Technical bouncing revs

[frustrated]

Another problem fiat in for its mot they changed suspension arms and cat. Now the revs are really bouncing and diagnostics can't find a fault any ideas

 

[bigbrava]

chances are the ecu needs resetting due to the new cat and if the battery has been disconected aswell, by the way disconnecting the battery does not fix this problem the eeprom inside the ecu needs the perameters reset and the diagnostic software can only do it. also has a new 02 sensor been fitted to the cat ?

 

[frustrated]

Picked it up today, allegedly started fine first time although i know guy from alfa garage went there last night with his diagnostic kit, plus they admitted refitting all air pipes and cleaning throttle body. Thing is now revs idle around 1000 where as before more 700

 

[m20b25]

Picked it up today, allegedly started fine first time although i know guy from alfa garage went there last night with his diagnostic kit, plus they admitted refitting all air pipes and cleaning throttle body. Thing is now revs idle around 1000 where as before more 700

There must be a small leak in the manifold still. Check your breather, that its properly fitted back. Check the condition of the pipes, you'd be surprised what a small leak or a crack in the pipe could cause. Also check your lambda sensor is working correctly and your ht leads are in good condition, these can affect the revs quite a lot

 

[frustrated]

Had a quick look round the engine today. Notice one of the pipes wasnt on properly. They told me diagnostic showed all senosrs, including lamda working correctly. What i have noticed they have done is place a screew behind idle motor. I put it back to normal and when started revs went up to 3000rpm, so put this back to normal. This idle motor is only a couple of months old so cant seee how this has broke.
There must be a small leak in the manifold still. Check your breather, that its properly fitted back. Check the condition of the pipes, you'd be surprised what a small leak or a crack in the pipe could cause. Also check your lambda sensor is working correctly and your ht leads are in good condition, these can affect the revs quite a lot. where is this?

 

[m20b25]

If its a 1.2 you have this might help...

 

[frustrated]

Thanks but i have read this previous, i tried the spacer method before i bought a brand new one. This is why i dont understand why they needed to do this to correct the high rev problem which has never happened before they changed the cat. Whereabouts is the manifold breather so i can check? Would this cause the revs to be really high?

 

[m20b25]

What year and is it cable throttle?

I drove around for a while with no breather (straight pipe into the atmosphere, not recommended) so I know that won't cause high revs. There are a few things that cause high revs:

• Gap/opening in the manifold
• Stepper motor not reset
• Lambda sensor playing up

By the sounds of it you might just need to reset your ecu

 

[frustrated]

ok thanks. I did disconnect the battery for a bit today but not an hour when i had put the stepper motor back without the spacer. Put it back with the sapcer and running ok just sounds like it is blowing a bit