One cylinder misfire and weird power balance results?

Sounds like a typical MotorCraft smog era carb issue to me even though I don't believe you mentioned the make. Seems like the ones we had never liked the cold. Solution is a Holley non emissions carb but, I doubt that is the answer you wanted.

Supervel45 the answer I'm looking for is the one that solves my woes

OK since the car seems to run fine besides the stumble I guess I should pump some smoke in the intake and next try the vacuum test.

It really does seem to be a pretty good engine just that damn shudder once it gets warm. Again the miss is always there but starts to shudder as it gets warmer.

Good thing ive already written off the car since the heater core decided to start spewing down the firewall, the rear axle is a little wobbly like the shaft is bent, the wipers are ear shattering metal on fractured glass and the squared off tires make the ride a lot like those old coin op kiddy cars. I don't need another lawn ornament

Get this. The timing retards off idle before advancing. Initial is 14 and as you slowly pick up it drops to about 8 until you hit 1300 rpm and then it will climb as usual to full advance. I know for a fact some parts of the car had been replaced and in fact it came with several boxes of parts etc and one bucket has holley carb parts as well as what are clearly advance weight springs so this could be the result of some tuning but why would it drop before climbing? Vacuum advance plugged when testing

I found oil leaking out of a vacuum hose!

On this car there is an automatic parking brake release.

A vacuum hose comes from the intake manifold to a splitter that powers the transmission and headlights and other vacuum stuff.

A hose comes from that splitter to a vacuum switch attached to the steering column inside the cabin.

The vacuum switch has two hoses, the one from the union and the other end goes to the parking brake lever where a vacuum motor will disengage it when you shift out of park.

There is oil residue in the splitter from the manifold too.

I pulled the hose off of the vacuum switch under the steering column and oil poured out of there! Maybe a whole ounce!

What is this about?

OK I dont know what to think but now something is definitely ticking. Sounds ominous.

I haven't heard this until today. You can hear in the video that when it ticks is exactly the same moment that the idle dips like a miss. its not constant it seems to happen once every fourth or fifth power stroke. this is with the mic over the PCV hole where the sound is loudest

Before you spend any more money on this thing. you need to put a known good carb on it. Surely there is someone you know who has a decent carb to put on there for a few min. You are going to have to fix the cold natured part before you can think about the skip. The possibilities are endless here. Could be a wiped out cam lobe. measure the actual valve travel with a gage. Could be a cracked piston. this would explain the smoothness at cold idle. It hasn't had time to get hot and expand yet. I actually had this problem myself once. The engine would run great at W.O.T. but miss at idle. Was there a case of starting fluid in the trunk when you bought it?

Do you have a compression tester that will let you read the bleed off rate? Get it up on compression stroke and see how quickly it bleeds off compression. It's tricky to do but it will tell yu if you have a burnt valve. Most all modern testers have a check valve that lets the cylinder "pump up" the gage. remove the check valve so it can only read what the cylinder is doing on one stroke. Your tester may be lying to you.

And make sure you have the plug wires in a loom, not bundled together.

It's not the plug wires. I've put a gap tester on the spark plug and never missed once. Always strong enough to cross the gap.

It's smooth at idle but the cylinder still isn't firing! The cylinder practically NEVER fires at idle, but for some reason it shakes worse when hot.

Maybe I'll just do a leak-down with a gauge. I did pump the cylinder up before but heard nothing from the exhaust or carb. Also i watched the gauge and every cylinder takes 5 pumps to top out.

Somebody suggested a burnt valve after hearing the sound. Is it possible to get my test results if this is true?

A burned valve will show consistent low compression compared with other cylinders.

You have headers or manifolds sounds like a header leak or cracked manifold

Not trying to be negative... but this troublshoot has been going on for over a month... buy a top end gasket kit have a look at everything on the tear down , reassemble with new head, intake gaskets, seal properly, after accessing you do not have a bad piston, lifter, spring,pushrod, head/intake gasket, reassemble the top, and go through the carb and ignition...JMO

I agree with what Falcon said. Top end gasket set not but about $50, and a days labor to closely inspect all the parts. The symptoms point to a burnt valve or just a bad carb. 2 or 4 barrel? Given everything else you've already checked, I'd swap the carb. If that doesn't change anything do the gaskets. Like I said before, the possibilities are almost endless. How does it run when warmed up under load? If you take it down the road and punch it? Does it smoke at any point?

