2.4 power loss is defeating me - Alfa Romeo Forum
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(Post Link) post #1 of 48 Old 02-06-19 Thread Starter
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2.4 power loss is defeating me

A plea for guidance. 2008 on a 57 2.4 which has done 70K miles.

Started getting episodes of total power loss when pulling away, nothing at all whilst the revs built painfully towards 2,500 then woosh, off she went. That happened very occassionally.

Fast forward to the last few weeks and that same issue had become more prevelant.

Referring to the guide in the sticky I have so far.

1. Removed the EGR, cleaned it, checked the movement is smooth and refixed with the 4 hole restrictor plate and the 3 hole waster from AlfaWorkshop.
2. Cleaned the MAP sensor, which was a bit clogged
3. Disconnected swirl flaps and fixed them to the left ( which makes it start and idle smoother )
4. Checked and cleaned the boost sensor on the slam panel
5. Got MES to perform a forced DPF regen which completed
6. Sworn at it quite a bit.

Its worse.

Its slightly better if I put it into sport, but its become undrivable. Pulling away it can take a few hundred metres of almost idling along before the revs gradually rise.

There are no fault codes showing up that I can find although I sometimes get a glow plug warning when starting, but its been like that for years.

My thoughts are that it might be turbo related and I will check the 2 pipes that go to the boost sensor but what else could I check? In fact, whats the best way to check them?

Could the MAF cause the symptoms described? I've changed it in the past and I cold try disconnecting it I suppose. I'm reluctant to try too many things at once.

Anyway, thats what I need some wisdom on please and a virtual light ale to all respondants in the usual way.
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2.4 power loss is defeating me

I have some of the same issues. Following.
One thing I thought of was getting the turbo cleaned.
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sounds like sticky vnt vanes to me, need to check the vac circuit out first to make sure it is producing vac and you get full vac out of n75 down to turbo.
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(Post Link) post #4 of 48 Old 03-06-19 Thread Starter
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Originally Posted by johnnyroper View Post
sounds like sticky vnt vanes to me, need to check the vac circuit out first to make sure it is producing vac and you get full vac out of n75 down to turbo.
Now thats interesting. I've had a little google around and can't find much on how to get at teh vanes to check, or indeed if thats possible! Whats the best way to check the vac circuit? I will check the two small pipes by the slam panel but are the bigger pipes down below likely to be suspect?
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You want a mitivac/vac gauge with engine idling you should get over 20hgvac from pump,same at n75 inlet and roughly the same from n75 down to vnt actuator.

As for checking vanes if you can access the turbo try moving the actuator see if arm on turbo moves freely it’s entire length of travel. Should only have slight resistance from diaphragm. If you can see it the actuator should move arm to its max position when on idle if vac is good.
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Right, where my pump is situated on the side of the cam cover it seems to be leaking oil very slightly, are the pumps prone to this or is it a case of a new gasket?
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Oil leaks from the vac pump are relatively common, it shouldn't affect the vacuum produced though.

As others have said, I'd check operation of your VNT vanes, a mityvac or chinese clone from eBay will allow you to check movement, and you'll hear them when they close.

Another issue is the N75 valve, they do fail, and an OEM replacement is about 40-odd quid from Shop4parts, also another member on here found they plumbed theirs in wrong after some work, giving similar symptoms to yours - swap the vacuum hoses round and see how you get on?

Also, might be worth checking unplugging your MAF and running it, if it makes a difference, then your MAF is done, if so, replace it with a Bosch original part.

Have also seen just one of the swirlflaps closed, due to a work linkage which has caused issues.

Main culprits seem to be; boost leaks, stuck open EGR valves, dirty or knackered MAP and MAF sensors and sticky turbo vanes.

Apologies if I've missed, but has there been any engine warning lights, or fault codes?

Posting from my phone - excuse spelling mistakes
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(Post Link) post #8 of 48 Old 04-06-19 Thread Starter
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Originally Posted by amfalconer View Post
Oil leaks from the vac pump are relatively common, it shouldn't affect the vacuum produced though.

As others have said, I'd check operation of your VNT vanes, a mityvac or chinese clone from eBay will allow you to check movement, and you'll hear them when they close.

Another issue is the N75 valve, they do fail, and an OEM replacement is about 40-odd quid from Shop4parts, also another member on here found they plumbed theirs in wrong after some work, giving similar symptoms to yours - swap the vacuum hoses round and see how you get on?

Also, might be worth checking unplugging your MAF and running it, if it makes a difference, then your MAF is done, if so, replace it with a Bosch original part.

