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A little cough...

9312 Views 87 Replies 18 Participants Last post by  smhaze
Dear all,

Not a huge problem this, it certainly doesn't happen all the time, and it's mostly out of curiosity that I'm enquiring.

I find, occasionally, in 2nd and 3rd gears when accelerating slowly (such as when coming off a roundabout and getting back up to speed), that the 159 gives a little cough. It tends to happen at just over 2000 rpm. It's almost as if briefly the engine loses fuel or air supply.

It's a diesel, a 1.9 JTDm.

The EGR and throttle body have recently been removed and cleaned, as I thought this could have caused some of it. I have not had the EGR blanking plate / remap done.

Another thing that may valuable to know is that the acceleration profile in first gear (only) is not smooth. Up to around 3000rpm it is as smooth, but after this there is a giant kick up to 4000. I was thinking that perhaps the lumpy acceleration profile and the cough are related.

Has anyone else experienced anything similar, or have any ideas about what may be causing this?

All the best,

(Apart from this a very happy 159 owner)
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It is still highly likely the EGR has something to do with this, it may be sticking open a little too long. Try restricting/ blanking, and seeing if this makes a difference, a plate is less than £4, so a cheap check, and worth keeping long term.

Also possible that the MAF needs a check
Good news! Give your map sensor a clean too ( I used EGR cleaner and sprayed a bit in the manifold too.

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As I've said many times before, the EGR works well early on, but after a few thousand miles it really negatively affects car performance

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Guys, when you say it's a new car, do you find its got a more constant acceleration curve? Or is it power? Or is it something else....I'm wondering if an 'egr delete' gives the same results. Or is it the ease of fixing and cost of doing it which sold you both.. or....thanks for humouring me....
The acceleration below 2,000 rpm is noticeably improved. The essentials are that the EGR takes the exhaust gas off before the turbo, so in most running modes, the turbo is has less gas running through it. When you put your foot on the throttle, the EGR will close, but the effect is not immediate, so it takes longer for the turbo to produce full power....felt as turbo lag, this is even more pronounced when you have a leaky EGR!

As far as I am aware the car doesn't actually think you need all the power til you hit 2,000rpm, as such it is open below this value
But still....noone has tried to put in a blankingplate & drive with that alone before mounting the "simulator"?
You mean compare the the simulator with no simulator? Plenty have had just the blanking plate.

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Good stuff, when they introduced EGRs to the U.S. Truck fleet as a mandatory addition, the whole US fleet MPG over the U.S. got worse by 3%, so you should expect to see an improvement in that figure when blanked.

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It seems that my turbo overboosts, do not really know if that's because of the EGR blanking plate, haven't noticed this overboost before.


Think that's pretty normal, as the turbo now has all the exhaust going through it instead of some getting taken off to go through the EGR. The net result is the turbo starts from a much higher rpm ( and the vanes adjusted accordingly)

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also have the feeling the turbo pressure is just a bit higher than it would normaly be. For example, driving 120/kmph - 74 mph (flat road) the turbo gauge pressure would be around +- 0.5 and my fuel econemy would be 17kml/ 40mpg. The other case on the same road same speed ect.... would result in +- 14kml 32mpg and the turbo gauge would read +-0.7

Any of the other members using the cheater/simulator experiencing the same thing?

MES graph download link (Import the file with MultiEcoScan)

See post #78 :), it's just an effect of blanking the EGR

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Error codes will clear after a few drives
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