Could it be...

[shorty123]

The stepper motor?
Just been out for a fab drive down to Devon and all would have been well but for several near breakdowns...

My car was peforming as normal when after about 80 miles and on slow moving B roads I had a reduction in power accompanied by reduced cylinders firing, sounded like 2 or 3 down.
I switch the car off, wait 2 mins and start up again all is fine but slightly down on power, until i next start the car after a toilet break. Power is resumed.
40 miles later same again. but this time i can smell unburnt fuel in the cat.
Later on the way back i am on a dual carriageway hard accelerating in third and i get a big juddering (similar to bouncing of the rev limit but harsher and at only 4k revs) Cautiously carried on with no probs. Twice more on the way home i suddenly got the same 'firing on less trhan 8 cyls' problem, each time its resolved by switching the car off for a couple of mins and back on again.

I did wonder if it was fuel delivery, but kind of discounted that after smelling the unburnt fuel. It didnt feel like a spark plug failing either or cracked dizzy cap.

Any thoughts, could it be the mythical little stepper motor?

[sam gamgee]

if youve not replaced spark plug leads in a while, cuold be this (was recently on mine-and they were fairly recent magnecors-now running very well on standard jobbies). Loose connections can and have caused same, too. Thats after youve checked stepper....

Dave.

[RCA]

I'm more inclined towards the leads aswell, sounds like it could be a break down of leads or plug problem. cheers Rich

[bga]

mine started running a bit rough a few days ago - sounded similar to your problem but not so bad.
yesterday I swapped the coil, plug shrouds & HT leads & all is perfect again - better than before infact.

[gsw500]

I had this on Friday morning when out on a spirited drive.
Car was performing perfectly and then a momemtary loss of power for about a second or two, pulled over but could'nt find anything obvious.
Carried on with journey and does same again 10 mins later checked again and nothing so went straight home.
Should imagine under bonnet temps were pretty high and being a warm day did'nt help so think something must be breaking down under heat stress.
Think i'm gonna replace leads and plugs, cleaned stepper recently should I replace coil too looks like it has seen better days.
Anyone had a deal on leads, plugs and coil from anyone...?

Gsw500.

[shorty123]

i'd be suprised if it was the leads as i only fitted a new set of magnecors last year, could be though, id like to hear if magnecors are proving unreliable from other users.

maybe the coil? i think as a precaution i will change this and the dizzy cap. the plugs need doing on the iminent short service interval.

I didnt change the plug shrouds when i did the ht leads, maybe this?

will clean the stepper in the mean time.

any more suggestions would be good.

cheers again.

[N&N]

I had a simular problem. Cleaned the stepper motor which was sooted up, and it cured the problem. Its the best first step because it only costs you twenty minutes of your time!

[JEC]

Sorry to be dumb, whats the stepper motor?

I have a a sort of lag kiks in around 4K revs makes the car jerk! I think the perfomace is slightly better before the temp is up to 80! could this be the ht leads working less efficiently at higher temp?

John

[neejah]

I was under the impression that the stepper motor only provided a air bleed for the base idle? i.e. it allows some air into the plenum with the throttle closed to set the tickover?

If this is the case then it wouldn't have any effect on "rough running" or misfires throughout the range? Unless I'm talking a reet load of awld tosh!

[That Daddy]

it wont be the stepper motor at 4k rpm i would go for the leads dont know for certain but i read somewhere there may be a problem with the coil ht lead on the magnecors.or the leads to close to metal components on the engine.

[sam gamgee]

Hi, not in any way `knocking` magnecors but mine less than cuople of years old (under 10k miles) and they were replaced by standard jobbies, which did the job. Well...! Replaced the coil earlier. Like I said, suspect the coil first. Bought from ACT products.

Cheers!

Dave.

[shorty123]

Still got the old standard leads, will try the old HT again but will change the coil.

cheers me old babbers

[cossie.]

I had problems with the engine (intermittently) either losing power or cutting-out altogether. Changed the ECU, airflow meter and lambda sensors (done on the advice of the dealer and Austec - under warranty, thank goodness!). However, it still suffered so cleaned the stepper motor, changed the HT leads to Magnecors (not dizzy cap or coil as yet) to no avail. Got a new battery. It was better but still caught me out a couple of times. So, finally got a maintenance charger and touch wood it's run as sweet as a nut without so much as a hiccup.

[sam gamgee]

Yeah, me got one of those Accumate ones, pretty useful goodies. dont always use it but plug it in when I remember.

Dave.

[karlos tvr]

magnecors have to much resistance through them i have seen many people put them on also removing the metal plug caps and having the lead straight on to the plugs themselves if this is the case then put it back to standard both of these things will add to poor performance and we dont want that !!!!! kj tvr ( ex main dealer techi)