Edwards

took truck to dealer after trip to local shop. both shops say i need to replace the following due to codes they found.
MAF Sensor
All four Injectors
O2 sensor ( front )
Plugs

Truck has check engine light on and lost 75-100 miles from tank of gas.
has alot of black silt in tail pipe.
Use to get 22mpgs now 18mpgs.
Engine runs rough at Idle and a miss at higher RPMs.

They tell me thats the only way to fix the problem, but they can't garantee it.

I have read through and tried most all ideas . can any one add to my list of things to try?
Thse are codes I got from Auto Zone: PO172,100,110,120 and 300.

Just bought truck in July ( I thought I bought a toyota so I did not have to wrench on trucks any more.)

deathrunner

How many miles do you have on it?

MY buddy has a taco prerunner 27. liter and had a miss. A couple of mechanics recommended plugs wires, cap, rotor, injectors, 02, MAF...blah blah blah.

Turns out he needs a valve job. I talked to the some of the mechanics at protrux (toyota only shop) and they said it is a common problem on the 2.7. They said it is important to check the valve specs at least as frequently as the manual says to. More often is even better. For some reason the 2.7 likes to loosen up and if it goes unchecked you can really screw things up.

Maybe this isn't the case with your motor, but deifnitely something to check and it sounds liek what happened to my buddies taco.

ToyComa97

Could be those things. if i was gonna do it i would do them in the order u just listed them.

MAF Sensor
All four Injectors
O2 sensor ( front )
Plugs
the MAF i think could be the only problem, because it causes all the others to read bad, because the MAF would be like the begining to the truck running seeing thats where it gets all the air threw. i would change it first. i think that might fix all your problems.... sounds like its running rich since you say there is black sut... thats what the O2 senser is complaining about, and saying its bad. but i think its not.. Also, the MAF would tell the injectors to feed the truck more gas to replace the loss in air. so that would make the injectors say they are bad. anyways. IMO i would change the MAF and try it

I am not a mechanic, just running threw how a engine works in my head


But you know what i had a dodge that had that problem, i changed two $100 dollar O2 sensers, and it ended up being the CAT stopped up. after i gutted the cat, no more problem.

AgRunner06

Ha what a joke. I would replace the plugs and clean the MAF. That will most likely fix your problem.

This is why I always work on my own stuff.

NathanBERG

Most auto shops and all Stealerships love to throw YOUR money at problems and hope it will fix it.

In my opinion you should replace the plugs and o2 sensor yourself. That is if they are due to be changed anyway. then see how it runs. And never take it to the stealer, ever!!

AgRunner06

It also might help if we knew the year, miles, and last time it had a tune-up. You can't blame Toyota for a poorly maintained vehicle.

BTW there is a write-up on cleaning the MAF. They get dirty sometimes and can really screw things up.

The 02 sensor is easy to do but pricey. That is why it is 3rd on my list to tackle. The MAF is free to clean and the plugs are like $12.

Good Luck

:bounce2:

NathanBERG

I am with you 100% That's the way to do it> Cheapest thing first.
Like AgRunner06 said, clean the MAF 1st.

rimpainter.com

In addition to the last couple posts, I would like to add that you might want to review the diagnostic procedures for the symptoms you have described. You can download as much as you want from the Toyota FSM via the TIS website for a $10 day use fee. You will get PDF's of whatever you want. You are most likely going to need a multi-meter and some tools. You can even test many of the items that the shops suggested on your own and make the call.

Edwards

Thanks for the ideas will try them thursday. just came back from napa with cost to replace everything and a haynes manual. It has ways to test and i will begin with MAF sensor said about $800.00. I have cleaned MAF senor and throttle bodyand installed new ngk plugs. Dealership says compresson is good ,but I will test and check valves myself, thats what I thought was the problem in first place.

2000 w/96,000,auto 4x4 with 31x10.5x15 BFG MT's( stock )
have records to 36,000 after that orginal owner says no problems just oil changes.

not sure how to use this system yet hope I get message back to all replys.
just one more thing what does FSM & TIS stand for?

rimpainter.com

Factory Service Manual (just say no to Haynes!)
Toyota Information System

NathanBERG

No kidding!! Haynes = doo doo

MTL_4runner

P0172 System too Rich (Bank 1)
P0100 Mass or Volume Air Flow Circuit Malfunction
P0110 Intake Air Temperature Circuit Malfunction
P0120 Throttle/Pedal Position Sensor/Switch A Circuit Malfunction
P0300 Random/Multiple Cylinder Misfire Detected

Wow, that is quite a few codes all at once!
I might take it to another shop (or Autozone if they still do it for free) to get the OBD codes read again, who knows if that other shop was BS'ing you or not.

I would bet money you needed new plugs, clean (or replace MAF if cleaning doesn't work) MAF, and likely you should replace your O2 sensor to restore your good gas mileage again. I would very much doubt your injectors have anything wrong with them but I might run some BG44 though there too to clean them out just in case.

Unhappy99

It can be running so rich there are misfires, so all of those codes don't surprise me too much. Don't just blindy shotgun components, the FSM has test procedures to determine what exactly is bad.

1) Clean and test the MAF/IAT, although I don't think this is the fundamental problem, as dirty MAFs tend to lean the mix. But, having a lying IAT could easily cause very rich mix, so test them.

2) Test / replace the front O2 sensor. I think this is your problem, bad O2 sensors will generally run rich. In the FSM, there is a specific method of starting/driving/restarting test which is meant to isolate the Oxygen sensors to check them for response and operating range. The O2 sensor is particularly suspect if more than 80K miles.

Your injectors are most likely just fine. If your plugs have more than 80K miles, you might want to replace them as well, they are cheap. Clean / replace the air filter as well if its dirty.

Edwards

Tried all of the above, This is my findings: MAF checks out all injectors working at least by unpluging them, replaced o2 sensor. Still runs rough at idle ect. compression at 150 psi ,Installed new ngk v style plugs, numbers 3&4 look light brown 2&1 dark brown ,re cleaned MAF/throttle body. NOW for the one thing that is gone ( ENGINE CHECK LIGHT) .If I unplug MAF sensor it still runs ,plug back in and shuts down and check engine light comes back. when you re start it, might have to break down and buy MAF.But not till after deer season in Pa. hope it makes it there and back. or maybe
Thanks for the help.
Have a great turkey day

MTL_4runner

If 1&2 are dark that may indicate a coil pack that is going bad.

Can anyone verify what coil packs are hooked up to what cylinders on this motor?

That could also be a very good reason for the engine running rough as you mention.

PhiTau4runner

I have had similar problems with the check engine light and rough idle, I changed my plugs and had the 1&2 plugs dark as well. What does it mean. I have a 4cyl as well with 160k miles.