CEL code 24, stuck in limp home mode :(

[BackWoodsBob]

I swapped out an older, lower compression engine with a newer engine which idled perfectly, ran strong. I've had a code 24 for almost a year now (wiring related), but, it's never put me in limp home mode.

Car idles PERFECTLY, idles a bit high, then drops down as it warms up. But it wont let me rev past 1500rpm or I hit fuel cut.

Ideas? I'm pretty much ****ed if I can't get the car driving before saturday. ANY advice, help would be appreciated on how to bypass this code, or fix it.

Should be noted.

: AACV (brown/black) doesn't go anywhere off the ECU
: IACV's white/red wire (at the plug under the manifold) goes to my canister purge control (at the ecu).

[BackWoodsBob]

is code 24 for the system that's right on the xover pipe on the engine, or the idle air control valve connected to the throttle body?

[BackWoodsBob]

been doing some looking at the fsm and from some help from BRZ cory, it seems my code 24 is causing my issue. At least that's the only lead I have right now as to why I'm in limp home mode.

So far I have determined that my White and my Brown/white wires aren't 'emitting' the proper voltage. At least according to the FSM.

Also according to the FSM the third wire, the white/red (on the iacv/aux air control valve) goes directly to the main relay. Does this mean it requires +12v?

[BackWoodsBob]

The insane part is, I'm stuck in limp home mode. I don't understand why either. This code shouldn't cause limp mode should it?

Rev limiter at 1500rpm and such.

[BackWoodsBob]

Anyone know of any way to reset my way out of safe mode?

[icingdeath88]

So the AACV (the one on the crossover pipe) is not wired to the ECU? I would block off the TB and intake ports that it connects to in that case. Although it may work ok, since the bimetallic valve will warm up and gradually close as the engine warms up on its own, by design, the ECU controls a heater that can close the valve earlier than it would just from the engine heat, which I think is a good thing. With the AACV open, and no torque converter, my car idles around 1500 rpms, once it closes, about 5-600. AFAIK, disconnecting it shouldn't throw any codes, and shouldn't cause any serious issues, except perhaps some idling or startup issues in cold weather.

The EG33 IACV is a 3-wire pwm type. The middle wire is the +12V, and the other two wires are grounded at the ECU to either open or close the valve. So the middle wire does need to have a solid, +12V source. I would look into that if I were you, and see if you can improve the situation.

I don't know if the code 24 would put it into limp mode though...

Do you have a spare IACV or MAF to swap in to see whether that fixes it?

[BackWoodsBob]

aha, so the center iacv wire does require 12v. I'll try that tomorrow.? y aacv has +12 at the blue wire and ground at the black but died not go to the ecu. could an o2 sensor cause a 1500rpm rev limiter? I appreciate your response, thank you!

[BackWoodsBob]

maf was tested with the unplug test. no change other than running horribly. I do have another iacv on my spare engine but it threw the same code.

[Tapani]

Originally Posted by BackWoodsBob

could an o2 sensor cause a 1500rpm rev limiter?

No, it will just ignore the fuel trim function and use maps open loop. Even just for one bank.

/T

[BackWoodsBob]

damn. alright well there went that idea haha.

[BackWoodsBob]

I fed +12v to the center wire of the IACV plug, idles even better now. Eliminated code 24, now I have a code 34, which is EGR valve inoperative. I'm also rev-limited to 3000rpm .

I have a spare EGR solenoid so I'll tray swapping it I guess. I'm also going to reset the ecu real quick and see if that helps.

[BackWoodsBob]

Reset the ecu, back to a 2,000rpm limiter. :eyes4:

got codes 55,35,34, all of which are egr related. I'm going to yank those sensors and see what happens.

[icingdeath88]

Originally Posted by BackWoodsBob

I fed +12v to the center wire of the IACV plug, idles even better now. Eliminated code 24, now I have a code 34, which is EGR valve inoperative. I'm also rev-limited to 3000rpm .

I have a spare EGR solenoid so I'll tray swapping it I guess. I'm also going to reset the ecu real quick and see if that helps.

You should have more engine braking now too, since the IACV can now close when rpms up, but throttle closed. I'm surprised it worked as well as it did; the purge control pin at the ECU is a ground, not a +12v.

So before it got up to 1500 rpms and now after fixing the IACV it goes up to 3k?

[BackWoodsBob]

Originally Posted by icingdeath88

You should have more engine braking now too, since the IACV can now close when rpms up, but throttle closed. I'm surprised it worked as well as it did; the purge control pin at the ECU is a ground, not a +12v. This wiring is untouched

So before it got up to 1500 rpms and now after fixing the IACV it goes up to 3k?

Yes, previous to fixing the iacv I was re-limited to 1500ish rpm. After fixing that I could rev to 3000. I've just reset my ecu and now I'm stuck back around 2000rpm.

I'm checking all my connections as I go, nothing seems loose.

[BackWoodsBob]

Gonna try swapping crank sensors.