One cylinder misfire and weird power balance results?

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Re: One cylinder misfire and weird power balance results?

Post  83Farmboy on December 18th 2015, 6:36 pm

I don't have a thermometer, but unplugging that cylinder never shows more than 5rpm difference, and you can probably blame half of that number on the unsteadiness of the tach.

This motor has:
Hydraulic flat lifters
Non-adjustable rocker arms

I have just now replaced both valve springs on that cylinder. Interestingly, as I was tightening down the intake rocker, I noticed the intake valve opening...and then opening..and opening even more! It's about the thickness of the edge of the retainer!

Now I noticed that the #2 cylinder did the same thing, as I pulled the intake rocker off of that one to see if it's any different. But the #2 was slightly less.

Is it normal for these to move while torquing down?

Also, replacing BOTH springs on the cylinder made no difference. I moved the valves all the way in and out by hand and put MMO on the stems to be certain nothing is sticking there. Still dead on #4. #2 works though! This is driving me crazy

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Re: One cylinder misfire and weird power balance results?

Post  maverick on December 19th 2015, 4:36 pm

I asked about the choke because a closed choke will aggrivate a vacuum leak at the manifold.....Just a thought.

When you tightened the rockers and noticed the valves opening, was that cylinder at TDC?
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Re: One cylinder misfire and weird power balance results?

Post  jeffgfg on December 19th 2015, 8:42 pm

Are all the push rods the same length?? Are all the lifters the same??

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Re: One cylinder misfire and weird power balance results?

Post  83Farmboy on December 19th 2015, 10:29 pm

maverick wrote:I asked about the choke  because a closed choke will aggrivate a vacuum leak at the manifold.....Just a thought.

When you tightened the rockers and noticed the valves opening, was that cylinder at TDC?

No, I'm tightening using the ole EOIC guide. Just as the Exhaust begins to open.

Hm, now you got something. When I bought the car, the guy said the only complaint was that he had to pull the choke off every morning by hand! On a cold start, you let the choke snap all the way shut, then start it. It won't start, just burble once or twice and die. After that first burble, you slide the choke a little more open so that the idle screw is just on the end of the highest step of the fast idle cam and then start it again. After a few seconds of very VERY rough bucking and coughing, the pull-off will snap the idle screw down to the next step on the cam and so forth. But you can't drive yet. You have to wait at least 5 minutes before it can drive off without stalling HARD. I mean a dead lights-out stall. After the dramatic morning procedure, the car does OK until it's BONE cold again.

So how would I know that closing the choke is making it run like crap because of an intake leak vs the fact that engines run like crap with the choke closed when warm?

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Re: One cylinder misfire and weird power balance results?

Post  83Farmboy on December 19th 2015, 10:29 pm

jeffgfg wrote:Are all the push rods the same length?? Are all the lifters the same??

Yep, as far as I can see the pushrods are all exactly the same. Lifters I don't know because I haven't taken them out but they are designed to be the same.

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Re: One cylinder misfire and weird power balance results?

Post  460bronco on December 19th 2015, 10:44 pm

Put air pressure into that spark plug hole while both valves are suppose to be closed.  If you hear air leaking out intake or exhaust, you've got a valve that's not completely seating.  
2- while the engine is running, spray Wd-40/ starting fluid down the side of the intake mounting surface.  If it's sucked away, bingo intake leak.
3- try another distributor cap or 3! Ha
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Re: One cylinder misfire and weird power balance results?

Post  83Farmboy on December 29th 2015, 9:43 pm

Tried propane and water to test for vacuum leaks. I sprayed every imaginable place and got nothing. The whole dizzy unit, pickup, cap and rotor are new and timed correctly.

I found that the car runs MUCH worse with #4 unplugged completely. Was an accident but that was the result I found. It runs better with #4 plugged in, even though #4 only shows about a 5rpm difference in the power balance, which is within the error margin of the tach anyway.

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Re: One cylinder misfire and weird power balance results?

Post  supervel45 on December 29th 2015, 10:17 pm

Have you adjusted the idle mixture screws to see if it affects the problem any?

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Re: One cylinder misfire and weird power balance results?

Post  83Farmboy on December 29th 2015, 10:19 pm

Actually the son was over until today and he did all of the adjustments by the book. Started with the idle screws 2-turns out and adjusted using the tach since the vacuum needle was jumpy.

Adjusted with the engine hot going 1/4 turn at a time then 1/8 turn out from highest idle speed. I turned them 1/2 in and out from this setting while it was running and it got worse both ways. What are you suggesting? Chance that one of the screws isn't even with the other or ? Would it be possible that a certain setting would make it especially hard to feed one cylinder?

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Re: One cylinder misfire and weird power balance results?

Post  maverick on December 29th 2015, 10:51 pm

You say you have high static compression on the bad cylinder? Good spark but a grubby spark plug?
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Re: One cylinder misfire and weird power balance results?

