Tuning Panda 750 L Running Lumpy

[Toadwart]

Hi All

I've just acquired a little old Panda 750 L and am getting to grips with it. Having driven the car to work and back and round and about for the last few days I've noticed it runs rather 'lumpy' i.e. not the smoothest ride in the world and tends to stutter / jerk (especially when cold). Is this normal, or is there some clever work I can do under the hood to get my old Panda running a little smoother?

 

[Bougainvillea Rosso]

Hi and welcome to the forum,

If it's only running rough when cold it might just be a case of letting it warm through. That said, all Pandas enjoy a proper service. So if you haven't done so already, check/change the plugs, change the air filter, oil and filter etc. See if that improves things. If it's very juddery make sure the HT leads are OK too (if they are very old you might invest in some new ones as well).

 

[panda1408]

Are you adjusting the choke correctly?

 

[Toadwart]

Hi Bougainvillea

Thanks for the advice! I do usually let her warm up before heading off, but it seems that the 'lumpiness' is still a problem even when warm (although not as bad). The former keeper appears to have kept her in pretty good nic and the filters all look almost brand new. I'll definitely pull the plugs on the weekend though and have a lok at them, and inspect the leads too!

Hey panda 1408

I've been getting used to the choke, and found that my little Panda seems to like being choked! She drives much better if the choke is left on a little, although is still a little hesitant.

I put touch of Redex in her tank this morning and am hoping that may help clean out any gunk in teh system. When I pull her plugs I'll run some Redex through her carb as well and see if that helps any.

Thanks for the help!

 

[madrat]

Sounds like a full service and inspection is called for.

Check the choke pull down diaphragm and the diaphragm on the distributor. If these have gone they will let air in to the fuel mixture making it weak.

Also when were the points and condenser replaced? check the distributor cap and rotor arm as well.

 

[urchin]

check the vac unit on the dizzy too.

 

[Toadwart]

Wow, certainly sounds like I have my work cut out for me this weekend!

Thanks all for the input and ideas! I'll check everything that you've suggested and let you know how I get on. I must say, the old girl is growing on me so it'll be nice to get her running smoothly.

 

[Toadwart]

madrat, not a clue when the points and condenser were replaced, so will add these to my list, cheers.

 

[Toadwart]

Right, the condenser and points have been replaced in the last 12 months, and a new distrubtor cap and rotor arm installed. That's a fwe things off the list, although will check these all on the weekend if weather permits.

The old girl seems to be enjoying the Redex taster, so will definitely use a touch of that to clear the carb whilst I'm at it on the weekend.

I noticed what looks like a crack in the exhaust manifold this morning when I poked my head under her hood and am wondering if that may be contributing to her lumpy behaviour?

 

[Toadwart]

Right, loads checked and here's the verdict / an update:

Plugs and filters all clean and looking good.
HT leads new and working as they should.
Distibutor cap, rotor arm and vacuum advance unit all good.
Points and condenser good.
Choke pull down diphram good.

I set the idle screw a bit higher and made a slight adjustment on the mixture screw on the carb. Now she seems to run as smoothly as she should, but still hates being cold. Seems I may have been a little over-enthusiastic in setting the idle screw, so will take that down a notch. Very pleased to have her running smoothly now but not entirely sure what it was; the mixture screw adjustment!? Surely not just that?

 

[Toadwart]

Forgot to mention, the oil looks pretty grim, so will replace that and put a new filter on for her. Any suggestions for the best oil to feed the old girl?

 

[madrat]

You really need to check the state of tune.

Points gap
Dwell angle
Idle speed
Ignition timing
C.O content.

 

[madrat]

Bog standard 15w/40 or 10w/40

 

[Toadwart]

Thanks madrat, appreciate the advice

 

[lightweightmick]

my 4x4 has always seemed to need more choke than I would have thought - (with 2 other Pandas to compare against)
I've serviced it (though no reason to suspect HT problems as it doesn't miss as such but gets 'lumpy') - I think it's down to the jets in the crab needing attention as it seems to be lumpy more in the lower revs range - hard to pin down, but that's what it feels like, so I'd be interested to hear how you get round this,
cheers
lwm

 

[Toadwart]

Hi LWM

I'll certainly let you know how I progress. Hoping to get more time to have a poke around under the hood this weekend or next.

I've checked the jets in the carb, which seem absolutely fine, so not sure this is it although admittadly haven't checked that they're the standard size.

The mixture setting seems to have a noticeable effect and I've improved the running somewhat with this but have no doubt there's more to it than just that.

I've ruled out probs with the dizzy and leads etc. and firmly believe it's the fuel system to blame. I'll be pulling the carb apart and fine tuning that next I reckon.

Cheers
Toad

 

[Toadwart]

So I finally got my finger out and did some work on the old beast ...

Oil changed, filters (fuel and oil) changed, leads changed, plugs changed, timing set, mixture set, idle set, carb cleaned, fuel pump tested.

I haven't changed the coil but it seems to be working as it should. Checked the points, which are new, dwell angle, rotor arm, cap ... all good. Condensor checked and good.

Of course none of this helps as I can't actually take it for a test drive thanks to my wiper having fallen off on the way home on Friday. And do you think I can find a new wiper arm and / or motor!? Alas I may end up flogging her on e-bay if I can't find a wiper arm and get that sorted.

 

[Toadwart]

Forgot to mention that I found a charming crack in the exhaust manifold too and also can't find a replacement for that. Rest of the exhaust is new and shiny though, on the good side.

 

[Toadwart]

Stopped raining long enough for me to take a quick drive about and I was very happy that my weekend effort appears to have paid off. No more lumpy grumpiness from my old girl (or the car) and she's running smoothly. Have also found a chap with a wiper arm and motor so will be doing those soon and then the manifold ...