Engine Idle About 2.5k After Head Rebuild

[MartinR 0]

Hi all

 

The head gasket went on my 205, which is a bit of a pain in the backside seeing as the other 205 is in bits in the workshop...... (sods law)

 

Anyway, I rebuilt the cylinder head up from scratch, paraffin tanked everything, done the stem oil seals...... etc etc etc

 

Ive put the whole thing back together again, went to start it and it started pretty much on the button which was pretty damn impressive........ however, the idle is sitting at 2.5k

 

So i did the following...

 

Switched the engine off, made sure that the throttle clicky microswitchy thingy was actually switching when the butterfly was closed and it was so this is setup correctly.

 

Started it again, still idling (can i call 2.5k idling?) at 2.5k.............. so i thought, ok maybe i have an air leak. I checked that the bolt which holds the oil filler to the inlet manifold was in correctly, then i squeezed the pipe which goes to the SAD to make sure that wasnt stuck open and it made no difference. I then took the breather pipe off which goes from the top of the throttle body to the top of the oil filler and blocked that off to see if that made the difference.... it didnt.

 

Switched if off again..... thought ok, I have rebuilt the throttle body thing and cleaned that out, maybe i have done something daft..... switched the engine back on again, turned the idle screw right in and this made no difference... bugger

 

The inlet manifold has a decent seal to the head and has the appropriate gasket fitted. Im not hearing any obvious hissing sounds indicating an air leak.

 

Now then the only things i can think of are the following................

 

There is still an air leak somewhere, could I have all the breathers muddled up and its getting supplementary air and causing all this grief

 

However my finger of suspicion is beginning to point at the throttle body. The flap does close so its not that I have the adjustment screw for the throttle stop set incorrectly, so it cant be that. What I am thinking is that I have probably put the actual flap piece in 180 degrees out from what it used to be and that this might be causing the air leak as its not sealing the hole properly, is this plausable or am i talking crap?

 

Could it be that the throttle microswitchy sensory thingy has actually died and would this symptom be indicative of one of these going?

 

Basically I have a home tune guy coming on Thursday afternoon and i dont want him to tell me what the problem is with it which means I will have to fix it and have him come back again to actually time it and tune it costing me double......

 

Any ideas, suggestions would be great

 

Cheers fellas

[jackherer 543]

chances are you've left off a bolt on the side of the inlet manifold, by the oil filler IIRC.

[pug_ham 241 3 Cars]

chances are you've left off a bolt on the side of the inlet manifold, by the oil filler IIRC.

I checked that the bolt which holds the oil filler to the inlet manifold was in correctly

Really silly & obvious but have you reconnected the SAD hose to the bottom of the inlet manifold?

 

All breather pipes etc fitted & tight? Throttle cable sticking? Servo vacuum hose on? Seal between throttle body & inlet manifold fitted?

 

Throttle swicth plug connected Ok? (not that I can remember if it'd idle high if it wasn't on jetronic).

 

Graham.

[saveloy 8]

Have you tried adjusting the small idle stop screw(not the air screw) on the top of the throttle body?

[MartinR 0]

Morning guys.........

 

Thanks for the replies, here are some answers for you....

 

The SAD is connected to the bottom of the inlet manifold, the brake servo hose is connected to the right hand side of the inlet manifold

 

The breather pipes are connected and this is how they are connected.................

 

Filler cap has one connected to the top of the throttle body and one to the right angled air duct between the throttle body and the AFM. The oil filler body has a pipe from the side of it down to the crankcase and the bottom of it does the same via another pipe. Off of the otherside of the right angled air duct is a pipe which goes to the other side of the SAD.

 

If that throttle switch dies, i wonder what the consequence is.....................

 

Saveloy, im not 100% sure which screw you are referring too.....................................

[matt205xs 0]

Think hes refering to the idle adjustment screw on top of Throttle Body,

[MartinR 0]

if thats the one he is referring too, its screwed all the way in :S

[Guest rick03054]

The idle stop screw is the tiny one on the side of the throttle body, it adjustst how far the throttle can go back when you lift off. You can see it in this picture.

