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L20b power loss/valve problems?


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  • 1 month later...

Alright so i finally finished replacing the head gasket and the valve stem seals.

Seems the car is still getting some oil or gas (seems to have a gas smell but i'm no expert) onto the 4cyl spark plug and a little on 3cyl. I smell the same smell when i open the oil filler cap that is on the spark plug. 

Could it be

1. the fuel pump diaphram is bad, gas mixing with the oil, thinning out the oil and somehow making its way into the cylinders?

2. somehow its not burning up fuel all the way and its just gas on the spark plug, because it is still backfiring like crazy and i'm positive it is trimmed correctly.

and if any of those things were the case why is it really only affecting cyl4?

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Unburnt gas and your backfire are related I would think.  I would start with your plug wires - order correct I'm assuming?  A bad wire could show up intermittently and give you headaches.  missing - and you have unburnt gas in those cylinders.  

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Out the exhaust is raw fuel and air that was not burned in the cylinder. The simplest cause is an interruption of the spark to a cylinder or several cylinders. Fuel and air is pumped into the exhaust where it explodes. 

 

This can be from bad points. It can also be bad wires, cap or rotor that allows a spark from one cylinder to escape to ground and there is a misfire. 

 

As mentioned a cylinder that does not fire will pump gas into the oil.

 

 

I just ordered spark plug wires, plugs, coil, cap and rotor, and a fuel pump so hopefully that will do something. Order is correct and it's not missing

 

Don't forget the points!

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Put on the new cap, rotor, coil, plugs, plug wires, cleaned and set the points to 0.020. and its still afterfiring. 

Could my distributor be bad? i'm still really only smelling gas on cyl4 plug.

I've messed with the carb mixture screw to see if it was just running to rich but that's not the case.

Could this be a problem with my intake manifold somehow? i've got no damn clue

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Idle mixture screw only adjusts the idle mixture... and it adjusts ALL cylinders.

 

 

Put on the new cap, rotor, coil, plugs, plug wires, cleaned and set the points to 0.020. and its still afterfiring. 

Could my distributor be bad? i'm still really only smelling gas on cyl4 plug.

I've messed with the carb mixture screw to see if it was just running to rich but that's not the case.

Could this be a problem with my intake manifold somehow? i've got no damn clue

 

Take the cap off and watch the points open and close while turning the engine over with the starter. If the points open on all lobes of the distributor cam you must assume that everything is working.

 

If everything should be working maybe it is. This leaves a poor sealing combustion chamber. Do a compression check. Maybe you have a burned exhaust valve.

 

But first did you ever check the valve lash? Specially on number 4???

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Here's a video of the points in slow motion. seems the spark isn't consistent. Does this call for new points, condenser, or distributor?

 

Its pretty much 120 across all cylinders for compression test

 

I'll have to double check the lash but i believe its good

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A compression test might show a low cylinder but not why.. Even better a leak down test which are just two gauges separated by a small orifice. The input gauge valve can be adjusted to 100PSI and on the other side of the restriction the other gauge reads a percentage showing the loss. (because there will always be some leakage) 10% would be very good and also not that likely. 15% to 20% would be average to fair. Above 20% bears looking into. A leak down test puts compressed air into the closed cylinder. A leaking intake will hiss out the carb, leaking exhaust valve out the tail pipe. I'm leaning towards a bad exhaust valve or seat or both. Hissing sound out the valve cover breather can be broken piston and/or rings. Air bubbles in the rad can be a blown head gasket.

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Did u say that u tried adjusting ur carb and no change? When u turn the idle mixtute screw, ur rpm should either go up or down. Did it? Do this while the car is not on. Turn the idle mixture all the way in, cw, but dont force it. Then turn out ccw sttart the car, it should run. Drive around for a bit and check ur spark plugs. It should be tan in color, if its black and sooty then your running rich. Your rpm should be around 800. Btw where are u located

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Haven't tried that method of tuning yet. But i did turn it in untill it started stalling, and then backed it out about a full turn. It still after fired then and it felt like it was running lean. I'll mess around with it a little more and see what i can do.

I'm in washington, king county area

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