Decated 166 3.0 - issues with rough idle / engine misfire - Alfa Romeo Forum
You are currently unregistered, register for more features.    
 6Likes
  • 1 Post By -taf-
  • 1 Post By Mufasa
  • 2 Post By yetyGT
  • 1 Post By -taf-
  • 1 Post By yetyGT
 
Thread Tools
(Post Link) post #1 of 20 Old 25-12-09 Thread Starter
Status: -
AO Member
 
hyde21's Avatar
 
Join Date: Dec 2008
Location: Slovakia
County: Bratislavsky
Posts: 37
Hmmm Decated 166 3.0 - issues with rough idle / engine misfire

Hi guys, at first I would like to wish merry christmas to all members of this great forum and community


I have here another issue with my 166 3.0 99" where I am not 100% sure what could be the fault source. The car mileage is currently 130 000 KM so approx. 80 000 miles.

My car is decated with a stainless steel pipe very very similar to the alfaholics GTV6 3.0 decat pipe :

View image: decat pipe.jpg


The issue with the car is that time to time I have rough idling and I can't find out what is the reason. The idling engine revs are according to the first look stable(~680rpm), but from time to time the idling is pretty rough and seems to be missfiring and running only on 5 cilinders but the revs are still relative stable on 700rpm. This is mostly happening when the engine is warmed up to the working temperarature 90degrees and I am eg. driving in the city and currently waiting on the traffic light or just stuck in the traffic jam. The engine suddenly starts making medium vibrations for 10-30seconds but then it disappears and it is idling fine again. As I told this idling issue is mostly happening when the engine is warmed up but time to time it also happens at the morning after cold start and sometimes also in the summer after starting warm engine. The misfire always takes only several seconds and then disappears. During the misfiring the revs are pretty stable somewhere between 650-700rpm.

I was TWICE with the car in the garage on the diagnostics and there were no errors shown, MAF and O2 sensor were both giving proper vaules during idling and also during 2000/4000/6000rpm, no errors with coil packs or spark plug were shown, all sensors seemed working fine.
I have recently 6000miles ago changed the O2 sensor (BOSCH) and the sparkplugs (original NGK platinum) are 20k miles old so there I think should not be a problem. Air filter was changed recently couple of miles ago.
I have also several times performed the ECU reset - no affect on the rough idle, only the typical symptoms as improved fuel consumption and throttle response etc.


Before I was on the diagnostics, I was thinking that this could be supposed only by failing maf, but the guy which was performing me the diag told me, that the maf is according to his opinion giving correct values and the maf seems OK for sure. He also said that if the MAF would be really wrong, the issue will be reoccuring more frequently if not constantly. That I think can be true because I am sensing this behaviour of the car for the last 10000 miles and it is still the same.... The MAF is original BOSCH 0280217531 for alfa CF2 V6 engines and was changed before 4-5years / 20-30k miles.
When I informed the guy that the car is decated with the mentioned pipe, he told me that this could be the weakpoint as the O2 sensor may time to time (when the subjective engine misfiring / vibrations is currently occuring) receive wrong values as there is no backpressure due to missing CAT.
I have the CF2 version of the engine, so there is only one O2 sensor which is mounted in the decat pipe as shown on the screen of the above.


Two things that I now suspect are MAF (also due to fact that the values on the diagnostics were shown as correct) and the mentioned decat pipe which I have installed in my car.
At first I thought it could be also failed coil pack but as I heard, coil pack issues are everytime shown on diagnostics....

I can only guess if the missfiring can be due to the fact that the car is decatted because when I bought the car, the CAT was already near to death if not death and as I remember, the time to time vibrations / misfiring were at that time already present.
But I know about plenty of cars (bimmer E39 540i, bimmer E36 320i, AR 156 2.0TS...) which are decated and they are running and idling pretty normal.

Therefore I would like to ask you for help. I have already searched on this forum but did not find anything similar

Thanks in advance.

BMW E39 540i V8 6speed 210kW
ex: AR 166 Super 3.0 V6 24V 166kW
ex: AR 156 2.0 TS 114kW - R.I.P.

Last edited by hyde21; 25-12-09 at 12:48.
hyde21 is offline  
Sponsored Links
Advertisement
 
Status: I thought I've something more to say
AO Silver Member
 
klapanciusz's Avatar
 
Join Date: Nov 2006
Location: Ireland
County: Wicklow
Posts: 2,620
it seems you identified the problem, so next step would be to "borrow" an OEM pipe, and put it on for a week. Even a very used one from the breakers should do the trick. just an idea
klapanciusz is offline  
Status: -
AO Member
 
Join Date: Oct 2008
Location: Morocco
County: Casablanca
Posts: 53
Hi

I have the same problem with my 2002 3.0 V6 Sportronic 115 000 km

Rough idle sometimes at a cold start as if i'm running on 5 cylinders
Then in a heavy traffic, when driving few meters then stop then run few meters then stop and so on, There are vibrations in the engine and rought idle for few seconds.

