V6 Intermittent Missfire + Down On Power

[top_man_eldo]

Morning All,

Still got problems with my missfiring V6. Still not sure what the problem is, although the car will begin to missfire at normal operating temperature. There are big flat spots all the way up the rev range, including low down the revs, and after a few minutes of running like this, the car will begin to run normal again - this whole process keeps repeating itself and its driving me mad.

I haven't got access to Alfadiag or any other diagnostic software, and being after Christmas as well I am a bit strapped for cash, just like all of us, so was hoping to kind of "self diagnose" the car - which is proving to be a bit difficult!

I have cleaned out the throttle butterfly earlier yesterday afternoon, this didn't make any difference at all, although it was pretty gummed up - I cleaned it with a small amount of air intake cleaner. I have also unplugged the air flow meter - this made no difference to how the car run - if anything, the car may have possibly run a little better from cold, although once the car had warmed up, the missfiring and flat spots came back. It is also worth mentioning as well that the red "injector" warning lamp is illuminated when the AFM is unplugged, but when it is reconnected the lamp goes out.

One other thing I have noticed is that the car generally has lost much of its power - very sluggish lower down the rev range, even when running without an apparent missfire. The idle speed also occasionally drops to being very lumpy (not erratic).

I have heard a few things about air flow meters and lambda sensors - I have never had a lambda sensor go wrong, so I am not sure what the symptomns of these are. I just don't want to part with £170 for an air flow meter, and find that this isn't the failing part!

It may be worth noting that all six plugs were changed last summer by myself, so it is extremely doubtful that these are failing! Any help would be greatly appreciated!

Anthony.

[purple145]

it only costs £25 to get hooked up to a diagnostic machine at my indi, which is better than replacing parts on a scatter-gun approach. At least once pinpointed you can replace the part(s) yourself. The symptoms you describe sound less likely to be the MAF, these tend to go be being down on power at high revs first, but it really could be several things.

HTH

[danny13]

mines kangerooing!!!!!

Sounds almost identical to the problems I'm having with my GTV....I've been away for a few months during which time a friend would occationally take my car for a spin (pleasure was all his I believe!) He said its running fine although did cut out when he hit the rev limiter (mental note to never lend my car to this person again!)

I'm wondering whether its something to do with the extreme cold weather, never having owned my car through a winter.

My V6 seems to take 30 mins to get the radiator temp up, and will only go up to about 70 (unless in traffic jam) in warmer weather its happy days standing erect at 90!

On driving from cold the engine feels like its lacking power and misfiring...trying to accelerate through 1st, 2nd and 3rd gears at a medium pace results in kangeroo type acceration - however if i dip the clutch the engine revs cleanly.

weird.....had my MAF replaced a few months ago....so pretty sure its not that.....knowing pretty much nought about engines my only other guess would be the autochoke maybe....things improve when the engines warmed....but still not 100% there with a definate flat spot in the power.

will be booking it into a garage shortly - but wondered if anyone might be able to give advice on what was wrong....strangely read another post where some lucky V6 driver was getting more power in the cold....v jealous!

[midlifecrisis]

I had a problem with a misfiring V6 which drove me mad, as it kept throwing up error codes that showed the rear bank was misfiring. I took it to a specialist as local garages in Swansea did'nt have a clue about the Alfa V6! The specialist (NJS) diagnosed it as an incorrectly fitted cambelt. Basically the previous owner had paid a fortune to have his engine messed up by cowboys!

The V6 has 4 camshafts and if the camshafts aren't correctly locked down when the cambelt is removed then it messes up the timing. It took the specialist 5 hours to re-align the camshafts with the crankshaft! The result is a V6 that flies with no hesitancy or misfire or loss of power.

My advice is to find a specialist and let them investigate. By the way, NJS didn't charge me for the investigation work, only for the work carried out.

[danny13]

thanks midlife.....was just searching through the forums and found lots on kangarooing - hoping its just the Crankshaft sensor as Doc G writes in http://www.alfaowner.com/Forum/alfa-...e-panacea.html (Kangaroo finally cured - is it the panacea?)

Very nervous as my last fault (which i thought was simply running out of petrol) cost me £1800 - doh!

Who and where is NJS? Had a search around the forum and Waterfall garage in Bridgend seems a favourite in swansea area.

[midlifecrisis]

NJS are based in Pershore, Worcester. Its a slog from Swansea(2Hours) but the work and knowledge the owner(Neil) has is second to none. He races his 156 in the Alfa championship and has won it! What this guy and his team doesn't know about Alfas isn't worth mentioning. He looks after both my Alfas and the quality and price of the work is fab.

Dont touch Ashmoles apart from spares.

Out of interest what fault cost you £1800?

[danny13]

thx, I drive past worcester every other week so could be a good option.

It was in fact a culimation of faults - the running out of petrol (optimistic italian petrol gauge where 1/4 tank = empty)....was in fact the MAF...but whilst at the garage they pointed out the suspension was screwed...
hence needed to get the following done:
rear spring pan and dog leg suspension arms
O/S trackrod end
O/S front brake flexi hose
N/S front lower wishbone arm
N/S front wheel bearing
O/S front brake flexi hose
rear brakes clean and refit....

was very painful as the repair bill was 2/3 the price I had paid for the car a few months previous......

annoyingly after all of this the car appears to lean to one side, brakes squeal like hell, and the rear suspension still creaks (which I thought the new arms should have fixed).....but the V6 soundtrack makes it all worth it

If only I knew more about car mechanics....