Hi,

Yes, this is yet another Punto jerking thread.

The Car

• Year 2000
• Mk2 (not 2b)
• 1.2 8v Petrol
• ~40, 000 miles (known to be genuine)
• Regularly serviced at an authorised garage

Symptoms:

• Jerks/kangaroos when accelerating/decelerating in the rev range of 1000 rpm (1k) to 1500 rpm (1.5k). Smoother above and below(!) this range.
• Naturally difficult/annoying to drive in slow traffic with this
• Full throttle acceleration does not exhibit the problem - slow controlled acceleration in the affected rev range, does.
• No clutch use is occurring whilst this going on (actually need to depress the clutch pedal to avoid it).
• Particularly noticeable in 1st and 2nd gear
• Exists in a warm engine or cold
• Visibly unsteady idle needle
• Irregular idle "pulse" / "cough" every few seconds (irregular timing) can be felt in the seats/steering wheel also

What I don't think it is:

• Clutch. Recently replaced, no difference. I've experienced slipping clutches before. There's the fact that it's bad when decelerating (i.e. when I would imagine the clutch is under less load).
• Timing belt. Also recently replaced.
• Rear (dog bone) engine mount. Recently replaced.

I've found other posts with similar issues, but can't post them because I'm < 5 posts.

Has anyone who has experienced these symptoms positively narrowed it down? I was thinking cleaning the throttle body (as per the guide here) or replacing it.

• No clutch use is occurring whilst this going on (actually need to depress the clutch pedal to avoid it).
• Particularly noticeable in 1st and 2nd gear

so it is the clutch to blame? if you depress pedal you are not using your clutch

Try changing the sparks, i had a similar issue where i had a judder/temporary power loss of power at low revs very similar to what you describe.

Since changing the sparks not had a problem.

Only use NGK ... fiats seem to be fussy as to which sparks they like!

For the rough idle check the breather hose isn't split. And clean up the throttle body. Made the world of difference in mine

so it is the clutch to blame? if you depress pedal you are not using your clutch

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A reasonable question. There's absolutely no clutch judder when engaging it, or even just starting off. Also, it'll make a good effort at trying to pull away with the handbrake engaged - engine will cut out (can't ask much more from it than that I think).

It's fine when accelerating through the gears normally or cruising in 5th, say. It really becomes evident when creeping along in slow traffic, when there's a lot of light accelerator use at low revs (particularly in the rev range mentioned).

When I engage the clutch to stop it, I'm effectively disconnecting the engine (as you know) which drops to idle. So although using the clutch prevents it, I believe it's demonstrating it's use as a workaround rather than an indicator of the underlying cause.

changing the sparks

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Thanks for the suggestion! I kind of hope it's not something like spark plugs, since it has been exhibiting this problem for a long time and been through many services from a Fiat garage. I'll definitely look into doing that anyway as it's a less drastic procedure than the throttle body work.

ohh is this the judder you mean?

driving in 3rd or 4th or 5th gear real slow like, 10kmh and car judders

I'm experiencing this exact problem at the minute, actually got a topic open on it, I have tried many many things so far with no luck -- I will keep an eye on this topic and see how you get on, I'll also update if I have any info to provide

Similar issue in mine only at low revs just like you explained, happens in traffic etc. Will be changing the spark plugs in mine soon, will do exactly as KRaikkonenNo1 is doing and just keep an eye on it and if I find any progress will update.

plyons said:

I'm not quite as bad a driver as that! I wouldn't be surprised if the engine would cut out at those speeds in those gears. I would describe that as the engine "labouring" due to not enough revs.

No, this is driving slowly in 1st and 2nd. It can drive fine in 1st or 2nd with clutch engaged and no accelerator pedal in use (so both feet on the floor). But if I depress the accelerator slightly, and especially if I attempt to release it slowly again, it will cause the problem. Hence I would describe it as "jerking" rather than "juddering", as the whole car lurches forward and backwards.

To try and describe the experience in the car, I guess it might be like full throttle, then lifting off completely, then back on the power again, etc. only really quickly - at a frequency of about every half second. Except it's worse in reality because the Punto's throttle response probably isn't good enough to replicate it!

Just another note on the car, it's completely stock, no modifications at all.

Click to expand...

Couldn't have put it better myself! EXACT same issue -- you getting any codes?

KRaikkonenNo1 said:

Couldn't have put it better myself! EXACT same issue -- you getting any codes?

Click to expand...

