Intermittent revs drop and stall.

[H7OB]

Hello all. I wonder if anyone could suggest any tips for an unusual intermittent stalling issue?

I started the car this afternoon and let it warm up nicely. On occasions when I’ve blipped the throttle and take my foot off the accelerator the revs drop right off and it stalls. It will then start with no problems and idle but the fault seems intermittent.

As far as the engine goes it’s been recently rebuilt, set up on a rolling road and runs beautifully. It’s on a 123 distributor that has never been a problem. The coil looks a bit elderly.

Electrics are not my strong point and I’m thinking this might be more likely due to the fact that carbs etc have been set up and not touched since. It’s running beautifully other than this occasional dropping of revs and stalling.

Any tips from those more experienced than me would be gratefully received!

[christopher storey]

Paul : how warmed up was warmed up ? CMC reckoned at one of the E type days I went to , that it takes 35 miles - yes there's not a decimal point error - to fully warm up an XK engine, mostly because of the vast oil capacity . Now that ambient temps are dropping the stalling after a blip of the throttle doesn't really surprise me unless not only the water, but also the oil temperatures have risedn to operating levels

[H7OB]

Hi Christopher. I hear what youre saying, it was very warm but not fully hot. I then took it for a spin c10 miles and it stalled a couple of times when coming to a halt with no accelerator. It will restart perfectly and tick over smoothly at about 700 rpm but it’s definitely a new phenomenon.

[gtjoey]

Just for giggles ADD a half turn to each jet setting....meaning clock wise, sounds like your a little low on fuel.
Then see if you race to about 900 after you blip it....If so then turn the slow idle screws clock wise a half and your done.
good luck
gtjoey1314

[keithmac]

I confirm gtjoeys findings on my car. same symptoms, same cure.
Regards
Keith

[Joes66]

Yup
Sounds like it's a bit lean at idle
Joe

[H7OB]

Many thanks for your inputs chaps, I’ll take a look.

I’m just surprised that it seems to have suddenly started happening when, separate to this, it’s ran beautifully since it was set up on a rolling road in July last year. Cooler air maybe?

[MarkRado]

I had the same problem. I found that one of the throttle discs had a resistance to close completely (fractions of a mm), which was overcome when blipping. This could not be adjusted with the slow running screw, since either I got high idle without blipping all the time or stalling. Slight play in the bushes plus dry cork throttle shaft seals were the reason. As a quick non-rebush remedy I oiled the seals via the shaft and mounted the return spring differently. In a second step I readjusted the disc (carb off obviously). In the end I had the carbs rebushed.

[malcolm]

I had the same problem. I found that one of the throttle discs had a resistance to close completely (fractions of a mm), which was overcome when blipping. This could not be adjusted with the slow running screw, since either I got high idle without blipping all the time or stalling. Slight play in the bushes plus dry cork throttle shaft seals were the reason. As a quick non-rebush remedy I oiled the seals via the shaft and mounted the return spring differently. In a second step I readjusted the disc (carb off obviously). In the end I had the carbs rebushed.

Beat me to it! I was going to say "a sticking throttle"
I've often had cars where the throttle sticks a little open until you blip. Means if it's adjusted when open a little, it ticks over great until you blip and you no longer have a tickover.

[Joes66]

One other thought
Don't know about the larger su carbs but a common problem on MG's su carbs was throttle spindle wear
The ends of the throttle spindles wear out the hole they go into
They go oval and air is sucked in to the carb through the enlarged hole
This negates the butterfly to control the air flow through the carb and can cause what you are having a problem with
It also causes running on
Joe

[H7OB]

Many thanks for all your inputs chaps, much appreciated. It’s given me a few things to go at.

Now the only other thing I could do with help with is a kick up the exhaust to get me out of the house and into the garage on a damp grey Saturday! I might just need another large strong tea to contemplate that!