Morning All. My son's much loved 2009 1.2 500 called Indy has a little problem

When the engine is warm the revs at idel rise and fall slightly from say 800 to 600 then back to 800. while driving, it is no problem at all. The butterfly within the throttle body has been cleaned but I have seen comments about the IDLE CONTROL VALVE. but for the life of me I cant find it. Is the ICV actually the butterfly in the body? Vacuum pipes all seem fine (I have replaced one). could anyone point us in the right direction.
Also, could the ECU need resetting, if so how

Thanks for any help

Idle control is built into the butterfly with the air filter off and running look to see if the butterfly moves, probably not, new Iridium plugs are always worth a try if standard plugs are fitted.
What happens when cold at idle?

Oddball thing check the engine earth strap on the right side of the engine, also the ecu earth under the air filter, be very careful if you need to remove either of the air box breathers the small one tends to snap off!

Thanks for your reply John202020.
The butterfly does actually move just a little in conjunction with the drop in RPM and yes I was thinking of fitting new plugs.
when the engine is cold it runs sweet and steady at around 1200ish rpm
I will also check those two earth straps (probably at the weekend now.

Thanks again

Interesting our 59 plate 1.2 starts and runs at idle 800 rpm hot or cold so is the butterfly opening to prevent a stall?

phil groves said:

I was thinking of fitting new plugs.

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These are the cheapest I can find for the Iridium plugs good for 5 years, if keeping the car that long put some anti seize on the new plug threads and perhaps some silicone grease on the ceramic to prevent the plug leads getting stuck on over the long time?;
http://www.ebay.co.uk/itm/4x-DENSO-...953629?hash=item2332d93f1d:g:qe8AAOxy3zNSl0rR

Thanks again for your help John, pretty good price for iridium plugs! Guess i'll probably end up trying to find a replacment throttle body but at least now, thanks to you, i know exactly what I'm after.

phil groves said:

Thanks again for your help John, pretty good price for iridium plugs! Guess i'll probably end up trying to find a replacment throttle body but at least now, thanks to you, i know exactly what I'm after.

Click to expand...

I would not change the throttle body until it is confirmed as faulty .

First check for a vacuum leak, if it's sucking in air from anywhere it'll hunt for an idle.

I suspect though there's a fault with the fuel system somewhere.
The ECU, when it detects a fault, will protect the engine by running in an overly rich fail safe mode and this tends to cause the fueling to switch, up and down quite rhythmically.
Another sign of this is higher fuel use and a heavy exhaust gas.

Trouble with these faults is they don't always cause EML's and DTC's.
You could really do with logging what the fuel system is doing from a cold start.

If it's fully warmed up and restarted, does the idle return to normal and run ok?

Thanks for your imput Goudrons.
Firstly I have to admit that I was wrong when I stated that when cold the RPM was OK, it isnt. hot or cold the RPM is slightly eratic... even when fully warm.
Interesting that you should use the word rhythmical as that describes it perfectly.
The little car is off to have a broken manifold stud removed and and a new gasket fitted all to cure a leak from the manifold next Monday, I am assuming that this would not cause our RPM problem.
What would you suggest as to the cause of a potential fuel problem?? could the fuel filter need replacing?
Thanks again to you both.

How did the stud get broken and or what work was being done when it happened, exhaust or inlet manifold?

A leak between either manifold and head could cause the symptoms described.

The manifold leak could be the problem.

If it's on the inlet manifold, it could be sucking in extra air, leaning out the mixture so far, the ECU just can't compensate.
It'll keep trying to throw more and more fuel into the mix, but still keep getting a hot/lean O2 sensor reading.

If it's on the exhaust manifold and the gases are escaping, the O2 sensor would not be sending the correct signal back the the ECU as it's hasn't all the gas (and heat) passing over it.
The ECU will think it's rich, so will keep trying to trim the fuel out of the mix.

Either way tends to result in a leaned out mixture and cause the ECU to either try and fail to adjust the issue out, or just failsafe into a preset safe/rich mode.

Due to the way the fueling/O2 sensor works, by switching a signal voltage back and forth, so trimming the fueling rich and lean, these issues often fail to cause EML's and DTC's as it's used to seeing the extremes of either end of these voltage signals.

You end up with similar problems when the O2 sensors heater element fails or is too slow to heat before the fueling goes to closed loop, the O2 signal sends a wrong/corrupt signal back and the ECU tries and fails to trim it out, which tends to cause the rhythmic up and down, switching idle.

Thank you everyone. This is all very interesting info. It's the exhaust manifold that has a stud broken and leaking. Have no idea when or how it was broken as we've only recently bought the car ( kicking myself for not spotting it) Following the comments posted, we are really hopeful that the repair to the Manifold will cure Indy's problems. It's off to a Fiat specialist, not dealership and I get on well with the guys up there, so fingers crossed. Thanks again...I'll let you know the outcome.

Thank you to all who gave advise re the idle problems we had with my son's 500. The car has come back from our local Fiat specialist (not dealership) like a different car, no idle problems at all. They found that three manifold studs had broken probably due to poor quality as they said that this is not uncommon. All studs replaced, new gasket job done car drives great

Thank you for posting the out come .
Very Glad that the advice given was of help and problem cured.
Jack