Lean misfire

1983wagon · Post by **1983wagon** » Sun Dec 01, 2013 9:49 am

G'day guys
As most of you already know I have recently cleaned up my ea81.
I broke a bolt in my manifold so replaced that. Ever since I did I had been misfiring after it was warmed up which was about 5 mins after driving... I changed the coil and resistor and it seemed to have fixed the problem. For about 45 minutes anyway of driving. It's not doing it anywhere near as bad as before I changed the coil and it only does it after a good half hour. It's not pinging lets make that clear... I can pull the choke out a bit and sometimes makes it stop for a few seconds which leads me to think she is hungry for more fuel. But why does it start doing it after some time of driving and not right away???
I've put new plugs and leads and all tested fine. I've checked all bolts to be tightened and vacuum hoses all check out ok. I changed the EGR valve to check if that was the problem but still no good.

Let me know what you guys think because I may be missing something. Any more info you guys will need to know I will answer straight away.
The carby has been rebuilt. (Professionally) and am wondering if it needs to be tuned in some sort. The next step for me will be taking it to the carby shop because I have literally checked everything !!!

Cheers

Silverbullet · Post by **Silverbullet** » Sun Dec 01, 2013 11:47 am

Is your dizzy points or electronic? I can't recall. If it's points check the wire that connects to the points (fabric covered inside the dizzy usually) is completely insulated from the body of the dizzy, through the little port on the side and out to the engine wiring loom. I had an un-diagnosable misfire until I found that wire was shorting on the dizzy intermittently. It drove me completely insane as it would only do it up hills and on hot days under load, but not all the time.

1983wagon · Post by **1983wagon** » Sun Dec 01, 2013 11:52 am

It is points. Will check it out later on.... And yes that makes two of us in regards to going completely insane! On the positive side the amount of things im replacing to sort out issues everything is almost brand new in my engine bay... The wallet is hurting though.

Cheers

steptoe · Post by **steptoe** » Sun Dec 01, 2013 8:03 pm

so a 'lean' backfire could be a bum steer, could just be an ignition failure. Double up on the earthing between engine and body ?

1983wagon · Post by **1983wagon** » Sun Dec 01, 2013 8:12 pm

might be a bum steer but its the best way to describe it. every part of the ignition setup has been checked???

Subydoug · Post by **Subydoug** » Sun Dec 01, 2013 9:29 pm

Try new points, if it doesnt clear up you may have a lean idle. I know from tinkering with my engine and efi that the ea81 starts carrying on at around 14 or 15 to 1. They also start missing when rich at idle too, usually that bloody rich that your eyes and nose will run away from you.

To test if it is a rich miss you can unplug a vac and let it leak a little, usually leans the mixture out. To see if its lean maybe just spray some mist of fuel into the carb while its doing it.

So no stumble when you pull off from lights? Did you check all around the carby base for vac leaks? around intake gaskets etc?

Regards

Doug

1983wagon · Post by **1983wagon** » Sun Dec 01, 2013 9:39 pm

New points where put on 50 ks ago. And It doesn't do it at all, at idle so won't be able to spray a mist of fuel in there to see if it fixes it, if that's what you ment. No stumble at all at lights just randomly doing it. Yeah vac leaks was the first thing I checked because I immediately thought that was the issue. The thing that has me confused is why it only does if after roughly 15 ks of driving. Thanks for the reply!

1983wagon · Post by **1983wagon** » Sun Dec 01, 2013 9:40 pm

If it helps it always has a very smooth idle.

Subydoug · Post by **Subydoug** » Sun Dec 01, 2013 10:36 pm

Ooooh so missing while driving.... I follow now.hmm, did you replace the little capacitors on the disty and possibly one on the coil? I wouldn't think the engine would miss from being a bit lean, just less power (unless it's dirt floating around the bowl or something of the likes)

I'd triple check the points, make sure the gap is sufficient. New rotor cap and button? If not a clean to get the crud off of them should help. Have you measured voltages at the coil? Little rubber insulator in the distributor shaft installed? Badly warn lobes on the shaft?

