I've already wrote some questins to nice people who want to help but now I have new trouble with my pada ('87). please help.
The problem is that car is sometimes hard to start, especially when hot and when I press gas pedal over some limit (about 20%), the car loses power and 2, maybe even 3 cyilindars fail to work. and driving is possible only if I give just a litle bit of gas pedal... the motor shakes like hell and car goes very bad. but as soon as I release gas pedal little bit, then it's OK. this is a mystery to me. please help!!! SOS!!

Looking back through your topics regarding the 750 Panda..

although the spark plug leads look OK - have you tried measuring the internal resistance of each one (and the lead from the coil to the distributor as well)??

They should vary a bit - the shorter ones a bit lower than the longer ones - but all be less than 10K ohms each: maybe 6k or 7k for the shortest.

Anything much higher (or unmeasureable) is a problem:
the spark dissipates the energy from the coil, and usually this happens in the gap at the end of the spark plug.
When you accelerate there is a richer mixture in the cylinder - this is a lower impedance at the spark plug gap - and if there is a lower impedance route to earth than the spark plug gap, that's where the energy goes, and you get a misfire.

You can often see electrical problems like this under the bonnet when it is dark, if the discharge is external* to the wiring, but it is possible for the discharge to happen inside a worn out lead, which you won't see in the dark.

Measure the leads.


Regards


John H

* poor, or failed insulation. Often worse when damp.

If you can't measure the impedance (sp?), try wiping the leads clean and dry...or buy some more leads.

Electrical problems... I hate 'em!

Justin

In my part of the World you can buy a test meter for about half the cost of a decent set of plug leads (if you look in the right places).

YMMV.


John H

According to the C.O.D.

impedance n.

1 Electrical: the total effective resistance of an electric circuit etc. to alternating current, arising from ohmic resistance and reactance.
2 an analogous mechanical property.
[impede + -ance]

thank you John H for your time and trouble. it sounds logical to me and I will test that. THANK YOU VERY MUCH!

Why do plug leads have resistance (couple kOhms)? why their resistance isn't zero Ohms? isn't it an ordinary piece of wire?

my measurements show resistance
1. 1,5 kOhms
2. 15-20 kOhms
3. 15-20 kOhms
4. 15-20 kOhms

this is strange. the old wire should have greater resistance then the new one. ?!?

help John H!

All conductors have some sort of resistance...

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Uno 1.0ie Start. Standard.

Originally posted by panda_owner
Why do plug leads have resistance (couple kOhms)? why their resistance isn't zero Ohms? isn't it an ordinary piece of wire?

my measurements show resistance
1. 1,5 kOhms
2. 15-20 kOhms
3. 15-20 kOhms
4. 15-20 kOhms

this is strange. the old wire should have greater resistance then the new one. ?!?

Click to expand...

The leads are "radio interference suppressed"
Basically, instead of a piece of wire down the middle (and a resistance of the odd ohm or two) the inner is a funny carbon composite. Then this is damaged, or ages, there is less of the carbon in places - and the resistance goes up.

With the sort of values you quote, I'd replace them all except number 1.

Do the one from the coil to the distributor, as well.