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Discussion Starter #1
hey guys

well, beggining to hate the search function now as i cannot find what i am looking for and i am pretty sure it has been discused before. my 159 2.4 20v 200bhp had developed a problem that i know it's common but don't know the fix. the problem is like so, on full throttle the turbo cannot hold the boost or something. the turbo gauge fluctuates and the car accelerates in waves. anyone know what could be the issue?

thanks in advance
 

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Discussion Starter #2 (Edited)
anyone? it's annoying because i know it's been discused before but cannot find anything about it. iirc there was a guy with a red 8c brera that also had this issue.

LE: found the guy and his topic but he says for him was the turbo but i find it hard to believe as in other situations it was working great.
 

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Discussion Starter #3
anyone?
 

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Man youve been patient, what have you tried so far?
An hour job is to remove and clean map sensor see if any different.
Doesnt sound like normal egr type fault but again a few hours to removeand clean and again see if fixes.
After that maybe maf sensor clean.
The search will pick up guides or how to as i dont know the layout of your car.
 

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Discussion Starter #5
maf clean, map clean, intake clean and swirls on/off, turbo clean, heat exchanger clean, egr clean and off.

what next?

i know it sounds **** but it is, it's not only my car, i see alot of 200hp versions doing this and is hard for me to believe the turbo is gone on all.
 

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Not much help, but mine does this as well. I know it isn't the EGR as I've had a remap which switched it off and also a blanking plate fitted. I'm also sure it isn't the MAF/MAP sensors as they were cleaned with no difference and then replaced with new ones, also with no difference.

I suspect it is either the swirl flaps or the turbo that's causing it. I'm wondering if it's the turbo boost pressure solenoid?
 

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sounds like the ECU kicks in to prevent overboost. Could be a leak (small) somewhere, but only measurable under pressure (more like intercooler). Or sticking vanes.

Swirl flaps are only for smooth accelerating, but you could have a leak in your inlet collector (around the valves). That should be simple to see: there must be some oil around the small axles of the flaps visible.
 

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Looks like you could do with logging software or someone close to you with it who can help out, you need to do a few logs driving in the fashion that provokes the power oscillation.
Hopefully the data can prove whats going on.
A few logs with revs,IQ,desired boost,actual boost, vnt%, maf airflow,desired maf,atmospheric pressure.
Should help go a long way to see whats going on.
Regarding turbo vnt actuator, get someone else to start the car while you watch the actuator pull the lever to the stop smoothly, get them to stop the car and see the lever return to rest(open) position again smothly , should take a couple of seconds max opening and closing.
A 5 min test max. Tell us what yours does.

vnt operation for youtube.avi - YouTube
This is what you want to watch(mines on a bench though) so it should just pull towards you on start up , stay there at idle resting on stop screw, on switching off it should move out around 8-12mm not sure on the 2.4?
Also a quick check atmospheric pressure to boost pressure with just ign on to see how realistic map sensor is , i had a cheap map sensor not bosch that ran fine for a few months then on accelleration on carriageways etc i would see the same boost up n down without moving acc pedal off floor. bought new bosch sensor been ok ever since.
 

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I experience this in a mild form every now and then. It is possibly a small air leak in the inlet somewhere putting the car sensors out of balance. A common place for this to happen is where the main air inlet plastic pipe joins the metal pipe to the turbo. If you have what looks like an oil leak there then that is the first place to start as there is likely to be an air leak there too. Many people on here have found doubling up the union with a jubilee clip helps.
 

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This happened to my car a few weeks ago. I started using BP Ultimate which cured the problem. Before I had been using tesco fuel. So probably a bad tank full caused it. Try it and see if it fixes it!
 
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