Cylinder 4 misfire - Ranger-Forums - The Ultimate Ford Ranger Resource


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  #1  
Old 09-12-2016
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Cylinder 4 misfire

Refreshed this engine with new seals and gaskets. Engine came from an 01 and has the longer head bolts and the x webbing on the side of the block.

I've driven It about 80 miles since the refresh.

The other day I took it out for a short run. It started missing at idle on start up.
Drove fine the day before when I shut it down.

Came back and switched out the #4 and #6 plug wires.
Truck ran fine.

Came back out 2 days later and it was missing again at the #4.
Switched wires again and it didn't help.

.........diagnosis so far.

SPARK:
Plugs are new

I checked the plugs by unplugging all the wires except #4
So the truck wouldn't fire up......#4 was getting spark.

Checked the #4 plug.....by putting it in the #1 wire. It is Getting spark

Put the #4 wire on the #1 port. It got spark

Looked at the plug.....slightly rich. But not bad...still white.

COMPRESSION:
New head gaskets
New intake gaskets
Torqued to spec
Cylinders looked fine with original cross hatch.
My guess would be a 90-100k engine
With the plug out and the truck running it seemed to be getting compression from the sound.

Heads looked fine upon visual inspection
Engine came out of a low miles wrecked truck.

New air filter
EGR cleaned out when the intake was off. It was clogged up
Just replaced the o2 sensor on hat bank as well
No compression check has officially been done yet. Have no sprayed carb cleaner to check for intake leaks yet.

FUEL:
New filter
New gas

Truck sat for 1.5 years.
Fuel system was not replaced
Injector o rings are new and seated well.

The truck also ran fine until this.

Miss is a solid miss at idle.

What's going on here. Is it an intermittent problem with spark?
If fuel was clogged why would it run fine for that long?
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Old 09-12-2016
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Have gotten a bad plug before, swap it to another cylinder, and see if misfire follows the plug
If it stays at #4 then do compression check first, 4, 5 and 6, compression is black and white, so once it is off the table you can look at fuel and spark
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Old 09-12-2016
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Bought a spark tester and put the plug on the intake manifold. The spark look top notch on all the cylinders. I watched the tester signal and the blue flame at the plug.

However......the strange part.
I just got back from doing a compression test on cylinder #4 and #5

Both are showing 80psi. When I rev the engine it goes to 120psi on both cylinders.

These are the only two I've done so far. How could 2 cylinders lose that much pressure suddenly without blowing a head gasket or cracking a head. Wasn't overheated. Head gaskets are new. I'm going to test them all for spark and compression.
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Old 09-12-2016
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I'm on the 4th cylinder.
It's also 80

How would the truck even run well with 4 cylinders at 80?
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Old 09-12-2016
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So I checked all the cylinders.

While doing spark checks.....I had an ignition tester and an extra plug to test the ignition system. All 6 looked excellent.

All cylinders with the autozone gauge show at 80 across all 6 at idle.
I think he gauge is the problem.

So when I was done and all the plug wires were back on and the spark plugs were back in. The truck runs fine.

What......is causing this mess?
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Old 09-12-2016
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Turned the truck off. Let it sit a while.

Turned it back on.....cylinder 4 is misfiring

Long term fuel trim bank 2 is at 20 at idle
When the engine is reved up it goes back to normal
Short term is bouncing around -10 when reved up it goes back to normal

But a vac leak causing 1 cylinder to go bad?

So I'm running really rich on the short term and really lean on the long term and really rich on the short term

Last edited by Glhx; 09-12-2016 at 05:21 PM.
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  #7  
Old 09-12-2016
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Turned trick off and let it sit. Turned it back on and the problem went away again
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Old 09-13-2016
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Still haven't solved this.
Im pretty sure the fuel trims show a solid vacuum leak at idle on bank 2
The short term trims are running on the rich side maybe to pull the long term trims back into a normal range.

I'm looking at a smoke test at this point.

However. There's very loiter vacuum lines on this engine. There are some vac solenoids to check and the pcv system.....which the valve is new.

Dpfe lines
Breather separator
Egr
Brake booster
And 2 other small ones.

To have a trim of 23 at idle on one side is a huge vacuum leak
Or........a huge amount of extra air injected into s solenoid
Or........a clogged injector with absence of fuel leaves more air.

