camaross

Hello everyone,

I have had this problem lately where my 4runner is getting horriable gas mileage. like 8 mpg range.

i know i have larger tires, and stock gears, but im running 32" AT's so i should still see 12-15ish mpg instead of 8mpg

i noticed yesterday that my o2 sensor wires were touching the exhaust, so i repaired them and zip tied them to no longer touch again after fixing them.

i watched the MV on the o2 connector on the diagnostics port. i was seeing from 300-700mv on the multi meter, which should indicate the sensor is working. i am use to working with odb2 cars and the o2' are fast.

the o2 on my 4runner is very slow at shifting and does not jump up and down quickly.....

but ussualy when a o2 sensor is failing they will be stuck at a mv range, past sensors i had were 100-200mv range at proper idle which is due to a faulty sensor.

so i have basicly ruled out my o2

so now i am questioning the Cold start Injector.
i disconnected it yesterday and the 4runner ran decent and didnt smell like raw fuel.

then connected it this morning because the tail pipe was very hot, and sure enough it ran way more rich again and burnt a ton of fuel in a short drive.

is it safe to run like this for spring summer and fall? (not winter)

i also noticed that the exhaust tail pipe is hot enough to burn your hand when its touched after driving... but the colant temp shows right in the middle so it does not look like its overheating.

Thanks

Jay351

Its perfectly normal for the exhaust pipe to get hot....

My cold start injector is sticking aswell. Pull it out and clean all the gunk out of it

abecedarian

On the yota's the O2 is only used to signal rich or lean, not how far rich or lean. The ECU alternates between slightly rich and slightly lean, hopefully. When the O2 says "lean" the ECU starts to richen the mix until the O2 says rich, then the ECU leans the mix until the O2 reads lean. Given that, and that the O2 is a narrow-band sensor... mV readings are mostly meaningless. You'd be more interested in finding out what the ECU's trim is (where it spends more time- rich or lean).

But... if having the electrical plug connected to the cold start valve is affecting mileage, something is wrong. You could point the finger at the cold start injector time switch since it should not be turning the injector on above somewhere around 60-65F. But then again, it should not have any voltage when the key is in the 'run' position- it only should have voltage when cranking... meaning that even if the switch is defective, it shouldn't turn the injector on if the engine is running.

JDMSLIK

I was gonna respond a few hours ago but had a feeling Abe would show up.

I've never been a fan of repairing o2 sensor wires. I'd hafta to go over some old notes to find out what the exact values are but connectors and even straight sauter (soder?) deliver un-accounted for resistance.
Higher resistance in an o2 wire would produce a lower voltage signal to the ecu, lean. Like Abe said fuel trim patterns or a min/max function on your meter would be more accurate.
For the injector, check if your getting voltage. Weird things happen. If it needs to be cleaned unplugging it shouldn't make a difference.

abecedarian

anyhow...
here's something that might help-
http://www.well.com/user/mosk/Vfsignal.htm

JDMSLIK

Good one...I didn't think we had access to that outside the dealership. Probably applies to the 3vze too eh.
I briefly looked at teh diagram and saw a Vf on a check connector. Where do you put the leads?

camaross

Thanks for some further info, i will look further into this later today.

I found this morning that it will not start without the cold start injector.

hooked it back up, and it started fine, im going to check the voltage on the leads when in the run position, and when the motor is warm to make sure im not seeing any voltage on the cold start injector leads.

as far as the o2 sensor being a narrow band i was aware of how that works since i have been tuning my ls1 which runs factory narrow bands, but i have aftermarket widebands installed as well for getting the tuning just right as a narrow band is virtually uesless.

its like a switch. lean, rich, lean....

i also noticed im getting a diagnostics code of IIIII-II
which translates to knock sensor error. could this be due to some false knock from carbon build up from running rich? or is my power / mileage problem now more related to the PCM pulling timing from knock (or false knock).

JDMSLIK

Which motor do you have?

camaross

im sure you can guess... the 3.Slow

i would rather have a 22re.

my old 22r runs nicer thant the 3.slow

JDMSLIK

The knock sensor wire on the 3L is notorious for getting brittle and cracking. When I did my HG's last summer mine fell apart when I took it off and I've seen other guys on here have the exact same thing happen.

Could explain your rich condition. They go into a fail safe mode producing a rich mixture and adjusts your timing.

I'd look up the FSM and find out the test procedures for the KS. They're in there real deep under the intake. Couple hour job to replace it, so I'd spend some quality time with the test procedure.

https://www.yotatech.com/forums/f116...l-link-131168/