FTO AUSTRALIA

Hi guys,

I've recently had the top end of my engine apart.
So intake manifold, Y manifolds, cams, cam trays, and valve springs, timing belt, fuel rail, injectors etc were all out.

I've assembled everything and tried to start the car however the rpm are hunting.

I've disconnected the idle speed control valve and it made no difference.

What could this be?
Would a misaligned crank or cam sensor cause such issues?
Besides the hunting the engine is smooth and sounds fine (I did a tappet adjustment as well).

I don't think a vacuum leak could cause such hunting could it?
There is a slight injector leak as well where the o-ring didn't seat properly but it is very minor

Was the battery disconnected at all?

Yeah it hadn't been connected for a few months.

But it's never done this during previous times I've disconnected it + I waited until it warmed up completely and the hunting never went away.
Nor did the idle rpm drop into the 700 range

I've just had a look at the video I took when I first started it and the rpm were fine so the issue only started a little bit after it idle for a couple of minutes.

Any ideas?
So much has come off that I don't even know where to start looking other than going over and making sure all plugs are plugged in etc and perhaps do an error code diagnosis

Even though it's never done it before it's a common occurrence when the battery is disconnected and it has to relarn to idle.

BJK had the same issue recently, he claimed it had never done it before. He made a bet with me that his stepper was stuffed.

He lost the bet after driving it around for a bit and it fixed itself. :lol:

The issue is though that I unplugged the stepper motor and the rpm were still erratic.

I noticed that one of the injector o-ring isn't in properly so I am hoping maybe this is just causing a vacuum leak to one cylinder but I would expect the rpm to fluctuate so much over a bit of a vacuum leak?

Vectose wrote:Even though it's never done it before it's a common occurrence when the battery is disconnected and it has to relarn to idle.

BJK had the same issue recently, he claimed it had never done it before. He made a bet with me that his stepper was stuffed.

He lost the bet after driving it around for a bit and it fixed itself.

Yeah, but it wasn't hunting. It would just drop without any throttle input or motion.

Can do both

Thanks for the help guys.

So I started it up again today (after battery disconnect) and it didn't hunt anymore. Rather it did but really slowly and over about 100rpm or so that went away gradually.

I did find a vacuum leak between the plenum and throttle body.
I had the plenum bored out 5mm and part of it welded to get rid of an obstruction of where the 5mm extra size for the 6G74 TB was and I assume this must've done something to the two pieces that mate together as there is a bit of a ridge there now.


What would be the best thing to do here, use some kind of RTV sealant or get a machine shop to skim it flat?
Anyone know of a machine shop in Melbourne that can machine it flat?

Plenty of machine shops in Melbourne just google it.

If you're game, you can give this a crack - I would imagine it would be the same principal on a plenum to measure and get it flat

https://www.youtube.com/watch?v=SK2R2LdkLKs

Here's another one but with more detail:

https://www.youtube.com/watch?annotatio ... yKN52HD6RU

I ended up using some permatex sealant for the time being.

Have you had any experience with machine shops in Melbourne by any chance?

The last time I spoke to a machine shop to bore out the opening my 5mm they said they could do it but it may take them 1-2 hours to set up the intake manifold in their machine so the cost was prohibitive

I just used a carbide burr on a die grinder. Made quick work of it and no issues with sealing, even under boost.

How would that get it perfectly flat though?

I'd assume that the TB bolts need to be removed and the whole face machine down 1mm or so to get it perfectly flat

I meant for the boring out. Didn't touch the face so no issue.

You could just chuck it on a belt sander.

If you notice there is a bit of a tab that obstructs the opening once it is bored out to 65mm.
I had that welded up and then bored out so there is no obstruction.
So the welding must've shifted the metal a tiny bit hence the ridge now.

How would those 2 bolts be removed from the intake manifold for it to be skimmed?
If I do that I can take it to some machine shops to get it perfectly flat