Even though the cylinder misfire is going away. The lean mixture causing problems is not.
As I recall it up the lean mix goes away meaning I've isolated just idle
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  #9  
Old 09-13-2016
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Can't find a vacuum leak anywhere

Last edited by Glhx; 09-13-2016 at 03:25 PM.
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  #10  
Old 09-16-2016
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Not getting much feedback here from the ford forum. I went to the bmw forum where they do a lot of advanced diagnostic work and was able to methodically isolate some problems using fuel trims and getting theroy on performance from them.

So I'll post what ive found

...............Cylinder compression test
I got 80 because I didn't do the test thorough enough. Since I got 80 on all of them I was sure it was fine.....I went in to a more time consuming, accurate, and advanced test.
Removed all plugs
Opened throttle body and propped it open so cylinders can see all the air it could.
Each cylinder ran 170....this is a spec to go by. What's more important is that they were all consistent. If you read 150 and they are consistent your probably fine. If you read 5 150psi and 1 100 psi you might have a problem. I visually inspected all of this before putting it together.

This tells me I'm getting a good seal on compression
This tells me the intake valve is opening and letting air in. Spring not broken
Tells me I don't have a recessed or burned valve. You have to pay attention to air, spark, and fuel........and timing



.............changing plug wires around .....and plugs around
Changing plugs around.......see if the problem follows to the next cylinder
Problem stays the same.
Dead miss on cylinder 4

........Wet tested coil pack in pitch dark to see if any spark escaped.
Coil pack and plug wires as well as plugs not arcing at all.
If the spark isn't contained in the devices they travel in it will go anywhere. Then won't fire the plug. My spark is working well. Has to be pitch dark to se spark escape

..........bought an extra plug to visually check the spark. Layed plug on intake and watched it spark strongly.

.........even though the egr doesn't work at idle I checked it anyway. For clog and vacuum.
I applied vacuum to open the valve....the egr opened and let air in. Made it super lean and stalled the truck. This means it's working. What I was trying to do is see if it was stuck open and making a lean mixture as my fuel trims were stupid lean on bank 2.....however. THe egr feeds all cylinders. It goes into the center of the intake next to the throttle body. It would have made bank 1 and 2 lean. What I found though was that the egr diaphragm was weak. It's working fine for now and will for a while. The diaphragm would not hold vacuum. It very slowly leaked down. With constant engine vacuum on there it will be fine but it's not ideal. What I found........clean your egr out once in a while. Mi e was clogged solid before I dropped in this refreshed engine. Easy to clean and get to.

..........checked all the plugs....all of them were fine. Even #4
No fouling at all. Plugs were clean. This tells me it's not fouling out from too much gas. So why is that?

It's sparking.....it's got compression. It's getting air. It's timed right.
Maybe it's not getting gas!!!!!! To that cylinder.

Maybe it's pulling outside air into the new intake gasket I put on there and making that cylinder run lean....
Sprayed carb cleaner in that area with little spikes of spray. This should make the idle go up......it didn't. Intake is sealed well. New gaskets anyway so it should be fine.

........noid light.
Was able to disconnect the injector plug without taking the intake off.
Getting good signal from computer. Rented noid lights from autozone.

So what's the deal here?
I finally decided to remove the upper intake and switch the injectors around.

//////There is a better way to do this with an injector pulse device.
/////Hot wire fuel pump......go in through the harness at the computer injector ////and plug in and pulse the injector you can't get to. Use a pressure gauge and ////see if fuel pressure drops. Your basically hot wiring the injector to fire like it normally does and the fuel pump to watch the pressure drop. Scannerdanner on you tube has great diagnostic videos.

Our upper intake is to easy to take off to mess with all of that. But on some cars you really can't get to injectors. This is how you do that. Plus ohming out injectors tells you electrical.... the method above tells you electrical, clog, and mechanical. My way is ohming out electrical and switching injectors around to see if mechanical is the problem. You can ohm injector 4 without removing intake. But not 5 and 6

Decided to do an ohm test first on the injector
Each injector showed 14.7 ohms.......except #4.
#4 showed open circuit.....a break in the injector coil.
I switched all injectors around anyway to see if 4 would fire with the injector from #6 testing flow. My injector also broke the tip off so I couldn't put it back in to see how bad it was.

..........injector
Knowing the resistance was bad. I decided to go to the junk yard to find a good one. I did an ohm test and found one that was good. It was from a 99 3.0 ranger........and......it was useless. Because it was gray top

..........injector color.
3.0 out of a 99 ranger with gray injectors. Mine are green......damnit it's a flex fuel engine. They all were in the junk yard...... Flex fuel flows more gas and would run rich.. Can't use a gray injector, has to be green.
So I'm going to another yard tomorrow to find a green one. To late....but a Mazda might have had the injector I needed. I did not check that section of the yard.