Post  83Farmboy on December 29th 2015, 10:53 pm

Same compression. All cylinders build to the same pressure within 5-strokes WOT

Actually the spark plug on the "dead" cylinder is the same as all of the others. Clean white center with slight darkness on the base ring.

It really ran like crap without the suspect cylinder plugged into the spark lead. Makes me think this issue clears up with more throttle.

As for the screws, turning them more rich causes a harsher bucking and turning them more lean drops the idle speed.

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Re: One cylinder misfire and weird power balance results?

Post  supervel45 on December 29th 2015, 11:18 pm

83Farmboy wrote:Actually the son was over until today and he did all of the adjustments by the book. Started with the idle screws 2-turns out and adjusted using the tach since the vacuum needle was jumpy.

Adjusted with the engine hot going 1/4 turn at a time then 1/8 turn out from highest idle speed. I turned them 1/2 in and out from this setting while it was running and it got worse both ways. What are you suggesting? Chance that one of the screws isn't even with the other or ? Would it be possible that a certain setting would make it especially hard to feed one cylinder?
I was still stuck on the lean misfire idea, since it seems the mechanical end as well as the ignition checks seem to be ok. One other thing was the EGR plate under the carb. and gaskets. Those always seemed to be a problem on the old Ford's but, I believe you said they were a new.

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Re: One cylinder misfire and weird power balance results?

Post  supervel45 on December 29th 2015, 11:21 pm

Did you ever hook your timing light pickup on cylinder #4 and watch the flash and see if it was steady at idle?

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Re: One cylinder misfire and weird power balance results?

Post  83Farmboy on December 29th 2015, 11:25 pm

We have new gaskets under the carb. One is the thick black one thats typical for carbs and the other goes between the EGR plate to the manifold and is made of aluminum.

Yes, I have timing marks on my wheel for all 8 cylinders and all are even and steady. I did this even though my dwell is set perfectly because I'm anal and won't settle for just reading a gauge. Proof of concept if nothing else. Also the RPM reading on the tach is the same no matter which wire I choose.

Glad i'm not the only one banging my head here. This is the damnedest thing.

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Re: One cylinder misfire and weird power balance results?

Post  maverick on December 29th 2015, 11:37 pm

This thing is becoming a real challenge for more people than just you. I'm thinking about buying it from you so that I can either fix it or burn it.
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Re: One cylinder misfire and weird power balance results?

Post  supervel45 on December 29th 2015, 11:42 pm

This is not a points distributor is it?

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Re: One cylinder misfire and weird power balance results?

Post  83Farmboy on December 29th 2015, 11:49 pm

Boy I tell ya. My son was a ghost during christmas visit. Couldn't pry him from this thing seeing as how it seems to be the easiest hardest issue possible. I've brought the guys from the fab/paint shop over to watch em squirm and they quoted all the same stuff I would have said. Seems everybody that meets this thing gets very bold and doesn't mind pitching in free man hours just to be the one to crack it. Haha, can I complain?

Convinced our machinist friend to bring a whole bed full of tools to search for the worst of the worst in there. Stuck a bore scope into the cylinder to confirm there was a piston in there. Oh and it didn't have a hole in it. NO oil or gas puddled around it either. Just dark slightly wet crown. The others are pretty plain, dry carbon. We stuck it through the secondary valves to get as close to the intake of #4 as possible to be sure there wasn't a rag or family of squirrels in the tract. The rag has happened to me before. Small shop towel was used to keep the carb ports covered while the carb was off. Should have removed before flight.

How would I know for certain if the intake manifold gasket is sucking air and oil through the lifter valley side?

No points here. Duraspark. That's why dwell is perfectly set, it uses 8 teeth on a reluctor wheel, one for each cylinder.

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Re: One cylinder misfire and weird power balance results?

Post  supervel45 on December 30th 2015, 12:01 am

That's what I was getting at points cam rotor lobe worn on #4 ramp and I thought of a wheel blade also having some off the wall issue. I think the last guy with the valley intake leak had smoke at startup. This getting too much like an ASE test, we are running out of wrong possible causes and used up almost all of the correct ones.

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Re: One cylinder misfire and weird power balance results?

Post  maverick on December 30th 2015, 12:17 am

One last thing...and I'm really reaching here. With engine running, put a drop of heavy oil (like gear oil) on the carb throttle shafts right where they pass thru the carb base plate. Worn shafts/bushings can cause vacuum leaks that do funny things as the throttle opens. If the oil has no effect, I'd start thinking about lifting that manifold to check out the gaskets at the lifter valley.
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Re: One cylinder misfire and weird power balance results?

