Kolton5543

Alright guys, I'm nearing the end of my 3.4 swap. The engine is from a 98 4runner A/T 2WD going into a 94 4Runner M/T 4WD. I still have a lot of small little things to take care of but the major stuff required to make the truck run and drive right should be done. Before installing the engine I replaced the timing belt kit, knock sensor harness, plugs, wires and every seal I could see. To connect it to the dash harness I made an adapter harness from pigtails and didn't modify either harness. The only modifications to the harness was re purposing the neutral safety switch wires for the VSS and reverse light switch. Everything else remains untouched.

My issue is, the truck will start up and sputter, stumble and usually stall at idle. Won't rev cold but revs ok hot but not as nice as it should. Almost not drive able cold. Hot it seems to drive ok under half throttle. Sputters a bit still but has reasonable power. More than half it will usually bog hard. Coming to a stop it stalls often but will always fire right back up.

I'm kinda expecting a bad MAF. The engine I bought didn't have one and both style MAFs always showed when searching for one. I decided I wanted the slot style MAF rather than the can style. I first connected it but couldn't get it to run at all. I later found Toyota changed to the slot style MAF in 99 and changed the pins around. I repined the connector but I think I may have partially fried the MAF. I ordered two more to test with but they're not here yet. If I start it without the MAF it ides great hot or cold. However trying to rev, it simply wont. If I ease into the throttle very lightly it will rev a littler but gas it at any kinda speed it will stall.

I connected the scan tool and check codes. The only codes I have managed to set so far with a few trips around town driving is transmission solenoid circuit codes and a neutral safety switch circuit code. Both are expected as neither are connected. The computer thinks its in neutral but after driving it believes it should be in drive and sets that code. I'm going to try wiring it to think its in drive and see what happens. I don't expect much difference and I think I might see a new code for the engine starting while in drive. It's entirely possible the ECU is going in limp mode over the solenoid circuit codes however many have said the auto to manual swaps drive fine with the codes set. I'll try wiring resistors in but I have low expectations.

Scan tool data looks all good. The only thing that concerned me at all was the TPS percentage showed as 10% closed and 75% WOT. After searching on Mitchel, this is completely normal. The MAF readings seemed to be working but could be entirely inaccurate with a faulty MAF.

Things I've checked/done:

Vacuum leaks ok
MAF unsure
TPS apparently ok
Crank position sensor ok
Camp position sensor ok
Crank pulley bolt torque ok
Intake air leaks ok
Coolant temp ok 175/ little cold. Needs the 180 stat but the 170 was in stock.
IAC valve ok
Dashpot ok
Coolant temp sensor ok
Knock sensors ok
Compression ok/ 180 on all 6
o2s ok/ shouldn't matter when cold
Trans VSS okish/ not connected but no codes
Trans temp sensor okish/ not connected but no codes
Fuel pressure ok/ 35 idle 45 on accel. No drops over time.
No counted misfires ok
Timing marks alignment ok
Crank/cam reluctor condition ok
Disconnecting the battery
IAC relearn procedures.
Grounds ok
New NGK twin ground plugs
New wires
New PCV valve

That's all I can think of off the top of my head. What do you guys think is going on? Am I missing a sensor somewhere? From what I read, it should still run ok with the MAF unplugged. It's not the case with mine. I have tried disconnecting the battery a bunch of times between different test hoping to reset corrupt fuel trim tables.

Let me know what you guys think. I'll try to get those other things done asap but otherwise I'm almost stumped with this.

wyoming9

iTrader: (1)

Did you install a new fuel filter??

Kink a fuel line doing the rerouting ??

Since your not getting any engine codes not even a random miss code I think a fuel delivery issue

These swaps can be interesting to every thing is dialed in

Kolton5543

I didn't do a fuel filter with the swap but it has been changed about 5k before hand so its still pretty fresh. The fuel lines all check to be good. If it were a fuel flow problem I should be seeing some low pressure. I can accelerate as hard as I can and fuel pressure never drops a bit so it oughta be good. The gas in there is only a couple weeks old so shouldn't be bad. Its definitely something fuel related as a I can hand feed it fuel and it will run good. The way it does its thing though doesn't seem to be an injector problem at all. I'm pretty sure it has something to do with air metering. I think the ecu thinks this much air is going in but its not. Seems rich most of the time actually. I think the MAF is showing way too much air.

Kolton5543

Alright I lied. I don't think is showing enough air. If I hit it with starting fluid while revving it will revs awesome. Smells rich but is certainly way too lean.

vital22re

iTrader: (2)

It should not run without a maf. Unless you just have the fuel pump running with ignition on. The MAF triggers the COR to kick on which is what runs the fuel pump. Have you verified your repin to use the drop in style sensor is correct? The other thing to do is check your Fuel trims. Short term is what the ecu is doing right now for fuel, Long term is what its doing to hold a certain curve. Most often this will tell you if you're dealing with vacuum leaks or poor fuel delivery to the engine.

Kolton5543

Well I think I'll call it good. One of the cheap MAFs I ordered came in. I just installed it and it runs great now. This thing is a whole new truck. Its still a little off at idle but I think it has to do with the REALLY cheap MAF. This thing is so cheap it has a resistor in place of the cold wire. I just got this one since it would ship quick. Took only two days. I still have a Denso in the mail.

wyoming9

iTrader: (1)

With all these Issues not one Code ??

Is your OBII system working ??

Kolton5543

OBD seems to be working perfect. Even the live data. It makes sense thinking about it. I installed a 170 stat since it was the only one available in town. Its too cold not allowing it to enter closed loop mode. If the MAF sends a incorrect signal the ECU doesn't know it. It thinks that's how much air is going in so it will fuel for that. Being its in open loop it won't know if its rich or lean. If it were to enter closed loop it would be able to adjust for the most part meaning it would run better hot vs cold.

I appreciate any help. Everything I could think of pointed towards a bad MAF but I had a hard time believing my brand new Denso MAF was bad. I'm sure it got fried from the incorrect wiring. Hopefully it'll do better when the other Denso comes in.

Noil

Just went through something similar with replacing a 97 MAF with a 99 MAF on a 3rd generation 4runner, after I cleaned the used MAF and installed it still had issues. What ultimately resolved things for me with 2 new O2 sensors and a newer MAF was unhooking the battery for about 40 minutes (after unhooking turn the key on to let any power drain) to let the computer reset completely. When hooked the battery back up everything was good as new and ran as it should.