Problem solved! Se7en was right about the choke cable. I guess when I went to start it I pulled a little too hard which cause the cable to come lose and the lever got stuck. When I noticed that the choke was a little stuck I pushed it back into position and fired her up to check, and she's running like a champ now.

Thanks for all the help everyone!

You may have stumbled (pun intended) on it with the choke cable.  With the air cleaner off, pull out the choke and then push it back in and visually make sure it comes off choke/high idle.  If it's an HIF carb, the choke is a separate mechanism and can hang up even if the cable is in.  Mine does that occasionally, and I have to feel it back in with the knob, but I have a fairly tight cable.  With slack you may not be able to feel it, but you can rotate the cam back to the stop and the choke will then be off.  If it's an HS, the jet tube could be hanging - if the cable is slack, reach under the carb and push up on the tube.  If it moves up, that's your issue.

SE7EN

wow, Thanks for all the help. I'm going to have a look at it tomorrow morning.

I took the air filter off quickly last night to have a look around, but I'll take it off and have a closer look at the carb (maybe some more pics). Choke cable was hanging by a thread so I reattached it with plenty of slack for it to return to the normal position. I only use the choke to start the car and then push it back in.

Is it safe to drive it like this for a few miles? Say 6-7 miles max? If I can't fix it by Monday I'll have my mechanic take a look at it

The top half of the carb is easy to get off (the needle hides in there) - 3 flathead screws if I recall.  Just be aware that there's a long-ish spring in there when you pull it off and don't whack the (now exposed) needle on anything!

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My Higher Authority is the German Purity Law of 1516 . 

Does it have a float bowl on left side (looking from front) Then it is an HS. No bowl, then an HIF.

Sounds like it's running rich, fouling a spark plug, resultant black (unburnt gas) smoke. Check that your choke is returning to the stop when dis-engaged. Look on right side of carb (from front) for the cable end connection. (you're not using the choke all the time are you?) I'd change the plugs (NGK BP6ES) first and see how it behaves. Also check the wires. When you pull the plugs you may be able to tell which cylinder/plug is the issue. Then check the float and float level.

Make it idiot proof, and someone will make a better idiot....

 

From the picture, it looks like it's probably an HIF carb.  Someone correct me if I'm wrong, but it doesn't seem like that air filter could fit over an HS carb.

I had the same thing happen to me, only it drove fine to work, and on the way home, it was hard to start, and would stall if I didn't baby the accelerator.  Couldn't confirm it with the naked eye (or too lazy to REALLY look), but it was probably a stuck needle valve allowing the carb to overflow into the cylinders.  Anyway, I was lucky to have a carb rebuild kit at home (was actually planning this, what luck!), rebuilt it that night and all went well the next day.

Putting all that blabbing aside, I'd remove the air filter to get a better look at the overflow pipe as someone already suggested.  If you're lucky, the float doesn't have a hole in it, and maybe something just got past your fuel filter (if you have one), and lodged in the needle valve.  Remove the carb, take it apart, inspect, and clean it.  Take lots of pictures as you disassemble, as it can be confusing the first time you take one apart.

willy

I'm not quite sure which carb type I have. I just got the car 2 months ago and still have a lot to learn about Mini's. I think my next steps would be to check the spark plugs, wires, dizzy cap, and vacuums lines. Hopefully its one of those if not then I would have to take a deeper look at it and check the fuel bowl. I've search some older threads and the float was the problem in some of the cases with idle problems.

A disconnected vaccuum line would result in a poor idle due to a lean mixture. Not the case here.

What carb do you have? If it is a HS type, check to see that the fuel bowl is clean and the float valve is working properly and the float is set to spec. An over-full bowl will result in rich running. A leaking float valve will also do that, but in addition may allow raw gas to overflow the main jet and rund own into the engine cylinders.

If it is a HIF type the same can occur, but it is harder to check the bowl. On a HIF type raw when the float valve leaks, you'll get rough idling, eventually flooding out. You may also notice raw gas bubbling out the bowl vent. On some engines this vent is plumbed with tubing to drain way from the exhaust manifold, so you may not see it readily.

If the float valve does leak and your tank is more than half-full you run the risk of raw gas puddling in the cylinder (causing sooty exhaust with lumps!) and leaking down past the piston rings into your sump. Gasolene does not mix particularly well with engine oil - I have a couple of jugs of it in my garage.

Last fall my car ran fine until I was putting it away for the winter. While running fuel stabilizer in the gas up to the carb, it began to run rough, then stalled out. I parked it, but didn't drain the tank down until we noticed a small pool of gas on the floor below the carb. This spring, my oil level seemed about 1.5 litres high! Oil change time!

 

"Hang on a minute lads....I've got a great idea."

Sounds like a 286 cam.  

My SPi car was running goofy and it was suggested to me to check the distributor cap - when I did, I found that one of the little cups that the spark plug leads attach to was filled with black junk (carbon or something?).  Buddy of mine said one of the wires was probably breaking down and that caused the rough running.  Changed the bits out and she runs like a champ...err, at least the last time I drove it. 

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My Higher Authority is the German Purity Law of 1516 . 

Would a disconnected vacuum line cause uneven idling?

Martin.

My mind's made up - don't bother me with facts!

 

 

Black "smoke" excess/unburned fuel.  Blue "smoke" oil being burned.  Check your spark plugs - one or more might be sooty black and fouled, resulting in misfire, maybe running on three cylinders only.  Could be faulty plug, spark plug lead disconnected/loose or failed, fault in dizzy cap.

Mini friends!  Mini rides!

Restored/modified Mini 1000 with 1380cc power unit, 2.95:1 FD, adj. suspension, S discs/drums, 10x5 Minilites, 165x70 A008s, custom trim and matching custom trailer.

My MKIV Mini's developed a weird idle problem overnight. It drove fine one day and the next day it started to idle really rough. I've check the engine oil, dash pot oil, and air filter. At first I thought it was out of gas so I filled it with 2.5 gallons this morning and it started up fine but then the weird idle came back. It sounds like a throaty muscle car with cams and its also spitting black stuff from the exhaust. Is it safe to drive it like this to my mechanic?

Under the hood

Crappy Vid clip, but you can hear the "blop blop blop" and see the black stuff on the floor