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Gaz205

Another high idle issue

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Gaz205

I have searched many times on here about the high idle issues many have faced and have tried many of the tactics to no avail.

 

The engine - 93k 1600 phase 1 1987

 

The issue - engine starts fine and idles smooth and even, the sad is working (pinch pipe when cold the revs drop, pinch when warm there's no change) . The car did rest at around 1400 with the idle screw FULLY IN.

 

Work done - new cambelt in case the old one slipped a tooth or 2. Replacement AFM set up at an mot centre with o2 meter etc. Timing set up ( the car goes like stink and has no 'clutch in' car cuts out issues). 3 breather pipes replaced, oil filler checked and the screw nice and tight.  Throttle body checked and cleaned out... Here's the thing... Now it sits between 1400-1600!

 

All pipes checked again, air tight. If I lift the oil filler cap it drops to around 1200.

 

any other suggestions or can anyone volunteer some time to physically look? My mechanic is good but just can't allocate much more time to looking at it and not charging.

 

im happy to pay for the issue to be resolved. He did manage to drop the rpm by altering the timing but the car went flat as a fart.

 

so to summarise, the only issue is high idle, nothing else at all.

 

thanks in advance

 

 

 

 

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Tom Fenton

Air leak somewhere, or the throttle disc opening is set too wide, or perhaps the throttle switch is holding the throttle open? Cable set too tight?

I’ve never failed to sort one out, they really aren’t that complex.

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Gaz205

Can you look at it Tom? I just want it sorting! 

 

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welshpug

I'd look at the things Tom suggested, from your tests of the sad pipes and lifting the oil cap the leak wont be big if there is one, so could be the initial throttle settings or tps.

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Gaz205
5 minutes ago, welshpug said:

I'd look at the things Tom suggested, from your tests of the sad pipes and lifting the oil cap the leak wont be big if there is one, so could be the initial throttle settings or tps.

Unfortunately I have to concede that even if they are simple tasks they are beyond what I know how to do. The throttle cable is relatively loose, but doesn't feel slack. I've been told the tps had been checked by my mechanic.

im more of a discs and pads mechanic than a skilled trick of the trade one

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Telf

Sure you don't have a crack in the inlet casting or similar?

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Gaz205

I'm not sure, haven't checked that, I'll make sure I do.

im wondering if some of the above relates to the throttle cable stop? Maybe the car isn't allowed to settle at lower rpm as the cable is held too tight. I'll see if there is any room for manoeuvre. It's really annoying as the car drives so well now :unsure:

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Telf

release the cable from the throttle body and see what its doing- the throttle should be visibly closed at idle

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Gaz205
1 hour ago, Telf said:

release the cable from the throttle body and see what its doing- the throttle should be visibly closed at idle

Will give that a go thanks, I'm reading the Haynes manual and I'm sure I'm not alone in thinking WTF. Hats of to you people that can work your way round one of these things let alone build one from scratch 

Edited by Gaz205

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Gaz205

Does the throttle body have a gasket? I've cleaned it on the car but considering removal. Obv don't want to be stuck without a gasket in place.

ta

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Anthony

Not a gasket but a large diameter O-ring provides the seal between throttle body and inlet manifold on an 8v.

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Gaz205

Cheers

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Gaz205

Throttle body off and cleaned, and replaced nice and tight. If anything I think the idle has gone up now marginally :angry:

 

unfortunately replacing the hoses and cleaning everything has increased my idle from 1400-16/1800. I've checked all the work I've done physically and with carb cleaner and unless the new pipes have holes in them then they are air tight. The butterfly valve in the body sets itself to what I see to be fully closed on idle.

still runs very very smooth and picks up perfect.

im stumped once more.

i wish I knew how to do the other suggestions above :blush:

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jackherer

Did you totally remove the idle screw? You need to take it out and clean it until it shines as well as the air bypass it screws into.

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Gaz205

Yeah I took it out and cleaned the hole and wiped the screw, I didn't pay too much time to it so I can certainly try that too 

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Telf

I presume you have made sure the classic oil filler bolt to the inlet manifold is fully tight - if its loose it will let air directly into the inlet

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Gaz205

Yes mate I saw a post of yours on another thread and removed and replaced it.

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bensonmi

Start the car up and spray wd40 around the inlet and throttle body etc and see if the engine revs change,  it's a good way to check if there's a air leak!

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Gaz205
46 minutes ago, bensonmi said:

Start the car up and spray wd40 around the inlet and throttle body etc and see if the engine revs change,  it's a good way to check if there's a air leak!

Thanks mate, tried that dozens of times to no avail 

 

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speno

I will have a look when i pick these wheels up 

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Gaz205
2 hours ago, speno said:

I will have a look when i pick these wheels up 

Nice one... Sunday afternoon might be good if you just drop me a text

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Gaz205

Possible development...

spraying over the injectors dramatically reduces rpm to the point of almost stalling. Is this to be expected or a common air leak ?

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jackherer

That's definitely an air leak, the injectors have O rings on them so it's probably one or more of those although the inlet manifold gasket is obviously very close too.

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Gaz205

Yeah I wondered if it was that, possibly both.

ill get a 2nd opinion but a fair guess that it wouldn't hurt to change both. I'm guessing gaskets will be thin on the ground and O rings are just O rings 

thanks for that 

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jackherer

The gaskets are still widely available, they're just paper gaskets. You can even cut your own out from gasket paper in a pinch or a cornflakes box if you can't even find gasket paper!

 

The O rings are Bosch injector O rings so again widely available. Each injector has two seals, top and bottom, so you need 8 in total.

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