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Discussion Starter · #1 · (Edited)
Going to try and make this as short as possible

1998 Dodge B1500
V6
150,000 miles

Around 3 months ago, before I got my rear snow tires, got stuck in the snow, normally because the transmission is still bad I have to baby the van and drive low RPM, at least when starting, so the engine (without having a tachometer and knowing for sure) probably never sees above 3,000 RPM, or so, however, because I was stuck I was revving the engine pretty high, guessing around 4,550 or so + RPM, forward reverse, forward reverse, to get unstuck ... got unstuck, then noticed a very rough engine idle. Van was previously running pretty smooth, unplugged spark plug wires and identified the miss in cylinder #2, swapped out the fuel injector with one I had lying around, same miss, swapped out the fuel injector with cylinder #6 fuel injector, same miss, installed new spark plug, same miss, thinking maybe I blew out a cylinder.

Flushed the engine with an engine flush(oil), (changed oil 3x to make sure the flush was completely removed), engine ran smoothly briefly, then the miss re-appeared, for lack of better words going to describe the miss as 1/4 miss sometimes, 1/2 miss sometimes, 3/4 miss sometimes, this miss went on and off, but mostly on, for about 3 weeks then all of a sudden the miss stopped, back to running as smooth as it was running before this happened. Was running smooth up until a few days ago when I took an 80 mile trip on the highway, going around 70 MPH (guessing, speedometer still broke) most of the way, then afterwards the miss re-appeared (going to say 1/4 miss), not sure what cylinder was missing, didn't check, but assuming it was the same miss as before, after the next day the van started to smooth itself out again and is running smooth now.

Was talking to my "go to parts guy " several weeks back and he told me back in the day when his buddies were racing cars that when they were racing and the engine high RPM that sometimes the engine would run rough afterwards then eventually smooth itself out, he called it a " floated valve ", I this is what I think I am dealing with here, was wondering if anybody heard of this before ? The only think I can think of is that the lifter is getting hung up and not riding on the cam completely. Do not hear a " ticking " sound so not thinking the lifter is collapsing. Thinking that the engine may have previously been overheated before purchasing and possibly causing some kind of issue, which is why I baby her and run a 180 degree thermostat.

95% positive this is a mechanical issue opposed to a faulty fuel injector, spark plug / cap / rotor / wire, or a vacuum leak.

Any thoughts ? So long as she is running smooth I am not going to worry about it at the present time, other things to fix, just wondering what may be causing this ?
 

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A leaky valve will tend to show up at lower engine speeds than higher engine speeds. It may be temperature dependent, particularly exhaust valves when they get hot.
I've had to drive cars hard and fast to get them to misfire sometimes.

A cylinder leak-down test should find the culprit. Pressurized the cylinder with the valves closed. If you hear a hiss from the throttle body, it's the intake valve. If you hear the hiss at the tailpipe, it's the exhaust valve. If you hear the hiss from under the oil filler cap, it's the piston/rings.
 
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Discussion Starter · #3 · (Edited)
A leaky valve will tend to show up at lower engine speeds than higher engine speeds. It may be temperature dependent, particularly exhaust valves when they get hot.
I've had to drive cars hard and fast to get them to misfire sometimes.

A cylinder leak-down test should find the culprit. Pressurized the cylinder with the valves closed. If you hear a hiss from the throttle body, it's the intake valve. If you hear the hiss at the tailpipe, it's the exhaust valve. If you hear the hiss from under the oil filler cap, it's the piston/rings.
That makes sense, but the thing is it did / does not appear to be temperature related at all, at least not according to the temperature gauge, had the same miss when the engine was cold, had the same miss when the engine was hot, regardless outdoor temperature, then it just disappeared as suddenly as it appeared. Right now the engine appears to be back to running smooth again.
 

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Mechanical or valve issues tend to be 'all the time' or at least 'repeatable', not like intermittents that come & go.
Has it set a P0302?
I have seen this a couple of times on the 3.9L. If the fuel pump begins to send air bubbles into the fuel line, they tend to 'pocket' at the front of the right fuel rail. This can cause a #2 lean misfire if this is what is happening.

When the misfire is present, detach the fuel hose at the rail, jump the fuel pump relay and run a sample into a clear soda bottle. Use due care and precautions in the presence of gasoline and fumes.
Look for bubbles in the fuel stream. Replacing the fuel pump has fixed this.
 
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Discussion Starter · #5 · (Edited)
Mechanical or valve issues tend to be 'all the time' or at least 'repeatable', not like intermittents that come & go.
Has it set a P0302?
I have seen this a couple of times on the 3.9L. If the fuel pump begins to send air bubbles into the fuel line, they tend to 'pocket' at the front of the right fuel rail. This can cause a #2 lean misfire if this is what is happening.

