EA81 misfiring at cruise

[el_freddo]

My brumby (in Oz) developed a misfire at cruise recently. 

It uses about 1mL of oil per km, detonates in warm weather unless an octane booster is added (which was done for two tanks prior to this tank of fuel), is run on 98RON fuel. From memory the timing is set at 4° btdc, anything more and it pings hardcore.

No issues under load or when accelerating slowly or going hard with the misfire. Just at cruise it misfires giving small jolts in loss of power. 

The old plugs were pretty toasted so new plugs went in with no change with the issue.

I’m open to ideas on this one as I can’t work it out and I want to keep driving it before a long winded EJ conversion happens to it. 

Cheers 

Bennie

[moosens]

First thought is distributor. 

[el_freddo]

11 hours ago, moosens said:

First thought is distributor. 

Any bit in particular? 

It had a new coil and ignition module in 2019. What else should I be looking at/for? 

Cheers 

Bennie

[moosens]

Wobble, excessive play, and maybe that little carbon cylinder thing atop the rotor. Geez it’s been a while and I’m right around the corner from running an even older distributor engine - EA71 once again. 
 

You know I’m no mechanic, right? I mean I have a long history of using and abusing and wrenching but I’m not sure what else to think at this time. Maybe a short in a wire. 

[el_freddo]

I’ll put those things on the list. Thanks Moosens! 

I’m not a mechanic either but know these things quite well/well enough - just that I’m stumped on this one as having a load on the engine there’s no issue. 

I’ll report back with what I find. 

Cheers 

Bennie

[czny]

Check your engine harness connectors. Make sure they are clean & bright, no corrosion.

I just had to rebuild my 87 GL TBI harness with wiring from a 92 loyale donor. It was doing the same - missing/cutting out at part throttle cruise.

Is yours TBI or carby? If carby maybe the float level?

[czny]

Add to this a possible cracked distributor cap or rotor. Condensation inside the cap causing tracking.

I've once found tracking going thru the rotor center to the distributor shaft too.

[Rupart]

hi, i have some suspect that you have the timing a couple degrees fast,, if anything more than this gives hard pinging, it is very close to too much advance, especially using the 98 fuel. is that like premium here in us?  anyway, at cruise, the vac advance can and does advance the timing a bit, any acceleration from that point will slightly retard the timing some, heavy acceleration will fully retard the timing to the extent of total movement of the timing plate in the distributor.  i have had the same symptom on some of my vehicles, usually feels like a slight surging feel at cruise on level road. mark the dist at its present setting,, then retard it 2-4 degrees, test drive some to see if the surging sensation is still there,  if yes then no harm and no cost to move it back. also check for play in the dist shaft as someone mentioned, a little is more than it should be, is this a points type or electronic pickup type?

[Steptoe's photos]

it is payback for your dislike of it's younger sibling - the EA82

Is it a complete jolt cut-out and back again or just one cylinder?

4 degrees on 98 (AUSRON) seems very odd to me as you know, many run 8 dbtdc on lower RON fuel

I thought it was odd of you not to have replaced everything in the tune dept before asking in here. Sure you have not been hacked ?

I remember years back, a problem with Willie's EA82T that had the online community baffled, his local NT available people, and think it made it's way to SA where problem still not resolved. I ended up buying the heads. From memory, my head reco guy was muttering about a K-line valve stem insert gone bad, poor installation or watever, had wear, and assumed it was intermittently allowing valve to go out of line/centre whatever, and lose compression. Sticky valve at temp ? More good reasons to do your EJ conversion.

[el_freddo]

@Rupart  4° btdc isn’t much and certainly not over advanced. They’re usually tuned at 6° to 8° before top dead centre. I think you might have the retard and advance the wrong way around in your description. 

I know this engine consumes oil and this brings down the effective RON rating of the fuel, even if it is slightly. 

@Steptoe's photos I don’t see how my EA81 would punish me for not liking the EA82 much, the EA81 already knows it’s a superior engine… 

Admittedly I am limping this EA81 along and I know that it won’t like this coming heat over summer. The next engine swap will be the EJ and it’s known this for a long time as it’s collected the various parts with me.

