Technical Misfire

[paulg]

I have just returned from a 800 mile round trip this weekend,running fine,1/2 way through a tank of petrol,this morning started misfiring after 1/2 hour of gentle driving.Sometimes it runs fine,especially if thrashing it right round the rev range,idles ok with only a hint of occasional misfire from the exhaust sound,and seems to be more of an intermittant problem when driving slowly though a village.I thought dirt somewhere,fuel starvation,as it ran perfectly after work,I thought dirt had dislodged,and became a problem again on the journey home,as I slowed to go through the village again.It was intermittant again from then on,but once going,gentle (but not slow) driving,it performed fairly well,with the misfire cutting in and out throughout the journey home.I don't know much about fuel injection systems,and the electrics are beyond me.Any Ideas anyone???? Are injectors easy to get out and clean,or do you think I am barking up the wrong tree? Any help would be grateful.Paul

 

[LittleRedB]

Difficult to say without seeing the car, I have had a similar experience in the past - I serviced the car and the issue went away. As you say it could be a number of things, colgged air-filter, dirty plugs or injectors, split air intake pipe, dirty fuel filter - its a process of elimination, have you noticed a decrease in mpg and power or is it just a misfire and are you getting a smell of petrol in the car?

I had a similar problem on my wife's old BMW, turned out to be a tiny split in one of the injector pipes, bloody good job I found it as it was a fire waiting to happen

I would suggest starting with the basics, check the plugs are clean, check the HT leads have not split, check the intake pipe for splits, run some injector cleaner through the car, check the air filter, change the fuel filter.........

 

[paulg]

Hi.There is no smell of petrol,and when it is not misfiring,it goes like .Early days to notice fuel consumption,but I will keep my eye on it.Thanks for the ideas,keep 'em coming.Paul

 

[Mad Matt]

I suppose you're not Suzy's brother?

Anyway, back on topic, have you taken the plugs out and had a look? The colour can give away some problems.

Carb cleaner is fairly cheap and easy to use.

Does the problem get worse on damp days?

Not much else that LRB hasn't mentioned.....

 

[paulg]

Hi.Had a quick look this evening,but not much time.Unfortunately for me,I bought a modern low mileage car instead of my usual 1960's sports cars for a bit of reliability.You can see where this is going!!:bang:.I would have had the old cars stripped,fixed and back working within a couple of hours.It nearly took me that long to find the plugs,but i still haven't found the fuel filter. Tomorrow,I will drive the car to work,and call out roadside assistance,(in France where I live) and see if the very nice man can plug up and save me a lot of time,and probably money.It was serviced just before I bought it,so don't want to put on a load of new bits for nothing.Oh wellPaul

 

[LittleRedB]

i still haven't found the fuel filter. Paul

Deep breaths - it will be fine!!

The fuel filter is under the car towards the back where the cabin/floorpan finishes, looks like a metal cylinder.......easy to change, takes less than 2 mins!

Keep the faith man - it will be fine! What you fail to mention with your 1960's sports car is it would have been a much bigger engine to produce 130 bhp and would have handled like a bucket of soup in comparison with the b!! I would also have been the points gap or the twin carbs out of balance causing the misfire - easy to diagnose!

 

[Mad Matt]

Does take a bit of getting used to after older cars, but it's very easy to work on compared to my Dad's new Mini Cooper S. There's just no room in the engine bay!

 

[BILL33]

Deep breaths - it will be fine!!

The fuel filter is under the car towards the back where the cabin/floorpan finishes, looks like a metal cylinder.......easy to change, takes less than 2 mins!

Keep the faith man - it will be fine! What you fail to mention with your 1960's sports car is it would have been a much bigger engine to produce 130 bhp and would have handled like a bucket of soup in comparison with the b!! I would also have been the points gap or the twin carbs out of balance causing the misfire - easy to diagnose!

Not all B models have fuel filter.Only the early ones have.

 

[docorangepeel]

1999 -> on dont have the inline filter. The filter was moved into the petrol pump in the tank and never needs changing. (So Fiat say)

 

[LittleRedB]

There you go - I have learnt something today!!

