12 replies to this topic

[Ajay]

British open classic - 1275cc with a Hif38 carb
1993 Rover

Well, here goes. My car is wonderful, it's fast, responsive, it's been awesome in the cold and the wet, doesnt let me down when I need it. HOWEVER, When i'm going down the motorway, cruising at 60 for about 20 mins until I get to the junction I need, when I put my clutch down the revs drop as normal, to about 900rpm, but sometimes they then keep going lower and stalls, but it will start up again right away

The engine does try to recover itself and 7/10 times it keeps running long enough for me to pull off and keep the revs up myself. The general performance seems unaffected, it's only after it's been at 3000rpm or higher for a long period that this problem occours

I mean, sometimes it doesnt stall out, which is the bit that confuses me. I have noticed something before it stalls though. I have a vacuum guage and it usually idles at 21 (nice healthy air intake) but it seems to go down to 15-10 before it stalls out. I have a K&N style filter on it, so I dont think there would be much chance of a blockage and besides, if there was a blockage, then it would stall out every time wouldn't it?

Have any of you experienced anything like this? is there anything I could replace or check?

The idle when it's behaving is fine at about 900rpm and adjusting it (as I have tried once) doesn't solve this problem

Edited by Ajay, 10 January 2009 - 12:20 PM.

[Retro_10s]

when you fitted the Air filter did you have the fuelling altered accordingly? The engine will have different requirements once you start upgrading the air filter efficiency.

[taffy1967]

Yes a slightly richer needle and a session on the rollers is usually required?

[Ethel]

Less inlet vacuum would just be a consequence of less revs. It could well be temperature related, is the manifold heated?

[Ajay]

Ok, in reverse order, The manifold is not heated, I did take it to be crypton tuned after I fitted the filter and he said the idle mixture was perfect.

Would you reccomend a different carb?

[Grayedout]

I think it's simply a factor of that type of air filter. Every Mini I have had with that kind of filter has done the same thing after a long run in cold weather. My diagnosis is as you travelling down the motorway at speed then the car is sucking in very cold and very dense air which is fine because you are opening the throttle to give it enough fuel to run. Then you suddenly come to a stop, let off the throttle and greatly reduce the fuel quantity going into the carb but there is still very cold dense air around the filter and hence the mixture is just not rich enough for the engine to run.

I bet you restart it straight away and it idles fine. That's because the air now being drawn into the carb is warmer and less dense as it's coming up off the hot exhaust.

The solutions are either return to the standard filter box with the hot air takeoff from the exhaust manifold or accept this is part of the fun, know when the car is going to do this and learn to heel and toe or left foot brake to keep the car going for that few seconds when you come to a stop !!!

[alicetheauto]

And dont forget that the first 1/4" or so of the choke pull is actually a fast idle! That is how I keep mine running if the ignition is rough or the advance pipe has come off......

[taffy1967]

Ok, in reverse order, The manifold is not heated, I did take it to be crypton tuned after I fitted the filter and he said the idle mixture was perfect.

Would you reccomend a different carb?

A rolling road tune would probably solve the problem as they'd be able to fit the perfect needle to suit your Minis set-up.

But you don't need to replace the carb as a HIF38 is very efficient.

[Ethel]

The Hif is a perfectly good carb, if it's on a water heated manifold get it plumbed in. If the carb has part throttle mixture control (the rubber pipe that loops back from above the throttle that may have been effected by fitting a K&N.

[taffy1967]

I remember that we blocked a rubber pipe that runs off the inlet manifold on our Mini when we fitted a K&N years ago and I've not suffered any problems.

[Ajay]

I havent got a water heated manifold but I am thinking of looking in to it at some point anyway, as well as a lot of other performance parts.

I have decided (not because of this problem) to take the mini off the road for now and do it properly. It was a rolling restoration but the restoration has stalled due to work and stuff (and the fact i'm too chicken to take it apart as it's my only car). I'll probibly be on here a lot more asking for advice on how to rebuild the engine eventually lol.

Cheers for the advice though, the manifold looks like my first step

[clubman katie B.F]

How long has this been going on? is it since the weather turned cold? or is it more long term. I am motorway driving every day at six in the morning and since the weather has turned really cold, I am having the same problem, only in the morning when it's bitterly cold though I have just increased the tick over speed slightly and this has fixed it for me, will turn it back down when it warms up slightly.

[Ajay]

It's been going on for a while, the weather doesnt acctually seem to make much difference, then again, I have not had chance to drive it in summer. I know the mixture needs looking at but I'll do that when I have made the modifications I want to do