Misfiring Ke70

[low n slow]

my ke70 (road car until recently) has a misfire when you sink the boot in. i have replaced the spark plugs, leads, dizzy, alternater, carby, and noone can tell me why it still messes. i have had four different mechanics look at it but they keep tellin me it is the leads, I'm on my sixth set in 2 weeks. :P

[Xany]

try just simple things......such as.

 

fuel filter

 

if your fuel filter is dirty, it can lead to problems such as a misfire, or sound like its misfiring, when acutally its not getting enough fuel.

 

dunno.......what kinda leads you using?

[low n slow]

the leads are 7mm topgun and i just replaced the fuel filter two minutes ago (i had one in my toolbox and it hasnt helped!!!!!!!!!!!!!!!!!!!!!!!!!!

[Xany]

the only other thing i can suggest is to get some thicker leads. also check the points gap and the timing.

[Felix]

coil?

[Redwarf]

Find somewhere really really dark, open the bonnet, start the car, see if there's sparks going down the leads. (Honestly). Glowing lead: time to replace. 7mm leads sound a little thin, but I'm assuming its stockish? Otherwise as Felix said, coil?

 

Can you narrow it down to fuel or spark?

 

Rev range?

 

Spark plug brand? I've never had success with Bosch plugs in a Corolla. Dunno why.

 

Where are you, if you're nthside I'll take a look for you.....

 

Cheers

 

R

[Xany]

coil?

i thought coils either worked.....or didnt work......i didnt actually think they broke down over time.

 

I've never had success with Bosch plugs in a Corolla. Dunno why.

 

i've got bosch spark plugs in mine atm......what kinda problems did you have with them?

Edited September 13, 2004 by Xany

[Redwarf]

They can occasionally play funny buggers....

[irokin]

Ive had problems with bosch plugs. I run NGK plugs when I can...

 

Have you checked the carby float level??

[Redwarf]

I've had a lot of problems with Bosch plugs breaking down, even when new(ish). Problem usually occurs at the 3500- 4000 rpm range under load. NGK are the way to go.Never had a dud. My theory, Jap car, Jap plugs! :P

Edited September 13, 2004 by Redwarf

[Felix]

i've had coils go slow and die in the upper RPM range. the old oil filled bosch GT40s were bad for this. had 2 of them die. the transistor ones are good.

 

also check the voltage at the coil. i had a dead alternator for a while and found when the battery voltage got low the car would start misfiring at revs.

 

it is one of those things that is hard to diagnose over the web.

 

i would check valve clearances, compression (hasn't got a burnt valve?), spark voltage at the leads if you have a spark testor.

 

have you changed the dizzy cap and rotor button when you changed the coil? carbon tracking can occasionally be a problem, moreso with the earlier smaller diameter cap and button on the ND dizzies.

 

is the carb standard? has it been rejetted or anything? i have run into lean misfire and also rich misfire before.

[irokin]

hasn't got a burnt valve?

I think that might be whats wrong with my motor....what are the symptoms of this?

[Felix]

it'll run on three. at first more under load, but as the exhaust valve gets worse all the time.

 

a compression test will give you a good idea if anything like that is wrong. do it both dry and wet. if the reading is down on one cylinder dry, and then doing it wet makes no difference, suspect a leaky valve or maybe head gasket..... if the reading comes up wet, then it is rings.

 

 

a leakdown test at a mechanics is even more informative if you want to go that far.

 

also you could try a balance test, where you run the car at idle, removing a single plug at a time and record the RPM drop for each cylinder. if one cylinder drops less than the others it is not doing its fair share and it is time to look further.

[Sir_Daywalker]

There is a simpler test to find out if head/head gasket is dead or dying its called a co2 test and most mechanice will do one for around 5 bucks.

 

they have a blue liquid in a tube they take the radiator cap off and hold it above radiator if the liquid gos green there is co2 in the radiator and either the head or the head gasket need replacing!

 

this was done on my ke70 to find out that my haead gasket was blown and valve one in head was cracked stright thru.

 

after removing head i find red loctite both sides of head gasket and ring up previous owner and abuse him for n hour!!!!

 

however on a 4kc a head replacement was easy got a mildly worked one 4 $88 and repco supplied all the required gaskets for $50 so i supplied some rum and coke and tools and shit and got a mate to help me change it over.

 

all up including parts an new coolant radiator flush crap and oil it cost me $189 for head change over on a 4k-c not diffucult once u can get the bloody manifold off.

[Felix]

a few years ago, my brother had a burnt exhaust valve in the 4k in his ke30 he had at the time.

 

i just stripped the head off, and got an exhaust valve out of another head i had laying around. using a drill (on the stem) and some coarse grinding paste i ground the valve and seat in. a bit rough, but cheap, simple and effective. cost like $40 for a VRS kit and that was it. ran like a charm until he took it off the road around 2 years later.

 

i wouldn't do it for an engine if you are after performance. for a dunger you don't want to spend money on it is fine.

 

only costs like $100 to get a machine shop to do a valve job and face the head. that is providing you give them the head clean and dismantled. ie. just the bare head with only the valves sitiing in it. if you do most of the work yourself you can save quite a few $$$