Temporary, intermittent loss of power/hesitation

[FLYNAVY53]

Yea I hear ya....thought mechanically it all makes sense. That being said, I've got two other project cars and this is my daily....not trying to get that far into it....

I wonder if you could just take it to a Toyota shop and tell them it needs a timing belt and a new crank cog. Dont even give them the opportunity to attempt to diagnose the issue for you.

 

[brillo_76]

Yes. I have never seen a 3.4 clog do that. However, that is the issue on that engine incorrect timing....;/

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[HiLife]

Wow, I too never saw a crank key wear like that too.
If your looking into that, the cause in your situation, I highly doubt that caused your P1126 as engine timing and throttle body magnetic clutch circuit are 2 different areas.

 

[96RedRunner]

A cog or key issue I don't think that'd be intermittent. I do know that a bad/intermittent ground can raise cane.
There is a grounding bundle attached to intake behind engine dianostic port that if loose will cause these symptoms.
My case was loose from VC job, that'd be first place I'd look. Don't just check tightness check for corrosion their dissimilar metals sand em clean.

All I got.

 

[gamefreakgc]

The power loss is back along with code P1126. If anybody has made progress on this please let me know. I’m going to take it to a shop to try to diagnose.

That's an extremely uncommon code. I had to look it up in the FSM and this is what it says:

DTC P1126 Magnetic Clutch Circuit Malfunction
CIRCUIT DESCRIPTION
Magnetic clutch is mounted between the throttle motor and the valve, and it connects the throttle motor with the throttle valve. Therefore, the throttle motor opens and closes the throttle valve through the magnetic clutch. If the electric throttle control system has a malfunction, the magnetic clutch separates the throttle motor from the throttle valve in order not to operate the throttle valve by the throttle motor. If this DTC is stored, the ECM shuts down the power for the throttle motor and the magnetic clutch, and the throttle valve is fully closed by the return spring. However, the opening angle of the throttle valve can be controlled by the accelerator pedal through the
throttle cable.

Sounds like your throttle body motor is to blame, or at least the ECU thinks so. I think a shop will just result in throwing parts at it as I don't know where to even begin diagnosing this one without throwing parts at it.

 

[96RedRunner]

[MENTION=115347]gamefreakgc[/MENTION], thats exactly what happens goes into limp mode pedal to floor gets you 30-35 mph.
With it coming and going I don't see it being a bad motor maybe on it's way. That don't jive completely.
Any/most shops would love seeing this show up throw parts at it big bill.

 

[gruenegenes]

A cog or key issue I don't think that'd be intermittent. I do know that a bad/intermittent ground can raise cane.
There is a grounding bundle attached to intake behind engine dianostic port that if loose will cause these symptoms.
My case was loose from VC job, that'd be first place I'd look. Don't just check tightness check for corrosion their dissimilar metals sand em clean.

All I got.

I appreciate the suggestion. I had already inspected and cleaned the grounds in the engine compartment. When the problem came back I removed and inspected that particular bundle. It was fine.

 

[gruenegenes]

That's an extremely uncommon code. I had to look it up in the FSM and this is what it says:

DTC P1126 Magnetic Clutch Circuit Malfunction
CIRCUIT DESCRIPTION
Magnetic clutch is mounted between the throttle motor and the valve, and it connects the throttle motor with the throttle valve. Therefore, the throttle motor opens and closes the throttle valve through the magnetic clutch. If the electric throttle control system has a malfunction, the magnetic clutch separates the throttle motor from the throttle valve in order not to operate the throttle valve by the throttle motor. If this DTC is stored, the ECM shuts down the power for the throttle motor and the magnetic clutch, and the throttle valve is fully closed by the return spring. However, the opening angle of the throttle valve can be controlled by the accelerator pedal through the
throttle cable.

Sounds like your throttle body motor is to blame, or at least the ECU thinks so. I think a shop will just result in throwing parts at it as I don't know where to even begin diagnosing this one without throwing parts at it.

I appreciate the info. I had replaced the throttle body with a new OEM part.

 

[gruenegenes]

Update: I took it to a dealership for the first time yesterday and by the time they got, it had thrown a new code, P1129, which I guess is kind of encouraging because the procedure in the shop manual for this code is to replace the ECM which I was considering anyway. I found them refurbished by these folks for $255. It’s either try it or sell the vehicle. I’m gonna give it a try. By the way, the problem is gone again

2002 Toyota 4Runner 3.4L - PCM ECM ECU | 89666-35591 | Flagship One

 

[gamefreakgc]

Update: I took it to a dealership for the first time yesterday and by the time they got, it had thrown a new code, P1129, which I guess is kind of encouraging because the procedure in the shop manual for this code is to replace the ECM which I was considering anyway. I found them refurbished by these folks for $255. It’s either try it or sell the vehicle. I’m gonna give it a try. By the way, the problem is gone again

2002 Toyota 4Runner 3.4L - PCM ECM ECU | 89666-35591 | Flagship One

Last thought, any visible damage in the wiring (cracking, peeling, severe discoloration of wire sheathing) from the plug on the throttle body to main engine harness? Any splicing or hackjobs visible further down the wiring harness?

A simple inspection of the ECU may be enough to tell. It's easy to get to, just pop the glove box out by taking out the 10mm bolts and it's two screws to get the ECU out. Then you can remove the cover and look for any black marks or discoloration revealing a short or a damaged/leaking capacitor (the tall battery looking things).

 

[gruenegenes]

Last thought, any visible damage in the wiring (cracking, peeling, severe discoloration of wire sheathing) from the plug on the throttle body to main engine harness? Any splicing or hackjobs visible further down the wiring harness?

A simple inspection of the ECU may be enough to tell. It's easy to get to, just pop the glove box out by taking out the 10mm bolts and it's two screws to get the ECU out. Then you can remove the cover and look for any black marks or discoloration revealing a short or a damaged/leaking capacitor (the tall battery looking things).

I don’t see damage to individual wires, but the harness casing is in bad shape. Once the new ECM arrives and I have it replaced, if the problem returns, I’m considering replacing the individual wires that go to the throttle body. Either that or sell the vehicle.

My first job out of college as an engineer was with Motorola at a factory that manufactured engine and body control modules. Our quality was great, but when when we had a failure, the most common defect was a poor solder joint which can be intermittent. Hopefully that’s what’s going on here. I’ll keep you guys updated. Really appreciate all your help.

 

[Difi__]

I don’t see damage to individual wires, but the harness casing is in bad shape. Once the new ECM arrives and I have it replaced, if the problem returns, I’m considering replacing the individual wires that go to the throttle body. Either that or sell the vehicle.

My first job out of college as an engineer was with Motorola at a factory that manufactured engine and body control modules. Our quality was great, but when when we had a failure, the most common defect was a poor solder joint which can be intermittent. Hopefully that’s what’s going on here. I’ll keep you guys updated. Really appreciate all your help.

I know this thread is old but I’ve been looking at it often over the last year.
I was having this issue, particularly at 1/4-1/3 tank of gas. Eventually it got so I wouldn’t even get power back and would have to clear the code to drive again. I was also not able to start on the first or second try after refueling without pumping the gas pedal. Turns out I probably had a bad purge valve on my charcoal canister that made it get super clogged and flood my engine with fumes when gas was low, or freshly refueled, causing that randomass code.
I tried new ECU, new throttle body, to no avail and then I was telling someone about my refueling issues and he guessed it right away. We weren’t expecting it to necessarily fix the code, but it seems to have worked. About 800 miles since installing a new charcoal canister, no stalling, no codes. And starts right up every time after refueling.

So if anyone here is still dealing with this, check that out,