I have not tested for codes myself. Correct me if I'm wrong, but wouldn't I get an engine management light if codes were being generated? I don't think the EML has come on during the normal operation of the car. I'm not the sort of person to ignore EMLs, so I think I'd remember it happening, even if it was a while ago.

I believe the EML will reset after a number of up to temperature drives (three?). If true, I would have thought the EML would still reappear if the codes are still being generated?

Regardless, I'll have a check!

plyons said:

I have not tested for codes myself. Correct me if I'm wrong, but wouldn't I get an engine management light if codes were being generated? I don't think the EML has come on during the normal operation of the car. I'm not the sort of person to ignore EMLs, so I think I'd remember it happening, even if it was a while ago.

I believe the EML will reset after a number of up to temperature drives (three?). If true, I would have thought the EML would still reappear if the codes are still being generated?

Regardless, I'll have a check!

Click to expand...

No the eml does not have to illuminate -- the codes can either be stored in the ecu memory or they can display on the dashboard light, for example right now my eml isn't on but I know I have a p1135 code "preheating resistance 1 above catalyser" -- this Is stored: sometimes this can get worse and the ecu detects that it has gone out of the limits that the ecu thinks normal so the light will illuminate (like it did for me the other day),

I've had this code for a while and it disappeared after I replaced the 'suspected' lambda..only for the code to return now and the problem still be present -- so now I'm inclined to think it may be a cat issue..

Why should a pre-cat lambda code implicate the cat?

Swap the lambdas round -- what happens?

fingers99 said:

Why should a pre-cat lambda code implicate the cat?

Swap the lambdas round -- what happens?

Click to expand...

Swapped them round and code disappeared, soon as I swap it back code returns?

Hello I'm getting this problem. Especially when the car is cold but when it's warm it doesn't. It makes you look a idiot when it happens. I'm gonna get some new ht leads and sparks. I've heard ht leads can fix this problem.

C009Y said:

Hello I'm getting this problem. Especially when the car is cold but when it's warm it doesn't. It makes you look a idiot when it happens. I'm gonna get some new ht leads and sparks. I've heard ht leads can fix this problem.

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dont start buying stuff prematurely
for example look what this guy changed and still didnt fix his similar problem to yours

you can go on an excellent adventure by typing erratic idle in here

I'm only saying what other people have said in past will defo keep eye out on the thread Hope you sort it

Just a quick update.

No codes reported according to the BlueDriver I used. Having said this, I've read that cars older than 2002 may not be 100% OBD II compliant.

I need to look again to see if there's anything else I can infer from the various readings.

Another quick update. I've swapped in a second-hand throttle body that I pre-cleaned.

On the plus side, it's no worse than it was. Unfortunately, it's also no better.

The readings from my BlueDriver.
1. The O2 Bank 1 sensor 2 bounces between about 0.07 to 0.7 in a very regular wave. As understand it, this completely normal.
2. The O2 Bank 1 Sensor 2 on the other hand seems to bounce between 0.05 and 0.15. This one is more erratic though. Sometimes it was reading flat zero, a other time is was reading between 0.6 and 0.7. My particular symptoms don't appear to change with this different readings.
3. Timing Advance for #1 Cylinder hovers around 15-20 degrees under about 2000 RPM, but locks on at 40 degrees above that. I don't know the significance, if any, of this.

There's no EML, and the bulb isn't broken.


Some other symptoms:

1. Trying to keep the revs within the 1000-1500 RPM is difficult when stationary (i.e. trying to keep the throttle steady). It will flip back and forth in a rhythm every half second between about 1000-1100 RPM.
2. Above that, it tends to climb to 2000 RPM.
3. It also idles between about 728-760 RPM

I've noticed a crack in the pipe leading from the top of the rocker cover into the bottom of the air filter. I need to check of there's actually a leak from it. There's also a small notch (about 5mm) where it meets the air filter at the end, but seems too symmetrical to have broken off (i.e. Looks like it's by design). Is this the breather hose mentioned by FiatPuntoMad here https://www.fiatforum.com/punto-ii/355874-1-2-8v-1000-1500-rpm-jerking.html?p=3533985?


I need to check the spark plugs yet. I've seen them in handier places on other engines... (pointing towards the front!).



Hopefully some of this info might prove useful in diagnosing the problem.

have you fixed it?

KRaikkonenNo1 said:

Swapped them round and code disappeared, soon as I swap it back code returns?

Click to expand...

If the car runs OK like that, leave them swapped!