Technical Idling issues

[paulw656]

Hi.
Thanks for taking the time to read and possibly help.
In September my Panda 1.2 Dynamic 07 plate, 40k on clock, had idling issues it would idle at about 1200 rpm most of the time, sometimes slightly higher, but sometimes it would also drop to its normal idle of 800rpm.
When stationary if the car was revved up to about 300rpm, then released the revs would drop slowish (not instantly) down to 1200, it would then stay there for 2 -3 seconds before dropping down to 800, but wouldn't always drop to 800. I took it to the garage who plugged it in, no errors, but said that the thermostat was sticking, so changed it, problem solved.......until yesterday when the exact same problems came back.
If it was the thermostat surely it should last longer than 2 months.
Any ideas of what the problem could be or advice before I take it back to the garage on Friday.
Thanks for any help

 

[grantleyrich]

Sounds like a classic case of a leak in the inlet. Check all the hoses and connections, it could be that a gap is opening up somewhere as the engine moves on its mounts - sometimes but not always, hence the variation. Or it could be a simple leak in a breather pipe.

If it were the thermostat you would notice that the car would not be warming up.

 

[Tigertone2000]

I've had the exact same problem with my 1.2 - erratic/high idle speed. I mucked about swopping oxygen sensors to no avail but then removed and thoroughly cleaned the throttle body (loads of carb cleaner squirted in!) - success! Had a reliable 800 rpm idle ever since.

 

[paulw656]

Thanks for that grantleyrich, sorry it's taken so long to reply. have checked all the pipes, nothing wrong there unfortunately.

 

[paulw656]

Tigertone2000, will try that next, fingers crossed.

 

[paulw656]

Tigertone 2000, cleaned the throttle body, rpm drops quicker, but unfortunately still idling too high, next step, I think, is to look at the idle control valve. I knew it wouldn't be that easy.

 

[DaveMcT]

Fast idle is either engine thinks its' stone cold (temp sensor issue) or there is an air leak and the ECU is adding petrol to correct the fuel air ratio. Over-tight throttle cable will' also do it. Make sure its not snagged

Spray cold start (ether) around throttle body and gaskets etc if revs change you have found al air leak.

 

[Tigertone2000]

Did you actually remove the throttle body assembly from the car and thoroughly clean it?
I know that with mine I really went to town on it - in and around the idle control valve assembly which if I recall correctly, you can't remove so has to be cleaned in-situ. I know I sound like I'm banging on about it (!) but my symptoms were exactly the same as yours - in fact, it's suffered twice (several years and many miles apart, maybe as a result of that awful supermarket petrol I inflict on it...) and both times a thorough clean has resulted in a lovely 800rpm idle.

 

[akika150]

hi, your problem was solved?

 

[DaveMcT]

The inlet manifold is made from cross linked plastic. An overheated engine can melt the joint face leading to air leaks. If the car has been rebuilt after cylinder head failure, always make sure the inlet manifold is checked for damage.