When the misfire is present, detach the fuel hose at the rail, jump the fuel pump relay and run a sample into a clear soda bottle. Use due care and precautions in the presence of gasoline and fumes.
Look for bubbles in the fuel stream. Replacing the fuel pump has fixed this.
That was my thinking, if it was a bad valve or a bad lifter it would be all the time, unless it was heat related, like your example, or a leaky head gasket or a leaky intake manifold gasket that might become prevalent the warmer the engine.

Come to think of it, the other day when this happened again, I ran the van pretty low on gas, close to E, usually pretty good about making sure I have about 5 gallons or so of gas in the van, maybe I should try to keep it above 1/4, had to make an unexpected trip out of town and the gas gauge slipped past me, when I pulled into the gas station noticed the rough idle, first thought was I was pulling air into the pump, it just didn't smooth out right away after filling, or however much 40 dollars gets you now a days, but it could have been a trapped air pocket in the fuel rail, I just automatically assumed it was related to the prior incident. As for the 3 week long rough idle several months back, a 3 week long air pocket ? Maybe, couldn't even begin to guess on that one. I am more inclined to think a ' floated valve ', if there is even such a thing, so long as she is running smooth now I guess I will be OK not knowing for sure. Other than the 3 week event 3 months ago, and the incident the other day, van has been running pretty smooth the last 6 months or so, ever since I installed the missing catalytic converter. I was going to post about this 3 week miss before the incident the other day, just didn't get around to it.

Or thing is for sure, figured I would try and save .80 per gallon running 89 octane, but she definitely seems to prefer the 92 or 93, so that is what I run. and I thought I ran 89 long enough for the computer to self adjust. Maybe something to do with the higher mileage.

As usual, thank you for your assistance.
 

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Discussion Starter · #6 ·
BTW, the code several months back was a P302. And the miss was more noticeable at idle, when I revved the engine the miss seemed to go away, but that could have just been my perception ..... Also, at idle, when I disconnected the plug wire to #2 cylinder, I could not notice a difference in the engine idle, rough, however, when I revved up the engine and disconnected the plug wire to #2 cylinder I could notice the miss, again this could have just been my perception.

Over the last summer, before I installed the missing catalytic converter, I was repeatedly getting a P301 and P302.

She has steadied out over the last many months, runs pretty smooth, not perfectly smooth, but not sure how much slack is in the timing chain or the condition of the 200,000+ mile catalytic converter.
 

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You shouldn't need to use premium fuel. I believe that the owners manual says 87 octane is acceptable.
What does it do on lower octane, ping?
 
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Discussion Starter · #8 · (Edited)
You shouldn't need to use premium fuel. I believe that the owners manual says 87 octane is acceptable.
What does it do on lower octane, ping?
Seems to run noticeably smoother using either 92 or 93, tried switching between the octanes a few times. My higher mileage '03 318 was the same, preferred 92 or 93, but my 50,000 mile '02 V6 seems to prefer 89. Wonder if it might have something to do with the valve timing from some slack in the timing chain, or something.
 

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One other thing that might be worth a check is a broken valve spring.
 
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I have seen broken valve springs on these. Usually they make a noise.
 

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I had a broken valve spring on the original TR4 head. I drove it for two years before I realized it was broken. It never came apart but it would spit fuel out the side draft carb onto the fender well when revving. At the time I had no idea why it did that sometimes, not always, so you never know, she never ran rough or lacked power. Thought it might have been the grind on the cam itself, and being solid lift and adjustable rockers, never could get it to stop, so didn't think too much of it.

Guy was walking by one day and saw the car, wanted to know if I wanted to sell any parts, asked if the number two valve spring was broken, so guess it was a common thing to happen. Go figure.
 

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"Valve float means the valve doesn't fully close at the proper time, because the return mechanism (usually a coil spring) isn't strong enough to close it. This usually happens at high RPM. It can damage an interference engine if the valves make contact with the top of the piston."
 

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Discussion Starter · #14 · (Edited)
"Valve float means the valve doesn't fully close at the proper time, because the return mechanism (usually a coil spring) isn't strong enough to close it. This usually happens at high RPM. It can damage an interference engine if the valves make contact with the top of the piston."
So there is such a thing as a floated valve ....

She is still back to running smooth again, has been for several months now (other than the 24 hour rough idle the other week, but that was probably an air pocket in the fuel rail from running low on gas) so I can't explain it. Pretty sure it was mechanical because everything else is new .... injectors, plugs, cap, rotor, and wires.

Only thing I can think of is that the engine may have been overheated previously and something may have slightly warped (valve, lifter), then settled back in place, then was hanging up again from the high RPMs, then settled back in place, however, a piece of carbon knocked loose and stuck under the valve, or a broken spring that settled back in place sounds just as, if not more, plausible I suppose. Still need to do a lot of other work to this van so it would be nice to be able to slide by without having to do any engine work anytime soon. Have no problem babying the engine for now, and the new radiator and 180 degree thermostat should help.

