Technical How to calibrate throttle body for idle RPM ?

[Arun Chauhan]

Dear Friends
I have fiat Grande Punto 2010 1.2 Petrol. I got the throttle body cleaned by a local mechanic, taking it out of the car. After fixing it back, cars idle RPM are not stable.
I took my car to authorized service center, they say there is no wayout to calibrate it and are insisting to buy a new throttle body, which costs INR 36500/- . This is a huge cost for an old car. has anybody faced and fixed similar kind of problem? please help me out if someone can.
Thanks

 

[The Panda Nut]

I would seek out a second hand one froma breakers yard. There are plenty about and the cost would be a fraction. eBay would probably lead you to either the second hand one or to a suitable cheaper replacement. Five years ago Seat told me the same about our Leon and wanted £750 to fix so I cleaned it again more thoroughly and its still going today.

 

[Mike1alike]

I think your TB is the same as the one on my Punto. Had terrible trouble with it and I've fixed it by replacing only the IACV (idle air control valve), wich is way cheaper than the hole TB.
Here is how you take the IACV out of TB:

And the code no. for IACV is Meat&Doria 84055.

 

[Arun Chauhan]

I would seek out a second hand one froma breakers yard. There are plenty about and the cost would be a fraction. eBay would probably lead you to either the second hand one or to a suitable cheaper replacement. Five years ago Seat told me the same about our Leon and wanted £750 to fix so I cleaned it again more thoroughly and its still going today.

Hi , I am not sure if buying second hand one will also serve the purpose, since, that might also require the calibration. It would be helpful if the existing one could be calibrated, as I know, everything else is good in it, but just require a reset, which I am not aware. More strange fact is, the Fiat service technicians are also not sure how to do this

 

[Mike1alike]

Don't know about that "everything else is good in it". It doesn't need calibration, it's plug and play. You can do a phonic wheel reset, that's all the calibration you can do and that does set the TB parameters. But I don't think that will do you any good, as I suspect there is some technical problem and you need to physically repair that, not by software settings. So, please give a little more details about this problem, so we can establish what's wrong there. How is the idle RPM not stable?

 

[Arun Chauhan]

Hi
My problem has been resolved to almost 95 % by driving my car to several hundred kilometres, i.e. with AC, without AC , with and without other loads and the idle RPM got calibrated and it it doesn't go up and down when idle. I am left with only one problem now. When I am driving and pressing brake and clutch pedal , the rpm needle takes a dip upto around 500 RPM, which causes AC tripping again and again, especially when i am driving in bumper to bumper traffic and it keeps happening all the times and I can't keep my AC on. This doesn't mean that it happens only when AC is on, but just AC tripping can be avoided by turning it off. Do let me know if you have experienced this ever or you have a solution for it.

 

[GrandePunto PL]

There is nothing to "calibrate" in throttle in the Grande model. This is simplified design (no idle valves, motors, whatever).
You can buy new or used one on eBay and just plug&play, you will notice no changes. You can clean it all day too.
Throttle body is the last thing (literally) to mess with in case of bad, rough idle.

Car needs general maintenance done on regular basis, then it will heal itself:
- oil and filters change, no "long-life" intervals (never, ever), no short trips, regular use (no sitting for weeks or months),
- valve clearances (8V engines), plus camshaft lobes wear (yes it happens, but no one checks this),
- timing belt, sensors (crankshaft), VVT operation (related to the oil quality),
- intake/vacuum leaks and fuel pressure, PCV system, EVAP, brake servo,
- AC good (if it's faulty/empty, it can load the engine irregularly),
- alternator good (if it fails, it can also load the engine, adding to idle roughness),
- exhaust leaks/restrictions, catalytic converter and lambda sensors natural wear/ageing, testing with gas analyzer,
- ignition system in good condition.

Basic recipe to maintain any car. Most people don't care and then there is a problem, a "mystery" fault (not really).