Hi,

I have a Fiat Grande Punto 2006 1.4 that jerks around 30mph. If you are constantly changing gear or accelerating through the gears then its fine, however if you are keeping a constant speed around 30mph, after a while the car will usually start jerking (sometimes lightly, sometimes more violently). Changing gears after it starts jerking then makes it stop. It only appears to happen when travelling between around 30mph.

The spark plugs, ignition leads and air filter have been replaced but this has not helped cure the jerking round 30mph. Does anyone have an idea of what could be causing this based on this description?

Thanks in advance for any help / suggestions!

Does this happen ALWAYS and in ANY gear ?

BRs, Bernie

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Bernievarian said:

Does this happen ALWAYS and in ANY gear ?

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It doesn't happen always and only seems to happen in 3rd or 4th gear. For example I went on a 4 mile trip one way today and it jerked a lot when travelling consistently around 30 - 40 mph, however on the same 4 mile trip back there was a lot more traffic, therefore i was changing up and down the gears more often and it didn't jerk at all (possibly did ever so slightly once).

Hope that helps.

Can anyone suggest which part(s) may be the issue based on the description as I don't really know where to start in trying to fix this problem?

1.4 8v?
1.4 t-jet?

Does it do it always? cold and hot?
Do you only do short trips?
Any problems at higher speeds? Motorway driving?

check engine/gearbox mounts (should be at least 3), exhaust mounts/hangers.

aurick86 said:

1.4 8v?
1.4 t-jet?

Does it do it always? cold and hot?
Do you only do short trips?
Any problems at higher speeds? Motorway driving?

check engine/gearbox mounts (should be at least 3), exhaust mounts/hangers.

Click to expand...

Hi,

Its the 1.4 8v. I think it can be prone to jerking when the engine is cold and hot, however it definitely jerks once the engine is fully heated up. If you drive at a fairly constant 30mph (or there abouts) it will always do it at some point, sometimes sooner, sometimes later, sometimes once or twice, sometimes many times. If you are not doing a constant speed its less prone to happening, if at all.

I generally do short trips (to and from work which is around 10 miles each way) however I do go on occasional longer trips (25 miles+ each way) about once a week.

Have not seen any problems at higher speeds / motorway driving.

I have the 1.2 8v engine and it does exactly the same thing. It's almost as if I'm in too high of a gear for the speed but it's not that.

The Imaginative Lad said:

I have the 1.2 8v engine and it does exactly the same thing. It's almost as if I'm in too high of a gear for the speed but it's not that.

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What RPM is the engine running at when this happens ?

BRs, Bernie

If someone here helped You fix -or better, understand- your issue, hit the thanks icon @ bottom right corner, it's free and makes us feel helpy ;-)

Bernievarian said:

What RPM is the engine running at when this happens ?

BRs, Bernie

If someone here helped You fix -or better, understand- your issue, hit the thanks icon @ bottom right corner, it's free and makes us feel helpy ;-)

Click to expand...

Around 1500-2000rpm is when it most happens, which is where the RPM sits at 30mph in 5th gear. Even with a warm engine it'll jerk the car so I just sit in 4th, simple solution really I know it's probably something else causing it but not worth the hassle.

Isnt that too low a speed/rpm for 5th gear?..

lmrtw said:

Can anyone suggest which part(s) may be the issue based on the description as I don't really know where to start in trying to fix this problem?

Click to expand...

You are the problem. You drive a petrol engine as it was diesel. Too low RPM for given gear.
Second guy (1,2 8V) is trying to stall the engine too...

The two last posts are very pertinent: use higher revs, it's not mandatory to stay @ 5th gear when driving (relatively) slow. Ideally your engine should rev at its maximum torque or a bit lower, that's where its efficiency is at the top !

BRs, Bernie

If someone here helped You fix -or better, understand- your issue, hit the thanks icon @ bottom right corner, it's free and makes us feel helpy ;-)

The Imaginative Lad said:

Around 1500-2000rpm is when it most happens, which is where the RPM sits at 30mph in 5th gear. Even with a warm engine it'll jerk the car so I just sit in 4th, simple solution really I know it's probably something else causing it but not worth the hassle.

Click to expand...

Really hope that was sarcasm.

30mph is good for 3rd gear or 4th if not accelerating.

am afraid it wasn't

The 8v engines like to cruise around 3k rpm, any lower than that and you'll start getting this jerking. Strangely, my wife's old Corsa would happily cruise all day at 30mph in 5th so it took her a while to get used to keeping it in 4th when she got her FIAT.

Edit: Just re-reading the OP's posts and it looks like they're using 3rd and 4th primarily when this happens so it doesn't sound like an under revving issue.
Would be good to plug in MES and see if any codes are presented, where are you lmrtw ?

That depend of the final gear ratio of the Corsa vs the Grande ...

Eklipze3k said:

The 8v engines like to cruise around 3k rpm, any lower than that and you'll start getting this jerking. Strangely, my wife's old Corsa would happily cruise all day at 30mph in 5th so it took her a while to get used to keeping it in 4th when she got her FIAT.

Edit: Just re-reading the OP's posts and it looks like they're using 3rd and 4th primarily when this happens so it doesn't sound like an under revving issue.
Would be good to plug in MES and see if any codes are presented, where are you lmrtw ?

Click to expand...

Sorry was away for a few days. Yup, I am definitely not using 5th gear whilst doing 30mph! Once I get to 30mph it definitely feels like it's reving unnecessarily with 3rd gear, hence I change up to 4th gear soon after 30mph as the engine sounds right for the change up. I can take it out and gauge exact rev's its using at 30mph in 3rd and 4th if that may help?

You say plug in an MES, is this the standard hand held device that reads codes? if so this has been done however there was nothing to go on, just a couple of 'unknown' codes.

No, MES is MultiECUScan - aftermarket software specific to FIAT family ECUs, so will be able to pick up not only all of the "unknown" codes but also provides realtime monitoring. It costs £50, requires a Windows laptop and an appropriate set of cables, but is a must if you want to do your own maintenance.
As you take the car to a garage, I suspect you're not too handy with a set of tools? So, if we knew where in the country you were, one of us with MES could come and have a look at the car and see what we can see

My engine management light flashes away if I sit in 3rd at 30mph lol, but that's another issue (phonic wheel and misfires or something like that) so 4th is best for me.

You really need to monitor a max of sensors signals/actuators response to find what's wrong. Here again: MES is a must have tool !!

BRs, Bernie

If someone here helped You fix -or better, understand- your issue, hit the thanks icon @ bottom right corner, it's free and makes us feel helpy ;-)