8 replies to this topic

[GermanMoreno]

Hello! Sometimes, after taking my foot off the gas pedal, the revs come down very low, between 400 and 600, and then slowly go back up to 900 to normal idling. Sometimes the car stalls. I can start it back again, car has power, cruises great. I reckon i drove the car in rainy days and maybe there is humidity in the distributor.

I also filled the dashpot with SU oil. It was low. It helped but the issue came back. Any pointers? from research Ive read maybe a vacumm leak, the line seems ok from the distributor to the carb, but I noticed 1 hose that connects to a series of lines going to a breather on the radiator side of the car, and also connecting to the left side where the booster, and breather, is cracked. I will be replacing that one.

What else can I check? Where can I start troubleshooting?
I had to temporarily increase the idling screw on the carburetor as a temporary band-aid.

 

1991 Mainstream Cooper.

 

[cal844]

You need an optimisation session, to get the best from your engine

[ACDodd]

Sounds like classic throttle shaft wear. Maybe time for an overhaul.

Ac

[Ethel]

It could also be a clogged air filter. AC is probably right, but it'd be easier & cheaper to eliminate. You may not realise you're compensating by putting your foot down more beyond idle. Inspect it, they can soot up pretty quickly if there's an exhaust leak. A short run without one fitted would confirm. You might manage to make a temporary improvement, if it is the throttle spindle, with a tactical splodge of grease. A quick grab for the choke should also improve the situation, but don't use it as a work around for any length of time. 

[Lplus]

Hello! Sometimes, after taking my foot off the gas pedal, the revs come down very low, between 400 and 600, and then slowly go back up to 900 to normal idling. Sometimes the car stalls. I can start it back again, car has power, cruises great. I reckon i drove the car in rainy days and maybe there is humidity in the distributor.

I also filled the dashpot with SU oil. It was low. It helped but the issue came back. Any pointers? from research Ive read maybe a vacumm leak, the line seems ok from the distributor to the carb, but I noticed 1 hose that connects to a series of lines going to a breather on the radiator side of the car, and also connecting to the left side where the booster, and breather, is cracked. I will be replacing that one.

What else can I check? Where can I start troubleshooting?
I had to temporarily increase the idling screw on the carburetor as a temporary band-aid.

 

1991 Mainstream Cooper.

 

A hole in the crankcase ventilation system pipework will allow extra air into the carb after the jet. Replace the cracked pipe and see if there's an improvement.

[alpder]

I had all sorts of idling issues, including it stalling in traffic (specifically the sequence: idle for a minute or so, pull sharply forwards for a short distance, quickly de-clutch: at which point it would then lose revs, stall, and be a s*d to re-start.) I also couldn't get idle mixture do anything sensible, when tuning it in the workshop.

 

Spent hours looking for air leaks. Eventually I found that my (HIF38) carb had been badly £recon'ed (emphasis on the "con") with seals that were both wrong size and fitted back-to-front. Result was air leaks around the spindle plus over-fuelling via a leaky choke.

 

So I rebuilt it with new seals, most crucially shaft seals (the new bigger* type - and fitted the right way round) plus correct new seals and O-rings on the 'choke' mechanism (for these, do check with Burlen - their parts list is seriously confusing on which O-rings you need to fit and where: I sent annotated photos to them asking for the correct part numbers).

 

That pretty much cured those problems (the car still has others!). And my fuel consumption improved, too.

 

*The bigger type won't fit all carbs. But they're not expensive so just order a pair of these plus a pair of the originals. Fit the big ones if possible - they clearly offer a better air-seal.

[GermanMoreno]

Sounds like classic throttle shaft wear. Maybe time for an overhaul
Ac

Hello! Do you still have HIF44 around? 🙂 to your spec

[ACDodd]

On the shelf £450 exchange plus shipping.

Ac

[68+86auto]

Make sure that the piston returns to the bottom fully. I found one that wouldn't quite return to the bottom so would lean out the mixture. When I removed the dashpot, the piston stayed with it.