Technical Rpm issue(1200-2200)

[Gankdalf]

Hey guys, we own used Punto Evo 1.4(cng) 2011 and since we bought it we have issues with rpm, when i slowly press accelerator pedal it rises to roughly 1200rpm, then comes a little bit of dead zone and then it jumps to roughly 2200 which is very annoying when taking off any ideas ? Does it on neutral / when taking off in first gear, while i drive in second and up i am able to hold it lets say at 1600. Thanks!

 

[bugsymike]

Hey guys, we own used Punto Evo 1.4(cng) 2011 and since we bought it we have issues with rpm, when i slowly press accelerator pedal it rises to roughly 1200rpm, then comes a little bit of dead zone and then it jumps to roughly 2200 which is very annoying when taking off any ideas ? Does it on neutral / when taking off in first gear, while i drive in second and up i am able to hold it lets say at 1600. Thanks!

Guessing I would say the pedal position sensor/potentimeter, but if you are able to get hold of a MES diagnostics or similar that shows the pedal recorded position in it's live data section that may give a better guide.
CNG is not in popular use over here, so not really familiar with it.

 

[Gankdalf]

Guessing I would say the pedal position sensor/potentimeter, but if you are able to get hold of a MES diagnostics or similar that shows the pedal recorded position in it's live data section that may give a better guide.
CNG is not in popular use over here, so not really familiar with it.

Hi, ive checked pedal sensor/tps with basic elm diagnostics and pedal starts from 20% and goes smoothly, no dead zones, throttle body is at 10-11 and when i gently press pedal goes to 12.5 andjumps to roughly 14 at 2200rpm which i believe is not enough to cause such spike on itself, MAP shows roughly 35kpa before/after cleaning, i also tried clutch sensor which made no diference…

 

[GrandePunto PL]

OBD2 is for data collecting and analysis. Try to grab some data (FES or MES program) and make a graph/plot like that. Examples.

Gas pedal does NOT "start from 20%"! It's near ZERO. Then you can "floor it" to the 100%.

So you have a gas pedal and/or throttle body problem (or bad connections). Or it's mechanical (gearbox, engine/gearbox mounts).
Or CNG is different (throttle control strategy)...
Try to make a gas pedal and throttle reset/adaptation (FES, MES, AlfaOBD programs).

 

[Gankdalf]

This is best i can do with this cheap diag, ignore drops to 0 it does it evrrywhere so probably BT issue, first is gas pedal second is throttle body, which is now clean and has a new gasket which was missing, when throttle body opens to 15% car is at 2200rpm

 

[Gankdalf]

OBD2 is for data collecting and analysis. Try to grab some data (FES or MES program) and make a graph/plot like that. Examples.

Gas pedal does NOT "start from 20%"! It's near ZERO. Then you can "floor it" to the 100%.

So you have a gas pedal and/or throttle body problem (or bad connections). Or it's mechanical (gearbox, engine/gearbox mounts).
Or CNG is different (throttle control strategy)...
Try to make a gas pedal and throttle reset/adaptation (FES, MES, AlfaOBD programs).

Forgot to click reply, however car idle/start/drive normally, idle rpm 850, performance seems to be ok both on cng and on gasoline so i guess it is not directly fuel/timing related, i think it might actually be throttle body as i am able to go by 0.4% above 15% and from 11.8% to 12.5 then comes that 2.5% dead spot in between

 

[GrandePunto PL]

Universal OBD scanners are useless (they report wrong data, fake). You need specific software for Fiat.

Do you have regular/normal throttle, like non-CNG cars? Try this Guide for Grande...
https://www.fiatforum.com/guides/throttle-body-disassembly-porting-testing-1-4-8v.723/
Faults are electrical (motor or potentiometer tracks) or mechanical (for example broken gears).

 

[Gankdalf]

Universal OBD scanners are useless (they report wrong data, fake). You need specific software for Fiat.

Do you have regular/normal throttle, like non-CNG cars? Try this Guide for Grande...
https://www.fiatforum.com/guides/throttle-body-disassembly-porting-testing-1-4-8v.723/
Faults are electrical (motor or potentiometer tracks) or mechanical (for example broken gears).
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View attachment 470290

Honesly, that testing seems to be little complicated for me however, ive had this part open when i was checking my TPS so i can replace it but i found out it cannot ne replaced as it is integrated into that plastic cover so i didnt actually check gears, i will look into it tomorrow, if they will be fine i will probably buy same used throttle body and replace it as a whole piece… thanks for tip, will report how it went

 

[Gankdalf]

Universal OBD scanners are useless (they report wrong data, fake). You need specific software for Fiat.

Do you have regular/normal throttle, like non-CNG cars? Try this Guide for Grande...
https://www.fiatforum.com/guides/throttle-body-disassembly-porting-testing-1-4-8v.723/
Faults are electrical (motor or potentiometer tracks) or mechanical (for example broken gears).
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View attachment 470290

Tooths are fine so i guess it probably is electrical fault…and there is weird shiny spot on pic 2, might this be na issue ? I cannot check other side as it is welded in …

 

[bugsymike]

Tooths are fine so i guess it probably is electrical fault…and there is weird shiny spot on pic 2, might this be na issue ? I cannot check other side as it is welded in …

Does it correspond with the dead position on pedal?

 

[Gankdalf]

Does it correspond with the dead position on pedal?

Pedal data works smoothly by 0.4% even in this dead rpm zone so i ruled out pedal, this dead spot between roughly 12.2-15.5 is reported only on throttle body so i guess this might ve na issue, ive ordered used one for roughly 40$ so i will try different throttle body and will see if issue persists or not.
EDIT-i checked value while driving, app shows 85% open throttle body when gas pedal is fully pressed however as RPM go up, throttle body starts closing to roughly 70%? Isnt this weird behavior ?

 

[Gankdalf]

Tooths are fine so i guess it probably is electrical fault…and there is weird shiny spot on pic 2, might this be na issue ? I cannot check other side as it is welded in …

Update:replaced TB with used one, same result however i noticed difrerent values in o2 sensors, see pic below, might this cause ?

 

[GrandePunto PL]

Use FES or MES and collect data (CSV file), then make XY plot, not screenshots like that (mostly useless).
In the 1500-2000 RPM range, the VVT starts to operate.

Another thing to diagnose (besides throttle/gas pedal and lambdas, fuel pressure, MAP sensor and so on).