VolVette

I bought my '98 4Runner about 3 weeks ago and everything has been fine on it. Yesterday the check engine light came on and I hoped it was just a fluke and would be off when I drove this morning. Last night after getting out of the car and noticing the light, I checked to ensure the gas cap was on tightly. It may not have been tightened to the point where it clicked so I tightened it. The light is still on this morning. I have not done anything different with the car and am trying to figure out what the normal causes of this are.

Yesterday I filled it up with gas and added a lucas fuel treatment (one of the fuel injector cleaners) that I always put in my vehicle's tanks when I change the oil. I'm wondering if I should have used 93 octane as opposed to 87 and that the engine is not firing as it normally would thus causing the light? I've never had any issues before adding the injector cleaner but I thought I'd throw that out there as a possible factor because I don't normally add the fuel injector cleaner.

So, what do you think is causing this?

BajaRunner

If your not getting much of a performance decrease, I'd check your Mass Air Flow Sensor (MAF). Its the unit which sits inline of the intake, right behind your air box. These are able to be cleaned with electro contact cleaner (and now they make MAF cleaner). You have to pull it out, spray it out, and let it sit till its dry.

To clear your CEL, you can just pull the EFI fuse from your fuse block for 10 minutes.

Not sure with other states, but California just "outlawed" car parts stores being able to pull the code for you. It was a free service until recently. OBDII scanners aren't all that expensive either.

VolVette

Thanks, Baja.

As for as performance problem, I'm not seeing anything and my gas mileage is right around 18mpg for driving around town. I figure that's about as expected. Since my performance doesn't seem to be off, that's why you believe the MAF may be a problem?

brian2sun

A code reader is what you need. Or go pay a shop to read it for you. Either way, I would think you'd be interested to see what the code is so you can have a point to start from. Otherwise, you'll only get a lot of guesses. I've never had a CEL because of a little injector cleaner.

Doddy

Go to your local Auto parts store and they should be able to read the code for you for free. Then come back with the code and ask your question, other wise your just shouting into a crowd.

FYI - 93 octane will not get you any performance gains over 87. Toyota designed these motors to run on 87 octane. The amount of octane your motor needs is based on compression ratios, so unless you have a high compression engine (you don't) then there is no need to run a high octane gasoline.

VolVette

Thanks, I'll take it there and see what I can learn. I just thought it was odd that I added the injector cleaner and the CEL appearred- so I suspected that injector cleaner may have lowered the octane level enough to affect the engine firing thus giving the code. I'm learning...

TheDurk

I've added a bottle of Techron to my '99 before every oil change since about '01. I have never had a CEL because of it. The only thing that might be is you have another problem, and the cleaner made it worse, enough to set a code. But without knowing the code, further speculation is a waste of time.

Western Canuk

You can get the code yourself just by jumping something like T1 and E in your computer diagnostic behind the fuse block in the engine.

on my '88 22RE it's

1. turn ignition ON
2. jump T1 and E
3. read the flash code(s) off the check engine light in the dash.
4. remove the jumper

jeepmanmike

Or it could be they cleared the code before they sold you the car and it just came back, read your codes, I have a intermittent O2 sensor code that pops up, I have not been able to change out the O2 sensor yet since my nuts are rusted solid(have not been trying to hard though). If I disconnect the battery the code goes away for a couple weeks and then it comes back.

VolVette

I went to Advanced Auto and used their tool to read the code.

JeepmanMike was right... The code that the read was for the O2 sensor. Is this a common problem or misread or should I just go ahead and replace one of them? The code read 1/2, does this help tell me which one of the O2 sensors needs to be replaced?

brian2sun

The front O2 is the only one that would have an effect on engine performance (the rear is just to monitor the cat). Sparkplugs.com is having a sale on the front one (1st one on the list):

http://sparkplugs.com/results_app.asp

EDIT: The link apparently doesn't work to that page so just type in the year, make and model and select O2 sensors from the drop-down list. Then select Denso and 4WD. The first one on the list is the Denso OEM with the correct connector (not the cheaper universal type that you have to splice the connector on to.)