Zetec Se Occasional Rev Hunting?
Posted 28 April 2012 - 01:36 PM
Focus mk1 facelift 2002 1.6 zetec se.
Not had this car long (3 weeks) and I have noticed my revs "hunt" occasionally its not much this is why I'm having trouble diagnosing the fault.
It does it after its been warmed up and i come to start it again the revs go up and down by about 100 rpm (not much I know) and if i leave it, it will do it all day long. But if i quickly blip the throttle it goes away and doesn't return.
I have been able to replicate this a few times by putting the both heated screens on and taking them back off, when the go off the revs begin to "bounce"
I have cleaned the idle control valve out twice (it didn't even look dirty when i did it) and I've cleaned the throttle body out (again really clean)
I found the PCV hose behind the inlet manifold to be collapsed I changed this but made no difference.
It might also be worth noting that when the revs begin "bouncing" it sounds like there is some sort of gurgle noise comes from where the airbox is but still does it when the airbox is removed.
I suspected a vacuum leak but after spraying every hose and gasket on the engine i can see with carb cleaner I dont think this is the case
I dont want to go round chucking parts at it if it's not 100% going to work I did this with my last car, spent £400 and still didnt fix the problem
Maybe MAP or MAF sensor? Although from what I have read those problems seem much more pronounced than what I have been experiencing
Also it drives perfect, no hesitation or misfire etc just idle problems.
Again thanks to anyone that takes time to read this lengthy post
Posted 28 April 2012 - 05:45 PM
Also the battery voltage seemed a bit off, with engine off it was reporting 11.4v and when driving it was reporting 14.1 and with full load on engine at idle the voltage reported 11.7v.
These figures suggest my battery is dying, has anyone ever heard of a low battery causing a car to hunt?
Posted 28 April 2012 - 06:40 PM
My son had a similar problem on his at the back of the inlet manifold you will see two white vacuum blanking caps on my sons car these had come adrift (appear to be non rewnewable) we could hear it hissing manged to tape them up (reseal) and has cured the problem its worth a look.
Posted 28 April 2012 - 09:52 PM
This is where the hissing appears to be coming from, (not my pic) have sprayed carb cleaner around there but didn't appear to be any change in engine revs
Thanks for replying.
Posted 29 April 2012 - 09:27 AM
Posted 29 April 2012 - 10:40 AM
Posted 30 April 2012 - 08:02 PM
I pulled over turned engine off, restarted and it was fine. Got home from work and decided I'm going to have another go at this.
I found the hissing noise to be coming from the fuel regulator and/or the fuel return pipe with those stupid quick release clips (these are a nightmare to get off!)
I'm going to the dealers tomorrow to replace these parts, I will keep you updated.
Posted 01 May 2012 - 05:14 PM
The erratic revs happened when i was waiting for the Mrs to come out of the asda I moved the steering wheel about an inch and that was it, the revs wouldn't stop bouncing until i blipped the throttle.
It does seem to drive better now and the idle until it starts hunting sounds a lot better.
Anyone want to shed any opinions on this? Ive also noticed that when coming to a stop from 30mph it seems like it wants to stall, it never does and the revs do recover but it feels weird. Also need to resolve the the gurgling noise from the engine bay.
Posted 01 May 2012 - 07:33 PM
Posted 02 May 2012 - 06:51 PM
My obd scanner came today I connected it up and took it for a drive, all live data looked fine oxygen sensor, MAP, fuel trims look fine and there were no codes stored in the ECU. I was thinking idle control valve at first but it does it when accelerating and as far as i know it only plays a part at idle? I then thought coil pack but wouldnt it do it all the time?
I'm going back to basics and I'm going to try changing the fuel and air filters the weekend.
Posted 04 May 2012 - 10:07 PM
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