Engine swap IAC problems...

oookay this is a doozy.

Bought my 1998 Taco about four years ago. 137k miles, 2.7l 4x4 manual trans. Got UVB and bought it from out of state, drove it 1100 miles home. Only some funky issues over the first couple years like a weird braking shudder blahblahblah.

Things started to go downhill and I come to find out the engine was pretty knackered. 100% leakage from first cyl and 50% from fourth. Leaks. Other issues.

So I put a new engine into it. Well, my mechanic and I did (I wanted to learn). We went to a Japanese import place in LA and picked up a 2.7l that matched up.... well as we do it there's a couple differences. The only thing we really ended up using was the block itself. It had two dipsticks (?) one of which caused an oil leak later that I plugged.

That was probably a year ago, maybe 15-20k miles. There's a sensor on my truck that doesn't go into the new engine... and honestly it was running great and I didn't need new tags so I've been putting it off. The idea was that we had to drill and tap to put the sensor into the new engine. Well my mechanic found a work around with a 10k ohm 1/4 watt resistor. This is where stuff starts going over my head.

Long story short the code is an IAC system error. My original engine was the E3Rz-N73, and in trying to research to figure out what the hell this engine could've come out of... I'm more confused than ever.

The IAC has been replaced.

Has ANYONE heard of an issue like this or maybe know what the problem is? I feel like it's something simple-ish that we haven't figured out.

Also yes I've read the other posts about the diff 3rz engines, the one I got was not a distributed version but set up for coils as the og one did.

Thanks in advance!

 

What sensor are you bypassing? With the resistor back out does the problem go away?

 

The RGA sensor (if I recall correctly... no many abbreviations haaaaaugh I wish I was better at this stuff but I'm still learning). I proposed that the sensor was the entire problem but the resistor is *supposed* to bypass / fake it out.

And no, we just added the resistor to try to bypass the issue. Now it's idling 650-750 where it should be (was around 3-500 before) but the friggin check engine light is still on and it's throwing the same code.

 

Rga? You mean EGR?

 

Haha yes! Was distracted and had heard about a thousand abbreviations that day.

Update: despite it idling exactly where it needs to be (600-750) and having a new IAC valve, my check engine light hasn't come back on in over 150 miles, it just failed DEQ for idle air control problems.

Any help would be greatly appreciated. I'm supposed to be leaving on my road trip for 6 months next week but have to pass DEQ first (reg expires October).

 

We also did a smoke test and checked for any vacuum leaks... there are none.

 

How did it fail DEQ? And what is DEQ?

 

It failed for idle air control problems.

Same p0505 IAC code that I'm posting about being the entire issue.

DEQ is emissions testing.

 

These are all possible causes of that code:

• IAC valve is stuck or closed
• Open or short in A/C switch circuit
• Open or short in IAC valve circuit
• Air induction system
• ECM

Also, here is the FSM for a 99, should be pretty much the same for a 98 https://www.tacomaworld.com/threads/1999-3rz-fsm.491605/
Search for that code and you will find the diagnostic procedure.

 

- IAC valve has been replaced
- "
- "
- smoke test shows no vacuum leaks
- you saying the ECU could be having a general problem resetting and reading or deleting the code?

Appreciate the input.

 

First things first, have you tested the function of the IAC?
You can do this on the vehicle by connecting terminals TE1 and E1 on the diagnostic port under the hood. This should raise the idle to 1000-1500. This is just disabling the IAC and I believe that it opens it fully. This is on page SF-34 in the FSM I posted.

 

Did you get it fixed Alicia?

 

The IAC is working properly because it can be messed with using the snap-on diagnostic tool.

No, and I've got some more info.

I believe the issue lies somewhere in the fact that I used the whole air intake, throttle body, etc, from the "new" (45k mile japanese import) engine. I talked to the guys I got it from, JDM in LA, and they said that the issue is probably that the intake and throttle body are Japanese parts and therefore different sensors/sizes/systems that don't match perfectly with the ECU.

After finding out it could've only come from a T100, Tundra, or Tacoma in Japan... a few more things have been figured out. My mechanic said he believes my engine is out of a 2000 or later T100. Now I need a pre-2000 intake and throttle body.

I would really love to know if there's a way to "fake out" the computer here. Truck runs great and I need new tags.

 

T100 was last produced in 99-00, the Tundra replaced it. Tundra never had the 2.7L, only 3.4 or 4.7.

did you use the MAF from the new engine or use your old one?

 

Did you clear the codes? Once cleared, there should be no codes unless the check engine light comes on. The readiness monitors will still take some driving to be ready.

 

From what I've gathered it doesn't have the EGR valve on her new intake. OP could you take some pictures of the manifold and throttle body and post them? Also I picture of the vacuum diagram under the hood. If its still there.

 

Here is the diagnostic procedure for that code. Obviously your setup is not stock, but if it were me I would follow this procedure as closely as you can. If you need the other pages just download that entire manual I linked to earlier.

The sensor that your mechanic bypassed was most likely the EGR temp sensor. This is the only sensor that the EGR system uses. He probably wired a resistor in to make the computer think that the EGR valve is opening at certain rpms(hot exhaust gas entering the intake).