Very fast idle

[minorissues135]

Hi, after suddenly conking out and waiting 3 hours for recovery I finally today managed to track down the faulty powerspark module inside the distributor. Managed to get her running but with stupid fast idle. Turned timing back a bit and it slowed, but awkward as running much too fast to leave it for a few mins while i fiddle under the car with the timing light and try to adjust carb. Got timing roughly right, but no adjustment left at idle screw. Choke doesn't appear to be affecting it. Reading other posts, it is most likely an air leak somewhere, or maybe butterfly not shutting correctly. I had found a damaged wire from module to base plate, and some damage to the insulation on the red lead from distributor to coil. Also replaced coil prior to module replacement. Any thoughts appreciated pls.

She is 1962 1000, with some mild mods put there by previous owner. Never been able to get her running as well as I thought she should, and now idle around 3500!

Thanks

[svenedin]

3,500 rpm is a ridiculously fast idle. There are 2x screws on the HS2 carb that can affect the idle speed. One is on the choke side and affects how the choke also increases the idle speed. The other affects where the accelerator cam comes to rest. Make sure that the accelerator cam is able to move sufficiently to contact the idle screw. It is possible the accelerator cable is stuck and cannot release to achieve normal idle speed. Check the accelerator return spring is properly attached. It is also possible the accelerator pinch bolt is adjusted with the cable too short to let the accelerator cam rest on the idle screw but I can’t see how that would be a new problem out of nowhere. The idle screw cannot do anything if the cam is not resting on it.

When you set the timing with your strobe you need to be able to get the idle very low, 450 rpm or so. Otherwise, mechanical advance is already happening in the distributor. Of course disconnect and block the vacuum advance at the distributor end.

Stephen

[mogbob]

hI
The folks on the Forum will need a little more information to get their teeth into before they are able to offer specific advice.
They will need to know what carburettor is fitted , be it an SU model or some other manufacturer.
Could you expand on the statement " some mild mods put there by the previous owner ".
At this stage, I assume you have not investigated the possible air leaks.Is that the case ?

Certainly revs of 3,500 is way too high but we need to go through the basics first before attempting to tune the carb.
The "damaged wiring" in the powerspark module is concerning. If you were able to load up some photos , that would either horrify
or reassure people and appropriate remedial action can be suggested. ( it's obviously working , but an iffy distributor does not induce
peace of mind ! ).
It's going to be an action plan of checking for air leaks , tightening all the bolts on the inlet manifold , carburettor mounting, integrity of
gaskets, etc. A leak test with soapy water to find the " bubbles " where air is escaping. Checking over the mechanical and cable operation of whatever carb you have fitted.Checking the Float level of petrol, needle operation, sticking pistons drop test, absence of damper oil.Checking any fuel filter
in line whilst your in there. Petrol supply is it a standard SU fuel pump or has it been substituted by a higher pressure electric pump.
Basic timing must be set up either the timing gun or even statically , if you wish.

Some more info required please , so we can avoid the headless chicken approach to solving it for you.
Bob

[oliver90owner]

hI
The folks on the Forum will need a little more information to get their teeth into before they are able to offer specific advice.
They will need to know what carburettor is fitted , be it an SU model or some other manufacturer.
Could you expand on the statement " some mild mods put there by the previous owner ".
At this stage, I assume you have not investigated the possible air leaks.Is that the case ?

Certainly revs of 3,500 is way too high but we need to go through the basics first before attempting to tune the carb.
The "damaged wiring" in the powerspark module is concerning. If you were able to load up some photos , that would either horrify
or reassure people and appropriate remedial action can be suggested. ( it's obviously working , but an iffy distributor does not induce
peace of mind ! ).
It's going to be an action plan of checking for air leaks , tightening all the bolts on the inlet manifold , carburettor mounting, integrity of
gaskets, etc. A leak test with soapy water to find the " bubbles " where air is escaping. Checking over the mechanical and cable operation of whatever carb you have fitted.Checking the Float level of petrol, needle operation, sticking pistons drop test, absence of damper oil.Checking any fuel filter
in line whilst your in there. Petrol supply is it a standard SU fuel pump or has it been substituted by a higher pressure electric pump.
Basic timing must be set up either the timing gun or even statically , if you wish.

Some more info required please , so we can avoid the headless chicken approach to solving it for you.
Bob

Agreed that things need checking out properly. The only obvious point, emboldened above, is that I would avoid the soapy water - I cannot see that as being relevant as leaks on the inlet side will invariably be into the engine and not outwards

[svenedin]

Perhaps I am being daft here, I often am, but I don’t see how an air leak is going to cause a 3,500 rpm idle. An air leak “after” the carb will weaken the mixture and it may have an effect on idle speed but not of that magnitude. If it is an SU carb it really must be that the throttle butterfly is not closing sufficiently and as I suggested above it is important to check that the idle screw is actually interacting with the accelerator/throttle cam. Agreed OP needs to confirm exactly what is fitted until anybody can advise further. I assumed “mild” mods meant electronic ignition.

[Bill_qaz]

Disconnect the throttle and choke cable and manually hold the throttle in idle position.
If its still reving at 3500 ram then the butterfly must be open. Ignition timing could not make it idle so high.

[minorissues135]

Solved but not running for now....

Oddly the cable to the carb from accelerator was too tight. It hadn't been moved at all by me so pretty weird that. Now starter motor stuck engaged with flywheel so that's next job, starter out and check that over, check wiring etc to starter etc.

Problems logging in so sorry for late reply/update

[Bill_qaz]

Glad your idle sorted, check the cable outer has not been moved or unseated so pulling the inner. Is your engine earth good, if not can try to use cables as earth, in view of you now having a starter issue. You could try rocking car back and forth in gear, ignition off, to free starter..

[svenedin]

I suspect what happened is that the accelerator cable slipped in the pinch bolt when the accelerator was pressed and then the cable stuck where it was with the cable set too short so that the cable could not go back to the idle position.