure has been tested at 60psi!! (in both the rails and pre-rail)
• Everything in the fuel system (except the pump) has been replaced with known components, no difference
• Pump flowed well over 300L/hr at 10.5V
• Injectors were cleaned a couple of years ago, used for a few months, and then put on the shelf.
• A second set of injectors were tried, no different.
• Voltage at pump is 13.5:1
• A tuned Delco ecu/loom/map/etc was on previously, had the same problem, was hoping stock ecu/etc would solve the problem, unfortunately not.
• 99% confident there are no leaks after the AFM

So yeah, if anyone has any idea's, I'm all ears.

How can the fuel pressure be 18psi higher than stock (making the 215cc injectors closer to 260cc) and still be running lean ?

[fixeruperer]

air, coolant, o2 or afm sensor ?

[Duk]

Where is the EGO sensor placed?
If it's at the tail pipe that is farely large, the sensor can give a false lean reading during low(ish) exhaust gas flow.
Another thing to consider is the condition of the sensor.

[oldcorollas]

i'd suggest O2 sensor also.. if it has crud on it or is dying, then it will give lower voltage... i forget if lower voltage is rich or lean tho

check itS' voltage during cruise tho. it should flich back and forth around 0.5V (0.2-0.8?) if it is working with the ECU correctly (every few seconds)

[woggin]

ecu ticking over to cruise mode, i know some soarers can run as high as 17:1 in cruise/lean mode, its used as an economical thing.....but thats just wat i have heard/read!

ecu's run off open loop and closed loop dont forget!!!

wog

[thechuckster]

What fuel pressure do you get with motor running at idle?

what is sensor? A proper wideband item or one of them accurate narrow-band bosch items? And is sensor data from ECU or another device?

Can you disconnect the O2 sensor to the ECU (so you can confirm that open loop is safe) and then re-connect (to go closed loop) and monitor these via a separate sensor?

[abently]

Having an oversized fuel Pump increases Fuel pressure.

But if the AFR at part and full loads are nice throughout the rev range, then just leave it as it is ?

[CrUZida]

The o2 sensor I'm using is a TechEdge 2J1 (bosch wideband)
Its placed about ~1m from the last port, horizontally (under drivers ass).
Sensor/Kit is brand new, and has done about 5-10hrs use.
Also the floor under pedals is almost too hot to touch, so I'm confident its correct in saying its lean.

60psi at idle, untested while driving.
I've never seen the AFR drop below ~13.5 which is unheard of for a stock toyota tune. It should be dropped well below 12 under WOT according to most dyno graphs I've seen.
I also want to replace the pump with a Walbro or so, which should reduce the pressure back to the normal 42psi (which at the moment would obviously make it even leaner).

It is NOT any sensor on the engine as the ecu's I've tried require different sensors.

Factory narrowband o2 sensors are working fine as after an ecu reset the AFR's under cruise are closer to 17:1, but after 20km's of cruising the ecu riches it up to it limit, which is when we get 16:1.

[CrUZida]

Also, I'm thinking its more mechanical than electrical at the moment, but I have no idea how or why.

I plan to reinstall the fuel pressure gauge in one of the rails and retest on a drive. Pity its such a pain in the ass to install the gauge (I need to change the rail out for one thats been customised to take the gauge).

[JustCallMeOrlando]

Random thing here from my own poor experience with my TechEdge gear. Is it a) calibrated and is it b) reading correctly? My car rear 14.5:1 on cruise but was more like 9.5:1 in reality.

[Duk]

A tuned Delco ecu/loom/map/etc was on previously, had the same problem, was hoping stock ecu/etc would solve the problem, unfortunately not.

This is really odd.
Double check all the minor things, TPS is set correctly, base ignition timing. Again proably not actually going to cause this problem but it eliminates variables.
Double check power to the injectors. What is the required voltage for the injectors and is it getting it consistntly (no voltage drop because of high current drain or bad wiring)?
After that, the only thing that I can think of would be checking the cam timing, but I can't see how it would make the engine run lean if it was incorrct.
Maybe a compression test to eliminate riding valves (valves that aren't closing)......now I am clutching at straws

[ed]

take it for a quick dyno session, and get a second opinion

[CrUZida]

Everything is spot on (cam timing/tps/injector voltage/etc etc etc etc etc etc). This I can verify 1000%.

The wbo2 was not a kit, was purchased complete. I followed the auto calibration instructions properly the first time I turned it on.

The fact the exhaust is hot enough to cook my feet on the other side of the firewall suggest the wbo2 reading is roughly correct.

Also when the pump was only getting 11.5V the AFR was 19.0:1 and was running lean enough to burn your eyes.

Dyno is a woftam, all they'll do is verify something I already know.
Considering taking it to an EFI specialist who will at least attempt to find the source of the problem.

[Duk]

Have you checked the steel fuel lines, especially the delivery, for damage or some other mysterious blockage?
Could the fuel be getting airated from a cavitating pump or a blocked pump inlet? I know you said you have megga fuel pressure at idle, but the fuel isn't getting used as quicly as it would be when driving.
Fuel getting heated some how?

[oldcorollas]

if it is missing at all, then it will read lean also