Technical MK1 Punto Idle Revving / High Idle

[majobusa]

With engine running connect a volt meter between clean metal part of engine and battery- ve post. Does voltmeter read zero?

Then connect voltmeter between clean metal of body and battery - ve does meter read zero ?

Not sure if I understood you well. So the test is red cable to the engine, black to negative battery, right? I've done like that and to the engine has read -0,01, to the body 0,00. What does it indicate?

 

[jackwhoo]

Not sure if I understood you well. So the test is red cable to the engine, black to negative battery, right? I've done like that and to the engine has read -0,01, to the body 0,00. What does it indicate?

It shows the voltage drop across the lead between battery negative and engine and battery negative and body.

It is better to do these test with a lot of current flowing but there is no apparent voltage drop so the negative leads probably ok.

 

[jackwhoo]

Engine has to be running during test.
Plus the test of battery negative to body better if you turn on as many electrical things as you can , lights , rear window heater , vent fan

 

[majobusa]

Tested again with light, fog lights, fan and rear window heater. To engine fluctuating between -0.20 and -0.30. To the body zero.

In addition, I've reset the idle motor with IAWScan2. That works much better, but still nor perfect. At cold start starts at 1100 rpm aprox, and dicreases slowly in the same rythm as coolant temperature increases. When warm idle is fiz at 944 rpm, so perfect. When fan starts changes to 960 aprox, and back to 944 when fan stops. This is perfect. The theory says it has to be 900 rpm +-50. However, from time to time when shifting gears it makes a small stop at 2100 rpm more less, to drop later to 950. Fair to say that now it always drops to idle, but, as I said before, randomly it doesn't drops linear.

Workshop manual indicates cut-off strategy is based on: engine speed, coolant temperature and air temperature. All three sensors are new.

 

[majobusa]

By the way, I've notice as well when accelerating from 1000 rpm, at 2100 it makes a irregular revving, disappearing when passed that revs. It reminds me when I had a problem with coils. I've checked them with IAWScan2 and no error logged. Maybe just starting being faulty? Can the coils be the reason of high idle when shifting?

 

[majobusa]

A picture of IAWScan2

 

[jackwhoo]

Tested again with light, fog lights, fan and rear window heater. To engine fluctuating between -0.20 and -0.30. To the body zero.

In addition, I've reset the idle motor with IAWScan2. That works much better, but still nor perfect. At cold start starts at 1100 rpm aprox, and dicreases slowly in the same rythm as coolant temperature increases. When warm idle is fiz at 944 rpm, so perfect. When fan starts changes to 960 aprox, and back to 944 when fan stops. This is perfect. The theory says it has to be 900 rpm +-50. However, from time to time when shifting gears it makes a small stop at 2100 rpm more less, to drop later to 950. Fair to say that now it always drops to idle, but, as I said before, randomly it doesn't drops linear.

Workshop manual indicates cut-off strategy is based on: engine speed, coolant temperature and air temperature. All three sensors are new.

Those voltage readings indicate there is resistance in the -ve wire between the engine and battery-ve lead. Either fit a new - ve lead between the engine and battery negative post or add another thick wire between engine and battery - ve

 

[jackwhoo]

When engine at idle warm does the o2 sensor voltage fluctuate between about 0.2v and 0.8v?
Read that using iaw software

 

[majobusa]

When engine at idle warm does the o2 sensor voltage fluctuate between about 0.2v and 0.8v?
Read that using iaw software

You mean the Lambda probe correction? I didn't find any other related. If so, it fluctuates between 0,92 and 0,98. No idea if inside limits. A video to help here
https://youtu.be/h3w2BRFLgfU

 

[majobusa]

Those voltage readings indicate there is resistance in the -ve wire between the engine and battery-ve lead. Either fit a new - ve lead between the engine and battery negative post or add another thick wire between engine and battery - ve

This can cause the problem I'm facing? It has the stock electrical installation. Same cables from new. I'm a bit lost on electrical, not one of my strengths to be honest...

 

[majobusa]

Let me add that tonight I've driven the car and couldn't repeat the revs hanging on at 2000 rpm. This afternoon it was so hot where I live (Spain, small town close to Madrid) around 40 degrees. Tonight it's still hot, 27°, to be at night but not that much compared to this afternoon. Can it be related? Just trying to give you as much info as possible

 

[majobusa]

Today I have checked all again. Baterry is charging with an external charger, maybe not related but I cannot lose anything. I've noticed that air filter box was not adjusting completely, so I've applied some Teflon (picture attached, not my car) to the seal in the throttle body. I've tightened the lambda sensor just it case, it has moved no more than 10° (visual measure). Tomorrow I'll test it, battery is still charging. Let's see if there is any improvement. If not, this is my plan b https://products.liqui-moly.com/additives/injection-cleaner.html

 

[jackwhoo]

How many total kms
Has car driven?
You may need a new catalytic converter to get through mot.
New lambda sensor first maybe cheaper.

