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Old 16-03-2017   #1
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Question Rough running at idle and serious judder at low RPM in gear

This sort of follows on from;

https://www.fiatforum.com/punto-ii/4...-hot-cold.html

The engine cutting out seemed to go away once I got a new alternator.

However....

Engine was running rough on idle although luckily not stalling. Every few seconds it seemed to choke, when I had engine running with the airbox removed I could hear an air suction sound when the choking was happening. Still not sure if this is a sympton of anything.

As well as this, and actually a lot more annoying is how the car performs when driving at low RPM. At almost any speed although I think worse at lower speeds, when I back of the accelerator, the car judders really quite badly. I have to drop the clutch to stop it. It also hesitates / judders when putting my foot back on the accelerator. It's basically un-driveable in traffic with foot just pressing the accelerator slightly as it judders then too.

I had thought it might be misfiring so changed the spark plugs. It actually got worse and now stalls after maybe 10 seconds or so unless I give it some rev when it sounds like it will stall.

I'm reluctant to bother changing the HT leads as well (quite expensive), my feeling now is that it might be the MAP sensor. I randomly removed the power from the MAP sensor and it idled much better. However the juddering whilst moving still remains so not sure if the two are even linked.

Does anyone have a ****ing clue what might be going on ?

I'm thinking I might try and remove the MAP sensor and clean it? Not that it'll probably make any difference. Have to buy a star/torq whatever the hell it's called screwdriver to do this.

Summary of ramble;

Symptoms;

1) Rough Idle, choking every few seconds. Since changing spark plugs now stalls.

2) Awful kangaroo judder when backing off accelerator, driving with just a touch of throttle, and hesitation / judder when putting foot back onto throttle.

Have tried;

- Changing spark plugs. Car now stalls on idle
-Removing MAP sensor power cable, seemed to improve idle but still judders when driving.

Cheers,

Paul.
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Old 17-03-2017   #2
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Re: Rough running at idle and serious judder at low RPM in gear

Can also remove the idle stall problem by unplugging what I think is the throttle position sensor, the higher, smaller further back one on the left hand side of the throttle body and plugging the MAP sensor back in.

Either way I still have the awful kangaroo judder issue when removing my foot from the gas or having it just slightly on at constant speed.

Paul
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Old 17-03-2017   #3
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Re: Rough running at idle and serious judder at low RPM in gear

there is no point in buying new parts
get used ones and change them on the spot, explain to the seller if car will work normaly you will buy it
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Old 18-03-2017   #4
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Re: Rough running at idle and serious judder at low RPM in gear

Quote Originally Posted by flisko View Post
there is no point in buying new parts
get used ones and change them on the spot, explain to the seller if car will work normaly you will buy it
flisko,

That is a good idea, but I don't know anywhere here in Finland I could even do that ?

Paul
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Old 18-03-2017   #5
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Re: Rough running at idle and serious judder at low RPM in gear

Does this video help to understand what is going on when I have the MAP sensor plugged in and engine is idling ?


The engine stalls a few seconds after the end of the video.

Without MAP sensor, e.g. unplugged, it doesn't stall but does run a little better. Though when driving still have awful judderyness.
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Last edited by PaulTobiasx1/9; 18-03-2017 at 13:44.
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Old 18-03-2017   #6
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Re: Rough running at idle and serious judder at low RPM in gear

you sure yellow engine light isnt on?
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Old 18-03-2017   #7
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Re: Rough running at idle and serious judder at low RPM in gear

Quote Originally Posted by flisko View Post
you sure yellow engine light isnt on?
Definitely no light. Maybe the light is broken ?

Do you think I'll be wasting my time getting a MAP sensor ? Should I consider buying a fault reader or just taking to a garage ?

