IACV Location

[Steele]

G’day, once again I have a pretty amateur question compared to what most you fellas are doing out there but I’ve gotta start somewhere.

would someone be able to post a photo of where the Idle Air Control Valve is located? I’m experiencing a pretty rough idle and guessing I need to give it a good clean out

 

[AlWorms]

It won't give you a rough idle - more unstable... and they don't fail as often as people seem to want to replace them anyway.

It's a giant looking Nut thing, on the RHS of the plenum, at the rear.

You're in Aus, right? so you have a 3.9 with 14CUX. Most on here are US based, so they got GEMS from 95, so a lot of that info doesn't apply to your car.

 

[Steele]

Yeah by rough idle I for sure mean unstable. Not only unstable but an occasional (daily) stall when I go from driving to stationary. Which makes me think it’s not getting enough air. Just swapped out all spark plugs and leads and still experiencing the low and fluctuating revs in idle.
Now I do have dual fuel, unleaded and LPG and I’m not experiencing the fluctuating revs while running LPG so could it be a tuning issue?

yes I’m in Australia.

also, when you say giant looking nut thing, is it the one with a spring on it? Otherwise I’ll definitely need a photo lol.

 

[kris812]

I would start looking for vacuum leaks before changing parts. Albeit it does sound like a IAC issue, a vacuum leak does similar things. Check over the intake Tube for cracks, look over hoses, suck down the brake booster and make sure it holds vacuum.. Then buy a 20$ IAC on eBay to test with.

 

[Steele]

I would start looking for vacuum leaks before changing parts. Albeit it does sound like a IAC issue, a vacuum leak does similar things. Check over the intake Tube for cracks, look over hoses, suck down the brake booster and make sure it holds vacuum.. Then buy a 20$ IAC on eBay to test with.

Yes you’re probably right, I’ll give that a go but if it is the IAC, I wasn’t planning on replacing it, just cleaning it with a carbon cleaner. Then if it’s not doing its job, replacing it would be the way to go but not until I find it and clean it.

any chance someone could show me where it is with a picture? Or any links to diagrams of where it is?

 

[boxster]

Yes you’re probably right, I’ll give that a go but if it is the IAC, I wasn’t planning on replacing it, just cleaning it with a carbon cleaner. Then if it’s not doing its job, replacing it would be the way to go but not until I find it and clean it.

any chance someone could show me where it is with a picture? Or any links to diagrams of where it is?

4.0 SFI and 3.9 MPI

 

[AlWorms]

I'd suggest building/buying a rovergauge cable, and start there.

What year is it, and does it runs Lambdas?

It's a really simple EFI system, but plenty of people fiddle with things and bodge them up.

Check your timing. Personally, I run 10 BTDC on my high compression with lambdas, and run 95 octane (I'm in NZ).

You need to check your Throttle Position Sensor (TPS) is working too. It controls whether it's in idle mode or not.

Clean out the entire PCV system including the "flame trap" and the restrictor in the tee behind the distributor. Make sure the system in entirely intact, indluding the inlet on the rear of the rocker cover with the oil filler. Clean out the idle bypass screw path, make sure the throttle plate closses to perfectly vertical (should be 0.5mm max difference, top to bottom from the intake snout).

Once that's done, set a base idle as low as you can get it, with the IAC closed (with rovergauge), or remove the pipe and completely block both ends. You should be able to get a stable base idle of 525RPM +/-25 on a properly warmed up engine. The lower, the better as long as it's smooth/stable.

Can you post a pic looking down on your engine bay? One of the whole thing, and one more just the engine itself?

 

[Steele]

As I’m sure you can see, my Airbox needs replacing. I’ve had backfiring occur in the past which has blown it to bits. In the process of finding a new one. Anyone know if I can get a replacement out of any old disco or does it have to be the exact make and model?

 

[kris812]

I SPY a missing vacuum hose on the intake to the right of the 3.9!!!
I SPY a loose intake hose on the MAF sensor. Along with possibly too short of intake to TB hose.


VERY VERY IMPORTANT all air goes through the MAF and not through open ports or leaks on the intake!


I also spy a missing fan Shourd. But how's that Rad holding temps and who makes it??

But to answer your question, The air filter box "appears" to be the same as my 96 USD

Not using the Snorkle???? PIPE from MAF to snorkel and ditch the air box for battery/tool/jack storage.

 

[Steele]

You’d have to point out that missing vacuum hose. To me it all seems to be there.
And I’ll definitely have a better look at the MAF
Yes it’s just a fan, no shroud around it but yes, the radiator is pretty dope, temp never goes past half. Never overheated. No idea who makes it.
As you can see the snorkel is also blown, obviously the backfiring has been an ongoing issue since before I bought it.
And I’d say the Airbox is where it is because it’s been converted to a dual fuel so they’ve had to put the lpg motor there.

 

[Steele]

P.S. I apologise for my naïveté when it comes to vehicles. It’s my first car, I’m only just learning a lot of this stuff. When I first bought it I didn’t even know about coolant let along all this stuff. So it might take me a little while to get on the same page.

