A little cough...

Alfa Diesel 'cough'

Hi all

I've been reading through various threads over the last 2 to 3 years on the topic of Alfa Diesel 'coughs'. I have a 2009 159 JTD Ti 2.4 wagon/estate and it's hands down drop dead gorgeous. It has about 63k km's on it now and for the last 15k-20k it has sadly developed this annoying cough. I've read some of the comments and I would like to detail what I have done in order to try and fix it (which to date I have not):

1 - Injector cleaning - all 5 injectors were taken out and professionally cleaned by a mobile Bosche mechanic. This did nothing although probably extended the life span of them so I wasn't too unhappy.

2 - MAF sensor replaced - This did actually cure the problem however withing 3 weeks it was back. I don't believe it was realted.

3 - EGR - Cleaned, checked, tested by same Bosche mobile mechanic. No dice, no change whatsoever.

4 - DPF - This has had more Wynn's DPF cleaner in it than I care to remember. Although it seemed to have an effect, it wasn't consistent and the percentage blocked readings always ended up at the same % (I have all the software and connection leads to activate a DPF regen)

5 - Running on higher RPM to engage regen - for some time, I traveled to work (40 minute trip of which 20 mins is at around 100km/h in manual mode and keeping the revs above 3000 rpm. Sometimes when I got to work and cruised into the carpark, the engine/exhaust has a deep rumble to it which gave me cause to think I had initiated a DPF regen. However, this did nothing to the coughing situation.

6 - Back drilling the DPF - I got so fed up with the DPF cleaner that I back drilled the DPF after cleaning it out with an industrial pressure washer. This was the several holes version that go through 2/3rds of the DPF, leaving the forward 1/3rd intact. Noticeable increase in performance and response but coughing continues.

7 - Full fuel tank - Thought this had an influence, the fuller it was the less coughing but I'm not convinced now.

8 - New fuel filter - Alfa laughed at me for that one. I've kept the perfectly ok one I replaced in case I need a spare as there was nothing wrong with it.

9 - Now this is weird but I genuinely think it is relevant. Travelling around corners makes it cough violently. There is gentle-is left hander in a 60km/h zone as I leave work and it is guaranteed to cough. Sometimes it is really quite harsh, more harsh than any straight line occurrences. In a similar way, it coughs when I go through a small chicane on the way to work and the left hander after it.

10 - It happens at around 2000 RPM under light acceleration. I've even managed to make it cough on cruise control by setting the speed and using it to increase the speed when on a shallow incline at around the RPM range.

I have spent roughly $3000-$4000 trying all the suggestions on the forums and advice by diesel mechanics. I've posted my findings here so that you can at least ignore the points I'm convinced had no effect.

My latest hypothesis is that it is wiring related and a suggestion in this forum mentioned it could be the injector leads. It's possible that lateral 'g' forces disturb a fault in the leads and that's why it happens more on corners (I know I'm reaching a bit here but I'm running out of reasons).

Alfa would love to have it in but a) it's way out of warranty and b) the chief mechanic has suggested it may be cracked inlet manifold, head issues or worse and given that all the suggestions so far that mechanics were convinced would fix it havent, it's a last resort. the garage bill for that would be probably 2/3rds of the car value.

Anyway, I'll keep an eye on this thread and see if anyone updates it. If I have any breakthroughs I'll post it here. I have some contact cleaner which I will try tonight. When the diesel mechanic replaced the MAF sensor it was faultless for a few weeks and I wonder if some of the wiring was disturbed in that process which cured it for a short time.

I still love it though and I'm not giving up. There is a problem in there and I will hunt it down

Happy motoring

Update on cough

Seems to be a global issue HengistPod and yet Alfa service agents (at least in Australia) seem to know nothing of it. I can only assume admitting it's existence would open a tidal wave of warranty issues or worse. However, as I don't want to wake up next to a horses head, I'm not laboring that point.

If I knew for certain that blanking the EGR, deleting the related ECU map along with the DPF delete for good measure would fix it, I would have it done. I've been quoted around $1200 to have the work locally but as the DPF isn't giving me issues (I can regen it and clean it with the Wurth DPF cleaner if it does block up) I wonder it it makes sense just to have the EGR delete done. Would any of you more knowledgeable members care to comment on this? I know it's been done to death but some of the posts related to this topic are getting on a bit so a refresh would be appreciated. I'm ignoring the legality issues for the moment, even with this the mod, the 159 JTD would pass emissions tests in the UK so I'm certain my carbon footprint would remain considerably less than the multitude of diesel utes that haven't seen a tune up in decades I see on the roads (no such thing as an MOT in Aus, only when you sell it).

It's not the only problem I have with it but the rest of them are minor in comparison. If I could sort this one issue out though.....

Yep, same here.

Hello to all.

Yes same here. I have a 2008 JTDM 1.9 manual and have the same annoying stutter (and accompanying raa, raa sound) around 2,000 revs.

I have spent many hours trawling through this and various Fiat problems but cannot find a single fix.

I have put in an EGR restrictor plate (Diam shaped plate with the 9mm hole) and that has helped, but it is still there. I know the EGR is working fine as that was recently replaced.

I keep thinking that it maybe a vacuum leak somewhere but have just about eliminated that concern by carefully checking every hose. No leaks.

My current thoughts are:

1) Turbo VGT mechanism that is sticky.

