Frustrating misfire!!

[msherry21]

Hi all, I'm struggling to find a misfire on my rev3 turbo.

I've replaced the spark plugs and the leads, dizzy cap and rotor arm are all in good condition.
I've had the coil pack out but looks in good condition, was replaced when Tim rebuilt the engine. Coolant temp sensor replaced and Lambda sensor replaced too.

I've checked for vacuum leaks and checked every earth strap I could but still she misfires!

I've removed the Unichip too just in case that was an issue but nope!

When I start her from cold, she sits at about 1250rpm and sounds fine, then after about 2 minutes, still reading cold on the coolant gauge, she starts to misfire

Really need to get to the bottom of this as I can't drive it until I get it sorted!

Any help appreciated.

Cheers, Michael.

[PsyKen]

Have you checked the timing?

What is the unichip?

Ken, via TapaTalk 2.

[msherry21]

Hi, timing was done at the rebuild by TBDevelopments so will be correct.

The Unichip is a piggyback ECU. Now that I have removed it, it's out the equation.

Cheers, Michael.

[Chris_D]

What's the nature of misfiring ? regular i.e. 3 cylindering or just random missing. Is it just at idle or under load or under boost ?

Have you checked for error codes ?

[msherry21]

Seems to be random, as I said, seems fine for the first 2 minutes then starts misfiring in a random way.
No error codes stored.
It hesitates when driving, I don't even want to drive it just now incase I'm doing damage.

[littlemisstubby]

What does it idle at when fully warmed up? Does it still misfire when its warm?

Try swapping the IAT sensor with the one on the engine bay lid. See if that helps at all.

[msherry21]

Sorry, what ones the IAT sensor?

It idles at 900rpm approx when warm which is fine but still misfires.

[littlemisstubby]

The IAT is the air temp sensor that's in the stock airbox.

What ht leads are you using btw?

[msherry21]

It's a Rev3 I have and don't have a standard air box.

I have fairly recent Toyota leads.

[_Al_]

Any chance of a video?

[msherry21]

Good timing.

Here's a video of it starting from cold. At 4.13 you can see the revs drop a bit and it starts to misfire.

http://youtu.be/xtCDjYSo3GE

I hope someone can diagnose this!

Cheers, Michael.

[Howlin_Mad]

Knock sensor!

It's not very happy from the start, and the hotter the exhaust gets will pronounce the misfire even more. But it's pulling timing at 4 minutes when the ECU switches to closed loop mode, which happened on my V6 due to a blown knock sensor. Sounded exactly like yours. Coolant temp sensor might be worth a look too!

HM

[msherry21]

I've just replaced the coolant sensor to the ECU so that should be fine.

Where is the knock sensor? Is there anyway to test it?

Cheers for the help.
Michael.

[msherry21]

Ok, so I've just been under the car and disconnected the knock sensor, when I fire her up I still get the same result. Does that mean its not the knock sensor?