 

[kris812]

At the Very least CAP that intake port that's open! That's a huge vacuum leak! It's BAD fix that

Loosen those hoses and push them on better and tighten them.

Then re test, I bet it runs a LOT better capping that port.

As for the temperature, the gauge is worthless and always reads halfway. Get an ELM327 and torque app on your phone or a rovergauge to see real temperatures. People warp heads at halfway on the gauge..

Nothing wrong with learning! Just make sure you listen whenever people tell you things.

The RAV manual for these things are pretty easy to follow and free on here somewhere.

 

[AlWorms]

That looks like a massive vacuum leak, right there, plus that's the PCV system, that puts a light vacuum on the crankcase. That TEE is the one with the restrictor in, that can get clogged too. It's plastic, so be gentle! With the engine idling, if you cover the end of that metal pipe, the engine speed shoudl reduce dramatically. That thinner black hose should be on that metal pipe.

Air should be whistling in there! I'd be VERY surprised if that wasn't you idle issues (mostly!).

And you need a fan shroud.
I have that same radiator. Without the shroud, the fan circulates more air than it pulls through the radiator, the temp creeps up to 100C and the electric fans kick to to cool it down.

With the shroud on and a functioning Viscous fan, my temp sits between about 87 to 92C at idle and cools quickly as the engine speed increases. I'd get one for sure.

There is a little blue fitting on the firewall behing your throttle. Does that connect to the rocker cover, and the airbox? There is a hose that should, similar diameter to that.

The air filter would normally bu much further back - the MAF wiring just about touched the washer fluid bottle! If it's backfired that much (on LPG I assume, igniting in the intake!) the MAF might not be too happy either. In Aussie, just about all EFI Discos would have that that housing, or the round cylindrical one made of metal. Any plastic one should work, thought yours must have a "custom" mount under it, or extra mounting holes etc.

 

[AlWorms]

Link to where the hose should be:
https://www.defendersource.com/attachments/ohcah459rg28a-wavcuvha-jpg.398168/

 

[p m]

Is that a propane/LPG injection thing between MAF and throttle body? Are you using LPG?

 

[kris812]

Yes the OP is also using LPG. No issues on LPG.

Now to explain some things for the OP. The IAC is a stepper motor that opens to allow a controlled vacuum leak so that you can idle. If you have any leaks like that missing hose, your IAC will be fighting or at its limits of adjustment.

Fix that leak and report back.

It's possible you have something else going on like plug wires in the wrong spots, distributor turned, or skipped/loose timing chain causing backfires.

And get a fan shroud, ask us how we know.. Save yourself a head gasket and headaches..

 

[AlWorms]

It's running a 14CUX ECU, so Rovergauge is the only really useful diagnistics tool. Outside of the US, all the Disco 1 V8's ran 14CUX as EFI.

 

[Steele]

Link to where the hose should be:
https://www.defendersource.com/attachments/ohcah459rg28a-wavcuvha-jpg.398168/

I’ll take a look at that and let you know. Thank you for your help

 

[Steele]

View attachment 66235That looks like a massive vacuum leak, right there, plus that's the PCV system, that puts a light vacuum on the crankcase. That TEE is the one with the restrictor in, that can get clogged too. It's plastic, so be gentle! With the engine idling, if you cover the end of that metal pipe, the engine speed shoudl reduce dramatically. That thinner black hose should be on that metal pipe.

Air should be whistling in there! I'd be VERY surprised if that wasn't you idle issues (mostly!).

And you need a fan shroud.
I have that same radiator. Without the shroud, the fan circulates more air than it pulls through the radiator, the temp creeps up to 100C and the electric fans kick to to cool it down.

With the shroud on and a functioning Viscous fan, my temp sits between about 87 to 92C at idle and cools quickly as the engine speed increases. I'd get one for sure.

There is a little blue fitting on the firewall behing your throttle. Does that connect to the rocker cover, and the airbox? There is a hose that should, similar diameter to that.

The air filter would normally bu much further back - the MAF wiring just about touched the washer fluid bottle! If it's backfired that much (on LPG I assume, igniting in the intake!) the MAF might not be too happy either. In Aussie, just about all EFI Discos would have that that housing, or the round cylindrical one made of metal. Any plastic one should work, thought yours must have a "custom" mount under it, or extra mounting holes etc.

Well that’s embarrassing definitely fixed the low/rough idle + stalling when starting issue. What a quick fix jesus.
I also reconnected the other rubbers to get rid of any small gaps from the MAF. She sounds a lot better.
I’m sure you’re all slapping your foreheads and shaking your heads thinking “no shit Sherlock”. Thanks everyone

 

[kris812]

Ya, well all this talk and I went out to clean my IAC today for giggles and a 500rpm idle the other day. Tune-up Sunday!
Hey at least I did something today! 5 mins work cough cough.. Honey I'll be working on the Rover for a couple hours!