Think I am do for another oil change ( speedometer still broke, sigh ... been too cold to work on it ), when this first happened I went with this additive (1 quart) and Valvoline 10W30 conventional oil.

Bottle Liquid White Bottle cap Fluid



I usually try and avoid additives, but supposedly this is approved by automotive manufacturers, I was hesitant because it is really thick and going into winter I was concerned about cold start-ups, but then they say it sticks to the engine parts. The oil pressure gauge sure is significantly higher, imagine compensating for some engine wear, so thinking it might not be a bad idea going forward, anybody have any thoughts on this additive or running thicker oil in the warmer months ?
 

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Additives are snake oil. Stick with the recommended oil only. My last two Daytonas went 308K and 257K miles on the original engines, ran like new, no oil burning or leakage.
 

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Discussion Starter · #16 · (Edited)
Additives are snake oil. Stick with the recommended oil only. My last two Daytonas went 308K and 257K miles on the original engines, ran like new, no oil burning or leakage.
Normally I would agree, however I suspect the engine may not have been maintained as recommended over its lifetime so I think I may need to adapt.

The reason I tried the additive initially is because I suspected a possible weak lifter and figured this might help, however, with the noticeable increase in oil pressure reading on the gauge I think I might be well served to use an additive, or run thicker oil. The engine does not sound real loose, but not exactly tight either.
 

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Discussion Starter · #17 ·
It's back, before the transmission went out started with the intermittent miss again, but mostly missing, number 2 cylinder again. Could it be a weak lifter or spring ? I can't see it being a bad valve seat with it being intermittent, and it doesn't appear to be temperature related, at least according to the temperature gauge, but it did seem to come back with the warmer weather, but who knows.

Pretty much figured was more than likely on borrowed time with this engine as well as the transmission, bought the van unseen, kinda figured may have had an upper engine or transmission problem, especially a 1998 coming from down South with the heat.
 

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Possibly fuel pump sending bubbles into the rail? Needs diagnosis. Is the misfire because of a lean fuel mixture? Or low cylinder pressure?

Valve float is what happens at higher engine speeds when the valve spring is too weak to close the valve before it is time to open it again.
It may be a 'leaky' valve or seat.
Lean mixtures can burn exhaust valves.
 

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Discussion Starter · #19 · (Edited)
Possibly fuel pump sending bubbles into the rail? Needs diagnosis. Is the misfire because of a lean fuel mixture? Or low cylinder pressure?

Valve float is what happens at higher engine speeds when the valve spring is too weak to close the valve before it is time to open it again.
It may be a 'leaky' valve or seat.
Lean mixtures can burn exhaust valves.
I have no idea, started happening right before the transmission went out and didn't look into it much further. Sure would be nice if it was something as simple as bubbles in the fuel rail, how would you diagnose something like that ? I still have the brand new fuel pump I bought last fall that I never installed.

Noticed this though, about three weeks ago noticed a slight drop in oil pressure, used that Lucus oil stabilizer last oil change, and it noticeably raised the oil pressure, but because the speedometer is still broke not sure how many miles since the last oil change, but from my driving history not thinking more than 4 or 5 (probably should have fixed my speedometer instead of fixing the turn signal), anyhow, changed oil and used the Lucus again and the oil pressure came right back up, so I am thinking I must have some engine wear going on, somewhere, probably everywhere, it was after that the miss started to show up again, but I do not think those 2 things are necessarily connected, but I do think the engine must be right on the cusp, or slightly past losing clearances. I have really tried to baby this engine and transmission the last year.

That is why I was curious about the Chinook, when the transmission went out I was stuck on the other side of town, overheated the transmission a bit getting back home, figured it was spent anyhow so I wasn't worried about it, but then I noticed a steady oil drip from the housing, it was dark, as if it could be oil from the rear main, but then my mechanic friend said that is where the overflow is for the transmission, and it would be dark, so it could have been that. Anyhow, not sure how much I need to tear into this engine, thinking of maybe replacing the rod and main bearings, seal, while this is apart, or slightly afterwards, then maybe the lifters and springs if I need to, and hopefully get rid of this miss if that is the cause, of course not ideal because the crank and cam and cam bearings may have some slight wear, but if the valve seats and heads / head gaskets were still good and the rings held up might be able to squeeze another 50, 75 out of the engine, so it might be worth it ..... then there is that 47,000 mile engine where this transmission came from, that according to the guys at the boneyard, " ran excellent ", but then not really trying to swap an engine, but if I did, but then it is a '98, that I use as a work vehicle, so how long am I trying to keep this thing on the road ? .... everything would be so much simpler if Dodge didn't stop making the cargo van in '03.
 

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Does the #2 plug look any different than the others? If it’s running rich or lean that plug may look different.
 
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