1st Gen Check Engine Light comes on during acceleration, no codes.

[MrAhso]

My 1986 4Runner 22RE Auto when I'm running uphill or for long stretches on the highway with the gas pedal held down for a while, the check engine light will come on and stay on while the pedal is pressed. I can then lift off of the pedal for a couple seconds and press it again and the light turns off for a while. Consistently works the same way to turn the light off by lifting off the pedal. Any idea what this could be?

Another thing is, if I'm climbing up a hill I can't quite make it up, the truck will stay at 2k RPM revved but goes no higher. I've seen others spinning tires and revving like crazy. Is this a combination of lack of power and oversized tires?

 

[ajohnson]

Sounds like the 02 sensor, my '85 did the same. Find out what code it is.

 

[MrAhso]

Thanks for the tip, I'll check it out but there are no codes. I guess the parts are cheap enough I can replace them anyway.

 

[KidVermicious]

My 1986 4Runner 22RE Auto when I'm running uphill or for long stretches on the highway with the gas pedal held down for a while, the check engine light will come on and stay on while the pedal is pressed. I can then lift off of the pedal for a couple seconds and press it again and the light turns off for a while. Consistently works the same way to turn the light off by lifting off the pedal. Any idea what this could be?

Automatic? Only does it on long hard pulls? Check for transmission codes. I forget how exactly, Google should help you out. I know they're different from the engine codes.

Another thing is, if I'm climbing up a hill I can't quite make it up, the truck will stay at 2k RPM revved but goes no higher. I've seen others spinning tires and revving like crazy. Is this a combination of lack of power and oversized tires?

Mostly. The torque converter will slip and allow higher RPMs than your wheel speed justifies, but it's not indefinite. And the wheels won't spin if the torque isn't there. That's not to say that you don't have some other power issue with the motor though, what gear ratio and tire size are you running?

 

[nevada]

Thanks for the tip, I'll check it out but there are no codes. I guess the parts are cheap enough I can replace them anyway.

these are pretty basic EFI systems. I don't think they store codes. in order to pull the code, the light has to be on at the time.

get the light to come on, then pull over and check it.

 

[MrAhso]

I know I need to fix the linkage for sure on the transmission and the PO told me he had just replaced the torque converter a few months before I got it. Then again, there were a lot of things the PO told me that turned out to not be true.
I'm running 4.30 gears that come with the Auto and 33x10.5R15. I am trying to get cash together to go to 4.88 with rear locker but it'll be a few weeks.

So on my list are to check O2 sensors, Torque converter and trans codes and definitely move on re-gearing.

 

[wallytoo]

perhaps the '86 and earlier are different, but the '87-on stores the codes, even if the light is no longer on. the only exception is for knock sensor.

the CEL comes on when there is a malfunction in the system. the CEL goes off when the sensor reads a "correct" signal. the code will be stored until the efi fuse is pulled, or the battery gets disconnected.

if your O2 sensor isn't sending a signal to the ECU, it should trip the CEL, and the code will be stored. it may also work sporadically, and the CEL will go out because the ECU is receiving a signal.

 

[nevada]

perhaps the '86 and earlier are different, but the '87-on stores the codes, even if the light is no longer on. the only exception is for knock sensor.

the CEL comes on when there is a malfunction in the system. the CEL goes off when the sensor reads a "correct" signal. the code will be stored until the efi fuse is pulled, or the battery gets disconnected.

if your O2 sensor isn't sending a signal to the ECU, it should trip the CEL, and the code will be stored. it may also work sporadically, and the CEL will go out because the ECU is receiving a signal.

that's possible. I just remember having an intermittent light years ago. I had a hell of a time getting the code. finally, I was driving down the road and it popped on. I pulled over, jumped the plug and got the code. prior to that, the only thing I got was the "all ok" code.

 

[flyinhawaiian01]

And that begs the question, is it giving the "all okay" code, or is it not giving anything to you?

If its not showing the all good code of "1", your TPS could be out of whack. The TPS has to be set correctly for it to give you the code.

Having said that, if this is the case and you don't get the single flash, depending on which way the TPS is out of adjustment, try touching the throttle ever so slightly to see if you can get it to start flashing at you. This won't work if the TPS is out of adjustment the opposite way, and either way, you should get it set back to the correct setting.

As for the CEL coming on when on the throttle for a long time, that definitely sounds like an o2 sensor going out.

Just a related FYI, I bought a Denso o2 sensor from Rockauto a couple months ago, it was bad right from the factory! Local shop replaced it with an NTK brand and my truck immediately passed smog!

For the extra 5 bucks from rockauto, I'd suggest going with the NTK brand if you end up having to replace the sensor.

 

[wallytoo]

it's what the FSM claims, and it's what i've experienced w/my '87. i am getting an intermittent CEL, which is indicating O2 sensor. the code is stored even when the light is off. after clearing the code, the CEL eventually comes on for a short time, then goes off. on, off, on, off, depending on speed/temp/conditions etc. stores it until i clear it.

i'm sure the O2 sensor didn't like the heavy volume of raw gas that was being passed through because of my failed, leaking injectors. perhaps a month or two initially, and then again after the "rebuilt" originals from witch hunter started leaking immediately after putting them in, which i had to live with for another month or so.

 

[KidVermicious]

I think it depends on the code. I've pulled stored codes from my '86 and '85, but there's been times I should have been able to and couldn't, too.

 

[GeoRoss]

This is exactly what my 4Runner does. I sort of doubt that it is the O2 sensor but some sort of fuel delivery issue during prolonged climbs.

Have any of you solved this issue with a new O2 sensor?

 

[89FourRunner]

Mine does it too, I thought it was some lean/rich issue with fuel as well. Since it has done no harm I could care less.

 

[GeoRoss]

Mine does it too, I thought it was some lean/rich issue with fuel as well. Since it has done no harm I could care less.

Agreed. The 4Runner got 22 mpg on these very steep highway grades with the AC on when this CEL came on intermittently. I'm not going to worry about it unless it becomes more persistent.