Paul
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Old 19-03-2017   #8
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Re: Rough running at idle and serious judder at low RPM in gear

Well I guess I'll just buy the sensor and report back. Not sure what else to do right now.
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Old 19-03-2017   #9
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Re: Rough running at idle and serious judder at low RPM in gear

first plug it to computer to check for errors, what city are you from
if you live near kajaani i know someone there who can check for errors
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Last edited by flisko; 19-03-2017 at 11:26.
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Old 19-03-2017   #10
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Re: Rough running at idle and serious judder at low RPM in gear

Quote Originally Posted by flisko View Post
first plug it to computer to check for errors, what city are you from
if you live near kajaani i know someone there who can check for errors
Unfortunately not close at all...

I got mousebuttontrigger happy and ordered a new MAP sensor.

I've just noticed that the oil is also going missing pretty swiftly, I'm guessing this is probably another symptom that either is bad and unrelated, or bad and related and means the MAP sensor will make no difference.

Could misfiring cause quicker fuel burn ?

Paul
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Old 20-03-2017   #11
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Re: Rough running at idle and serious judder at low RPM in gear

Quote Originally Posted by PaulTobiasx1/9 View Post
Unfortunately not close at all...

I got mousebuttontrigger happy and ordered a new MAP sensor.

I've just noticed that the oil is also going missing pretty swiftly, I'm guessing this is probably another symptom that either is bad and unrelated, or bad and related and means the MAP sensor will make no difference.

Could misfiring cause quicker fuel burn ?

Paul
I meant quicker oil burn
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Old 22-03-2017   #12
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Re: Rough running at idle and serious judder at low RPM in gear

MAP sensor didn't work.

Can make the engine run on 2 cyclinders by unplugging one coil at a time so would guess it's not that ?

As far as I can see I'm left with;

-Some air leak
-Problem with Throttle Position Sensor or Idle Air Control valve / motor thing
-Engine Timing / head gasket / some other thing I don't understand.
-ECU even ?

I think I might change the throttle body unless there is some implication with the ECU ? Then take to a garage as anything else I wouldn't be able to do myself anyway.

Paul
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Old 22-03-2017   #13
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Re: Rough running at idle and serious judder at low RPM in gear

mine has this sorta weird hunting issue as well
the revs drop and engine recovers and it'll then stutter again

except mine isn't getting like your to the point the anti-stall is kickin in hard

The Bypass idle valve sounds like it sticking
But tbh on a punto i've never tried to cure it

mine is often worse of heavy electrical demand

Ziggy
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Old 22-03-2017   #14
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Re: Rough running at idle and serious judder at low RPM in gear

Quote Originally Posted by Ziggy122 View Post
mine has this sorta weird hunting issue as well
the revs drop and engine recovers and it'll then stutter again

except mine isn't getting like your to the point the anti-stall is kickin in hard

The Bypass idle valve sounds like it sticking
But tbh on a punto i've never tried to cure it

mine is often worse of heavy electrical demand

Ziggy
Have not really tried with/without electrical load to test difference.

I've gone through so many theories now I think it's probably time I have to give up and take it to a professional.

I suspected maybe throttle position sensor or stuck IAC valve.

I did a small test and found that the TPS is on multimeter giving expected readings, 0.75 and climbing as throttle opens.

I'm getting misfire / stutter with revs well above idle as well so I'm guessing I actually have some serious issue inside the engine, piston rings or valve something or others ?

I noticed only a couple of days ago I seem to be burning oil quite fast. I think this ties in with the piston ring thing, and I guess would explain the misfire as well ?

I managed to try another map sensor at a scrap yard which made no difference, luckily didn't have to buy it.

If you didn't read all my earlier posts, current situation is that I cannot drive anywhere unless TPS is disconnected. Why this is I actually have no idea. At one point I could drive it with either the TPS or MAP sensor disconnected. Now it's down to only going if I disconnect the TPS. If I disconnect the Idle Air Control motor and start engine it revs to infinity. Is this expected behavior as the valve is set to full open with engine off maybe ?

Never had this many problems this quickly with any other car in my life !

Paul
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Last edited by PaulTobiasx1/9; 22-03-2017 at 17:08.
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Old 22-03-2017   #15
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Re: Rough running at idle and serious judder at low RPM in gear

bad coil pack would turn on engine light, but still if you wont scan for errors you are just guessing, without another car for parts its not that easy
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