ACSig

For a while now, I've been getting the check engine light codes 25 and 26, the two about air-fuel lean and rich malfunctions. The first thing I did was change my O2 sensor, it looked pretty bad ever since I've had my 4Runner. After driving around for a week, I got the same two codes. What would most likely be wrong with it?

I've used Seafoam to try to clean out the injectors. Other than that I'm not really sure what to do.

I have a 1995 3.0 V6 4Runner.

sb5walker

Usually with 25 & 26, if not the O2 sensor, it's clogged injectors. Seafoam is good at cleaning the intake & valves, but for injectors, the only in-the-tank products that work have polyether amine in them. Used to be a bunch of choices, including techron, bg44 & gumout regane, but they all stopped using PEA. The only two left (that I know of) are Red Line's SI-1 Complete Fuel System Cleaner (30-50% PEA in msds) CRC's "Guaranteed to Pass Emissions Test Formula" at 25-35%.

If your injectors are real bad, having a shop feed the concentrated cleaner directly into the fuel rails works better, but the best job will be done by witchhunter performance (witchhunter.com).

It would help to pull your plugs, and if possible, post pictures of them. If some cyls look lean and others rich, it's probably injectors.

Have you recently changed plugs, cap, rotor, air filter & are the wires clean, soft & flexible?

Have you ever changed the fuel filter? If not, that'll be worth doing.

Another possibility is bad pressure regulator, but that's rare.

Clogged cat might also be possible, but that would also cause noticeable loss of power.

Edit: Couple other thoughts - exhaust leaks also could cause bad O2 sensor readings, and you might run a compression test to make sure you don't have any burnt valves or other compression problems.

ACSig

Great, thanks for the help.

I'll start with the fuel filter, I remember trying to look at it, but it was so badly corroded that I couldn't get it off. If that doesn't work I'll check out the injector cleaner.

When I first got the vehicle I pulled the plugs and they looked good, but that was a year ago so I'll be checking them again.

Changed the plugs a year ago, didn't change anything else. The wires all looked good, I don't think they'll be a problem.

DupermanDave

according to the chevron website, the techron additive still has PEA.

http://www.chevron.com/products/ourf...tives/tcp.aspx

sb5walker

Yeah, that's what their website says. But what of the mandated by law material safety data sheet? Not a word:

COMPONENTS CAS NUMBER AMOUNT
Distillates, hydrotreated light 64742-47-8 < 55 %weight
Stoddard solvent 8052-41-3 < 35 %weight
Solvent naphtha, light aromatic 64742-95-6 3 - 7 %weight
Benzene, 1,2,4-trimethyl- 95-63-6 1 - 5 %weight
Xylene 1330-20-7 0.1 - 0.5 %weight
https://www.cbest.chevron.com/msdsSe...true&region=NA

Polyether Amine, CAS # 39423-51-3, is a "Highly Toxic" substance:
http://www.polytechnologies.net/MSDS...amine-T403.pdf

As such, it would have to be listed on Techron's MSDS. It isn't. Used to be, but not anymore. Red Line's and CRC's products list it:
http://www.redlineoil.com/content/files/tech/32.pdf
http://www.crcindustries.com/faxdocs/msds/5063.pdf