It was flawless in its two trips to Sydney, the first one being at the drop of a hat and the second one planned. It was on this second trip that I ran the octane booster to avoid pinging in the warmer inland temps on the way home. I think I’m on my second tank of fuel since then and now is when this issue arose.

To answer other questions - electronic ignition, new NGK spark plugs. Dizzy cap inspected and seems good, rotor button and tabs on dizzy cap had signs of corrosion. They’re cleaned up now and look good.

Carbon button in dizzy cap present and in good shape. Shaft play would be less than 1mm in any direction. 

Can’t test drive today as it’s a great drinking arvo while tinkering away and I love having my licence… so I might drive her to work tomorrow (~80km round trip, what could go wrong?) to see if there’s any change with the build up on the dizzy tabs removed. 

This still doesn’t explain why there’s no issue under load when the ignition system is under the most stress. 

I’ll report back when I’ve got an update  

Cheers 

Bennie

Edited November 19, 2023 by el_freddo

[moosens]

Oh man I’d better wake up first. Pardon the huge edit.

 

Edited November 19, 2023 by moosens

[moosens]

https://www.flickr.com/photos/147728513@N07/53342190948/in/dateposted-public/

 

https://www.flickr.com/photos/147728513@N07/53342424035/in/dateposted-public/

 

 

And again I’m half asleep. So not under load but at cruise. 

Well I uploaded a couple pics that you can probably find yourself easy enough these days. 

But now I’m back to carb as culprit. 
 

If I’m successful there’ll be a couple of pics of the 1980 USA 4wd distributor for the cars so that would be the same as the EA81 second gen Brumby. 

 

[el_freddo]

@moosens- after today’s drive home I’m leaning towards the issue being the carb too. 

This morning’s drive to work was pretty good. But I noticed that gear changing to go faster would result in a jolt from loss of power then instant power return as I put my foot on the throttle. But if I let it over rev a little bit as I disengaged the clutch to change gear there wasn’t an issue. 

The drive home tonight was the same every gear change and the misfiring at cruise was back. And I’ve noticed when down shifting the burble with engine braking isn’t what I’d call normal, it’s popping and farting without a pattern to it unlike its regular rhythmic subaru burble during engine braking.

Also at idle it sounds like it’s sick - almost as if it’s got a hot cam in it but it’s missing that cool semi misfire noise about it, and it’s not liking to idle. I’ve bumped the idle “up” to get it to ~800rpm atm which helps raise the red flag for the carb. 

Fun fun, I’m not wanting to put any time into the carb! Efi is where it’s at for me, much easier to deal with. 

If I do anything about the carb I’ll post back here, don’t hold your breath! 

Thank you for everyone’s thoughts on this issue! 

Cheers 

Bennie

[czny]

Bennie, it sounds like the float level could be low, leaning out the mixture.

If it were a sinking float with a leak in it, the needle & seat would be open too much of the time, high level fuel  flooding over into the venturi. Some times you can see drips of fuel while at idle. This sounds like a gurgling while at cruise. 

If it were a brass float, leaks can be found by putting it in a pan of boiling water & watch for bubbles escaping.

Carb kit on fleabay, item # 254556737560

I'm guessing at your MY.

Edited November 20, 2023 by czny
Correcting myself. Not enough coffee!

[Steptoe's photos]

I usually put load issues to ignition, cruise issues to the carby, so , you know what to do eh? 

Gees, those runs to Sydney would be 1500km return trips and ran so well

Pooey idle could be unwanted intake air leaking in.

I collected bits for my intended EJ conversion, but as things happen with me, I tend to go overboard and keep driving the donor

My first donor idea was an RXA tht got  manual conversion, an LPG conversion and gave 8 fun years , 110,000km km not without other end of scale of fun - issues.

Now the Foz is doing it's main relay injector cut stuff again on another used relay. Hoping another rely will sort it in minutes rather than months like last time. Curiuosly is not spelled this way but gonna just leave it - i went to eBay, entered "brown relay" and came up with a Victorian supplier of brown relays 20A six pins for about 25 bucks plus postage - well under what Subaru want for their brown six pin relays

[Steptoe's photos]

brake booster hose fitting secure? Dizzy vac can hold it's suck ? All the vac controls in cabin work and hold at all positions ? L sereis sometimes had air vac leaks behind dash

[el_freddo]

@czny- I hadn’t thought about buying a carb kit, but near $AU200 for a kit (postage is half if not more!) I’ll opt out of that, not that I’m keen to strip the carb down - but it might have to come to that yet. Glad it’s not my only ride!

