General engine floods when cold? 999cc fuel injection

[Jaff_Fox]

This is a problem i've been having for 3 years and its got no worse but it really bugs me sometimes (because its three years obviously its not sparks, distributor, leads, timing, gasket or dirty oil! these have been changed)..

When i first start the engine (after its cooled) it *sometimes* fires up as if the engine was flooded (or it was running on only three cylinders), when i start shuffling the car around my drive to turn it round it almost stalls.. if i stop the engine at this point and disconnect the injector and try to start the engine it actually fires up for a second or two with no fuel being injected to the cylinders at all!! Engine flooding? if so how can i stop this? It also seems to have a flat spot sometimes which i'm sure is related to the same problem.. i'll move off from lights and it will have barley any power and then suddenly the power kicks in (if i rev it before moving off this won't happen)..

Just curious if anyone can fix my 3 years of frustration..

 

[John H]

I don't know the cause of your specific problems, but I'll post some ideas here about specific known "features".

ECU'd cars (of many different makes) get really confused if you stop them very shortly after a cold start, and then try to restart.

I think what happens goes something like this:
ATS and CTS are both the same high value, indicating a cold start.
At the point of cranking a suitably rich mixture is injected to enable starting - this mixture is decided by a look-up table and is the "correct" quantity for an engine which was stopped hot and has no trace of any petrol in the bores.
When you stop it after it has only run for a short while (say less than a minute to move it on the drive) on attempted restart both ATS and CTS still indicate a cold start and you get the mixture as before, but into bores which are already wet with fuel.
The engine is not firing, there is no feed back from the lambda sensor to indicate rich mixture as it's stone cold and needs to be hot to work, so the ECU gives extra fuel.

The way some ECUs are mapped to recover from this mess is if you hold throttle to the floor (which is what you'd do with a carbed engine flooded) the lookup tables give lean mixture when engine speed is below something like 500 rpm (IE cranking).

There are other interesting things mentioned somewhere in here

http://www.parttrackers.com/library/1/24/36/

under the "blind spots" section.


Yet another issue is sluggish response from the lambda sensor (when it's warmed up and working) ECU gets demand for more fuel (throttle position increase), injector open time increased, but lambda says it's still running lean for a second or so - what's an ECU to do under those circumstances??
If you look at the waveform from the lambda on a scope you still see it switching.. but it's a bit behind the action.


For what it's worth my Panda also gets a bit confused during warmup on freezing mornings during the first minute, and can sometimes get so rich as to grind to a spluttering halt if you're driving with a heavy right foot.

Gentle rightfoot is OK.
Let it tickover for a minute before driving is OK.
Warmer mornings (most of the year) are OK.

Life's to short for me to bother -
I can't justify the time, or money, to fix it[:0]

 

[Jaff_Fox]

thanks for your help... i noticed something else interesting today that might be related.. it was raining and on my way to work every time i stopped at lights the engine started throbbing and almost stalled like it was flooded and the wiper was not wiping so fast (it was wiping at the speed it would if the engine was not running, you know, you start the engine and the lights go brighter etc?).. if i give the engine a little gas the wiper speed went to normal and the engine smoothed out.. i think somethings getting wet electrical which is stopping the plugs from sparking correctly. maybe that thingy that generates the electric that i don't know the name of? hehe.. could also explain a groggy start...

 

[John H]

Hi again.

Just properly read your reply.

If the tickover is way too slow the alternator may not be going quickly enough to generate power to overcome the load of wiper, blower, HRW and anything else which is running.

Under those circumstance the voltage is likely to be 12volts or so, compared to the 14.7 volts a happy alternator will push out.
This difference is enough to alter fan speed and light brightness.

The thing is though, if your engine management is doing its stuff, the tickover speed should be maintained around the 800 rpm mark (almost) regardless of load.
Provided that the engine operating happily, and the stepper motor which controls your tickover speed by adjusting the butterfly valve position working as intended.

One my CLX I can tell the stepper motor is OK, as I can see the throttle pedal move down when the ignition is turned on immediately prior to a (very) cold start.
It's possible my throttle cable is a bit too tight, but you can hear and see some activity under the bonnet, especially if the bore of the throttle body is exposed.

Before you do anything desperate though, consider that FIAT electrics aren't the best in the world, and poor connections cause no end of difficulty - which usually end up with new components being thrown at a problem, which only temporarily fix it. (Connections disturbed, but not sorted out properly).
Disconnect, clean, and remake the connector to your stepper motor.

Another option which can cause rough running in damp conditions is poor plug leads.

 

[Enzo]

I think the rigid climate doesn't help those little and cheap cars to work properly[xx(]...fortunately I live in the south of Italy, and near the sea, so I never drive on the snow[8D]!then the salt usually thrown on the roads to avoid icing brings nearer the death sentence for Fiat tinsB)...my Panda:no visible rust after 12years and never an electrical problem,unlike my Renault 5 whose backlights needed a re-grounding.
The only annoyance my car gives me is on cold (and damp) startups, because the engine sometimes runs with 3 cylinders for 5-10sec and then keeps on working fine...I recently replaced the cap, but not the rotating brush and plug leads...maybe they're gone[?]

Passion has neither brands nor models!

La passione non ha nè marche nè modelli!