93 Corolla 2e plugs keep fouling

[Uhtred]

Hey everyone,

I have a 93 Corolla EE100 1.3 engine with a Aisan carb.  I have spent many hours trying to work out its issue with no success. 

Issue description: Fitted new plugs and when engine gets hot performance declines, idle becomes rough till it eventually stalls, , sometimes it will start again.  I remove the plugs (all are black and dry looking) and clean plugs, and reinstall.  noting: I can see a slight fuely liquid build up on top of piston in all chambers.  Corolla starts and runs primo and drives well until its hot.

Work done: Carb cleaned and new kit fitted, new plugs, rings, valve stem seals, timing checked, drained fuel tank (just in case fuel was old), timing checked, belts replaced. 

Any advice greatly appreciated 

[smokin'joe]

downdraft or CV type carb ?

[kws]

Does it have an auto choke/cold enrichment? Could that be sticking on when warm?

[tortron]

Bad coil, spark degrades as it warms up, leading to fouling the plugs

 

When it stops running, pour some water over the coil to cool it off and see if it starts immediately 

[ajg193]

Almost certainly bad coil

[Uhtred]

Hey everyone, thank you all for your replies. So today I replaced the coil and ran smoothly for a while until I drove it hard or high revving then started to idle rough as usual till it eventually stalled, then hard to start.  So the same as before. 

Smokin'Joe: it is a downdraft carb

 kws: auto choke 

 

[h4nd]

Sound to me like auto choke issues. Can you test it operates correctly? Smells fuel rich?

[igor]

When it does run is it hogging the juice? That would tend to support an auto choke issue would it not?

[smokin'joe]

to fix the CV style 2E corolla, i used factory downdraft manifold and a 4K carb with manual choke.
worked a treat, but was tuoch and go to fit the auto-kickdown

 

[ajg193]

You can get manual choke carbs that are actually for a 2E though, could be worth hunting down.

 

Then again, can't really go past the reliability of a 4K carb

[Carsnz123]

I have had this issue with a couple of those 2E engines. The culprit both times was the transition circuit on the secondary barrel. It's a very small passage that lets a little fuel in just as the throttle plate cracks open so it doesn't lean out. It has a small air bleed at the top of it to help emulsify the fuel. When this air bleed gets blocked (which is very easily) the transition circuit can syphon out the fuel bowl into the manifold. While driving there is enough air going into the engine to keep going all be it run very rich. But at idle the fuel just pours in and fouls everything up. Appears to only happen when the carb is hot. Not sure why. Maybe the heat soaked fuel expands the right amount to start a syphon. 

[Uhtred]

On 15/05/2022 at 19:27, Carsnz123 said:

I have had this issue with a couple of those 2E engines. The culprit both times was the transition circuit on the secondary barrel. It's a very small passage that lets a little fuel in just as the throttle plate cracks open so it doesn't lean out. It has a small air bleed at the top of it to help emulsify the fuel. When this air bleed gets blocked (which is very easily) the transition circuit can syphon out the fuel bowl into the manifold. While driving there is enough air going into the engine to keep going all be it run very rich. But at idle the fuel just pours in and fouls everything up. Appears to only happen when the carb is hot. Not sure why. Maybe the heat soaked fuel expands the right amount to start a syphon. 

I recon you are onto it, I have checked automatic choke and all is working as it should.  I recon carb is doing exactly what your description says. How do I locate this small passage way on the carb? Do I need to remove carb? Cheers

[h4nd]

Any updates? Was curious how this panned out.

[Uhtred]

I wish I had good news, 2 weeks ago I replaced the whole distributor because I discovered red / rusty looking dust in the distributor which apparently is a sign of a failing distributor.   So feeling confident that this was the issue only to find that I still have the exact same symptoms... so over it!! not sure where to next ...