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Technical Flat spot/loss of power

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Technical Flat spot/loss of power

philipb82

philipb82

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Hello

I'm adamant I've got a flat spot or lack of power on my JTD. It was more apparent today when driving up and the down the hills of Holmfirth! When going up a steep hill I could feel a drop in power then it'll pick up again. However before this I could hear a 'whine' noise but I have no idea what this is...problem? turbo? I get no fault codes and I've even mentioned it to my mechanic friend who said it could be anything as there are no fault codes. I've read on here about MAF and the boost solenoid valve could be the culprits, hes checked some hoses/pipes and said there are no splits. Also I had a new EGR valve fitted a few weeks ago so thats that ruled out! It doesn't always do it though, when it doesn't, it pulls through the revs nicely.

Whats the best thing to do? I would rather try things out first rather than paying for diagnostics. Its not always noticable on flat roads but I live in Yorkshire so its mainly hills :)

Thanks

Phil
 
Last edited:
philipb82 said:
Hello

I'm adamant I've got a flat spot or lack of power on my JTD. It was more apparent today when driving up and the down the hills of Holmfirth! When going up a steep hill I could feel a drop in power then it'll pick up again. However before this I could hear a 'whine' noise but I have no idea what this is...problem? turbo? I get no fault codes and I've even mentioned it to my mechanic friend who said it could be anything as there are no fault codes. I've read on here about MAF and the boost solenoid valve could be the culprits, hes checked some hoses/pipes and said there are no splits. Also I had a new EGR valve fitted a few weeks ago so thats that ruled out! It doesn't always do it though, when it doesn't, it pulls through the revs nicely.

Whats the best thing to do? I would rather try things out first rather than paying for diagnostics. Its not always noticable on flat roads but I live in Yorkshire so its mainly hills :)

Thanks

Phil
Click to expand...

Phil

Disconnect the MAF connection and go for a drive up the same hill, if there is a marked improvement, then you have your answer. If not then as you have done the EGR, then consider and re check the hoses, esp the air intake one, that is in the near side front wheel arch, as this chaffs against the inner wing lining.
 
With regards to disconnecting the MAF, do I just unplug the electrical connecter?

Shadeyman said:
Could the whinning noise be more of a whooshing noise?
If it is your loosing boost, probabely from a split pipe ...
Click to expand...

I'm pretty sure its more of a whine noise than a whoosing! Maybe thats something completely different.....probably would be :rolleyes:

Thanks

Phil
 
philipb82 said:
With regards to disconnecting the MAF, do I just unplug the electrical connecter?
Click to expand...

Yes, just unplug the connector from the top of the MAF and take the car for a drive. If it feels better than with the MAF connected you probabely have a faulty MAF.

Try cleaning it first, if may cure the problem. If not its an expensive part if you purchase direct from Fiat, about £185 I think.
 
Right, I've unplugged the MAF and took it for a drive around on a good stretch of dual carriageway and it did pull smoother through the rev range. I didn't have time to take it to the hill I mentioned in my question but I will do to know for definate. So the early signs are looking good (y)

Couple of quick questions, firstly is it normal for the air filter box and that big pipe that comes off it :confused: to have a bit of play? While I was unplugging the connecter all that area wiggled a bit :)

Secondly will it do harm to leave the MAF unplugged or is it best to plug it back in after ive finished testing?

Thanks

Phil
 
philipb82 said:
Right, I've unplugged the MAF and took it for a drive around on a good stretch of dual carriageway and it did pull smoother through the rev range. I didn't have time to take it to the hill I mentioned in my question but I will do to know for definate. So the early signs are looking good (y)
Click to expand...

You have a faulty MAF Sensor, giving it a good blast with electrical cleaner(Halfords- £5) may cure it. If not you need a new one.

philipb82 said:
Couple of quick questions, firstly is it normal for the air filter box and that big pipe that comes off it :confused: to have a bit of play? While I was unplugging the connecter all that area wiggled a bit :)
Click to expand...

Yes it should have some movement in it. The pipe is corrugated rubber to allow for engine movement, a solid one would rip the airbox off it mountings.

philipb82 said:
Secondly will it do harm to leave the MAF unplugged or is it best to plug it back in after ive finished testing?

Thanks

Phil
Click to expand...

It wont do any harm for now but its not a permanent solution.
 
philipb82 said:
I have some of that so I'll give it a go. Do I have to remove the MAF to clean it or is there a way of doing it whilst its attached?

Phil
Click to expand...

Best to remove it.

You'll see two platinum wires inside, they may look clean but they're not so give them a good blast with the cleaner. Don't touch them with anything, use the spray cleaner only. The force of the spray should be enough to remove anything stuck to them. Clean them 3 or 4 times allowing it to dry out before cleaning again.

The platinum wires are heated, as the air rushes past them into the engine they are cooled. The cooling effect is measured and the amount of air passing through the MAF can then be accurately calculated.
 
philipb82 said:
Technical question.....how does the wrong calculation of air produce a flat spot?

Phil
Click to expand...

The amount of air entering the engine is used to calculate the fuel air mixture very precisely. If the MAF sensor is sending incorrect signals to the ECU the fuel/air mix will be incorrect causing all sorts of problems. Power loss, smoke, etc..

By removing the MAF the ECU reverts to a default air/fuel setting that allows the engine to run but not at it's peak efficiency so it will be down on power and its MPG will be worse than normal(with a good MAF).
 
Last edited:
Hi all, I want to do a MAF clean as well.

Quick question for any one.

To remove it, once you have unplugged the connector, do you remove those annoying security torx head screws to take it out?

IMAG0127.jpg
 
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