Exaclty same symptoms as you described

MAF and O2 sensors (i think there are 2 sensors) are both Ok accroding to Alfa diag.

Last thing I have to check is the plugs cables (i don't know how we call it in english - in french it's bobines d'allumage). may be a lack of fire on one of them when engine is warm.

Merry christmas guys
Lovalfa is offline  
(Post Link) post #4 of 20 Old 25-12-09 Thread Starter
Status: -
AO Member
 
hyde21's Avatar
 
Join Date: Dec 2008
Location: Slovakia
County: Bratislavsky
Posts: 37
Quote:
Originally Posted by Lovalfa View Post
Rough idle sometimes at a cold start as if i'm running on 5 cylinders
Then in a heavy traffic, when driving few meters then stop then run few meters then stop and so on, There are vibrations in the engine and rought idle for few seconds.
Yes, I have these same symptoms


Quote:
Originally Posted by Lovalfa View Post
Last thing I have to check is the plugs cables (i don't know how we call it in english - in french it's bobines d'allumage). may be a lack of fire on one of them when engine is warm
You mean probably also coil packs which are so called spark-plugs cables.
But as I know in case of coil pack failure the diagnostics should detect this failure and show also on which cylinder is the problem. But I may be wrong ...
hyde21 is offline  
Status: -
AO Member
 
Join Date: Oct 2008
Location: Morocco
County: Casablanca
Posts: 53
I don't think the alfa diag shows that.
Lovalfa is offline  
(Post Link) post #6 of 20 Old 25-12-09 Thread Starter
Status: -
AO Member
 
hyde21's Avatar
 
Join Date: Dec 2008
Location: Slovakia
County: Bratislavsky
Posts: 37
But in that case I cannot imagine how to find out which coilpack is failed without deinstalling all of them, and that is not very comfortable especially in case of the coipacks in the rear cylinder-bank
hyde21 is offline  
Status: -
AO Member
 
Join Date: Oct 2008
Location: Morocco
County: Casablanca
Posts: 53
Yeah, hopefully the faulty one is in the front side
Lovalfa is offline  
Status: 166 gone but not forgotten
AO Silver Member
 
alfa166italian's Avatar
 
Join Date: Jan 2009
Location: United Kingdom
County: Surrey
Posts: 1,383
Have they had the de-cat pipe off at all? If not it may be worth checking out. When you say the de-cat pipe is very very similar do you know who made it? Could be MAF, but I had a similar niggle at the start of the year which I thought was MAF failure but all the diag readingss were normal, but all that happened with me is that the engine warning light came on.

My theory on this is that the de-cat pipe has got a crack in it somewhere but it is facing the underside of the car. The only way to find out is remove it & see.

Good luck with it

Italians are crazy people.... but their cars are objects of desire

alfa166italian is offline  
Status: -
AO Member
 
Join Date: Jan 2009
Location: Malta
County: Balzan
Posts: 136
Have similar problem on my 3l V6... engine light occasionally comes on (P0300, P0301, P0302, P0303 codes) especially after goin down steep slopes - MAF is new and engine doesn't cut out or anything... am thinking it could be a leak in exhaust as "random misfires" in an entire cylinder bank would be noticeable if they really happened!
dahacker is offline  
(Post Link) post #10 of 20 Old 28-12-09 Thread Starter
Status: -
AO Member
 
hyde21's Avatar
 
Join Date: Dec 2008
Location: Slovakia
County: Bratislavsky
Posts: 37
Quote:
Originally Posted by alfa166italian View Post
Have they had the de-cat pipe off at all? If not it may be worth checking out. When you say the de-cat pipe is very very similar do you know who made it? Could be MAF, but I had a similar niggle at the start of the year which I thought was MAF failure but all the diag readingss were normal, but all that happened with me is that the engine warning light came on.

My theory on this is that the de-cat pipe has got a crack in it somewhere but it is facing the underside of the car. The only way to find out is remove it & see.