Stranger68 it never smokes

going down the road you would have no indication that it's limping. The biggest issue when driving is that if you slam the pedal all the way to the kick down point it will pop loudly inside the filter housing as it loses power for one split second and then catches up with a big roaring boost. I've got the tire to chirp at 30 hitting the kick-down.

the carb I could agree with. may be sucking air but I haven't gotten my oil can to test that. Some people say a burnt valve sometimes will or sometimes wont show up in static compression so which is it really?

A burned valve stays burned...until you replace it, compression will test consistently low on that cylinder.

That's good news except that it could still be a loose valve guide or wiped cam. Time to get the smoke tester and if that aint it I'll need a hoist for that manifold!

Wiped cam lobe? Non adjustable valve train? Hmm

Couldn't it be the camshaft? no valves are all plain old rockers without adjustment I still dont understand why theyd do that

83Farmboy wrote: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

Should have picked up on a flat cam lobe or loose valve guide on cyl #4 at this point.

83Farmboy wrote:Couldn't it be the camshaft? no valves are all plain old rockers without adjustment I still dont understand why theyd do that

Have you had the valve covers off,are all the valves opening and closing?If yes then the camshaft is fine and it's probably a burnt valve.

supervel45 I'm not sure what you mean? You're saying that these are the likely cause?

Mark Miller the valves are all moving the same. So if you think its a burnt valve and everybody else says a burnt valve wouldn't show good compression then obviously it's nothing and im crazy and have a good night. Haha trust me I'm ready to take this manifold off just to have closure

I'd put a good known carb on it before I took the intake off

83Farmboy wrote:supervel45 I'm not sure what you mean? You're saying that these are the likely cause?

Mark Miller the valves are all moving the same. So if you think its a burnt valve and everybody else says a burnt valve wouldn't show good compression then obviously it's nothing and im crazy and have a good night. Haha trust me I'm ready to take this manifold off just to have closure

No I don't think it's your problem, and you would have likely noticed a loose rocker arm from a wiped cam lobe as well as felt a loose guide when you had the springs off. Change to a know good carb. as I said before and see what happens.

Have you checked the valve stem height? Don't remember seeing the year model on here anywhere. When older model cars are ran for years on unleaded fuel the valves will beat out the seats in the head (the lead acts as a cushion/softner for cast iron seats). The head of the valve will actually be recessed in the port. there fore you get really poor performance Can't say I've ever seen one do what you are describing because of it tho. But I suppose it could make a pop, and likely have a slight miss.

I've only had one truck personally that had this. It just ran like crap. Maybe you have a more extreme case of it???

One way to easily check this would be to remove all the rocker arms and put a straight edge across the tops of the valve stems. If any of them are sunk there should be some irregular heights.

man you guys nailed it. phoooowee I'm glad i found you all.

I swapped for another motorcraft carb off a later Lincoln 460 and it is eerily smooth i mean its like my 04 expedition with the v8

I wonder what it would take to rebush the old carb and if there could be other issues relating to that throttle like a bent shaft or the shaft worn with the bushings too.

I dropped just the tiniest drops of carb cleaner on the shaft either side and it dropped like 45rpm and the same for the secondary shaft.

that sucker is a solid beast just every bit what i expected.

By the way, this isn't really going to matter but what would cause the car to start fine one moment and then have trouble even a few minutes later like a dead battery?

It's a coin toss whether the starter will spin like normal or act like its dead and turn for a microsecond before stopping. I'm using a seperate solenoid and remote starter now but the issue is the same. the wires all look good and tight and not green from acid or nothing. thoughts?

Sounds like the starter does it spin fine cold then once the engine starts to warm up it acts up if so the starter is more than likely bad

Nope it's a complete toss-up. No pattern. I can start the car and let it idle for a minute and it's good as a new car but then I can shut it down, put the air filter housing back on and try to start and it goes "grrrrrrun....grun...grun grun grun" like it just barely isn't getting enough voltage.

When this happened, I jumped it off with a battery box then unplugged it and let it run for two minutes while I adjusted the idle speed and then turned the car off to plug all the vacuum hoses in as a final experiment and by the time I tried to start it it was fine again and jumped right to life.

damndest thing