MudHippy

Well, that sucks. But you make the best with what you've got.

BTW, hold onto that gutted cat. You may end up somewhere that doesn't have smog regs, and it's a huge performance booster due to the lack of flow restriction. That's how I have mine, half-way gutted anyway. I'd gut it out all the way, but since I don't have a muffler, it'd be a little too loud. It's twice as loud as it was before I half-gutted it. And I've been pulled over for it being too loud once already.

22REFORME

in total the following have now been replaced

cat
02 denso
fuel filter
coolant temp sensor
pcv

the truck is smoking white smoke and burning oil. the engine has less than 5k on it.

i called the place where i bought the new engine and the guy told me it was either the pcv or it needs a new ecu. The truck did not throw this code running the old motor.

i have an appointment with a local shop on the 6th but i would love to sort this out on my own before then.

thanks for the help

sb5walker

Code 25 is not a "bad O2 sensor" code, it's a lean mixture code. That means that the O2 sensor continues to report lean mixture, even after the ecu has taken measures to lengthen the injector interval. It's code 21 that's the "bad O2 sensor" code: caused either by a bad O2 sensor heater circuit (short or open) OR, slow switching (usually caused by fouling of the sensor tip).

So, you need to determine if the exhaust really is lean, or whether there's a problem in the diagnosis loop (ecu, sensor or wiring). If the exhaust is really "clean", (low HC and low CO), especially with a gutted cat, then mixture could be lean.

One thing that comes to mind, since the motor was replaced, were the injectors replaced also? Or are you using the originals? Because the injectors changed between 88 (low ohm) and 89-forward (high ohm). If higher-ohm injectors were used, they may not be firing properly.

22REFORME

they are the original injectors... they are the last thing it could be though i suppose. maybe some dirt got in one of them..

22REFORME

besides one of the injectors malfunctioning is there anything else that i haven't checked ?

sb5walker

Lean mixture can be caused by low fuel pressure, clogged injectors, an out-of-range air meter, and possibly vacuum leaks, including cracks in the hose between air meter and throttle body. Also a bad O2 sensor can cause a lean condition, but you've eliminated that. And a bad ecu, of course, but that's pretty rare. Not impossible, tho.

The only really effective in-the-tank injector cleaners have polyether amine in them. Only two products still have it: Red Line SI-1 Complete Fuel System Cleaner (30-50% PEA) and CRC's "Guaranteed to Pass Emissions Test Formula" (25-35%).
http://www.toyotanation.com/forum/sh...72#post2868772

sam333

Like I said before, one of the most common causes of a lean biased 02 sensor, is leaks in the exhaust system( from the exhaust side of the head to the o2 sensor). Its easy to test using a shop vac.
Almost always, if you have a vacuum leak ( induction leak) bad enough to affect the engine at high RPM's, the engine wont idle. At high RPM's the engine is pulling so much air, most vacuum leaks have little effect.

You said you were putting out white smoke and burning oil. Burning oil has a bluish tinge to it and smells like burning oil. Coolent is white and smells like antifreeze. Both of these will ruin your o2 sensor( coolent very quickly ,oil takes awhile).

Its easy to test your o2 sensor by backprobing it( with a analog or a graphing meter) just follow the manuals directions. There are other tests you can do also with just a meter. Once your meter is hooked up, add propane to the induction system and your o2 sensor should go rich ( high voltage, around .9 volts ). Or pull a vacuum line and the sensor should go lean ( low voltage, around .1 volts).You can also unlpug the o2 sensor and hook a single cell battery( run the battery down slighty or use a resistor to get to around 1 volt) to the ECM side of the connector and your meter to the o2 side of the connector , the ECM will read a rich mixture and will lean it causing the the o2 sensor to go lean and give a low voltage. A scanner is best and will tell you alot if you can afford one.

22REFORME

how do i use the shop vac to test for leaks? blow air up the tail pipe? whats a good way to make it more visible?

its seemingly just whitish smoke, the coolant level has been staying the same but i have noticed oil consumption.

also, not sure if i mentioned this before, but the light will not come on if i just start the truck and idle it. its only after 2500 rpms or so that the light comes on.

thanks so much for your help so far, this thing is truly driving me crazy.

sb5walker

Usually with exhaust leaks, since they allow fresh air to be drawn in to the exhaust stream, the O2 sensor reports to the computer that the engine is running lean (too much oxygen), and as a result, the computer injects more fuel. This will cause the motor to run too rich, and since you've gutted your cat, the results at the tailpipe will be seen in higher levels of HC (unburned fuel) and CO (formed by incomplete combustion - a sign of a rich condition).