Good luck with it

Well I was already thinking about this that there could be a hole or crack on the exhaust placed somewhere before the O2 sensor.
The decat pipe was custom made by a guy who is making custom exhausts - there should not be a problem directly with the pipe. But as I said already, I was having this issue already since I bought the car and at that time it still used to have an original cat which after several months died. Therefore I have also chosen to put there a decat pipe because to find a used bud solid cat in good condition in my country was impossible and buying a new one for 1500euro was even more impossible

I was wondering if this issue could not be due to small crack somewhere on the exhaust manifold or downpipe and due to this small hole is the O2 sensor time to time receiving wrong values. I am going to replace cambelt on my 166 sooon so probably there will be also necessary to check if there is really not any hole in the exhaust

Last edited by hyde21; 28-12-09 at 19:32.
hyde21 is offline  
Status: 166 gone but not forgotten
AO Silver Member
 
alfa166italian's Avatar
 
Join Date: Jan 2009
Location: United Kingdom
County: Surrey
Posts: 1,383
Exactly hyde & dahacker. small cracks in the exhaust system or manifold is likely to send the O2 sensor scatty. Cocincidentally ahacker they were the same error codes my car was creating.
alfa166italian is offline  
(Post Link) post #12 of 20 Old 28-12-09 Thread Starter
Status: -
AO Member
 
hyde21's Avatar
 
Join Date: Dec 2008
Location: Slovakia
County: Bratislavsky
Posts: 37
I will have to check it.

But on my car the engine light never came on (only when the MAF was disconnected during some experiments - the ignition light came on typically) and also never any error code occured on the engine diagnostics.

hyde21 is offline  
Status: -
AO Member
 
Join Date: Jan 2009
Location: Malta
County: Balzan
Posts: 136
Do check it, as mine crops up every 3 or 4 weeks and follows a pattern (good run then steep garage slope at idle - which makes sense as the steep slope slightly flexes the chassis), i still have to take mine to a specialist place to get it fixed though, but after checking injectors, MAF, coils, plugs, timing and fuel quality there is not much left to go wrong!
dahacker is offline  
Status: -
Newbie
 
Join Date: Jan 2019
Location: laval
County: france-
Posts: 6

Member car:

alfa 166 3.0 v6

Hi everyone, I have the same troubles of misfire. The car was running great just before i disconnect the battery. Since i plugged it back I have misfire. I cheched the spark plugs this morning nothing visualy wrong, coil packs too. I checked all the intake from filter to throttle body ok too.
I started it again unplugging the lambda sensor, no reaction at all and seems to run on 5 cylinders. I disconnected the maf while the car idling and the car idles better but got a dashboard fault.
The car is a 99 3.0 v6 289000km sportronic
If anyone had the same troubles could help me to sort it. Just before the battery off she was running really great.
Thanks
fanch53500 is offline  
Status: -
Newbie
 
Join Date: Jan 2019
Location: laval
County: france-
Posts: 6

Member car:

alfa 166 3.0 v6

Hi everyone, I have the same troubles of misfire. The car was running great just before i disconnect the battery. Since i plugged it back I have misfire. I cheched the spark plugs this morning nothing visualy wrong, coil packs too. I checked all the intake from filter to throttle body ok too.
I started it again unplugging the lambda sensor, no reaction at all and seems to run on 5 cylinders. I disconnected the maf while the car idling and the car idles better but got a dashboard fault.
The car is a 99 3.0 v6 289000km sportronic
If anyone had the same troubles could help me to sort it. Just before the battery off she was running really great.
Thanks
fanch53500 is offline  
Status: -
AO Member
 
Join Date: Aug 2018
Location: Estonia
County: Harjumaa
Posts: 10

Member car:

166 3.0

Hi
I had similar problem, but luckily had a good idea to start with. In my car the air hose near the MAF was already taped and the diagnostics showed faulty MAF. Before changing more complicated stuff my mechanic advised to make sure that there are no leaks in the air hose. So I removed the old duct tape and did some proper taping afterwards. Now it is running smoothly. Next step is to find a new silicone hose, as the original material is ...
In conclusion, make sure there is no cracks in the air inlet hose. The engine moves while cornering, accelrating etc, and it may get some additional air that cause errors.
Mufasa likes this.

Last edited by -taf-; 09-07-19 at 05:34. Reason: Typo
-taf- is offline  
Status: The artist formerly known as Roarsbaby
AO Silver Member
 
Mufasa's Avatar
 
Join Date: Dec 2007
Location: Ireland
County: Dublin
Posts: 5,885
Garage

Member car:

