Advice on what to do from here

I started several threads on my 1998 tacoma 2.7 (3rz) 5 speed. I purchased it with a high idle and basically threw a lot of parts at it to try and fix it. After replacing the MAF, throttle body, plugs and wires. I finally came to the conclusion my high idle was from the computer loosing contact with the throttle body. I would occasionally get a P120 code. I then ordered a computer (ECM) from a salvage yard on ebay with a money back no questions ask policy. While i was pulling the old computer out to replace with salvage yard ECM. I noticed a lot of wire splices on one of the plugs that goes into computer. I had found some wire splice also under the hood mostly for the charcoal canister evap system. Now im thinking mice had gotten into truck at one time. After replacing the ecu with salvage yard ecu I started truck and let it idle for about 10 minutes which it did fine but only got down to about 900 on rpm’s. I then went on a drive. The truck ran rough in the lower gears but seemed to run fine after a few miles. It then throws a P505 code which It has never thrown with me before. I clear it with scan gauge. I get to where im going which allowed me to kill the truck for about 10 minutes. Then on my trip back home it seems to sputter in lower gears but runs fine in higher gears and I threw another P505 code.
My question are what to do next?
I think I probably need a new wiring harness but would you send the salvage yard ecu back? The truck never actually loss connection like it was with old ecu but it didnt act up in lower gears and throw a P505 code with old ecu either. What would you guys do at this point?

 

You mean P0505 right?

I would reassess the wiring repairs. If they under e-tape, I'd be taking that off and inspect whatever method they used to rewire it. I'm a big fan of soldering and sealing with marine shrink wrap for critical stuff like that.

 

Yes I mean P0505. Im really starting to think its in the wiring harness because every wire on one plug has been cut and reconnected. I pulled on them but thats about all the reassessing I have done. I just don’t understand why I would get that P0505 code with the salvage ecu and a P120 with my current ecu.

 

Honestly if electrical work isn't something you're really good at, and you're not head over heels in love with this truck, I'd consider selling it. This sounds like something that could get really expensive to solve, if you get forced to outsource the labor to properly diagnose this problem.

Not trying to be overly-negative, but sometimes selling something at a loss early can be the smarter route in the long run.

 

Some start pts….

 

If the splices are made with crimp connectors your problem probably is there.

Soldering isn't a difficult or expensive skill to learn, if you are handy and have the time inspect & repair the splices.
Solder & good quality heat shrink make a permanent repair.

 

Lots of possible causes pointing to throttle body…..both codes

 

Ask vendor to trade ECM for throttle body?

 

Start the list cheapest to expensive
-check for intake leaks….while truck running, spray carb cleaner around intake hose(s)…..if RPM jumps, there is your leak
-pvc valve and grommet
-take off TB and clean ……lots of vids out there including a thread of mine (mine is 96 thou)
Then re-address the situation

If that incorporated ETCS sensor, TB needed
GL
Let everyone know plz

 

Vacuum and intake leaks greatly interfere with idle and low speeds...
.....and then clean out at higher speeds...

thats what Id chase 1st.

There are ton of places for these to leak as they age....booster, pvc, egr, iac feed, or any of the lines.
All before 2001 had the pcv gromet thats famous for splitting below the valve cover giving a massive vac leak, and you never even know it..


If you have a way to watch fuel trims while driving around, that will tell you alot.

 

Thanks for replying guys. Controlcar thats a new Toythrottle body on the truck.
O’Silver_Taco why would my original ecu only occasionally throw a p0120 and nothing else. Salvage ECU throws the P0505 code. I would think both ecu’s would throw the same code. Definitely will change out the PCV grommet. On the fuel trim I have an option on my scan gauge that looks at the IAC loop open and closed. Is that what you would monitor?

 

Anybody got a schematic on those computer plugs? That would help me isolate what im dealing with. Looking for the plug that keeps the memory alive.

 

Swap back to OG ECU and observe. Cheap test and will tell you if the symptoms are tied to ECU or have drifted due to harness manipulation while swapping.

 

Well at last the culprit has been found. Thanks for all the replies and the time it took to type those replies. After basically taking the engine wiring harness down to just the wires there was a butt connection that was eliminated and soldered. To finally be able to drive and not loose my tps actually felt good. Again thanks for your help.