Ke70, missfireing only when engine warms up

[MarkIIRx12]

Hi

Again i hope some people out there have any good suggestions on my ke70.

The car runs fine when its cold, when it gets warmed up, it starts running on 3 cylinders only and its kinda hard to tell but i think the engine makes a knocking sound too. it will just die ideling when warm.

sparkplugs are brand new denso power, breaker points are new, the condenser is not new and i dunno if its good or now, but since it runs fine when cold, can i assume its fine?

since its happening when the engine gets warm, im leaning to think that one of the valves dont get enough oil or just gets stuck in the head or something, but i dunno.

anyone experiensed this problem before and have any ideas or suggestions?

Thanks in advance for all ur help

[Scoobzd]

Just for fun I'd get another new sparkplug and with the engine warmed up then go and switch it in one plug at a time. Same thing with the leads too. Borrow a dissy cap from a friend?

Last resort, take the tappet cover off and run it at idle and visually check the valve movement.

Condensor is like $12?

Process of elimination without the $95/hr mechanics bill - lol

[Hiro]

Believe it or not, I read about a similar problem in a Falcon many moons ago in the Dirty Wheels column of Wheels - car ran fine when cold but dropped a cylinder when warm - turned out there was a hairline crack in the dizzy that was opening up when everything got warm and expanded, which was shorting out one particular cylinder. The crack was so fine that you couldn't even see it but one new cap later and it was perfect.

[lexsmaz]

There is quite a few things it could be, but the first thing i would be changing is the condensor as they usually start to fail when they get warm & they will cause misfiring, etc, etc ...

[MarkIIRx12]

Thanks a lot for ur answers.

the dizzy cap is almost brand new, but its worth a to buy another to try since they are cheap.

i think i will try the condenser first then, a friend of mine said he thought it could also be the coil, any thoughts on that? the plug leads looks fine but i suspect they might be old, but i should be able to rule that out by taking them off one by one when the cars running.

I will take the tappet cover off and look at the valves if none of the above helps.

More suggestions or ideas are as always welcome

Thanks again for taking ur time to answer.

[WDE_BDY]

Do you know which cylinder? Pull each lead of one at a time to narrow it down. Being a K series I would also look at a manifold leak, particularly if running extractors. They love to leak and blow out the gaskets.

Callum

[KENut]

I'd suggest
Check leads, see if they are shorting across each other
Check diz cap - gaps could be to big, build up of corrosion (check each lead connection is clean)
Check timing etc - clean points
good luck!

[Dazza]

It could be your coil playing up. They do start breaking down when hot and will come good when they have cooled down. Check your coil lead because a crook coil lead can make your coil overheat.
It could also be a fuel blockage in the carby. When the engine is cold the choke will be on giving you a rich fuel mixture. The knocking noise could be detonation caused by a lean fuel mixture. A lean fuel mixture will make the engine surge really bad also.

[wa5]

Hiro, I am also a fan of Noel Tuckeys' collumn.... I recall reading something many moons ago, about a teacher with a KE Corolla, which also had a miss.... He looked at electrical and compression first... took him a long time to figure out that the manifold was loose, most of the nuts were only finger tight... this would have been written in the 80s...

[MarkIIRx12]

Hi again

Thanks for all ur answers.

Today i bought a new coil, coil lead and condenser, none of it makes a diffrence.

its definitly something to do with the sparks/dizzy, i couldnt get a new dizzy cap and rotor today cuz they had to order it so i will get it tomorrow. Reason why im pretty sure its a spark problem is i changed leads, diffrent set from a running car, took them off one by one, cylinder 1 and 2 has a very weak spark and sometimes it seems like its no spark at all, the car practicly runs on just number 3 and 4 cyl. Also another weird thing is when i took 1 and 2 lead to cyl off, sometimes the sparks turns from the coil all the way to ground/earth, weird or what? i also changed number 3 and 4 leads to 1 and 2 just to make sure its not the leads and it was still the same problem.

So im left with the dizzy cap and rotor as the solution i hope, or can something be seriously wrong with the dizzy itself? it looks fine tho.

I also did what u guys suggested, checked for airleaks in the manifoild, used start spray, checked if the bolts are thight and everything seems good on that end. Looked at the valces thru the tappet cover and everything seems to be moving like it should.

Im hope its as easy as changing the dizzy cap, but at the same time i think thats weird if its that too since its almost brand new.

Any more thoughts on the problems or solutions?

thanks again for ur help

[WDE_BDY]

To test the dizzy cap you should be able to turn it 180 degrees and swap the leads to suit, if the problem doesn't move cylinders it isn't the cap. Potentially the distributor is worn, check if the shaft look even where the points run. Or if it just stays with 1 and 2 being your problem it may have blown the headgasket between the cylinders, compression test will tell you.

Callum

[MarkIIRx12]

Thanks for ur answer.

I was thinking about turning the cap 180 degrees, but it got late here in Norway, 12.36 am as i type this, so i will just get the new cap tomorrow and put it on and see how it goes.

i looked at the dizzy shaft, it looks even, but its hard to tell for sure. at least i cant see any majorly wrong with it, but maybe i need to measure it to find out?

i dont think its the headgasket since i get the missing/weak sparks on the mentioned leads, but if i get the normal spark back and the dizzy checks out fine i will just take the head off and have a look, get the head shaved at the same time too.

Thanks again for ur suggestions

[toyboyracer]

If you have the spray lube "Inox" available in Norway, give the inside of the dissy a good drenching. Inox is oxygen free and way superior to WD40 or RP-7.

[allencr]

... car practicly runs on just number 3 and 4 cyl. ...weird thing is when i took 1 and 2 lead to cyl off, sometimes the sparks turns from the coil all the way to ground/earth,

WHAT'S the compression???????????
What's the difference between cyls. when the plug wires are shorted/pulled, when the idle is up - about 1500-2000, are they all even then?
Is it only running on 3&4 because carbs aren't synchronized?
The coil is protesting that its insulation can't handle 40,000volts with nowhere to go & wants out any way it can. Keep doing it & it will be doing permanently as it follows a new carbon track path of least resistance.
**********************
Also,the point gap should be the same on all 4 lobes when the dizzy shaft is straight.

[Dazza]

Try checking to see if the distributor shaft is bent by checking the point gap on all four lobes as mentioned above