1MZ V6 misfire/surging when engine cold

[1JZ-Rolla]

Last resort to call for ideas/advice here please.... Toyota have had my 2001 Camry in for fault diagnosis four separate times now to no avail.

Issue presents as a sharp hesitation/misfire with cold engine temps (first few minutes of running in the morning), and mild surging under full load once hot. At all temps, engine idles and cruises perfectly, you have to be under reasonable load to cause the miss.

ECU shows no fault codes. Spark plugs appear fine, and have been replaced as a precaution anyway. High tension leads have been tested ok, coils tested ok (though one was replaced as "suspicous" but made no difference).

PCV valve is apparently clear, EGR valve has been removed and cleaned. There is no evidence of coolant loss (so hopefully no BHG). Injectors have been cleaned. 98 octane fuel has been tried to ensure it wasn't an octane/knock detection issue.

WTF do I check next?


ANY ideas welcome.

Cheers
Phil

[litldv8]

what gap do the spark plugs have?
have you pulled them out to check for a faulty plug ( i did read you replaced them)?
cleaned the throttle body?
just a few easy suggestions
neil

[1JZ-Rolla]

Can't gap the plugs, they are a pre-gapped with 4 (yes 4) ground electrodes.

Issue happened both before and after the plugs were changed.

Will check the TB, though was supposed to be cleaned same time as the EGR valve.

Thanks for the ideas, keep them coming!

Cheers

[Dazza]

Blocked fuel filter causing low fuel pressure maybe.

[1JZ-Rolla]

Thanks for the reminder, fuel filter has been changed already also. No improvement

[barned01]

same thing happens with our soarer but i put it down to old age of the computer and some old capacitors/electrical connections.
Is it a possibility to borrow a computer?

[wa5]

Fuel pressure reg (are they located in the pump housing on these?)

[neal]

My brother had very similar symptoms on his 1MZ as described but his turned out to be a faulty coil pack. The issue was very intermitent and would not happen all the time.

[cambelt]

They are a twin ground electrode and you can gap them smaller.
Dave

[william]

i replaced an injector on a forester last week doing exactly what you described. how were your injectors cleaned in car or on a bench?

[CELICASUPRA7M]

I'd chuch a set of new genuine spark plug leads on it.

[1JZ-Rolla]

Why would you gap the plugs down smaller than specified? This would only mask a shortfall elsewhere in the ignition system, rather than determining and rectifying the cause yeah?

Injectors were cleaned with a rig on-car. I'd prefer that they'd service them off the car, but they are a kent to remove.

[allencr]

Why would you gap the plugs down smaller than specified?

Because it's better then guessing & throwing new parts at it.

[1JZ-Rolla]

Might have made some progress on this.... Had a thought to disconnect the EGR valve sensor yesterday to see what happened, and nothing did. Didn't get worse, didn't get better. So I grabbed a replacement sensor from Toyota (cheapest option rather than replacing the EGR valve yet), but that wasn't the problem.

I removed the EGR valve assembly itself from the car this morning, its not blocked or anything, but it does nothing when vacuum is applied to the diaphragm. So it appears the valve is stuck, or diaphragm faulty.

Maybe this is the cause of the surging/misfire, maybe its not. But I guess I have to replace it if the valve is not operating at all, problem is, they are over 500 bucks....... so I'm hoping like hell that it actually is that!

Cheers
Phil

[TurboRA28]

Put it in an old celica with an autronic. Problem may go away.