Those are good points Jonno, I checked the dizzy advance diaphragm before the last Sydney trip and it seems to hold going by they way it holds the tip of my tongue on the end of the hose until I remove it. 

Only got the air recirc stuff run by vacuum in the cab and that’s all good too. 

I’ll have to check the brake booster - I haven’t noticed any chance in braking feel/performance or any noises either. 

What I do get twice every year at around the same time (changes then about six months later it returns to “normal”) is a change in the behaviour from the carb. When the weather cools for winter it typically seems to use more fuel and idle nice at a steady 700ish rpm. Then at some point as the weather warms up the idle increases for no apparent reason and my fuel economy moves back to good economy without any power loss. 

I have tried the spray method to find vacuum leaks but am yet to find anything - unless I’m doing something wrong there (something stupid no doubt). I’ve checked that the throttle butterfly isn’t being held open by the throttle cable. Several years ago I put new genuine intake manifold gaskets in thinking the issue was a vacuum leak at this point in the system. No change. This is an issue that’s plagued this engine for a long time so I’ve just lived with it, now it’s manifested into this that I don’t want to live with! 

That’s it for now. 

Cheers 

Bennie

[czny]

Bennie, that carb kit # 254556737560, is on sale right now out of Ontario Calif. for $33.99 USD and ships for $23.40 USD. MUCH less than $200 AU.

Even if it isn't the quality kit you get over there, at least you'd have something to work with if needed.

[Steptoe's photos]

not holding my breath Bennie. Any changes? 

Edited December 15, 2023 by Steptoe's photos

[el_freddo]

On 12/16/2023 at 7:03 AM, Steptoe's photos said:

not holding my breath Bennie. Any changes? 

I moved it from near a tree when we had some fierce winds the other night. It was good to just be in it for that short amount of time. 

I haven’t touched anything else on it - since we’re in the high to extreme fire danger period I’d rather have it in one piece and running than in bits and immobile. 

Plan/thinking there is if there’s a fire and I’m home the brumby will be one of the two vehicles leaving the place, with the other vehicle being the family bus driven by Mrs El Freddo. 

This might change once on the Christmas break when I’ll have near zero work load and a carb kit in my hand. 

Cheers 

Bennie

Edited December 21, 2023 by el_freddo

[el_freddo]

Ok finally got an update on this one! 

I bit the bullet on buying a carb kit - for a DC 306 hitachi carb. This was a HTK-421 kit. Apparently for the needle and seat for the float valve I’d need the one from the kit HT432 but I didn’t bother and didn’t swap this bit as it wasn’t flooding the bowl.

 

All went well with the rebuild. I’ve had to readjust my idle since tuning. Other thing I need to look into is why it’s hard to start when cold. The old double pump  and crank trick doesn’t get it started. 

Once warmed up she fired up no worries! It runs well without any misfiring which I’m stoked about! 

Cheers 

Bennie

[88SubGL]

Is the choke operating correctly?

[el_freddo]

10 hours ago, 88SubGL said:

Is the choke operating correctly?

Worked perfect before I touched the carb. I didn’t strip any of it down and left it as is since the rebuild. It’s also summer down here atm - not very cold for morning cold starts. 

Cheers 

Bennie

[Steptoe's photos]

You must have cleaned out too much gunk to now get changes in starting abilities. Well done for biting the carb rebuild bullet.

 

[el_freddo]

On 2/20/2024 at 4:11 PM, Steptoe's photos said:

You must have cleaned out too much gunk to now get changes in starting abilities. Well done for biting the carb rebuild bullet.

 

Thanks mate. Got the starting and idle issues sorted it seems. I think the idle mixture was too lean and driving it around hard for a bit may have moved come internal crud. Who knows?! Good news is it’s running well and seems to be returning good fuel economy.  

Cheers 

Bennie