Have also seen just one of the swirlflaps closed, due to a work linkage which has caused issues.

Main culprits seem to be; boost leaks, stuck open EGR valves, dirty or knackered MAP and MAF sensors and sticky turbo vanes.

Apologies if I've missed, but has there been any engine warning lights, or fault codes?
Thanks for that. No codes in MES other than an intermittent glow plug issue thats been ever present since I first checked it some years ago.

The N75 valve is the one on the slam panel??? I have a vacuum tester being delivered today courtesy of good old Amazon. I need to check both sides of the valve do I? I presume somewhere at the end of the 'out' hose if so.

I have has MAF issues in the past and I havent tried running it with the MAF unplugged. I know that will give a warning light but it just defaults into a standard map. That should at least show if it helps the lack of revving.

I need some help on checking the actuator on the turbo as well. I have found a video on removing the turbo on a 4 cylinder but nothing on checking the vanes operation. Any pointers??
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With your vac tester check what’s coming from pump first,you should get roughly same figure on N75 outlet. And yes that’s the valve on slam panel.
If you have a hand tester on outlet pipe pump up to say 17hgvac and see if the actuator on turbo will hold a vac
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That's correct, the N75 is the one on the slam panel, 2 vacuum hoses and a electric plug, the hoses are actually sightly different sizes, so shouldn't be easy to mix up, unless they get a bit old and flexible, as most will be by now - see pic pinched from @ajbruce4884

If you can remove the hose which leads down to the turbo, you can actuate the vanes, you'll see vacuum building up, and at a certain pressure, you'll hopefully see the diaphragm rod start to move - hold it a while to make sure it holds vacuum, and them release, if all is well, you'll hear the soft click of them closing again.

As regards to testing the valve, you'll need to disconnect the inlet hose - running to the vacuum reservoir and connect your tester, with the engine started, you should see the vacuum build, with the revs increased, you will notice this sharply return to zero once the valve opens, and build up again - on the outlet you will see the same, but in opposite, little/no vacuum at idle, and when the revs rise, and the valve opens the vacuum will increase.

The vacuum system is quite simple, hose from diaphragm to N75, hose from N75 to vacuum reservoir (under intake manifold, supplied by vacuum pump)

Re: unplugging the MAF, mine didn't throw any codes, and drove as before, albeit with increased fuel consumption.

As for removing the turbo, don't be too rash, it's supposed to be a pig of a job, and often the manifold studs snap - if the vanes are blocked, there are treatments which might help unstick them - some even use oven cleaner, but I'll leave that for you to research....

EDIT - I see Johnny beat me to it!

Also, just noticed you have an auto? any history of work done on the box - oil changes etc? I've seen plenty of auto gearbox issues manifest themselves as other issues.
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(Post Link) post #11 of 48 Old 06-06-19 Thread Starter
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The next saga. I connected my gauge to both sides of the boost sensor. There is a picture of how I arranged it by splicing it into each pipe.

There is a close up of the dial and I am referring to the white on black number on the inner dial noted as ins hg.

Outlet, started engine and at idle the needle sat at 18. When reved it was a bit eratic at first then sat on 12.

Inlet at idle 25 and on reving rose to 27.

In all 4 situations the needle was static.

That doesn't seem to produce the actions that are described above. Does that mean I'm a dimwit and doing it wrong or is the boost control valve buggered?
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A couple of other things to try could be:

Throttle pedal position in MES. Is it sending the right message to the fly by wire?
Throttle butterfly - is it open when you start the car. Sounds a bit like the throttle butterfly may be sticking closed until it's opened for the first time and then it's OK until the next restart.
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Quote:
Originally Posted by nogrip View Post
A couple of other things to try could be:

Throttle pedal position in MES. Is it sending the right message to the fly by wire?
Throttle butterfly - is it open when you start the car. Sounds a bit like the throttle butterfly may be sticking closed until it's opened for the first time and then it's OK until the next restart.
I don't think its the throttle. Tyhe lack of power is when you start off from rest, after its been running ok and you stop again, but the engine keeps running it will produce the same lack of power.

The question is, do I just get a new boost sensor and replace it just in case?

I was confused when last I used my MES. Its the paid for version amd I have the right lead but I couldn't get it to read any live data.
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Actually, thinking about it, a sticking butterfly could give the same issue. I'll have a google and a think about it.

Still want to understand about the turbo boost sensor readings though.
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There is no butterfly, throttle is controlled by ECU and fuels via injectors - the position sensor at the pedal end could still be an issue though.

