Fiat 126 BIS hell... missing at low load, hunting idle... cutting out...

[poxxxy]

Was another nice day so thought I'd drive the fiat again. Now I'm peed off!

All seemed to start with a slight miss under low load, then I come to an island and it cuts out on me ... struggling to maintain an idle. Managed to get the idle to keep the engine running sorted by screwing in the idle adjustment screw (crap FOS carb!) but its still up and down a fair amount. Revs seem to pick up then drop off lower than they should.

After the close call with the cutting out... I checked the timing over etc and all is ok there.

Car seems to run fine on wide open throttle and overrun though without missing.

Not sure where to look now.

Any pointers may help... bear in mind its had new everything in the last 12 months apart from coil. .

[lancianut]

I reckon its the coil! 

[dadandlad]

Sounds like a fuelling issue to me
Blocked idle jet ?

[poxxxy]

I'd be surprised if the carb managed to get blocked in the short time. It did have a thorough cleaning not that long ago, it seems fairly consistent in its missing at low load and cruising. I can't maintain a steady speed without it bouncing around a little lol.

Not sure the coil would cause the hunting symptoms? Everything was running perfect the other day and for the past few months too lol. Now the suns out and it want's to play silly buggers .

Was meant to get working on another project, not have another 7 months taken up by the 126 lol.

[Mics126]

air leak or blocked jet as said before.

[Pete126]

Check the vacuum pipe hasn't come off the carb also check the the vacuum pipes on the throttle kicker solenoid, Check for air leaks around the base of the carb, I use carb cleaner just spray around the base, If the revs pickup you have an air leak

[poxxxy]

All vacuum pipes etc are ok. Hmmm... don't think theres a leak at the base of the carb or anything either. Trying to remember what it was last time it was like this. Something to do with the carb but can't see it suddenly just not working lol.

[poxxxy]

Pretty stumped... seemed like it almost ran right for a second earlier whilst playing (hadn't dont anything through really at the point) as I had to turn the idle screw back down as the idle was rather high once again but after this it seemed to go back to its normal lumpy self and had to turn the idle screw back the other way once again.

Plugs all look ok.

Vac lines all in tact.

No air leaks.

Don't fancy stripping the carb down once again.

[Pete126]

Points, Timing, If you have some different plugs try them, compression test and valve clearances    

[poxxxy]

Cleaned up the points although they looked clean. Played with timing to no avail. Fuel filter was pretty blocked so changed that out. Filling this filter much more now. Maybe something has blocked the idle jet but otherside of the filter looked ok. Exhaust gases are clean burning so I don't think I'm having head gasket issues . Car accelerates fine but cruising it wants to kangaroo a little and still revs dropping down and hunting at idle. No leaks at base of carb etc. Vacuum lines all good.
Will strip the carb down again tomorrow I guess!

[Rusty's Uncle]

What is the condition of the fuel tank? If you are getting muck in the filter then there will be a lot more in the tank clogging the internal filter causing fuel starvation.

[poxxxy]

Yeah the tank has seen better days, it does need one really but removing it was a job I didn't particularly enjoy the last time around and will probably fabricate the next one . Snapped studs didn't help though which shouldn't be a problem this time around.

If it was fuel starvation I can't imagine it'd be running well at full throttle though when its demanding the most.

Would be nice to be able to make it to autoitalia... I need another spare 30 dgf as I need an accelerator pump and some of the butterfly valve linkages and then i'd have another to try. Certainly considering benefits of going EFI though should it be the problem.

[poxxxy]

Removed carb, blasted it all out with air compressor and replaced an oring. Running like a sewing machine again now .

[Bambino126]

That's good news!