Clio 172 Turbo - Idles okay but hunts after reving?

[Fishfire]

Hi all.

So I've had the top end off the engine to fit catcam valve springs and now the revs drop, surge a bit then go back to normal after giving the throttle a blip.

I've had this before a long while ago, and changed the crank position sensor and throttle body, which cured it, but the engine was running fine prior to working on it.

While the engine was out, it's had new belts, tensoner wheels, dephaser, water pump and spark plugs, oil and filter. Essentially a full service with belts and dephaser.

Any ideas?

 

[NorthloopCup]

There’s a possibility that the valve springs being stiffer aren’t opening the valves as far - this is based on the hydraulic lifters being put under more load from the stiffer springs.

The f4r doesn’t have good oil pressure from experience, so it could be the lifters not holding up to the extra load.

 

[Fishfire]

There’s a possibility that the valve springs being stiffer aren’t opening the valves as far - this is based on the hydraulic lifters being put under more load from the stiffer springs.

The f4r doesn’t have good oil pressure from experience, so it could be the lifters not holding up to the extra load.

Would it not do this at idle then too?
Starts, runs and idles fine...it just hunts after a throttle blip before going back to normal.

The valve springs aren't extreme tbh, only moderately stiffer and the same height. I'm just trying to prevent valve float at higher rpm.

 

[NorthloopCup]

Would it not do this at idle then too?
Starts, runs and idles fine...it just hunts after a throttle blip before going back to normal.

The valve springs aren't extreme tbh, only moderately stiffer and the same height. I'm just trying to prevent valve float at higher rpm.

It could be that the lambda isn’t seeing what it thinks it should be seeing after a throttle blip, so it’s trying to correct itself. The map will be saying I will see x amount of air/fuel at x throttle position. It could be getting the fuel, but not the air, so it would run rich

But I also do not trust the throttle body on these cars. On mine, it decided it didn’t want to play ball after not being used for a few months. It would start fine, but then when the engine was stopped, it wouldn’t fire up again. It made all the right noises and even did its self check with the butterfly too. Fuckin thing.

If you have a spare, it’s worth swapping over.

 

[Fishfire]

It could be that the lambda isn’t seeing what it thinks it should be seeing after a throttle blip, so it’s trying to correct itself. The map will be saying I will see x amount of air/fuel at x throttle position. It could be getting the fuel, but not the air, so it would run rich

But I also do not trust the throttle body on these cars. On mine, it decided it didn’t want to play ball after not being used for a few months. It would start fine, but then when the engine was stopped, it wouldn’t fire up again. It made all the right noises and even did its self check with the butterfly too. Fuckin thing.

If you have a spare, it’s worth swapping over.

My initial thoughts were:

- throttle body playing up
- crank position sensor
- air leak somewhere

Had very similar issues a while ago and fired the parts cannon at it, changing the TB and crank position sensor.

Would any of these throw up a fault code? Just had a look and the check engine light is on (though last time I checked, it was saying the vapour valve had gone tit's lol)

 

[Fishfire]

Appreciate the input

 

[NorthloopCup]

My initial thoughts were:

- throttle body playing up
- crank position sensor
- air leak somewhere

Had very similar issues a while ago and fired the parts cannon at it, changing the TB and crank position sensor.

Would any of these throw up a fault code? Just had a look and the check engine light is on (though last time I checked, it was saying the vapour valve had gone tit's lol)

Well the air leak is always a good shout, but I would expect it to idle higher from the get go. Worth spraying some brake cleaner around the inlet manifold area though to see if it raises the idle speed - obviously not spraying it near the turbo lol!

Have you let it get up to temp? If so, does it do the same thing?

 

[NorthloopCup]

Mine never put a check light on when the throttle body went fubar btw, but I was running a gen90, so not sure if they even do that?!

 

[Fishfire]

The vid was after it'd been run up to temperature with the fan kicking in.
It's been in bits since September, and this was the first time it'd been fired up since bolting it all back together.

 

[Fishfire]

Mine never put a check light on when the throttle body went fubar btw, but I was running a gen90, so not sure if they even do that?!

My car did similar a while back. Also had no fault codes so fired the parts cannon at it, which sorted it out.

Ideally would rather not do that again lol

 

[NorthloopCup]

Well I think plan of attack needs to be:

Check for leaks on the inlet
Swap out the throttle body

Gut feel though says the throttle body could be the root cause. If you can calibrate the ecu to run off track 2 on the throttle body, you should see a difference. That’s what was done on mine to sort it.

 

[Fishfire]

Well I think plan of attack needs to be:

Check for leaks on the inlet
Swap out the throttle body

Gut feel though says the throttle body could be the root cause. If you can calibrate the ecu to run off track 2 on the throttle body, you should see a difference. That’s what was done on mine to sort it.

Sounds like a plan.

I don't have anything that can access the ECU unfortunately, but from what you've experienced, it does point to the TB.

I may have a spare kicking around. If not, I'll find a good used one.

Thanks for bouncing ideas around....neon scratching my head over it most of this eve lol

 

[NorthloopCup]

Sounds like a plan.

I don't have anything that can access the ECU unfortunately, but from what you've experienced, it does point to the TB.

I may have a spare kicking around. If not, I'll find a good used one.

Thanks for bouncing ideas around....neon scratching my head over it most of this eve lol

No problem mate. I was that pissed off when I found out it was the throttle body on mine, I priced up a new one from Renault. Wasn’t as expensive as you’d think!

 

[Fishfire]

No problem mate. I was that pissed off when I found out it was the throttle body on mine, I priced up a new one from Renault. Wasn’t as expensive as you’d think!

Just looking now. Genuine TBs seem to be around the £400 mark