 

Also did you remember to put the rubber gasket that goes between the throttle body and manifold in?

[MartinR 0]

The flap does close so its not that I have the adjustment screw for the throttle stop set incorrectly, so it cant be that.

 

 

I, yes I have checked that one, thanks for the pic

 

The rubber o-ring has been "installed" (for want of a better word) between the inlet manifold and the throttle body

[Guest rick03054]

Have you tried spraying WD-40 at it to check for a leak? And also putting your thumb over the idle screw to seal it off to check that for leaking.

 

I see what you mean about the throttle plate, did you take it off the spindle? I don't know if they all have this but the one I'm looking at now has a little circle stamped into it on the top outward face, might be worth a look?

 

Could you check the throttle switch by taking it off (but leave it connected) and use your finger to move the barrel? Might be able to see if it makes a difference to the idle, esp. if its fine with the switch off the throttle body? Or you can check it the proper way using voltages but I can't find how to do that right now.

 

And clutching at straws here but when the engines idleing a take it you've checked the throttle cable is loose and letting the plate close every time? My throttle cable jacket was catching the grooved plastic but with the clip and and making my idle 2.5K for a while.

 

This has got me thinking now, it's getting more air than it should, so it's either set wrong (which it isn't) or has a leak, or somethings not working as it should (i.e. the throttle plate)

[Anthony 1,000]

You can disconnect the throttle switch fine - it's only purpose is fuel cut on overrun (fully shut throttle) or WOT throttle enrichment (fully open throttle). Easy to test if it's working with a multimeter as well - you'll get continuality (sp?) between two pins with the throttle closed, two pins with the throttle fully open, and nothing with the throttle partly open.

[MartinR 0]

Hi Anthony, thanks for the reply

 

So we can safely say that the throttle switch is not causing the issue?

 

Im guessing it could be this throttle plate then?

[luggy 13]

Hi Martin

Did you take the throttle plate out of the body? there is a right and wrong way of putting it in, the mounting screws are slighlty off centre.

How long was the battery disconnected for?. When I re-conditioned the head on my 8v about 3 years ago, mine did pretty much the same thing revving between 2 and 2.5 k, couldnt find anything wrong. Started the car up and let it run for about 10 -15 mins did this for 3 days and eventually the idle settled back to about 1k. Dont know if its something to do with the ECU not liking being disconnected from the battery for certain periods of time, possibly?.

 

Luggy

Edited November 22, 2006 by luggy

[MartinR 0]

Hi Luggy

 

Thanks for the reply. I doubt that the issue would be that as the ECU does not directly control the idle or have that much ability to raise the revs that much. I do have a stack of ECUs hanging about that I can try so I guess thats another troubleshooting step.

[Guest JonRP]

Hi Martin,

 

Mine did this after a head off incident, have you taken the SAD off? If so, make sure that you have connected the pipes the right way round for the air to flow through it. One way the vacuum sucks the valve shut against the SAD, the other way pulls the little valve away from the SAD body creating an air gap, which causes the high idle. There's a small arrow on the SAD to indicate the correct direction for air flow.

 

Might not be, but worth checking.

 

Cheers

John

[MartinR 0]

Hi Jon

 

Many thanks for your reply.

 

The unfortunate thing is that even when i clamp off the pipe to the SAD, it still idles high so im not sure that its going to be that

[veloce200 3]

Hi Jon

 

Many thanks for your reply.

 

The unfortunate thing is that even when i clamp off the pipe to the SAD, it still idles high so im not sure that its going to be that

sure it must be throttle plate - you don't need much air to get the revs up. mine sticks occasionally just open a fraction - revs to 2500 as well!

[MartinR 0]

i hope in a way that it is that throttle plate................ otherwise im totally buggered as to whats doing it

[MartinR 0]

FYI two things i found that were not helping.........

 

1 was that i had set the throttle switch such that it was holding the throttle plate slightly open!

 

The second i found was that my vacuum advance unit is completely dead as was all the other vacuum advances on 4 other spare dizzys i have.....................................

 

Grr

 

Idles fine now. Just need a bit of a tune up