ROUGH RUNNING

[johnnyc]

some suggestions/thoughts please.

up until a few days ago my 3.0 has been running perfectly. never missed a beat. got in it yesterday morning, kicked it over and is now running like a dog. rough idle, sounds like it has dropped to 5 cylinders. a quick check indicates all plug leads are secure and no other loose wiring visible.

at this point i am at a loss as to how this has happened. any suggestions where to start looking??  electrical gremlin or something else? thanks.

[dehne]

hi there
the first thing to start with is leads, start the car then pull one lead off at a time if it alters the idle its prob ok put it back on, repeat this process with each plug one of them will prob not alter the idle and if thats right pull that plug out and check it, its prob either black and gunked up or its just rooted, either clean it or put another plug in and try it.
if its the plug put a complete new set in
hope that helps

[johnnyc]

thanks dehne; the car has had all new plugs and leads about 6 months ago, plus belts, oil, filters etc. hopefully that will sort it.

[Anthony Miller]

Did it cough when you were starting? Check timing belt tension, if loose it may have jumped a couple of teeth. This happened to me with my 3.0l and the belts were done fairly recently too but apparently they need  abit of a nip up after settling in a bit or so I'm told by my alfa speciallist and 75 expert Gianncarlo 

[AlfaACT]

Another possibility ...
Did it backfire when you first attempted to start it?
Happened to me recently with my 3.
It didn't pop the plenum off, like the GTV6s are apparently prone to do, but the main intake duct from the air cleaner to the engine at the AC end. Wasn't much of a gap, just enough to bleed air, but it was enough to upset the running majorly. Easy quick fix - when I finally found it!

Good luck,
Peter.

[aggie57]

some suggestions/thoughts please.

up until a few days ago my 3.0 has been running perfectly. never missed a beat. got in it yesterday morning, kicked it over and is now running like a dog. rough idle, sounds like it has dropped to 5 cylinders. a quick check indicates all plug leads are secure and no other loose wiring visible.

at this point i am at a loss as to how this has happened. any suggestions where to start looking??  electrical gremlin or something else? thanks.

Hi Johnny,

I would like to reinforce what Dehne has already suggested that being that it is most likely a fouled spark plug. V6's do this when they are stop/started quite often. The easiest way to check is as Dehne said removing one lead at a time but can I suggest to avoid damaging leads and also burning fingers or copping a shock is with the engine off pop all the leads off and let them sit loosely on top of each plug. Don't worry this is perfectly fine for a stationary car. With the engine running, gently lift each lead off the plug until it either drops that cylinder or runs smoother. This will determine which is fouled. Sometimes just by doing this you can actually clear that cylinder. If you find all cylinders are firing, then the timing belt slipping a tooth is the next thing to look at. I wouldn't even bother with that though until you can be sure all plugs are firing.

Cheers

Mick.

Just adding to what Mick says, if you find that the errant cylinder fires with the lead 1/2 an inch or so away from the plug then hold it there and run the revs up to around 1500-2000 for a couple of minutes.  That'll hold a lean mixture.  The reason a dirty plug fires in those conditions is that the extra gap acts as a bit of a resistor for the spark so the spark that jumps the gap carries a bit more current than normal.  Least that's what my Daddy told me when I was small........

[ARQ164 Shane]

wet wether did that to my car .
tured out the plugleads were't on the plugs porperly and the water in the air got too them.

hope that helps

[johnnyc]

Hi all,

due to xmas and new year been distracted but have had a chance to follow up on dehnes' and micks' suggestions. pulled the plug leads  and let them sit on top as suggested by mick and kicked it over. still rough so gave it some throttle. still rough.

went through the process of lifting each plug lead to the point that each cylinder dropped away, but with a loud noise (electrical) which I am assuming is the lead "arching". a real loud "tick tick" sound if you can understand what I am trying to convey.

anyway, pulled the lead on # 2 cylinder and the idle didnt change noticeably, as it did on all the other cylinders. pulled the plug out of # 4 and 5, as a matter of interest and they were both really black. the plugs havent been in the car all that long and they were much blacker than i anticipated. getting the spark plug out of number 2 is a bit of a pain in the ass and had have to run around chasing up an extension bar. smaller bloody hands would be handy as well. i will try and post some pictures to show the state of the plugs, to see what you think.

anthony, no it didnt back fire at all, and the plenum is still where it needs to be.  hope all had a great xmas and new year. cheers jc.

[colcol]

Mark the spark plugs as you take them out and compare them, if one is blacker than the others, it may not be firing, mark the suspect one, put it back into the motor in an easy to get at place, start the engine, run it at about 2,000 R.P.M. for about 2 minutes, listen for a misfire, if its still running rough, remove the suspect plug quickly, and see if its wet, if yes, then its not firing, Colin.

[johnnyc]

col, you are correct. all of the plugs stank of petrol after i had been through the process suggested by dehne and mick. took them all out (except # 6 - painful to access) and cleaned the lot. Put them all back in and checked the hose clamps. The afm clamps were all loose, very loose (for that matter all of the hose clamps were loose) would the loose afm clamps cause the car to run rich? leading to foul plugs? Running very well now. took it out for a blast and it was running to 6000 rpm easily. amazing sound. have tried to post some photos but it appears the system cant cope. will keep trying.

thanks to all.

[colcol]

If the Air Flow Meter clamps were loose, there would be air leaks, causing a rough idle because there is too much air and not enough fuel, Colin.