Where here would be best to ask this... Engine light question

Bought this 2003 Tacoma 3.4 Auto 4x4 and engine light is on. Can't remember code number it threw out. If I can get down to O'Reillys I'll let ya know. I do remember it said Bank 1 Lean.... If code is turned off by them or battery disconnect it runs better. It smells as if its running rich and the O2 sensor was blackcarboned up pretty good. Cleaned that and it seems to run longer without turning on a light. It seems to have an issue with idling when the light comes on. Going down the highway it seems to be running good. However when I get to work and come down to an idle and reverse into parking spot it wants to almost die. Today not so much I bumped up the idle yesterday. It made it to work and almost home. So all total today about 45 miles. Was buzzing down the road doing about 75 MPH and for no known reason light came on. Originally found big vacuum leak and fixed it and replaced MAF sensor. Any clues? Gonna change spark plugs soon.

 

Sounds like you got a P0171 'system too lean bank 1' code. That dirty O2 sensor can cause it as well as vacuum leaks and dirty MAF sensor.

What kind of sensor did you replace the MAF and O2 with? On these trucks you want to always stick with OEM/Denso brand sensors, aftermarket ones (especially cheap Chinese ones from eBay and such) are known to cause problems.

Also beware of really cheap "Denso" sensors on eBay and Amazon...if the price is too good to be true then it's likely a fake Chinese knockoff. They are common online.

 

Not sure of MAF sensor brand bought it at autozone. It's was fairly expensive as I recall. Also hear some clicking that I can feel on throttle body.... Sometimes. Not sure what that is. Had a Camry throttle body that was coolant cooled. It corroded through and failed. So kind of leery about it also... Used cars with issues are hair pullers!

 

yeah the P0171 code is common on these trucks and can be a pain in the ass to track down. I had it for a couple months and it took a few mechanics to finally figure out there was a tiny vacuum leak that was causing it.

I would check up on that MAF sensor you got at AutoZone and make sure it's a Denso. If it isn't, see if they will let you exchange it for one. Not kidding about the aftermarket sensor issue, Toyota builds these trucks around Denso's exact specs and anything aftermarket is a gamble that it will meet those specs.

 

Didn't replace O2 it was just coated with black carbon. Used throttle body cleaner. It was worth a shot to try to clean it first. Looked great clean.

 

That could also be it then, I've never heard of anyone having luck by cleaning an O2 sensor...usually when they go bad and start sending bad signals they need to be replaced.

Although I did read today that someone apparently fixed their O2 sensor by whacking it with a hammer, so I guess anything is possible

 

That's interesting about Denso specs. Why would it run so good for so long at highway speeds and then kick on light. I kind of get other situations when it turned it on but that seems odd to me. Thanks for any and all help! Gotta head to house! Have a great weekend Tacoma Peeps!

 

Can confirm, my O2 sensor hasn't given me any troubles in 5 years after beating it with a hammer to get it to break loose. I had the same code originally and I haven't seen it since.

 

The MAF sensor is a duralast and was $86 at autozone. Called them and they said they could get Denso by tomorrow for an extra $20. I heard doesnt mean its true you could clean O2 sensor if it was a carbon problem but if it was white it was shot. I would hate to think you'd have to replace that everytime something else failed. Hammers are awesome! Where I work I knock out fasteners as I disassemble a large aircraft part prior to modifications to it. I get a lot of odd looks when swinging my giant ballpean hammer. It sounds horrible in that building. Even the engineers were getting concerned. It sounds like I'm murdering the part but I'm barely hitting it. I told them that its the non insulation covered cinderblock walls that are amplifying the sound. I have to get all the fasteners knocked out before morning meeting or I hear about it.

 

Was re-reading these posts and heard/read somewhere that if I am going to replace an O2 sensor I should replace all of them. Is that true? Been kinda hurting for funds of late because of various that's life disasters lately... Anyway just paid my Kansas taxes (to get tags) and that took a bite out of what I had extra... Gonna order O2 or O2's at Advance Auto to get much needed 20% discount!

 

I've never heard of needing to replace both O2 sensors just because one is bad. That's not to say it isn't true but I've personally not heard that.

But you do want to make sure you get Denso brand sensors...Denso is the OEM manufacturer. Toyota built these trucks' ECUs to work with the exact specs of Denso sensors, using any other brand of sensor is a gamble.

 

If it’s lean, you need to rule out vac leaks between the MAF and the throttle body. I know you said you fixed a vac leak, but you could still have a smaller one. Also need to rule out a bad injector or other fueling problem before throwing money at O2 sensors. Engine stalling and needing to increase idle while throwing a lean code aren’t really consistent with a bad O2 sensor in my experience...sounds like vac leak. If it’s that, you should fix it before you burn up an exhaust valve or piston ($$$).

 

Agreed on both. I've always heard that the front of sensor is the only one that matters to how the engine runs. The rear one is just checking if your cats are working.

 

unfortunately there are no "silver bullet" fixes, it is going to have to be diagnosed.

 

First part you should buy is an OBDII code reader/scanner. You can get a bluetooth one that works with smart phones for under $20. Diagnose before throwing parts at it or it will get expensive.