166V6,SudQO

Quote:
Originally Posted by -taf- View Post
Hi
I had similar problem, but luckily had a good idea to start with. In my car the air hose near the MAF was already taped and the diagnostics showed faulty MAF. Before changing more complicated stuff my mechanic advised to make sure that there are no leaks in the air hose. So I removed the old duct tape and did some proper taping afterwards. Now it is running smoothly. Next step is to find a new silicone hose, as the original material is ...
In conclusion, make sure there is no cracks in the air inlet hose. The engine moves while cornering, accelrating etc, and it may get some additional air that cause errors.
I ordered silcone hose for my 166 track car, MAF to cone filter from these guys:
About Us - AutoSiliconeHoses.com - Silicone Hoses
Although there might be someone more local to you?
PS the TB to MAF is madly taped up too.
Part of the project for next year will be to replace that with silicone too
Attached Images
File Type: jpg IMG_0573.JPG (68.8 KB, 10 views)
-taf- likes this.
Mufasa is offline  
Status: -
AO Silver Member
 
yetyGT's Avatar
 
Join Date: May 2010
Location: Slovakia
County: Bratislavsky
Posts: 1,174
Garage
Hello hyde21. Nice to see another 166 V6 from the same region.

Where did you get the decat piper from? Modra? I did the same thing just because mine is a 3.2. I have swapped front CF3 manifolds with a CF2 and had the bottom pipes made as equal length or close to that. While leaving the bottom cats in place.



Anyway when I bought the car from Austria had almost 200.000 km. Was remapped already. Strange is ePer is showing the model as the 220bhp version for Belgium market.




Shortly after purchase had developed a missfire on two cylinders. After swapping the coils missfire error never occurred again. However don't know if it wasn't having ignition problems before. You can see how bad the front cats look like.



Nevertheless after changing the coils and sparks car was running fine. Did 3 - 5000km with it. Emission test was also OK.

So I have removed manifold cats recently with new EQL pipes and after 1 - 2000 km started noticing sound like exhaust leak. Car started staling here and there after start and later even during driving. My first thought was I did not tighten the manifolds enough. However it got worse and worse. End pipe was black from inside. There was something really wrong with combustion. So I have asked Gus to help me with a new map. Didn't improve. Actually got worse (not the fault of new map of course).

Next was verifying the timing. Was 100%. However compression test revealed weak compression on three cylinders. Since there was absolutely no oil loss I was guessing the valves are not sealing enough. Removed front head to check. Lot's of carbon deposit on the valves as well as on cylinders. What immediately caught my attention are clean spots under fuel injectors. It's the same on all cylinders. Must have been flooding the chambers with fuel.




Frankly speaking the valves as well as all other engine components looks OK after cleaning. Seems like carbon deposits were causing valves not to close properly. And deposits were built by wrong combustion for sure. Being at this stage I took everything out and rebuilding the engine. Of course didn't want to risk and swapped the heads for refurbished ones. Otherwise engine looks very clean from inside. No carbon deposits on the sump neither in the camshaft chambers. Just on valves and pistons.





As I can't tell you yet if it will fix the issue yet - I'm assembling everything back together, maybe in two - three weeks. I would try to remove carbon deposits. Check out the spark plugs if they are not black instead of nice clean almost white as they should. And try removing the carbon using a specialist. There has been some good results on Wheelers Dealers. We should have specialist doing it in Slovakia. This might save you the hassle with engine out.
Mufasa and -taf- like this.

166, 159, 156, GTV916, 145, GTV6, 105 Giulia
yetyGT is offline  
(Post Link) post #19 of 20 Old 4 Weeks Ago
Status: -
AO Member
 
Join Date: Aug 2018
Location: Estonia
County: Harjumaa
Posts: 10

Member car:

166 3.0

Hi
Have to admit, I still bought a new MAF in the end. The old one started to act weirdly depending the time of the day (probably air humidity and temperature). The new sensor (Bosch) was originally sold for Opel (Vauxhall) and works as it should.
Mufasa likes this.
-taf- is offline  
(Post Link) post #20 of 20 Old 4 Weeks Ago
Status: -
AO Silver Member
 
yetyGT's Avatar
 
Join Date: May 2010
Location: Slovakia
County: Bratislavsky
Posts: 1,174
Garage
Right. Iím also considering to change the MAF or at least to clean it. As I have new lambdas and catalytic converters. This is the least I can do in addition although swapping it with another used I have at disposal didnít change anything. Just for the peace in mind. You never know.
Mufasa likes this.
yetyGT is offline  
Reply

Go Back   Alfa Romeo Forum > Supported Alfa Romeo Models > Technical & Vehicle Assistance > Alfa 164 & 166

Tags
166 , decated , engine , idle , issues , misfire , rough

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Similar Threads
Thread Thread Starter Forum Replies Last Post
Who's got the highest Mileage 166 on the forum? Stephen Manjai Alfa 164 & 166 578 1 Week Ago 18:07

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

 
For the best viewing experience please update your browser to Google Chrome