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Hi and many thanks to all who contribute to the forum. Having been a 'lurker' on here for a while and gained many useful insights as how to solve the many problems I have had with my various Alfas over the years, I am stumped with a problem on my Brera.

I purchased the car blind on ebay and was right and properly shafted by the previous owner and have spent a small fortune on getting the car finally running about right.


The car runs really well with massive power from about 1400 rpm and if you use the gears to keep the revs up all is fine, however if you allow the revs to drop below the 1400 mark in 5th or 6th and give it full throttle the car vibrates and shakes. Even at this relatively low engine speed you can see the turbo boost gauge climb but the engine doesn't like being loaded. If you back the throttle off the vibration goes away and the car will accelerate as long as the throttle is just 'tickled'


Over the last few months the engine has had a new cam belt and cam followers after a cam belt failure. New EGR Valve and MAP sensor. I've tied the swirl flaps up which made a profound improvement when starting. The car has been to a diesel specialist and had a couple of injectors, the compressions checked, new glow plugs of the longer type and the injectors re coded.
The car generally runs a million percent better than when I first got it but this low speed 'misfire' under extreme load has me stumped. If it was a petrol car I'd say it was a lead/plug/coil pack issue it has that kind of feel to it.


The engine has a rock steady idle and there are no engine management faults displayed.


Any ideas gratefully received.

Cheers Ian
 

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Got to be honest below 1400rpm in 5th and 6th is asking a lot of the engine in my opinion when giving full throttle.
If you keep foot planted does rpm gradually rise and vibration settle down?
 

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Yes if you can live through the quite extreme vibration once up to 1400rpm it does smooth out but if you are going uphill it is still a bit lumpy. It's just not happy under load. The 2.4 is a massively tourquey engine and should pull without drama from tickover.
 

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It will pull without drama, but not in the wrong gear, at the wrong revs. As said, trying to floor it in top gear at 1400 revs is asking too much from the engine, clutch and drivetrain. Drop it down a gear to bring it up to 2000 and then it'll go without a problem. I wouldn't drop mine below 1800, even on gentle cruising (which I hardly ever do)
 

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Is the money light on? Might be worth getting or borrowing a decent odb2 diagnostic device. Mine shows live data and charts etc., might give you some clues. I don't think 1400 rpm is too low for you to be driving a diesel. If it vibrates and misfires like you've described under load, then that can't be right. Mine (petrol) doesn't do anything weird if I do that, and the diesel Brera hire car I had for about a week didn't do this, but obviously I appreciate you should be in the correct gear for the conditions etc. If the car did what you say when it was brand new, you'd take it back, so I would say there is obviously something amiss.

Other than the basics I don't know as I've never worked on this engine.

If it's any help, this guy seems to have had the same problem, and has a 2.4 jtdm as well:
https://www.alfaowner.com/Forum/engines-ts-jts-jtd-andamp-v6/952529-2-4jtdm-bad-vibration-after-injectors-removed-and-cleaned-refurbed.html#/topics/952529?page=1
 

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Agree with all the above, asking too much at low revs and high gear. Your doing it no good, try getting the revs above 2000rpm
Assuming his Brera is say a 2006 model, then it'll be doing less than 2000 rpm in 6th gear at 70mph??? You know it's a diesel right?
 

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Assuming his Brera is say a 2006 model, then it'll be doing less than 2000 rpm in 6th gear at 70mph??? You know it's a diesel right?
Yes but his question was “Low Speed misfire” - Nothing mentioned about doing over 70mph?
Mine will judder if I’m in the wrong gear and low speed (2.4/210 Diesel) as will most cars.
 

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I've only ever driven a couple of 2.4s...Both would pull the top two gears from just off idle pretty smoothly...certainly no judder or misfire type feelings....I would not advise it and it certainly was not very quick to pick up (my 2.0 picks up smoother doing the same thing to be honest ) but it should do it. I don't think all your guys telling him its normal is going to convince him that it is normal!
 

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I don’t agree that this is normal, I tested this theory this morning on my way to work and I can put my foot to the floor at 1000rpm in 6th and have no judder or misfire feelinng. But as alfaitalia has said best not to.

I’ve now had 4 Alfa’s with a 2.4 diesel and none of them have behaved this way.
 

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I had a bit of vibration when picking up from about 14-1700rpm, especially when on the motorway accelerating from 70mph in 5th or 6th, normally 5th.

New VNT solenoid seems to have helped a bit - also the cheap tyres I had fitted at the time (Accelera) hadn't helped with the vibration at motorway speeds - either lost a balance weight, or just crap tyres.
 
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