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[24_Valve]

Desperate help needed... hope someone can help? My car (1996 Omega 2.5 V6 estate) has just started thrashing up to

about 4000rpm when it's in neutral and should be idling!!! As soon as I put her into gear and pull away the revs 

start to settle down, but thrash back up to 4-5k rpm once idling or clutch depressed (quite scary). Not mechanical (ie.

throttle cable isn't sticking). I've paperclipped the diagnostic socket for codes and its showing code 13 Oxygen

sensor - open circuit & code 39 Oxygen sensor - voltage high (rich mixture). Desperately need the car over

Christmas and its too late to book into the garage. I guess I must need a new O2 sensor? but really hope there

might be a quick fix, short circuit, or something I can do, to stay on the road next couple of days without revving

at 4-5k every time I'm sitting in traffic! Any tips or tricks  hugely appreciated! Cheers, Steve.

[Kevin Wood]

I'd be surprised if it were the Oxygen sensor, TBH. Sounds more like the throttle or idle control valve sticking open.

Kevin

[hotel21]

Clean the Idle Control valve in the first instance and take it from there....

On the V6 its on the right side of the engine as you look at it in a black rubber mount.  electrical connector to the rear, inch diameter rubber ippe to the front.  Disconnect and remove, clean with copious amounts of carb cleaner - do not use any implement down the slot to scrape off the crud - and oil with a couple of drops of 3 in 1 oil before refitting.

if it still revs, post back and we will sort out reading the coes for faults...




edit - we must really make a how to for cleaning the ICV - couldn't find one!   

[feeutfo]

wondering if icv is seated correctly or some other large air leak?
question. would an air leak allow the o2 sensor to see a fault? ie seeing more emmisions than the maf has mrasured?

would certainly be checking for the simple stuff first, as mentioned above, before changeing anything. imho.

try unplugging maf also

[24_Valve]

Thank you, I genuinely appreciate your help and advice. Will grab some carb cleaner first thing in the morning and

some 3 in 1. I have plenty of WD40 but don't suppose it's a viable alternative to carb cleaner? Can't thank you

enough. Hopefully I can stay on the road over Christmas!? thanks again, steve.

p.s. chrisgixer, if I unplug the maf do I clean & refit or just leave it disconnected? probably sounds like a dumb

question but don't know enough about it.. cheers, steve.

[Entwood]

I think .. not certain .. that WD40 is fine on the throttles and/or ICV but DON'T use it on the MAF ... MAF has a very fine heated wire in it and any sort of oil contamination really ruins it.

WD40 won't clean anything really, but it will lubricate slightly. Carb or brake cleaner is the best IMHO 

[feeutfo]

suspect maf will be least likely fault as pre face-lift  mafs seem very reliable but...
unplugging maf means ecu will run on a basic map in the absence of maf info. This means engine should  run better when a duf maf is unplugged. It wont run as new, but its a basic test to try to eliminate maf issue. IF No change, not maf. HTH

ps do NOT clean maf, just unplug electrical connecter see how it drives/behaves

[hotel21]

Dont use WD40 on te MAF.  its a water dispersant, nothing more, but can and will casue problems due to the MAF construction.

Clean the ICV and then take your prob from there.... 

[Kevin Wood]

My reasoning on this is that the engine needs plenty of air to idle at 4k+. If the throttle and ICV are working properly the ECU won't let it have enough air.

Either one of these is sticking open or the air is leaking in somewhere else.

If it were leaking somewhere else it would not be passing the MAF sensor, and would not be metered so the engine would go lean and run rough. Might be worth checking for air leaks while you're at it though - pipe to the brake servo from the plenum is a popular one.

Lambda sensor issue might be another problem, TBH, but if the idling problem is cured it may turn out to have been related.

So - first job - clean ICV and throttle body. While you're at it check the grub screw that acts as a throttle stop. This should allow the throttle body to close fully, but not so hard that it feels like it's sticking closed. This isn't used to adjust the idle speed. The main throttle should be closed at idle and the engine fed through the ICV. Frequently this is maladjusted to cure a stalling issue.

I would clean the above with carb cleaner and then lubricate the ICV with a little 3 in 1 or engine oil. See what happens then, report backa nd we'll have another head scratch.

Kevin

[24_Valve]

Thanks for all the info, all your advice noted. Will definately get carb cleaner & crack on with icv for now. cheers, steve.

[hotel21]

Thanks for all the info, all your advice noted. Will definately get carb cleaner & crack on with icv for now. cheers, steve.

 

If we on line don't know now, then we have a few folks who do and we can call upon at shortish notice....   

[24_Valve]

thanks hotel21 

[24_Valve]

thanks guys, removed icv and sprayed about half a tin of brake cleaner through it (loads of black crap poured out), let it dry off and lubed it with 3 in 1 oil, replaced icv and tightened it with a cable tie against to an adjacent vertical metal bracket (rubber mount slightly loose) and Voila! my lovely V6 is purring away like new. In fact running better that before this problem occured, with normal idle speed now approx 550-600rpm instead of previous 450rpm. Can't thank you enough - your collective advise has definately saved my clutch (was having to engage 1st gear at 5000rpm!) probably saved my engine from blowing up (she's quite old now and doesn't want to idle at 5000rpm +) and saved my Christmas day from disaster (only driver in the family!). Top stuff!!! 

[Entwood]

Good result ...