New Thread Misfire on Cyl #4

[Fubawu]

New Thread Misfire on Cyl #4(Found the problem)

Hey Guys

I thouht I would start a new thread as the last was very long. Well
I have gone through the basics and still can not find the problem.
Cylinder 4 will not fire?? I have swapped the leads, the plugs, the injectors as well
as the Dizzy cap and rotor arm. I also did a comp test again today and found cylinder 4 to be down a little over the others 152 compared to 152-156. Could the lower # have something to due with the other cylinders warming up properly? Or are those numbers close enough. I really due not know what the next step should be? :der:
John

 

[stumo]

Don't worry that the comp pressure is slightly lower, if it gets worse then have it looked at.

Is the spark ok now after changing the ign parts? (have you checked it?)

How many miles has the car done? how old is the fuel filter? Have you had the injectors cleaned and flow etc inspected?

Have you cleaned and checked all the earths?

 

[Fubawu]

Injectors are checked, spark is strong, I have not checked the fuel filter but would a dirty filter cause a problem in one cylinder? I also have not check earths or filter as I do not know where to start The car has low km though has been a track car for sometime 57k km's
John

 

[stumo]

How do you know it's only on one cyl?

Have you checked the injector resistor pack? (usually located at the rear of the engine bay)

 

[Fubawu]

I pulled each plug and only cyl 4 had no effect. I have not checked the resistor pack what would I look for?

 

[pulsarboby]

ok look at it from this angle
1) do you have a good spark at the plug? if yes then the problem is either fuel or mechanical, if no then it will either be a ht lead breaking down, plug breaking down or dizzy cap arcing across

2) fuel.....after the engine has been running on 3 cylinders, remove plug and see if its soaked in fuel! if so and you have a good spark then the problem is more than likely mechanically orientated.
in which case re-check compressions and also check that the cylinder head gasket isnt blowing between no 3 & 4 cylinders, this will also cause firing problems.
easy way to check that is by removing no 3 and 4 plugs together, then do compression check. if its blowing between the pots then removing both of those plugs together will drop the compressions.

the state of the spark plug will tell you an awfull lot;-) if its oily then it will be a mechanical prob
if black and soaked in fuel then chances are you dont have a spark
if its dry and whitish brown in colour then you may have no fuel going to that cylinder!
which will be caused either by an injector malfunction or wiring fault to the injector solenoid


also check that you have not thrown a rocker arm on number 4 cylinder, if you have then the valve will remain closed on either inlet or exhaust! this will still give you good compression but it will not fire on that cylinder as the valve cant open;-)

 

[Fubawu]

How would I check to see if I have thrown a rocker arm. Should I let the car warm to check the plugs for oil etc?
John

 

[neil240z]

whip the rocker cover off, its fairly simple though there are a couple of niggly bolts at the back near the metal fuel line, the best news here is that you have compression, chances of oil and water leaks on engine internals on an R are unusal even running high boost (unless your on stock pistons) but that is another issue.

you have been through the mill with this problem, there is a chance bob is correct, if a rocker has broke you will still have compression but the valves are not opening.

take the rocker cover off, inspect and inform us of your findings.

Neil

 

[Fubawu]

will do this week. Will it be obvious that something is wrong when cracked open?

 

[neil240z]

if this is the fault i would imagine, part of the rocker will have broken off so the cam lobe with be hitting the shim but not opening the valve, there may be some debris floating about, check to see if the plug is wet first then you know if fuel is getting in and do this when the engine is cold as when hot the fuel will probably have evoporated by the time you get the plug out, if it turned it was the exhaust part of the rocker and the car was combusting compressed fuel gasses then i have no idea what would happen to an engine that only has an inlet but no exhaust valve in operation.

 

[Fubawu]

I do see a touch of oil on the plugs? as for the rocker cover it is a bit of a pain to get off. Do I need to disconnect all lines to remove the cover. I am stuck trying to get the rear two bolts off. Lastly how can I tell if the pistons are stock? Will they be stamped 54c?
John

PS thanks for all the help guys!

 

[pulsarboby]

you will need to remove all the little nuts that hold it in place and the throttle cable and both breather hoses, then give it a tap upwards to break the seal. not a big job though!

dont like the sound of the oil on the plug though, should be no oil on the electrode end at all.

and yes 54c indicates standard pistons

 

[Fubawu]

Might be time for a rebuild I will try to complete the inspection tonight.
John

 

[neil240z]

could be piston lands.....:-(

 

[Fubawu]

Well if the engine is porked, what do you suggest for a rebuild? Would it be worth going to a stroker kit or just upgrade the pistons and what ever else could be broken? Keep in mind this car does not see the street as it will be strictly be a track car.
John

 

[Jonesy]

It could be your rocker cover leaking into your spark plug hole and running down the threads as you remove the spark plug. I've had this before. But the oil will probably only be on the threads and not on the electrode tip.

 

[Fubawu]

The oil is only on the threads and near the top away from the electrode?
John

 

[Jonesy]

You might be ok then bud, maybe its just the rocker cover leaking. Have a look around where the spark plug is for any oil.

 

[ard1ey]

if it turned it was the exhaust part of the rocker and the car was combusting compressed fuel gasses then i have no idea what would happen to an engine that only has an inlet but no exhaust valve in operation.

Just to answer the question, it'll start but it sounds a bit like an Impreza and won't do much over about 2000rpm. I somehow managed to snap the rocker arm pivot on #4 exhaust and the rocker arm went for a roam around the cylinder head instead of opening the valves. :-D

 

[neil240z]

Just to answer the question, it'll start but it sounds a bit like an Impreza and won't do much over about 2000rpm. I somehow managed to snap the rocker arm pivot on #4 exhaust and the rocker arm went for a roam around the cylinder head instead of opening the valves. :-D

cool! i didnt know an cylinder could fire just through the inlet!

jonesy could be right, however the plug holes will be SWIMMING in oil if that was the case, this happens when the rubber seals perish around the plug holes, is this the case? if its the piston lands it will smoke when revving the engine on the spot but not on idle, it disguises itself by looking like buggered turbo.

dont you just hate cars!...;-)