Alfa 156 2.5 v6 missfire when engine hot! - Alfa Romeo Forum
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(Post Link) post #1 of 11 Old 08-01-08 Thread Starter
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Alfa 156 2.5 v6 missfire when engine hot!

Hi guys,
I am just wondering if any body can help me with a problem i have with my car.
I bought my Alfa 156 2.5 v6 (reg date 1999) on 15/12/07. I took it for a test drive and was supprised how well a Alfa drives. A week later i decided to take my car for a wash inc the engine (big mistake) then took the car home still driving like a dream!
The very next day i took my car to work and found when the engine got worm it started to missfire but still got to work. On my way back to home i felt a total lack of power whilst driving the car it felt rough and the engine cuts out when i approach a traffic light as i press the clutch down to stop. The car still drives fine when the engine is cold but as soon as the temperature hits the first mark the starts to wobble.
I then took the car to my local garage to get it checked out as i do not have a Alfa dealership in Leicester he connected the car up to his diagnostics machine and told me that the third chamber is not working, also on his report shows that co2 fault was present on the vehicle and a injector fault showing. He then reset the fault codes to see if the fault shows up again but did not come up again. The mechanic then tested the injecter on the third chamber and found it is working.
I then asked him to check the coil pack on the third chamber to see if there is a fault. It seems like it is a massive job as the spark plugs are hidden away at the back of the engine compartment covered by all the running gear and so on. I would be grateful if any body can help with any advise/confirm it would be the coil pack or co2/lambda sensor, or any body had the same problem.
With Thanks,
Super...Ted
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(Post Link) post #2 of 11 Old 08-01-08 Thread Starter
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Re: Alfa 156 2.5 v6 missfire when engine hot!

Hello people, does anybody know how hard it is to change the spark plugs on a Alfa 156 2.5 v6, and what is required to do the job?
oh ... this a very complexed car...
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Re: Alfa 156 2.5 v6 missfire when engine hot!

Hi Ted, the front 3 are a walk in the park, the back three are a little more involved, just strip things down slowly and carefully, the plugs are under the plenumn chamber at the back of the engine, do the front ones first to get some confidence.
I have done lots of jobs under the bonneet on my 156 V6 and although I pop the bonnet and want to cry, so far ll jobs have been impler than I first thought.....
That being said I will pay to have my cambelt changed
The worst thing is you can't get a Haynes manual for a 156, and the ones on disc on ebay for a fiver are only any good for exploded diagrams.
To get the front plugs out you take the cover (that says Alfa Romeo) off the front engine bank and remove the coil packs and unscrew the plugs-easy. The back is the same but with lots more things to take off before the coil packs, place everything you take off in place in small sub assemblies in the same orientation that it fits on the car, this makes it a lot easier to reassemble. Dont rush and as with any job on a 156 use plenty of releasing fluid .
Good luck and keep us informed

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Re: Alfa 156 2.5 v6 missfire when engine hot!

Oh just thought try disconnecting the MAF as that can cause an erratic idle and the car to cut out at the lights........
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Re: Alfa 156 2.5 v6 missfire when engine hot!

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Oh just thought try disconnecting the MAF as that can cause an erratic idle and the car to cut out at the lights........
Thankyou very much jason156, i will give it a shot tomorrow and keep you posted on the outcome
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Re: Alfa 156 2.5 v6 missfire when engine hot!

Your welcome
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Re: Alfa 156 2.5 v6 missfire when engine hot!

The rear bank is simple enough but as Jason say, take your time and allow for about 2-3 hours.
The most awkward bit is getting the plenum off as it snags on the oil separator pipe where it attaches into the head. I find taking the pipe off the easiest solution but then getting it back on with the original clip is a pain. A jubilee clip is a good replacement there!
Also, you neet to disconnect the intake runners from the plenum to get it off so get down to Halfrauds and get some of the special clip removers and refitters. Without this you will be at it all day, but with it it's a doddle.

What did you wash the engine with? The rear bank is pretty watertight and I`d be surprised if there is water in the plugs. If a coil pack is malfunctioning you may be able to hear it cracking as it grounds the spark. Try to have a listen if you can keep it running long enough!

Also as jason says, I wouldn't be convinced about the coil pack and there are some simpler areas to look first. The MAF is a very common problem and the simplest to start with.
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(Post Link) post #8 of 11 Old 09-01-08 Thread Starter
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Re: Alfa 156 2.5 v6 missfire when engine hot!

Hi Jason156/Chris, Firstly thank you guys for taking time to help with good advise..

I gave it a shot today changed all the spark plugs and two coil packs at the back, my hands are covered in blood (because i have hands the size of spades) I did not even know i was bleeding until i completed the task! I tried starting the engine, once i put it all back together.... but no response, so i checked all connections but could not find why the car would not start. Then a old granny from across the road came over and asked... Whats the problem with your car???? I felt like hitting her in the face, but i explained what i had done. It looked like my words were going through her ears and out her ar*e. All the granny said to me was.. have you connected the battery? I looked at my battery and thought 'i am a Turkey' I did not connect the battery..
I then connected the battery then started the car, i told the granny its too cold out here go in get your self warm and i will see you later. This car is now fixed and it just sounds fantastic. Just before i carried out the work i checked the MAF, it looked to me it was working OK. The hole job took me 2 hours and 45 minutes, i found the job was not as big as i thought it would be as long as you have the tools.
At the end of the day i must once again thank Jason156 and Chris for your advise, because without you guys i would not be able to get my car working again.
This message is for all who read this post:_ Show 100% respect to all the granny!
With Thanks,
Super...Ted
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Re: Alfa 156 2.5 v6 missfire when engine hot!

Nice one Ted, loads of people have helped me on this site, its what we are all here for, it just adds something to the experience of Alfa Ownwership, now go and thrash it
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Re: Alfa 156 2.5 v6 missfire when engine hot!

I know the job has been finished but for anyone with the the same prob i found a realy good web site with a step by step guid in how to change plugs on a v6 Fun starts @ 3000! all the best johno
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Thumbs Up Re: Alfa 156 2.5 v6 missfire when engine hot!

A direct link to the V6 guide mentioned above is here

Replacing the spark plugs on a 156 V6 (1998)
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