Post engine swap issues.

So I had a head gasket blow in my 2004 prerunner and it dumped all of my antifreeze/water through my exhaust. I replaced the engine over the weekend with a used JDM engine and everything went pretty smooth for the most part. The initial startup and ride cleared the remaining water/antifreeze out the exhaust system and the truck runs smooth and has no problem idling at 700-750 rpm, ive driven it about 150 miles so far total to diagnose the issue. The check engine light came on about 15miles into the first good test drive with the P0171 code. I didn't have any codes thrown before the swap even with the water in the tailpipe. So I did the usual, cleaned the MAF and checked for vacuum leaks, cleared the code drove for about 20 miles in between the light coming back on. The O2 was replaced in late 2014 but I suspect this may be the issue due to the amount of water that passed though the exhaust. Has anyone else had an issue with water through the exhaust kill an O2 on the element side of the sensor?

 

Are you using your Fuel Injectors and all the sensors and ECM from your old engine .

Which is ??

PO171 is the engine running lean

Knocked dirt loose now you might have a clogged injector

Bent a pin putting a connector back together

Coolant temp sensor might need cleaned or at least tested to see if it works

It is possible the exhaust sensors got damaged and might be coated and just need to be cleaned on a wire wheel

With the old style single wire O2 sensors cleaning them after a head gasket failure brought quite a few back to life in my case

 

Thanks for the reply, I went completely over the engine last night and found a bad hose lurking, I replaced it and no more code being thrown. The JDM motor is running like a champ and I couldn't be happier with the swap. Just for some added info I did swap all major sensors from the old motor to the new one and replaced all maintenance items (water pump, timing belt plugs etc.). The exhaust bolts gave me the most grief during the build but I can say I am super surprised at how smooth the entire process went. Took 2 days to complete the swap and have the motor running.

 

I am assuming all brackets/flanges were a direct swap... no rigging anything? My prior experiences, not with JDM engines, is that there is always a hole that is not drilled/tapped or the replacement motor is the one year that requires the "special" bracket.

 

All brackets were a direct swap. No Drilling, Cutting, any of that mess. I swapped the cam position sensor, the sensor on the DR side of the block next to the oil filter and cooler and crank sensor? not sure what it was, i didn't spend the time to figure them out. The Oil filter location had to be swapped and I used my oil cooler on the JDM engine. The exhaust bolts snapped off at the manifold and crossover pipe and stripped out, those had to be drilled out and replaced but that was the worst of it. The harness fell back into place nice and neat like. I swapped all accessories and brackets over, A/C, Power steering and alternator without any issue. It really was a simple swap. I had the code come up but like I said I tracked it to a leaky vacuum hose and now the truck runs better than it has in a few years.