The IACV in the bottom of the TB has a coolant line in and out of it. You should expect a small bit of coolant to drip out of those lines and the IACV.

Give that IACV a good cleaning and be sure it moves freely.

 

Ah good to know, guessing the coolant runs up there to operate the IACV?

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Correct.

 

I've never heard of a P0171 being associated with a rich condition. Not saying you're wrong, just interesting to me.

http://www.obd-codes.com/p0171

 

I wasn't implying you were wrong either. This is the first time I have messed with a fuel injected vehicle before. I understand the basics of it but never worked with scanners or anything like that.

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Swimmer, take a look at the second link TheDurk posted above. You are correct, "When the DTC P0171 is recorded, the actual air-fuel ratio is on the LEAN side." However, the detection logic for P0171 is "When air fuel ratio feedback is stable after engine warming up, fuel trim is considerably in error on RICH side (2 trip detection logic)."

So, it appears, a LEAN actual air-fuel ratio causes the fuel trim to be RICH thus popping on the P0171.

 

I guess when I posted earlier about the engine going into "safe mode" is I meant the ECU is seeing a lean condition thus adding extra fuel. That explains why my fuel trims are so high, and maybe that's why I'm getting smoke out of the exhaust?

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Update

Finally ordered a new OEM MAF sensor from Toyota. Got it installed and drove around some and everything was like it should, until about after 15 min it started running rough and smoking then threw the p0171 code. Now I'm back to square one.

 

Smoking from the tailpipe? White, black, blue?

Are you using any coolant?

 

Yes smoking from the tailpipe. Black smoke. Haven't checked the coolant level since I first got the truck running.

 

Read this and since I've been all over that code myself for the past several weeks recently, I thought hey, I got help, now, keep it going...

You mentioned that this happened shortly after the swap and you tested for vac leaks with the starter fluid method...
What I did to test for vacuum leaks was use a vacuum pump with the gauge and connect it to one of the vacuum lines on top of the intake manifold. Crank the engine and assess the behavior of the needle. If the needle has a low reading, that can indicate a leak. Since you also did a swap (did you re-build it or was it just from another yota?), the vacuum gauge can also key you in on the condition of the internal components. Maybe a leaky intake manifold gasket? A search on vacuum gauge and diagnostics may be helpful...

Another suspect to rule out is exhaust leaks. I read and read on the various methods to check, so what I chose to do was simply get a funnel and long hose and use that (and my ear) to pinpoint any odd leaking noises between the exhaust manifold and the block, and down the exhaust system.

Because of the fact that you have black smoke, that's a whole other set of troubleshooting, in addition to the usual suspects for that p0171 code. A vacuum gauge may help get a snapshot condition of the engine pistons, valves, springs, gaskets...that could be contributing to the black smoke and rough idle, despite the MAF sensors, plugs, PCV, being replaced. You mentioned a p0450 code awhile ago...any other codes? That one clue points to the EVAP system.

Fuel system may also need to be checked. Is the fuel filter old or had its share of bad gas? Condition of the injectors is also another area to check.

I doubt it's the oxygen sensors. I'd replace them simply if the soot is affecting its ability to read and/or the mileage on them is already over 100k.

Hope this one got figured out already, but if not, there's my take on this illusive CEL. Long live the 4runner!

 

All good info right there^^. The truck has been sold for quite some time now so I never solved the issue. It had to be a wiring problem because the donor engine was perfectly running like three days before I bought everything.

 

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Just curious did you have air filter box or cold air intake. I had exact same problem with my swap