 

[paulg]

No wonder I couldn't find the bugger.LRB,you forgot to mention the oil leak that every 60's car has!! Anyway,an update. I drove to work,called assistance,and a guy turned up with a Landcruiser and a trailer.He doesn't look at the cars (like RAC,AA etc) he just trailers me to a garage.Nearest Fiat garage is 1/2 hour away,so off we go.We arrive,and the mechanic strolls,VERY slowly over and starts the car.Hand on hips,says it could be a bougie (spark plug).He and the recovery guy talk for 20 mins without glancing at the car again.He then turns it off,and the recovery man turn round,walks off,gets in his Landcruiser,and drives off.1/2 hour later,after kicking stones around and dealing with another customer,the mechanic approaches me and says " I can't look at it now,Go away and come back this afternoon" (It is 11 am at this point).So I drive back to work:bang::bang::bang::bang::bang::bang::bang:.Bloody useless.
I didn't return (can't think why?),so on the way home,I bought some spark plugs,and filled the car up with petrol.As I was waiting to pay for the petrol,I swear that the car was idling smoother,and the journey home was much better.I changed the plugs,not much better, there is still a small hiccup but it improved as my journey to and from work went on.It is now running 95%.It obviously wasn't the plugs,I am thinking it is all down to dodgy petrol,another refill should answer this for me.
A friend never fills up in supermarket stations as he has had 2 cars with serious fuel problems.I am starting to see his way of thinking. I will let you know what happens after the next fill up.Thanks again for all your help.Paul

 

[paulg]

Oh well,it's never that easy.I have filled up again,and no change. So,more ideas please.I am sure someone will come up trumps.It drives nicely now from medium to top revs,but hunts unevenly on idle,and jerks when driving slowly,revs down.Can you hear your fuel pump from the driving seat? Mine is quite audible,but had not noticed this before. Now I have done the clutching at straws bit, i will start working through possible problems this weekend.I will keep you updated.paul

 

[LittleRedB]

Hmmm, curious - mine is displaying similar behaviour but I know that mine has only been playing up since I fitted a slightly different induction pipe 'cos my old one had split in a number of places......

If you have filled up with dodgy petrol one tank will probably not clear it, try running some injector cleaner through it.

Defo sounds like a fuel/induction issue to me, have you checked the induction pipe to ensure that there are no leaks/splits?

Still think that you need to put a day aside and go through a process of elimination starting with the obvious stuff. When I was an HGV mechanic we had a similar issue in a Cummins L10 engine - a very complex and very powerful lump........it took 2 days of fault finding, removing injectors, blowing the fuel lines through, replacing filters etc etc before we tracked the fault down to a valve sticking on the fuel filler cap! Once the unit was up and running for more than a couple of mins it would smoke like a ww1 soldier and hunt like a tiger, all caused by the sticking valve creating a huge vacuum and preventing a high flow of diesel required to feed the unit! Not an obvious fault but by taking the fault finding one step at a time we tracked it down!

 

[paulg]

Hi LRB.I did the injector cleaner early on,may put in another load (still clutching at those straws).I have just done a search on the forum,and a similar problem came up,although the car in question was on the point of stalling.Mine is just erratic tickover,and erratic,jerky pickup at lower revs.I will try one of the suggestions on that thread of spraying carb cleaner in the butterfly.Worth a try.I will also take a closer look at the intake pipes.I did have a quick glance the other day,but with winter nights drawing in,and living in France,one hour ahead,everything has to be done by lead light,and it is never as easy.Lets hope that this weekend is nice and bright,and I will have a proper look.Thanks again.Paul

 

[LittleRedB]

Carb cleaner in the throttle body made a difference in mine! When you take the intake pipe off look inside the throttle body, mine had a build up of gunk from the oil breather pipes, carb cleaner fixed it in two mins flat!

 

[Ilkka]

...I bought a modern low mileage car instead of my usual 1960's sports cars for a bit of reliability...

You bought a Fiat for a bit of reliability...?

 

[Mad Matt]

 

[RnRollie]

You bought a Fiat for a bit of reliability...?

:yeahthat:

If its reliability you want: get a Honda S2000 :worship::slayer:

If masochistic : an MGB/TF or a Rover 214 Coupe/convertible :bang:

 

[superspotter]

I live next door to a garage. Every other week they have an MG in for a new head gasket, they are crap!!

 

[LittleRedB]

I live next door to a garage. Every other week they have an MG in for a new head gasket, they are crap!!

And they look poo and early ones catch fire..........oh and they are British so the build quality is even worse than the Italians - anyone see TopGear on Sunday?