Post  samiam on December 30th 2015, 12:26 am

83Farmboy wrote:Boy I tell ya. My son was a ghost during christmas visit. Couldn't pry him from this thing seeing as how it seems to be the easiest hardest issue possible. I've brought the guys from the fab/paint shop over to watch em squirm and they quoted all the same stuff I would have said. Seems everybody that meets this thing gets very bold and doesn't mind pitching in free man hours just to be the one to crack it. Haha, can I complain?

Convinced our machinist friend to bring a whole bed full of tools to search for the worst of the worst in there. Stuck a bore scope into the cylinder to confirm there was a piston in there. Oh and it didn't have a hole in it. NO oil or gas puddled around it either. Just dark slightly wet crown. The others are pretty plain, dry carbon. We stuck it through the secondary valves to get as close to the intake of #4 as possible to be sure there wasn't a rag or family of squirrels in the tract. The rag has happened to me before. Small shop towel was used to keep the carb ports covered while the carb was off. Should have removed before flight.

How would I know for certain if the intake manifold gasket is sucking air and oil through the lifter valley side?

No points here. Duraspark. That's why dwell is perfectly set, it uses 8 teeth on a reluctor wheel, one for each cylinder.
u

The neighbor had a suggestion once when I thought my gasket had slipped, went something like this,
About the intake gasket sucking air,plug off the dipstick, pcv, and breather. hook a vaccuum up to the oil filler hole, put that valve in the open position and see if you have a vaccum pressure from the spark plug hole..
dont know if it will work never tried it...I had already pulled the intake......



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Re: One cylinder misfire and weird power balance results?

Post  maverick on December 30th 2015, 12:45 am

I'm guessing you'd find vacuum at the plug hole since the rings/gaps are not a perfect seal. Maybe do tbe vacuum test, then shoot some oil into the cylinder and retest. That would help pinpoint the air movement.
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Re: One cylinder misfire and weird power balance results?

Post  83Farmboy on December 31st 2015, 2:41 am

samiam wrote:The neighbor had a suggestion once when I thought my gasket had slipped, went something like this,
About the intake gasket sucking air,plug off the dipstick, pcv, and breather. hook a vaccuum up to the oil filler hole, put that valve in the open position and see if you have a vaccum pressure from the spark plug hole..
dont know if it will work never tried it...I had already pulled the intake......

Maybe that will clean up the rear main seal and stop the drip. It's slow but having a sloppy bell housing has always been a peeve of mine. Vacuum it is when I get the time

Speaking of the reluctor, supervel45 I will pull the reluctor off and turn it 180 degrees and see if the problem switches to number 7!

If not I dread trying to lift that intake off. The last intake I did was an aluminum runner for a third gen camaro and what a breeze it was but now i'm looking at what looks like a monsterous iron oven. I see heavy duty chains and free young laborers in my future.

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Re: One cylinder misfire and weird power balance results?

Post  83Farmboy on December 31st 2015, 10:59 am

Before I'm off to work I thought I should update something I found this morning.

So both Dan and I have checked that the carb is clean, using new gaskets, and properly adjusted according to the factory manual. The choke is 100% adjusted to spec on a stock engine with stock filter etc. The pulloff throw, the coil housing position, the kickdown position choke opening gap is all set. Actually almost all of this was already set. It seems like nobody has ever touched this carb.

Problem here folks.

When the car is cold there is quite a process involved. All of these steps are necessary or it just won't start

first kick the pedal once
start the car and it will fire before it even turns over once. Sounds impressive until it immeidately bucks like a startled mule and is dead with spectacular spray of fuel coughing out of the carb opening and even through the bowl vents
Walk around the car to pull the choke down to the second step of the high idle cam
Start and it will rock and judder until it slowly smooths out more and more

It will idle nice and smooth at this point even though removing #4 plug wire makes no difference. Strange that the cylinder seems dead though it idles smooth when cold.
Another note to make is that NO MATTEr how I manipulate the choke I can't apply EVEN THE SLIGHTEST THROTTLE without the carb coughing up a squirt of fuel and gagging to death instantly. It's not the accel pump as I've tried disconnecting that and it's not a lack of fuel at first start since I've tried filling up the carb through a funnel to the fuel inlet and it made no difference.

Once the heart has some warmth in it, it will start better than a modern fuel injected car sometimes but other times will need wide open throttle until it fires.

One of you geniuses is going to recognize these symptoms and knock it out it's just a matter of time right?

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Re: One cylinder misfire and weird power balance results?

Post  460bronco on December 31st 2015, 1:36 pm

float is stuck if its spraying fuel out of the bowl vent
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Re: One cylinder misfire and weird power balance results?

Post  83Farmboy on December 31st 2015, 3:39 pm

It's just a squirt of fuel like a splash of air rushing up the intake and through the carb.

It ONLY does this cold when the choke is shut or partially shut. Never loses RPM at idle. Just a damn rhythmic shudder that seems to start stop start stop like it can't decide if it wants #4 to go or not.

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