Carburted car runs fine while it's day, stutters at night

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It's like a bad superhero. Runs fine and dandy during the day but then if I try to run it at night it constantly stutters in 1st and 2nd gear at lower RPMs, I know that's normal but it doesn't happen during the day. Temperature doesn't affect the stuttering, could be freezing during noon it will run just fine, and could be warm at night and it still stutters, and car does it both when the engine is cold and warmed up.
Carb was just tuned up, I cleaned it, changed the air filter and even poured in STP fuel cleaner to see if that would fix it, still does it.
 
Originally Posted by Duffyjr
The only difference between day and night would be your lights, does it do it at night if you turn the headlights off.


Yup, still does it, tried turning on the lights during the day, even brights, doesn't do it. And I don't see how electronics could affect stuttering in any way.
Only time it didn't do this is after I poured in the STP into the fuel and a week later when I filled up the tank again, then it did run fine all the way to my destination, but again when I turned the car back on it started again.

I am starting to think the gas I'm using might be affecting it, since the one time it didn't stutter I filled up at the more expensive gas station with "supposedly" better quality gas. I might even try switching from 95 to 98, maybe that will help.
 
What car? What type of ignition system? I'd look at everything spark plug wires, cap and rotor esp. If it has points, check them, file and gap them. Might try a new condenser. Day night thing does not make sense unless its a load like lights , a/c that the alternator can't handle and lowers power to the coil, but thats a stretch.
 
Originally Posted by spasm3
What car? What type of ignition system? I'd look at everything spark plug wires, cap and rotor esp. If it has points, check them, file and gap them. Might try a new condenser. Day night thing does not make sense unless its a load like lights , a/c that the alternator can't handle and lowers power to the coil, but thats a stretch.


It's a 1991 Peugeot 309. Don't know what kind of ignition system but it's definetly different from my previous cars. Doesn't have points since it's not that old. And I can conclude it's not a load thing as it runs fine with the light on during the day and still stutters during night.
 
Originally Posted by Glam_Stachee
It's like a bad superhero. Runs fine and dandy during the day but then if I try to run it at night it constantly stutters in 1st and 2nd gear at lower RPMs, I know that's normal but it doesn't happen during the day. Temperature doesn't affect the stuttering, could be freezing during noon it will run just fine, and could be warm at night and it still stutters, and car does it both when the engine is cold and warmed up.
Carb was just tuned up, I cleaned it, changed the air filter and even poured in STP fuel cleaner to see if that would fix it, still does it.


Possibly humidity as it's generally more humid at night, I'D CHECK THE FUEL-AIR MIXTURE
 
Originally Posted by Pelican
Originally Posted by Glam_Stachee
It's like a bad superhero. Runs fine and dandy during the day but then if I try to run it at night it constantly stutters in 1st and 2nd gear at lower RPMs, I know that's normal but it doesn't happen during the day. Temperature doesn't affect the stuttering, could be freezing during noon it will run just fine, and could be warm at night and it still stutters, and car does it both when the engine is cold and warmed up.
Carb was just tuned up, I cleaned it, changed the air filter and even poured in STP fuel cleaner to see if that would fix it, still does it.


Possibly humidity as it's generally more humid at night, I'D CHECK THE FUEL-AIR MIXTURE


So far it's the theory most people have brought up when I asked them, but honestly I just did the carb not 5 months ago and can't be asked to do it again.
 
Are you sure it's an engine issue?

Could it be a drive line issue that manifests during a more humid night?

Clutch chattering or skipping when it's damp that you don't see during more dry conditions?

If it is an engine issue, I'm thinking marginal HT leads / spark plug wires depending on which version of English car part names you use.

I'd certainly look into cap, rotor, wires/leads and maybe even the plugs.

If it all checks out, and voltages are good with the lights on as others have suggested, start looking for other issues such as a chattering clutch or similar.
 
Check spark plug wires and boots for dry/cracking or arc tracks. If they're old replace them. Check engine ground strap and ignition electronics to ensure a good clean ground connection. Misfire can only be fuel or ignition and you've eliminated fuel. The electronics with a nominal ground wont fire well and old wires/boots can arc across their surface.
 
What about humidity ?

Edit : way too late
smile.gif


Carb adjustement is finicky on these
 
Last edited:
Originally Posted by Popsy
What about humidity ?

Edit : way too late
smile.gif


Carb adjustement is finicky on these


Not really, not much more complicated than my old cars, except the stupid air filter which takes forever to take off. I'm just really bad at adjusting carbs and so far it runs good half the day.
Originally Posted by javacontour
Are you sure it's an engine issue?

Could it be a drive line issue that manifests during a more humid night?

Clutch chattering or skipping when it's damp that you don't see during more dry conditions?

If it is an engine issue, I'm thinking marginal HT leads / spark plug wires depending on which version of English car part names you use.

I'd certainly look into cap, rotor, wires/leads and maybe even the plugs.

If it all checks out, and voltages are good with the lights on as others have suggested, start looking for other issues such as a chattering clutch or similar.


Possible that it's the something to do with the spark plugs. I haven't touched them since I got the car, but only because I don't have a socket for removing them anymore, gonna have to get one of those first.
 
Not complicated, just that it tends to need adjustment often. Again my experience based on a 205 so I don't know, more space under the 309's hood so maybe less prone to need adjustment ?

Also there was two types of carbs on these, Solex and Weber. Solex apparently harder to tune ?
 
Stuttering's an ignition issue.

I replaced the factory carb on my 1985 dodge plow truck last year. The new one works great. They are a wear item that wears out, and all the adjusting in the world won't make up for that.
 
Had a similar problem many years ago and what we did was open the hood in a dark area and watched tiny sparks flash intermittently on the plug wires; Next day we misted the wires and the engine shook and stalled.
 
Ignition would be my guess, too, if it gets significantly more humid at night.

Have you ever opened the hood while it's running at night? If the plug wires are really bad, you might see them arcing in the dark.
 
Originally Posted by Popsy
Not complicated, just that it tends to need adjustment often. Again my experience based on a 205 so I don't know, more space under the 309's hood so maybe less prone to need adjustment ?

Also there was two types of carbs on these, Solex and Weber. Solex apparently harder to tune ?


Nah it's good if it's a 205, the 309 has the exact same front, only the rear is different. And mine does have a Solex, all my previous cars had Webers. Though Solex is still owned by Weber. Though the hood is plentifully open since it's the most basic model.

Originally Posted by eljefino
Stuttering's an ignition issue.

I replaced the factory carb on my 1985 dodge plow truck last year. The new one works great. They are a wear item that wears out, and all the adjusting in the world won't make up for that.


I've never seen a worn out carb in any car, and I had an old Merc with over 450 000 km, only thing I didn't need to change on it was the carb. Besides my car only has 90 000 km on it and owned by an older gentleman since new, probably hasn't ever been redlined.
Originally Posted by Rhymingmechanic
Ignition would be my guess, too, if it gets significantly more humid at night.

Have you ever opened the hood while it's running at night? If the plug wires are really bad, you might see them arcing in the dark.


Yup, several times, the plug wires look mint from the outside, though who knows when they've been replaced, might even be factory from all I know.
 
Do what @dinoburner said and wet down the ignition parts then test drive. Look for cracks in the cap or coil. The voltage may not be high enough to spark over a bad spot when the engine is idling, it goes up under load. Bad wires really can't be identified by looking.
 
I agree with everyone else, humidity is a possible difference. At night (and in the dark), can you see any arcing on or around the wires when it is running poorly?
 
This sounds like a cracked distributor cap. I agree with the above, it's in the ignition/firing and the the carburetor.
 
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