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Low Speed Loss of Boost. Takes along time to buildup.

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Old May 31st, 2021, 15:09   #11
cheshired5
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Quote:
Originally Posted by tomkirkland View Post
Sirobbs channel has helped me out no end with bits and bobs.
The latest video includes a complete service and cleaning of the Euro 3 D5 EGR actuator, valve and cooler.
Looking at the state of the front EGR mixer pipes is no indication of the the EGR valve performance at the back so you'll need to delve much further.

Also the fact that you cannot get a stable vacuum reading directly from the vacuum pump suggests the vacuum pump as the root cause then the resulting poor running of the engine produces excess smoke which in turn has likely coked up the EGR.

The location of the MAP sensor means that it will likely be filthy too.

The Euro 3 vacuum pump has no official service kit so prepare to replace it which fortunately shouldn't cost much as they are cheap from breakers due to low demand as they're generally reliable.

The airflow readings suggest that the airflow part of the MAF sensor is fine but do monitor IAT readings.
The IAT sensor is built into the MAF so if that is defective, the whole MAF sensor needs changing.
Once again not expensive to buy used genuine Volvo/Bosch working MAFs. £20-30
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Old May 31st, 2021, 15:52   #12
tomkirkland
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The latest EGR video is on my to watch list They are incredibly helpful vids.
That'll be my job on a few days that the car isn't been used.

Well I've made some progress.

I've now got the MAF readings to a better range by cleaning with Electrical Contact Cleaner that leaves no residue. Also cleaning all the oily residue off the fitting it to screws into. Everything was coated in a film of oil.

Idle now 25kg/h
1000rpm now 37.8kg/h
2000rpm now 98kg/h

Much better than the previous

Idle was 55kg/h
1000rpm was 63kg/h
2000rpm was 143kg/h

Tiny win.

Last edited by tomkirkland; May 31st, 2021 at 15:58.
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Old May 31st, 2021, 16:45   #13
cheshired5
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Both your before and after cleaning MAF figures are credible depending on EGR position.
If you leave it idling long enough, it will jump back up to 50 kg/h which is normal behaviour and suggests that the EGR is working correctly.
See my earlier post #9

Based on everything I've read of your situation, I would now concentrate on the vacuum pump and if you can't get a stable non flickering full vacuum at idle (around 29 in/Hg) when testing directly on the vacuum pump, change the vacuum pump and I'm confident that the boost issue will resolve itself.
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Old May 31st, 2021, 17:26   #14
tomkirkland
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I'll keep an eye on it all. Nothing more satisfying when working on cars than cleaning bits up back to near new.
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Old May 31st, 2021, 17:31   #15
cheshired5
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Nothing more satisfying when working on cars than cleaning bits up back to near new.
Agreed.
Although cleaning an EGR to new means that your hands won't be clean for a week.
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Old May 31st, 2021, 20:19   #16
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Originally Posted by cheshired5 View Post
Agreed.
Although cleaning an EGR to new means that your hands won't be clean for a week.
Give me an excuse to use the good soap.
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Old Jul 30th, 2021, 22:55   #17
mercgtc
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everyone up to now mentions map maf and other sensors but get back to basics diesels need fuel if they get starved they either stall or struggle you say you replaced the fuel filter but did you consider the in tank fuel strainer which is on bottom of priming pump if the screen is blocked /obstructed by any debris or worse diesel bug in tank it can cause these issues - ask me how I know - if the tank has any debris in it the strainer needs cleaned there are products to add into tank but the only true way of achieving it is to remove tank clean and reassemble not an easy or pleasant task but doable if you are used to diy mechanics . the tank sender pump unit needs to be dismantled to get to pump and strainer and if your car is high mileage its worth replacing this electric pump when you have it stripped out consider how many cycles it has gone through in its life you,ll kick yourself if you dont then have it fail not long after removing tank etc - again ask me how I know - any way clean the fuel side first then start looking else where if there is no improvement but I bet there is .
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