General Cutting out, what to check?

[791979]

I have a really annoying problem with my Marbella. It cuts out when driving, mainly (always?) when the throttle is backed off. The problem doesn't seem to be any different when the car is hot or cold.

So far, I have replaced the fuel filter and air filter, and the car seems a little more powerful and smoother too. I blew the remaining fuel out of the fuel filter and it was really pretty dirty, so I have been adding a product similar to Redex to the petrol in the hope that it will clean out the fuel system a little.

In the morning I will check the plugs and HT leads, but I have a feeling this is a fuel or SPI/ECU issue. Or maybe one of those components that I don't understand at all (like the sensor in the exhaust).

So, some questions... BTW my car has a Weber SPI, and a Magnetti management unit.

• Is it safe (or even worthwhile) to disassemble the SPI for a clean?
• Is there anything inside the SPI that may need replacing/adjusting?
• Are there any adjustments I can make to the SPI like mixture or idle speed.
• I think that the exhaust system is blowing a little, could this cause this problem?

On a couple of occasions the car has refused to start, but turned over on the starter OK. The battery seemed a little flat (which seems to be down to a dodgy hazard warning light switch). Anyway, after charging the battery the car started OK, maybe the battery charging is just a fluke and the car would have started anyway after a rest

So, any ideas?

 

[Alan.D]

If it's spi first thing i would check is the lambda sensor, clean or replace with a known working used one.

 

[791979]

Any knack to cleaning them, is it just a case of removing obvious deposits?

 

[Alan.D]

Pretty much, they are very tight so watch your knuckles and use a good fitting spanner or you will round off the nut. I used a plumbers type wrench to get one off that had plenty of grip and leverage.

Another thing on the panda that has simmilar symptoms is the advance mechanism allowing air into the carb, but not sure if the SPI had these?

 

[791979]

Well, I tried that and left the sensor in lemon juice overnight as suggested somewhere else on the forum. It certainly looked like a lot of debris was removed.

The outcome is that the car seems to run really well when cold, but feels like it's not running well when it has warmed up. I'm guessing that it is running rich when the engine is warm.

Of course it may be that the engine needs a few miles on it to settle down after the shock of lemon juice on it's sensor . So, I will give it a day or two of "italian tuning" and see what gives.

The Lambda is I think the original one, and the car has been round the clock at least once, so I guess it is very overdue for replacement. The 70 pounds price is a bit steep though for I car I got for free (with a dead clutch).

 

[Alan.D]

Look for a used one lots of people will have spares. But make sure it has the correct plug fitting some have 4 (2x2) others 3

 

[791979]

Thanks Alan, I will have a look around and see what I can find. BTW, I disconnected the Lambda today & the cutting out seems to have ceased. So I guess that proves that it was indeed the sensor.

I also guess that at the moment the engine will be running at less than it's best, so I will try and get a replacement ASAP.

 

[Alan.D]

No problem, glad we could be of help.