 

[majobusa]

355376 so far. Lambda is brand new, changed on february. I'm in doubt if a new catalytic converter will solve the issue, because CO at idle looks fine. If broken or in bad condition CO should be high in both CO idle and CO rev, shouldn't be?

I'm open to buy a new one, I found it for 95€ (86£). But what worries me is if I change it but problem is still there.

 

[majobusa]

How many total kms
Has car driven?
You may need a new catalytic converter to get through mot.
New lambda sensor first maybe cheaper.

You made me think twice about the catalytic converter. because there are some symptoms that may indicates it is not in best condition

- acceleration not fluent at 2000 rpm. Maybe not enough pressure in exhaust fumes and cat is blocking them
- the temperature is exceeding the half so often, although just a bit above the half. Maybe because of previous point, fumes blocked are provoking it. On the other hand, maybe it is just normal behavior.
- very few times I've heard a metallic noise from exhaust under driver seat.

I'll check it today hitting it a bit to check if there is anything broken in the interior

 

[jackwhoo]

355376 so far. Lambda is brand new, changed on february. I'm in doubt if a new catalytic converter will solve the issue, because CO at idle looks fine. If broken or in bad condition CO should be high in both CO idle and CO rev, shouldn't be?

I'm open to buy a new one, I found it for 95€ (86£). But what worries me is if I change it but problem is still there.

What brand lambda ntk/ngk Or Bosch?
Or Chinese no name sensor?
Yes I know what you mean about hesitating to try a new catalytic converter, I hesitated to suggest it. Don't be so sure that a cat works at idle must be fine remember a lot more exhaust gasses go through cat at fast idle so the cat has to work a lot harder. a failing cat is likely to be ok at idle but not ok with more exhaust flowing through it.

How many total kilometres has your car travelled? Is cat original Part?


The revs hanging will not be catalytic converter, but a different issue. Did you check the throttle cable has some slack when no pressure on throttle pedal?
No mat or carpet pressing on throttle pedal. Throttle pedal pivot point not stiff?

The video you posted was helpful.
The iaw interpretation of the o2 sensor uses a value (lambda correction) that I'm not familiar with , if it had shown the voltage output of the o2 sensor I would be able to say more.

Throttle position sensor reading correctly using iaw?

Can you down load the free multiecuscan software? That is very good and may help.

The iaw showed the o2 correction going up and down which looks to be a good sign.

Do you know anyone with a similar age punto that you could look at the panda correction graph and see if it is the same?

Something else check the back of the exhaust manifold for cracks a mirror may help.

Don't give up

Jack

 

[majobusa]

Lambda is Maxgear, https://www.autodoc.es/maxgear/9963487 , the replaced one was Bosch and last 4 years only. Because of the lockdown I have it at home as well, yesterday I cleaned it so I can double check if it still works or if Maxgear is working fine


I have the Multiecuscan installed but getting some Runtime errors when connected to the car in my Windows 10 pc that I couldn't solve yet either. Anyway, checking the options in MES simulation mode IAW can do almost the same

Cat is from stock, so it has 355376 km and 25 years :0

Makes sense what you state about idle gases and cat.

Throttle cable revised several times. Also tensioned, checked as well that rubber is not blocking the cable. Carpet in its place.

Throttle position sensor is new and seems to be reading properly. Not reset when installed as workshop manual indicates, but in limits, between 0 and 14°, and it is 4° im IAW. However I though to review it again.

How can be measured the voltage of the o2 sensor out of IAW? Any manual way?

Unfortunatelly I don't know anyone with same car. We had a very good group long time ago, but old cars like mine have been replaced by new ones. That's life

By the way, thanks for the encouragement and help, really appreciated

 

[jackwhoo]

It's great you are keeping such a car running.

Try the Bosch sensor and see if the graph of lambda correction exactly the same as new sensor.

I think it is worth trying a replacement cat at that number of kms.

No problem supporting , you are doing a good job

Start a new thread about trying to run multi ecu scan with Windows 10 it may help others as well as you

 

[majobusa]

it was my brother's first car, my first car as well. it has been from new at home and always working, while newer cars at home got broken. I've restored and improved the car with higher trims equipment. There is still work to do, painting and shocks mainly, but only if passes MOT of course. I'm very fond of it, that's the reason I keep pushing to get it solved. Actually it is still running, maybe to perfect, but running. The problem is just with MOT

I'll try today first mounting battery and checking if all I did yesterday make any difference, if not I'll try by setting throttle position sensor as workshop indicates and as well the cleaned Bosch lambda. Keep you posted.

I'll start the thread about MES, thanks for the suggestion

 

[jackwhoo]

Love that you have had the car from new , amazing