Technical 2011 Punto Evo 1.4 FIRE - minor juddering at low revs

[jamescr]

Hi all,

I'm hoping someone here can help me diagnose a strange issue I've been experiencing with my 2011 Fiat Punto Evo 1.4 FIRE.

I only purchased it around 5 months ago so don't know too much of its history (no service history) but soon after noticed that sometimes on idle or at low revs (mainly around 1500RPM), the vehicle would judder(/kangaroo?). It seems to happen more often when the engine is warm. One day it was particularly bad and I had the engine warning light come on but after turning the vehicle off and letting it sit, the warning light disappeared and has not returned so far (touch wood!)

To date, I've replaced the coil pack and spark plugs and also used 2 bottles of injector cleaner (the type that goes in the fuel tank). Whilst these seem to have reduced the issue, it is still occurring. I've now used an OBDII reader on the vehicle to try and diagnose as I thought this would confirm a misfire on one of the injectors but it showed no codes stored. I have also had the cam belt changed recently as a precaution.

My only remaining thought is that the injectors are still dirty or partially blocked and therefore may need manually cleaning although if this was the case I expected this to be picked up on the OBDII reading? Therefore, I just wanted to ask and see if this seemed reasonable or if I'm missing something completely here?

Thanks in advance for any help and guidance!

 

[GrandePunto PL]

SEARCH. Plenty of similar threads. Simple car. There is nothing "strange" about them (only incompetent mechanics and users).
Also, can you people be more specific? What "1,4"? Which one?
"Coil pack" = 8V I guess. OK...
Therefore: valve clearance. Never done probably (99,999% sure).
"OBD reader"? Which one? Use Fiat specific software (FES, MES, AlfaOBD).
If there is misfire, car cannot tell why (ignition, fuel, mechanical timing, valves, compression, intake/exhaust leak etc.).
It's your job to find out. No such thing as misfire code due to injectors - P0300 series faults are general (car doesn't know why it misfires).
Replaced spark-plugs...and? What? Show the pictures (you can judge the engine condition by the sparkplug colour, wear pattern etc.).
If you suspect fuel, take the rail out and test it, spray pattern, probably it's possible on the car (and MES software, you can prime the pump and open the injectors 1, 2, 3, 4). Do the basics: fuel pressure and oil pressure. Compression.
Timing belt job? Who did it? Any conclusions? What about VVT? Is it fully functional? It also can be tested via FES/MES (data log, test drive).
MOT pass/fail, exhaust gas analysis? You can always go and check emissions only (not as MOT). And compare it to the OBD readings (lambda).
On top of that, there are simple mechanical issues, starting with engine/gearbox mounts...

 

[jamescr]

Thanks for all the info here and apologies for the lack of info, I'm a novice so not 100% sure what is and isn't relevant.

To answer some of your questions:
- 8V as far as I'm aware, it isn't the MultiJet model.
- ODBII reader used is 'bdboutik' ODBII reader, app used for reading is Car Scanner.
- Forgot to mention I've also replaced ignition leads with coil pack and spark plugs. I've thrown all the old ones out and didn't take pictures of them frustratingly.
- Timing belt job was done by my local garage, they said the existing belt wasn't original and looked in okay condition but still couldve gone at anytime if i wasnt sure of its age.

Another point is that while experiencing these issues, there is often a fairly strong smell of petrol after turning the vehicle off after a long drive which further points me to potentially an injector problem?

In further information, I've had an engine check light come on again and now stay on after driving on Sunday. I used the same ODBII reader and app as previous but this time got some codes back: P0555 - brake booster pressure sensor - circuit malfunction & B1033(13) test failed (which seems to point to Daytime Running Lights).

I had searched forums previously to try and determine the issue which is what pointed me to spark plugs/coil pack/ignition leads but this doesn't seem to have been the issue. All other issues I found were so varied I didn't really know where to start without more information.

With now these additional codes and information, I am thinking it could potentially be caused by a bad earth connection and so I'm looking at cleaning these up following this thread: https://www.fiatforum.com/threads/the-electrical-gremlin-thread.318839/

Thanks for the point on valve clearance too and I've now found your thread on this so will have a go at checking if they need adjustment whilst I'm in there.

 

[PuntoGeorge1982]

I have a 1. 2 8v that does this, and there are theads about new cars doing that. It does not happen until the engine reaches operating temperature. It only happens at light loads between 1500-1900 rpm and stops when accelerating. Does not appear when accelerating through that rpm range. It felt diminished after 140 km of highway operation at 3500 rpm. My guess is that is just the simple ecu map. New spark plugs, leads and coil did not do any difference.

 

[GrandePunto PL]

Another one...
Can you people do some basic maintenance first and then jump on the forum?

Like valve clearances, shims (all 8V Fire units)? Most neglected item/task ever. Coolant and brake fluid are other two.
Basic checks: oil pressure (>1 bar idle, hot), intake vacuum (290-330 mbar idle), fuel pressure (3,5 bar)?
Exhaust gas analysis (it is as basic as compression test). The Most underrated test in the automotive industry.
VVT engines: timing is a VVT1 parameter (via Fiat software: FES, MES, AlfaOBD), should be in the 100-110 degrees range.
VVT operation (test drive and OBD2 data log, if the positions are OK, real VS desired), VVT kicks in at 2000 rpm or so.
Intake and exhaust manifold leaks (broken studs).
Oxygen sensors (you verify by exhaust gas analysis), remove, inspect (what's the colour, any dirt, residue?). Document (picture).
Sparkplugs replaced. Show us the old ones! You can "read" from used spark_plugs.
"Coil charge time" (ODB2 data) is in the 1,5-2,5 ms range (1,5 ms brand new coils, average 2,0 ms, worn and weak if jumps to 2,5).

Repair should be data driven (something must be done, not just parts replaced, but measured). Provide some numbers, parameters.