Touche, but I was going in the fact that the injector was already replaced with a fucntioning unit and the same issue re-occured. We as tech's always diagnose cars differently. Me personally would have pulled the plug and checked the cylinder first, checked fuel pressure then swapped injectors, wire and plug to its opposite cylinder. You might have done it in a completely different order. As long as we get to the right conclusion, i think thas all that matters.

 

I missed the reference to the injector in that previous post (maybe it's a good thing I'm retired and not doing this for a living anymore, they say the mind is the first thing to go)

 

You would think this is the case, but if you eliminate the possible, and consider the improbable, you are left with the impossible.

In layman's terms, **** happens.

Bkreutz, its all good.

 

Another possibility could be oil from the breathers working it's way thru the throttle body and plenum and sitting on a valve.
I noticed last week when I had it apart that the even side had much more oil than the odd side did. It poured out on my pants.
Seems as likely as the HG/coolant causing #4 to missfire.

 

Consider calling PT Schram , his number is in mt signature section, he has the best prices on UK parts.
Since we are nearly neighbors, send me your number and lets talk.

 

Thanks for the replies guys, already have all the parts and pieces coming in to do the job. Contemplating pulling the entire engine since I may have a rear seal leak as well, even though its very small. Just want to do it right the first time so I dont have to do it twice, and the heads are SO much easier to take off on an engine stand.

 

Correct. Water would leak into #1 and #2 in the front.
#7 and #8 in the rear.
Coolant jackets are at each end of the heads.

Not sure how water can get into the middle cylinders.

Coolant is run thru a heater on the intake - that could leak and get antifreeze into cylinders. Such a leak though would not favor a certain cylinder.

The intake manifold has coolant running thru it.
If you have a leak where as coolant is tricking along the intake runners where they hit the valley gasket AND you have an intake leak at intake 4 where it hits the valley gasket and then it would be sucking up antifreeze from a pool nearby like a shopvac.

But, this is a huge huge long shot.

Or your liner slipped a few mm down and there is a crack in the block. But, I totally doubt that too.

I would replace the ignition coil and the wire to that cylinder and see if things get better.
And, replace the plug.

You could also have a sticking valve which is causing a misfire.
Try running synthetic oil in the engine for a time.
I don't like this type of oil in a DII. But, it seems to clean out all the varnish in tight places.

This is for airplane engines - but applies to us as well

Each cylinder of your piston aircraft engine has two valves—intake and exhaust—that open and close by sliding in and out through a close-tolerance valve guide. A stuck valve is one that no longer slides readily in its guide. A stuck valve may refuse to open, or once open it may refuse to close. Either situation is quite serious. Stuck valves are usually caused by a build-up of deposits and/or corrosion on the valve stem. Because the fit of the stem in the guide is so snug, it doesn't take much build-up on the valve stem to interfere with free movement of the valve within the guide.
"Morning sickness"


The clearance between the valve stem and its valve guide are at a minimum when the engine is cold. Consequently, the first sign of a stuck valve usually occurs when the engine is first started, and is often identified by an intermittent hesitation, or miss, in engine speed. We call this "morning sickness".
Morning sickness is a warning that should be heeded immediately. Sticky valves never get better by themselves...they always get worse, usually fairly quickly. Flying an airplane whose engine exhibits morning sickness increases the risk of serious engine damage and possibly in-flight engine failure. Hence, the aircraft should be downed for maintenance at the first hint of valve sticking.


Engine operating environment

Environmental influences that create valve sticking are: high temperatures, dirty oil, high-lead fuels, hot engine shut-downs, and poor engine baffling. Improper leaning can also be a culprit: an engine that is run excessively rich will build up carbon, lead, and other combusion-related deposits on exhaust valve stems more quickly. On the other hand, an engine that is leaned excessively during high-power operation will experience high valve temperatures, and this contributes to valve sticking.
Engine overhaul shops can't do much to prevent valve sticking. They cannot change the engineering of the engine, and have little control over its operating environment. About all they can do is to use the correct parts (valves, guides, seats, rotators, etc.), to dimensionally match the parts carefully, and to control the surface finish of the guide by careful reaming and honing.
Your regular maintenance shop can influence the operating environment by checking the engine's health regularly (via compression checks, oil analysis, filter inspection, etc.), by making sure the cooling baffles are in good shape and the magneto timing is correct, and by changing the oil frequently.

 

Thats interesting. May get the valves cleaned up after I get the heads off, that way it will be all cleaned up and ready to go. Thanks for the info.

 

I’m having this problem too. Cylinder 4 miss on a cold start. Just did head gaskets and have recently done plugs, packs and wires. Had all the top end components cleaned at a machine shop before reassembly. Idk if he would’ve opened the valves to clean out inside

 

@blakslee720 did you make anyway diagnosing your issue? I also have a cyl 4 misfire on startup. Clears up after running for a minute or so and does not misfire while driving.