The throttle butterfly-looking thing which sits on the end of the manifold is an anti-shudder valve, and doesn't factor in any fueling.

Given by your vacuum readings, I'd say that your boost valve is possibly letting by, or stuck open.

New one here: https://www.shop4parts.co.uk/?name=s...4807&sku=54384

It's the same part on the 1.9 so if you can find a scrappy it'll be on tonnes of Vauxhall CDTis, amongst other things if you don't want to take a punt on a new one.

Last edited by amfalconer; 07-06-19 at 10:43.
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Quote:
The throttle butterfly-looking thing which sits on the end of the manifold is an anti-shudder valve, and doesn't factor in any fueling.
Yeah they get called all sorts but it still closes when you stop the engine to starve it of air and stop it running. The symptoms could indicate that it is sticking nearly closed for a little bit on start up effectively starving the engine of air until it eventually pops fully open and proper running and ECU controlled fuelling is as it should be.
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I have ordered a new valve from Alfa Workshop which I will have tomorrow. Lets see what that does initially as it seems clear the current one isn't doing what its supposed to.

All help and advice is much appreciated.
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Quote:
Originally Posted by nogrip View Post
Yeah they get called all sorts but it still closes when you stop the engine to starve it of air and stop it running. The symptoms could indicate that it is sticking nearly closed for a little bit on start up effectively starving the engine of air until it eventually pops fully open and proper running and ECU controlled fuelling is as it should be.
That's a good point, they are especially prone to getting caked in soot and crap!

Quote:
Originally Posted by Silverthorn2151 View Post
I have ordered a new valve from Alfa Workshop which I will have tomorrow. Lets see what that does initially as it seems clear the current one isn't doing what its supposed to.

All help and advice is much appreciated.
OP - fingers crossed it works for you, let us know how you get on!
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(Post Link) post #19 of 48 Old 07-06-19 Thread Starter
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Thanks. I will post a report. I'm thinking more about the butterfly. Where can I find that to check and de gunk it?

I've had a stressful day with lawyers and need to get my hands dirty!
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Remove the plastic engine cover, and see the metal hose running between the battery and the engine cover? - the end at the back of the engine bay is secured into the anti-shudder valve with 2 ribe bolts - once removed, pull the pipe out, it'll have a rubber seal on the pipe which will likely have stretched - you should replace this with a new one - if it's still tight, all good. the metal pipe goes into a hose, so you only need to remove the one end.

Once removed, the valve is held on with 3 other ribe fasteners, if you pull these and disconnect the electrical plug you can remove this - take care you don't lose the metal gasket as it can stick.

Clean and refit - done!

Don't know if this is as per a throttle plate, but don't move the butterfly with your fingers, I was always told this is bad news - if it's open you can clean it fully without moving it.
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Well, the new boost sensor seems to have improved the way in which the boost gauge responds. Thought it had cured everything as a 10 zip around the area was fine, with no lack of revs from idle. Hour later and popped out again and exactly the same problem occured. It's not every time, but makes the car dangerous to drive. You cant pull out of a turning or onto a roundabout for instance. Going to put some Wynns Turbo cleaner through it while I'm trying to fix the Spider (bloody Alfas) and then get the pipe off to check the butterfly. I realise that I've had that off before and yes, that rubber seal needs replacing every time.

What's the view on oven cleaner squirting down below the EGR? Worth a go? Getting to the turbo looks hideous!
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You may have cleaned the EGR but it could still be faulty and stuck open when fitted and connected. Try a cheap full blanking plate for a few quid and see if it fixes the issue.

Read this, especially the 3rd paragraph about the EGR sticking open and no power till roughly 3000 rpm. Sound familiar?

https://www.alfaworkshop.co.uk/alfa_159_guide.shtml
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The EGR has the latest blanking gasket from AlfaWorkshop fitted already.

Throttle body off, before cleaning.

Thoughts?
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I've seen worse, also have seen them where oil has passed into the control unit, not enough to stop it working mind.

Can't recall the earlier posts, but have you had any diagnostics work done or fault codes read?

Sorry, just re-read, you have MES
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No fault codes at all. Cleaned version below. What's interesting is that prior to cleaning the butterfly was fixed in place or it felt ir. I didn't waggle it but just using the toothbrush to gently clean it it didn't move. Post cleaning and gently wiping it made it rotate easily, with the resistance you might expect from the motor, but it moved.

All I have to do now is get the new O ring for the alloy pipe where it goes in and I can give it a try.
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