Technical Running Problem

[NottsCharger]

Hi there, I have a 1995 Panda CLXi which has a running issue which has me stumped. :bang:
It starts fine both cold and hot and pulls strongly, good acceleration and cruising speed and is returning excellent economy. However the idle speed is too high and rough as if it is over fueling. Also once it warms up it pinks just momentarily when changing up through the gears but not at any other time.

The injector light doesn't light when running, cambelt is set up correctly, no air leaks at injection pot base, new lambda sensor fitted, serviced with new fluids, filters, plugs and leads. 56k miles.

I know the pinking can be an issue relating to octane of fuel with the FIRE type engine so this could be secondary to idle speed and rough idle.

Any ideas please?

 

[Most Easterly Pandas]

Hiya.

Have you tried re-setting the ECU

Jon.

 

[NottsCharger]

I read about procedure for resetting the earlier Bosch ecu but this one is a magnetti marelli so wasn't sure same applied. I have tried disconnecting the battery for a while but that did nothing.

 

[CLXCraig]

:yeahthat: if that fails...

a higher idle would be to do with the throttle being open more than usual. There is a solenoid that opens the throttle slightly on startup(for cold start). It's on the left of the TB when you look at it. If it is opening to much then i suspect thats your cause of faster idle speeds.

start from cold, let the car run for a bit at idle, unplug, see if there is any difference. Don't touch the pedals though, if once unplugged idle speed drops, found your problem. might be faulty, so turn engine off, plug back in and start again. if idle is the same as it is now, i think that might be duff. don't ask how on earth you replace it. Tha panda's didnt have a fly-by-wire set up so this is the only thing i can think of.

 

[NottsCharger]

The cold start enrichment solenoid is working when initially starting but idle speed drops down only so far.

I have been trying unplugging the various sensors on and around throttle body, I was thinking of throttle position sensor, as when you blip throttle the idle speed momentarily drops as if to falter but then pick up again.

There is a valve type thing on a bracket mounted to the drivers side suspension turret that has a pipe from inlet manifold and another disappearing into front wing ( poss charcoal canister) and an electrical connection, unplugging this seems to make no difference at all to running as if it is not working.

 

[Most Easterly Pandas]

Tha panda's didnt have a fly-by-wire set up so this is the only thing i can think of.

Nope they didn't.

Could it not be a sticky/stuck accelerator cable though

 

[NottsCharger]

No throttle cable is free and smooth and throttle butterfly closes properly.:bang:

 

[s5jst]

Check this post Hiccups, high revs and irregular idle - possible solution if you can get any hint.

 

[Chas Uno]

Check for air leaks anywhere else in the induction system as these can cause a higher idle speed and the weaker air/ fuel mixture would be more likely to cause 'pinking'. Does a 1995 CLXi have a vacuum advance module? Check it is working if it does and also that the pipe between it and the carburettor base isn't split or leaking. Also, have you checked the ignition timing?

 

[jangcy]

First think...it's 1995 so there is no Bosch injection system so there is no vacuum advance module etc it's with twin coil system.
Also nothing can change throttle possition apart from dust, dents,short cable.
Steper engine (idle controler) in Magnetti system it's some kind of air valve. In bosch system it could change throttle possition. Also we can't change ignition timing (it's all ECU's job )

What I would suggest:
-make sure again that there is no air leak (it caused problems in my Panda for 4 months...) in my Panda there was leak between inlet manifold and throttle body (there is some kind of connector/adaptor) and seal was not good...
Check all other connection, pipes, have you got brakes power (can you hear some sound from it?)
-second it could be idle controller (steeper engine) - I had two and swapped them to check different and on one it was working slow on other faster. It could be dirty, worn or broken...It's good to clean it and also clean inside throttle.

-also it could MAP sensor

-if not it could be ECU temp sender-if it's broken ECU can think that engine is cold...when you disconnect it ECU will take 99deegree as default. You can always check.(it's that blue connector)

if not ... it could be injector pressure valve problem, fuel pump, throttle position sensor broken...

If nothing help I've got throttle body from Panda 1994 which I can borrow/sell to check...

Anyway - I would start with air leak from place I described and check idle controller...

 

[NottsCharger]

Cheers for that jangcy, most helpful. Can I ask on your third picture what is the sensor valve in front of the map sensor. It shares the same bracket and has two pipes and electrical connection?

Brakes are fine seems to have servo assistance no problem.

I initially found an air leak between throttle body and spacer as there were no paper gaskets, I used some bluecol instant gasket but made no difference.

I too thought of temperature sensor but again makes no difference disconnecting.

I have substitute parts from a Cinq Sporting and a Tricker with modified throttle body, I will try swapping bit around to see if there is an improvement.

The air leaks is also quite likely I had problems with air leaks on my previous Panda 4x4, was a bugger to sort.

Thanks again for the advice everyone is pointing me in right direction I am sure.

 

[jangcy]

. Can I ask on your third picture what is the sensor valve in front of the map sensor. It shares the same bracket and has two pipes and electrical connection?

You mean that one? (in red is what I think it could be...)

After all that job you've done it could be good to check (or replace) idle controler , check injector (replace) and reset your ECU

 

[Uno driver]

Check resistance of temperature sensor, should be between 2k and 200ohm IIRC. I had similar problems, resistance was infinite.

 

[jangcy]

Check resistance of temperature sensor, should be between 2k and 200ohm IIRC. I had similar problems, resistance was infinite.

you're right...but if you disconnect it ECU will record it as fault and take default setting which is 99C (or 90C) so engine should be hot for ECU and idle should back to normal...so I think it could be something else

 

[Uno driver]

I was playing with punto ecu diagnostic tool and without sensor it shows -30C or something similar. When I put 200 ohm resistor in connector (90C) car didnt want to start, i had to pump pedal etc to keep it runing. Why don't you measure just to be sure, it's a two minute job .

Could be also fuel pressure (pressure regulator, pump, filter). You could measure that too (put Y coupling at fuel input of throttle body (or behind fuel filter) and measure with manometer)

 

[jangcy]

I was playing with punto ecu diagnostic tool and without sensor it shows -30C or something similar. When I put 200 ohm resistor in connector (90C) car didnt want to start, i had to pump pedal etc to keep it runing.

Fiats....

Yes it's always good to check...