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Rich at idle, starting to hunt a bit

scam75

scam75

Well-known member
Afternoon all

My car has started to run quite rich at idle, seems ok across the rev range. I have a scivision so can't adjust idle mixture but car normally idles around 13 on afr gauge. Noticed its down in mid 11's and beginning to hunt a wee bit sometimes at idle. I have checked tps is adjusted ok and it clicks when it should. Any suggestions to try/check?

Cheers

Stuart
 
Hi
Most likely your idle control valve is coked up. It is situated under the manifold and bolted to the block/head with two (or three) pipes. I've read some have managed to remove it without the manifold, but I ended up taking the manifold off as I ended up tidying electrics insulation as well. I soaked the idle valve in gunk overnight. It now idles like a dream.

Simple to fix, but few hours labor to remove/replace. It will get worse if you leave it. Worth checking DME first too (with your essential spare).

Regards
 
I'd agree with Tony.
On my 2.5 I changed the ICV in-situ, but it is rather fiddly!
You may try carb cleaner sprayed into the pipe from the the from of the engine.
 
AFM for me. I had problems with rich lumpy idle. It made my eyes sore if I stood near it. I gave the black plastic cover a swift love tap with a spanner and it immediately ran better. Carefully removed the cover and cleaned up the sweeper contact, Hey presto!!. Not sure if the ICV would make it run rich???
 
Check vacuum at the fuel regulator, check fuel pressure at the rail, the icv could be stuck shut but it would be ok at cold but not warm.
Had simular problem with my 994s, it turned out to be the mixture screw at the maf.
hope this helps
 
Ok tried changing the DME relay, still the same. I will pop off the vac line from FPR to check for fuel then try some carb cleaner into the ICV on Friday when I get some free time. If it makes a difference I will take it out and clean it properly. FPR is a fairly new 3 bar reg but suppose it could still have went tits up!

Hopefully not the inlet manifold gaskets as they are quite new.

I do not have a spare AFM, it got lost in someone's garage! My scivision has no idle adjustment but seen as how the car runs fine and AFR's are fine on throttle I am hoping it's not that. I have heard that scivisions make the car super lean when they fail so hopefully not that!

The problem is the same when the engine is cold or hot.

Stuart
 
Can anybody clarify if brake cleaner would be the same as carb cleaner in respect of spraying some whilst the ICV is in situ? I just called to order some carb cleaner and my local garage mechanic says brake cleaner would work exact same. Was just wary of spraying it into the inlet manifold?

Thanks in advance

Stuart
 
Brake cleaner will work, but has high evaporation so unlikely cause damage (highly inflammable too). For a quick fix it might be possible to clean in-situ.

In the long term removing the manifold with a proper clean is best also a chance to check various pipework for leaks and perishing etc. as mentioned above.
 
ORIGINAL: wibble

Brake cleaner will work, but has high evaporation so unlikely cause damage (highly inflammable too). For a quick fix it might be possible to clean in-situ.

In the long term removing the manifold with a proper clean is best also a chance to check various pipework for leaks and perishing etc. as mentioned above.
Click to expand...

Cheers Tony, so ok to fire brake cleaner up the pipe in situ? Should I leave it a bit before firing up the engine or not?

Stuart
 
Update - defo a bunged up ICV. Have sprayed some cleaner in and improved the situation. Will remove and clean properly at some point!

Stuart
 
I have a similar problem to this on my '86 T, I've already had the mani off and have replaced a few hoses/clips to fix some leaks but it's still running very rich at idle so I wonder if I have the same ISV issue. I'm planning on renewing the HG soon but I think I'll have a crack at this first!

My doesn't hunt, but coming off throttle it stutters slightly before stabilising and the idle is a little on the high side despite adjusting the screw. I've also tried adjusting the AFM with a CO2 meter but to no avail...
 
ORIGINAL: A9XXC

Good news - and good luck with getting at the ICV!
Click to expand...

Cheers! Having assessed the ICV removal situation today I will keep it going with cleaner for as long as possible! I have idle AFR back up to mid 12's. 13 is what it was before the issue, the hunting has also gone. I hope it's ok for MOT at that, I know at 13 it was no bother.

Stuart
 
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