Flat spot/hesitation on -1993 Metro Quest 1.1c

[knac1234]

Hello,

I've been living with this since getting my Metro last year. It is in excellent condition, bought with 12700 original miles and now has about 2000 more.

When accelerating, especially from rest or after changing into second (so I suppose low revs), there is oftentimes a "lag" or flat spot or hesitation until the acceleration resumes smoothly.

This is the only fault with the car, but I want to correct it.

I checked the dashpot oil, and that is fine. The air filter looks reasonably clean, however I ran it without one just up my small street for a moment to see if that affected anything (as I am in the USA and a new filter is not readily available).....it did not.

Any other thoughts on how to diagnose this? Should I bring it up to temp and try adjusting the mixture? If so, is this similar to earlier SU carbs (I have a Robin, and the single SU has a mixture nut on the bottom....very easy to adjust).

Cheers,
Julian

[gazza82mp]

Which oil are you using in the dashpot?

Sometimes the SU oil is too thin so dashpot rises too quick and using engine oil may improve it.

Conversely engine oil can slow the dashpot rising so a thinner oil is needed.


Also you don't say whether this is with engine cold, and using the choke, or when the engine is up to temp. If the choke makes it better, it maybe running to lean anyway.

[knac1234]

Thanks for the reply.

SAE 20W oil, specifically this:

https://www.lowes.com/pd/3-IN-ONE-3-in- ... nt/1210103

At least for my older SUs, this has been the exact weight recommended for dashpots. Not sure if that is different on the Metro's one.

I'll have to try it with the choke on slightly when warm.....you're right, if better it is too lean.

Where is the adjustment on these carbs??

Thanks,
Julian