Regards

Doug

steptoe · Post by **steptoe** » Mon Dec 02, 2013 6:07 am

Gees, wonder if it is a fusible link with lotsa corrsoion ? If it has gone, there is no ignition, yet if it is broken and gets to cause intermittent trouble I'd expect it to stop things...who knows ???

Crud encrusted fuel line might mimic a miss - made mine mimic pig rootin', was intermittent, mostly on cool morning start ups in summer....

RSR 555 · Post by **RSR 555** » Tue Dec 03, 2013 1:08 pm

Two things come to mind..

1. Did you turn the carby upside down when you had the manifold off? I had this issue after I did this and couldn't fix it without re-kitting the carby.

2. Are you loosing any water? Just wondering if the gaskets are leaking into the intake.

1983wagon · Post by **1983wagon** » Tue Dec 03, 2013 1:25 pm

Hey Paul thanks for the response. I certainly had it on its side now and than. Not loosing any coolant. I'm almost at the point where I'm going to take off the manifold again and start over. Maybe the intake gaskets are leaking air.. I hope i havnt damaged them taking it off and on and ive missed it. Will have to find some time to have a look.
What issues did you have because you had it upside down?
Cheers

RSR 555 · Post by **RSR 555** » Tue Dec 03, 2013 2:07 pm

It felt like it was running lean and the only way to get it to work correctly was to pull the choke cable on but this caused it to use too much fuel.

I'd highly recommend new inlet manifold gaskets with a smear of silicone on them. Also make sure that all surface areas are clean and flat.

Silverbullet · Post by **Silverbullet** » Tue Dec 03, 2013 4:26 pm

^ Silicone based gasket goo! Not glazing silicone

I like the red stuff I can't remember the brand, or there's a grey one for high temp like exhausts.

RSR 555 · Post by **RSR 555** » Tue Dec 03, 2013 10:36 pm

I use Threebond 1207C on all the engine components and CRC Maniseal on all exhaust parts.

YouTube · Post by **El_Freddo** » Wed Dec 04, 2013 9:57 pm

RSR 555 wrote:I use Threebond 1207C on all the engine components and CRC Maniseal on all exhaust parts.

Never heard of that stuff. I use the red high temp silicone. Can't think of who it's made by at the moment.

Dad and I have been having the debate - but some on the EA81 intake manifold gaskets or not?

Cheers

Bennie

RSR 555 · Post by **RSR 555** » Wed Dec 04, 2013 10:07 pm

El_Freddo wrote:Never heard of that stuff. I use the red high temp silicone. Can't think of who it's made by at the moment.

Dad and I have been having the debate - but some on the EA81 intake manifold gaskets or not?

Cheers

Bennie

Threebond is the most popular silicone on the market and from memory, is the one recommended in the Subaru Workshop Manual.

http://www.threebond.com.au/liquid-gaskets.html

I'd would say no silicone if you can guarantee that both surfaces are perfectly flat and smooth.

Silverbullet · Post by **Silverbullet** » Wed Dec 04, 2013 10:10 pm

I always use it on intake manifold no reason not to IMO. I'd rather be safe than sorry when it comes to coolant leaks around those manifold bolts.

YouTube · Post by **El_Freddo** » Wed Dec 04, 2013 10:14 pm

Fair enough, I didn't want to "ruin" a set of genuine gaskets...

And to the OP (1983wagon), is the fuel bowl float set at the right height? Fuel pump good? Could be a worth while exercise to do the blow back to the tank trick to see if there's any crud in the fuel line that's causing an issue

Cheers

Bennie

1983wagon · Post by **1983wagon** » Wed Dec 04, 2013 10:19 pm

Thanks for the reply guys.. Will spend the weekend looking over it.. My intake gaskets where genuine aswell so I assumed it would be fine without silicone.
And to bennie: the fuel height seems to be correct. Not sure about the fuel pump I'm assuming its working ok. I will be changing the fuel filter over on the weekend also. Wasn't changed that long ago but better to be safe.
Cheers