Depending on the size of the exhaust leak, the ecu may be able to compensate for the extra fresh air being drawn in by running rich, in which case you won't get a code because the ecu thinks the motor is running balanced. Or, if the leak allows too much air in, (or the leak is around the sensor itself), the ecu won't be able to compensate and it will report a code 25 lean condition.

But in either case, you will see the high HC and CO at the tailpipe. Since your shop apparently didn't see that, it makes it less likely that an exhaust leak is behind your code 25, imho. Of course, I could be wrong, it's been known to happen.

Since you're seeing really clean exhaust, I think the motor really is running lean, and your diagnosis should be directed at finding out why it's lean. On my veezy, a vacuum leak will not make the idle rough, it will increase the speed of it, making it tough to get the idle down. For your motor, I'd run a bottle of an injector cleaner that has PEA through the tank which may help if the injectors are partially clogged, and check the values of VS (the signal from the air meter that tells the computer how much air is going in the motor) which can affect mixture.

There are two ways to check VS: measure the resistance between the VS and E2 terminals of the air meter, and to measure the voltage across the VS and E2 terminals of the ecu when ignition is on. The advantage of testing volts at the ecu is you're also testing the wiring, and you see exactly what the ecu is seeing. Checking the air meter can be helpful in trying to track down whether trouble is due to wiring or the air meter itself. You'll need to get the specs for your 88 - it is probably different from the online 93 manual; not sure. The 93 chapter on testing the air meter itself is here:
http://personal.utulsa.edu/~nathan-b...33volumeai.pdf
And the volt specs at the ecu are in the troubleshooting chapter:
http://personal.utulsa.edu/~nathan-b...27troubles.pdf

22REFORME

Wow good info man thanks for your time. One thing i would mention is that my cat is brand new, not gutted. The old cat was gutted and I had it replaced. I cannot hear an exhaust leak anywhere, but there could be a leak. So in terms of things that cause the engine to run lean, I am down to: problems with injectors, fpr or leak in the intake arm before the tb?

22REFORME

Oh and I just picked up a bottle of that crc product... ill be giving that a shot tmrw

sb5walker

Let us know how it works - it will take running about the whole bottle through before you'll see much difference...

I mentioned before, but double-check the hose between air meter and throttle body - a leak there will not increase idle, it will just allow air to get into the motor without going through the air meter, so the meter measures less air going in, which could cause lean running. I found a crack in the rubber elbow of mine, and I've read of lots of guys finding the same.

22REFORME

Good reminder thanks, will post my results.

22REFORME

well unfortunately the light is still on. i ran a full tank of gas through with the injector cleaner and also checked for any cracks in my intake and found none. any last ditch ideas before i take it to the shop?

sam333

Hook the shop vac up on blow and duct tape the hose to the tailpipe, turn it on and use a spray bottle with water soap mixture to spray all joints and gaskets from the exhaust side of the head to the 02 sensor. The leaks will be obvious( bubbles).

Its easy to test the o2 sensor. Just backprobe the o2 sensor connector with a meter. Run the engine up to temp and see if it is in closed loop ( talking to the computer) watch for the appropriate # needle swings( analog meter) and voltage range( you can use a graphing meter as well. The specs for #of needle swings and voltage range( frequency and amplitude) are listed in the manuals for the truck.

chad450r

any updates on your problem? I'm having the identical problem

yoterroller

i too have this extremely annoying problem. one unique part of mine is that when i remove my gas cap theres no release of vacuum pressure sound. i tested my gas cap and replaced my lines to the charcoal canister and still have the same problem. does anyone know if this will contribut to this problem?

Armalite

Is there any updates on this problem? I have the same problem with code 25. It is random when the engine light comes on and sometimes it will turn off at random when driving.

yoterroller

the code 25 says lean mixture. i got to the point where the truck was running roughly so i changed out the fuel filter which i must say is a major pain in the ass. otherwise i would have done it before. the filter had a fair amount of resistance compared to the new one but i havent been able to drive it a lot to see as its not registered now. if you havent chaned the filter recently give it a try. but its a pain

Armalite

Hey thanks for the update. I have replaced the plugs,wires,o2sensor, and the fuel filter and I can't find any air leaks.... Problem still persists. It would be so easy if I just knew what to replace lol.