I'm pretty sure I have a bad injector at this point. Now I have to put the intake back on and bolt it all together..




Power steering after market pump goes on tomorrow as well. The first one was loud and very whiny. Way more than normal. So I got another and hope for the best. The aftermarket pumps are junk.....I'm trying the second one. If it's bad as well I will just throw a bearing on the original factory one. It's actually very quiet because of some additive I put in there. Just has bearing noise.

So for all who read this.....I hope it helps.
. I thank ronD for his feedback And will report back if that was in fact the case.

Something I see very little of....final solutions being reported back....
.it's vey selfish and rude not to......If you figure it out....post back and hep out others.

Ps.......when someone tells you to change coil pack, plugs, wires and all this other stuff. Test it first. Don't throw parts at it hoping your right. There's enough you tube Info for people with no mechanical ability to do all of this stuff. Autozone and other parts houses rent the tools out you need for free.
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Old 09-16-2016
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Good write up, nice work.

Yes, if injector was out of Ford's 11 to 18 ohm range then that is at least one problem found.

An O2 sensor reads Oxygen levels in the exhaust
Too much Oxygen is Lean so computer adds more fuel, + fuel trims
Too little oxygen is Rich, so computer adds less fuel, - fuel trims

A mis-fire means no Oxygen was burned/used up with the fuel, so all that oxygen is dumped into the exhaust, since O2 doesn't see unburnt fuel only Oxygen it reports too much oxygen, so Lean and computer adds more fuel to that bank, fuel trims go higher into + trims.
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Old 09-18-2016
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You summed it up.
Also looking back....if you have a misfire on one bank like that it is probably a fuel problem with those numbers. I should have thought that out sooner.
I maxed out the trim...at 25 .....it takes a lot of extra air to do that.
One other fact here is that all the air was metered by the maf sensor.
What would that affect.....?
Really.....all there is would be cracked runner, bad gasket, bad injector to make only one bank lean. A larger central vac leak would make them all lean. I'm surprised I didn't get a single injector code. But I didn't.

For others.....the way a misfire code works is by crankshaft velocity. All cylinders will be balanced rotationally speaking. Same speed.
When on misfires the cylinder that's misfiring wil be slower. It has a different velocity. THe senors speed meter will see that and create a code for single cylinder misfire because that cylinder is slower than the rest.


It was in fact the #4 injector causing the misfire. Replaced it with a used one from pull apart.

Found lots of flex fuel again and looked at about 50 trucks. Only one had the green injectors.
F87E B2A

Truck runs really well now.
If it wasnt the fuel injector causing the problem I was going into wire harness testing or pcm.

Also.....these injectors ohmed out at 14.5-14.7 consistently. If I saw anything outside of say 14-15 ohms I would replace it even though 16 is in spec and 12 is as well. I would replace it just to be safe..

No parts were thrown at this diagnosis.
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Old 09-18-2016
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MAF sensor data is the "floating" 0 fuel trim.

Computer uses MAF sensor data to set the 14.7:1 air:fuel ratio calculation, and that becomes 0 fuel trim, obviously that 0 changes with RPMs, so it is a floating 0.

O2 sensor then reports oxygen levels after that 0 fuel trim air:fuel is burned
If too much oxygen(lean) computer changes to +1 fuel trim, thats +1 above the floating 0 what ever it might be at that time.
If too little oxygen(rich) then computer changes to -1 fuel trim.

Fuel trim is actually open time/dwell time for the fuel injectors measured in milliseconds
So if 0 fuel trim is .100milliseconds, +1 fuel trim might be .110milliseconds
If at higher RPMs, 0 might be .300milliseconds, and +1 .330milliseconds
All this very very easy for even a basic computer to do on the fly.

When fuel trim numbers get too far away from 0 the computer will notify driver with CEL and code number.
Long term fuel trims are used for cold starts or if there are other problems.
Over time fuel pressure will change, compression will be less, there will be small vacuum leaks, ect....just general wear and tear as vehicle ages.
Instead of having to relearn this every time computer starts up long term fuel trims are stored in memory, these are used to "off-set" 0 fuel trim computer calculates at startup.

Long term fuel trims can not be cleared with most scanners, need special scanners to clear them, and for good reason, lol.
So if you get long term fuel trim codes and then fix the problem you may still get those same codes for the next few weeks until engines short term fuel trims can slowly change the long term trims stored in computer memory
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