2) The vacuum hose that feeds the VGT solenoid plugs into what I think is the engine variable valve timing mechanism. Why, I do not know and don't yet understand how they interface, but maybe there is an issue with that.

3) Fuel mapping / Software. Maybe as the various engine components and sensors age a bit, the fuel mapping cannot accommodate the combined shift in variables. Guessing here as I do not know.

Like others, if you push the car a little harder through the gears, there is no issue. I also think that it is worse if putting around in traffic for a while as opposed to giving it a few revs down the freeway, then back into low speed. Maybe the extra revs gives it bit of clean out. (I have read that is called an "Italian Tuneup").

I did see a post on this forum somewhere where a guy had made up an interface (Cables and chip) that went between the MAF sensor, MAP sensor and possibly the EGR that I think may have cured the problem, but I can't find that post.:irked:

I keep looking for that magic cure, i.e, finding a post that says "Do this and the stutter goes, works every-time", but unfortunately not.

Looking forward to following this thread.

Update on cough Mk2

Hey Brenton - I've not seen that before, I wonder if anyone has had any success with that?

A small update for everyone who is interested. The weekend before last, I disconnected the injectors and cleaned them with CRC CO contact cleaner. I also removed the MAF sensor and cleaned out all the oily deposits on the sensor. Now, I say MAF however it may also be referred to as the MAP. To be clear, it is the sensor that is located in the inlet manifold near the fuel filter. It is removed with a single T20 torx cap head screw. Also, due to poor planning on my part, I filled up with local cheapy diesel as opposed to the religious use of BP Ultimate.

The net result of these 3 actions, and I have no idea if it was a result of one or all all none of them but the car hasn't run this well since it was supposedly fixed at a diesel mechanic about 6 months ago. It ran well for a few weeks then reverted to normal cough mode. I've cleaned this sensor before but it seemed to not make a difference. I just want to say that when it runs like this, I wouldn't part with it for anything, it's transformed.

I know this isn't that helpful as there isn't anything conclusive. You can probably rule out the fuel but I've noticed it runs better on a full tank. Anyway, as this is literally a ten minute job for both the sensor and the connectors, I would say it's worth a shot. It took a day to settle down, I guess you could reset all learnt parameters if you have the software/leads so it started from scratch however a day later, it's running really well. I hasten to add that it isn't cured, it's still there but the frequency and magnitude is vastly decreased.

I am planning to repeat the maintenance of the sensor this weekend. If it comes back, I'll clean the injector connectors. If I have anything conclusive, i'll let you know. :byebye:

Hi Britswiss

Yes, it was definitely the MAP sensor that you cleaned as the MAF is located front right corner of the car on the pipe from the air box (located near the front right wheel) and the pipe that goes to the turbo. I had actually replaced the MAP sensor on my car because it broke when I took it out to clean. When I did get it out it was fully caked up, even the little cage supporting the sensor was full up with soot. However, it did not seem to make much difference to the stutter.

I did fit a partial blanking plate, the diamond one with a 9mm hole and that did reduce the stutter greatly, however it is still there, although as you get use to it, I can drive "around" it, so to speak. Still, that's not good enough as I want to eliminate the stutter altogether.

I have ordered one of the EGR simulator kits and another full stainless steel blanking plate and will give that a try. I don't mind spending a little money trying these things because based on other threads on this forum, the cure can be quite hit and miss and many garages simply don't know. Not to mention that every trip to a garage is going to cost about $500.

I did get a quote for a remap and delete the EGR, but keep the DPF (the car just had a new DPF and EGR fitted just before I bought it, probably in an attempt to fix the stutter) and in Perth they wanted AU$950. Gotta be kidding me. So fingers crossed on the EGR simulator.

The Pasty.... I like that name. My Wife is originally from Cornwall, so Cornish pasties from time to time, one of my favourites.

The Turbo boost gauge on mine does flutter down with the stutter, but I'm not sure if that is more a symptom rather than related directly to the cause.

When my car stutters, I here a raa, raa noise that is in time with the stutter, which I thought might have been the Turbo VNT system, but lately I am more convinced that it is the swirl vanes actuator that I can here turning off and on, as if it is confused. IE, the ECU parameters that control the Swirl vanes are set too tight, so if a couple of other input parameters are fluctuating, it's causing the swirl vanes to over correct one way, then back the other while on light throttle, accelerating.

However I am guessing as I don't really know, but my "Google Research" on the same did lead me to read about some guy, I think on the Vectra forums, that did widen the swirl vane parameters that cured his stutter. Evidently he had a 2007 Vectra (or similar with a stutter) and a 2011 Vectra (or similar without a stutter) and using software, he compared the swirl vane parameters for both vehicles. What he found was that the 2007 engine had parameters +/- 50 while the 2011 had something like +/- 300 (Can't remember the exact numbers here or vehicle build dates as I linked it on my computer at work, but I think you see the point I am trying to make). So what he did was change the swirl vane control parameters on the 2007 vehicle to match the 2011 vehicle, then the stutter disappeared.

If the EGR simulator doesn't fix the issue, then I think I am going to head down the path of studying the Swirl Vane control parameters and software required to make the change, or find someone who can do it for me for a reasonable cost. I'd like to work out how to do it myself as I like to teach myself and learn how to do stuff. However, if the EGR simulator fixes the stutter, then the issue becomes redundant anyway.

Fingers Crossed. Hopefully the EGR simulator and full blanking plate turns up next week so I can play next weekend.