Cylinder 5 Misfire

Getting check engine code that says Cylinder 5 Misfire. I replaced the spark plug and ignition coil, then disconnected the battery for 10 minutes and reconnected it to clear the light. After 400 miles the light came back on.

1) Did disconnecting the battery really clear everything or is it possible I'm seeing it pop up again because I need someone with a touchscreen tool to clear it? Would it have passed during those 300 miles before the light came on?

2) I assume it won't pass an emissions test with this problem and therefore cannot pass inspection? Are there any other steps I can take besides just taking it to the shop?

 

Compression check

 

have you rescanned for codes? You are assuming that it is the same code, a P0305?
It will not pass smog with the CEL illuminated.
Yes, you sucessfully erased everything. If there is a local O'Reilly or AutoZone they will scan it for free hoping to sell you a part or 2. Dont buy the parts suggested, just get the code(s).

If it is a cyl 5 misfire again then do as suggested and get a compression test preformed on the motor. An even better idea would be a leak down test on cyl #5. This will tell you if it is something mechanical or not. If all of these tests pass, then she might need an injector, this is assuming that the wiring isnt damaged. Swaping an injector isnt that hard just a bit time consuming.

 

Thanks for the advice! Yes I re-scanned the code at an O'Reilly store when the light came on. I was planning on finishing the truck inspection that morning (needed to just pass the emissions test) but the shop was too busy that day so I was surprised when the light came back on later that afternnon. I'll do a compression test, hoping it's just the injector. Yikes. Truck has 240k miles on it. Would really like to make it to 500k. Just put on a ton of new parts...rotors, calipers, plugs, plug wires, ignition coil, fluid, etc.

 

it sounds like your daily driver... that is going to make what I suggest difficult. I have a few OBDII scanners and when I have to get a vehicle smogged I will clear the codes and complete the drive cycles and the moment the scanner says it is smog ready I drive it to the smog shop and park it overnight and I am the first one there in the AM. I usually do my smog driving after 10 PM when there arent many people on the road... going 45 mph on the freeway for 10 minutes will get you run off the freeway here in southern CA. Unless you are the most unlucky guy out there the CEL shouldn't pop while it is on the dyno... you didnt mention what year she is... if the smog is a non dyno smog, you should be golden. Now you have time to get her repaired and have the govt off you back and mind for another 2 years.

 

Thank you! It's a 2003 V6 3.4L. Maybe I'll pick up a OBDII scanner and give that a try. Are they all basically the same? I see some online for ~$35. I also was wondering, are a leak test and a compression test different tests?

$21 ANCEL AD310 Classic Enhanced Universal OBD II Scanner Car Engine Fault Code Reader CAN Diagnostic Scan Tool-Black

https://www.amazon.com/ANCEL-AD310-...obdii+scanner&qid=1556116286&s=gateway&sr=8-3

 

for a few dollars more $100 the blue driver scanner is very tough to beat. Other scanners have a high user frustration factor and are nothing more than toys in comparison.

Yes, a compression test and a leak down test are different. Both are tests used to determine the basic mechanical sealing ability of a cylinder. IMHO, the compression test is a go - no go test. All spark plugs are removed the compression tester is screwed into the spark plug hole, the throttle is open fully and the motor is cranked over and a reading is shown on the gage. All cylinders are compared and if there is more than a 10% difference in any of the cylinders further inspection is warranted. The weak point of the compression test is that the faster you spin the motor over the higher the compression so if the battery is not 100% the farther into the test could show lower readings and a misdiagnosis. You can acheive almost the same thing just by listening to the motor when it cranks over... crank crank crank then it speeds up, then crank crank crank.

The leak down test is where a special gage is screwed into the sparkplug hole and compressed air is put into that cylinder. The first gage, input air, is set at 100 psi and a reading is taken off the second gage, if the second gage shows 80 psi you have a 20% leakage. You take the oil filler cap off and listen to the sound there, you open the throttle and listen there, you listen at the exhaust pipe and figure which is loudest and that is where the leakage is, it could be all 3.

 

I’m having same issue with cylinder 5.
Quick breakdown:
Replaced fuel injector at cylinder 5 along with new plugs and wires. Mechanic said if same CEL code comes back(PO305) it would most likely be the coil pack.
One year to the day later I noticed some sluggishness under load, especially in 3rd and 4th gear. I discovered my muffler was split the entire length of the manufacturing seam. And that same day the CEL came back on with PO305. Replaced muffler then took to dealership to revisit repeated code.
The mechanic ruled out the plug, wires, and coil pack. He test drove it and did not notice the sluggishness uphill. The CEL did not come back on after test drive. Was told that if same code returns then he’d do a compression test and bore scope probe to check for head gasket leak and possible core crack. I drove it home easily from the dealership and did not notice any “skipping” for the 10 mile drive. No rough idling(yet). No overheating has occurred.
I am running through coolant but my heater control valve has a noticeable leak.
There is a lot of white smoke on cold mornings but smells like “normal” exhaust. I have not checked the inside of the oil cap bc I just read about that today.

I did read somewhere that this split muffler could cause a misfire. Is I it at all possible that the muffler issue would have tripped the last code the computer had noted last year?
I expect to see the CEL back soon and am concerned with the worst case scenario of an engine swap. I’m on board for having head gasket repairs bc I do not want to give up on this truck I’ve had for 18 years. An engine swap may not be possible for me, unfortunately. Got me a bit concerned.

Any thoughts or similar experiences would be appreciated.

 

There are a few possibilities.

First question is, What brand fuel injector did you replace it with?

Also, “white colored smoke” isn’t really a concern depending on the outside air humidity and temperature. It may very well be steam.

Also, the inside of the oil cap doesn’t mean much.
Short trips and not allowing the engine to run at full temperature long enough can cause condensation in/on the oil cap.

I’d address the leaking heater valve.
Then monitor the coolant level. If it continues to drop, you have a problem.
If the light hasn’t come back on, I’d drive it until it does or I feel the engine has a problem.

 

You most likely have a head gasket leaking. the HG leak is not severe enough to have other symptoms, but it will not get better on its own. To really pin point it, get an oil analysis done. That will show if it is leaking for sure. A good place to go is Blackstone Labs.

A HG Replacement is not terribly hard, just labor intensive. Make sure you send the heads to a machine shop and get the valves ground, seats checked, etc.

 

https://www.blackstone-labs.com/?se...abs.net/Bstone/(S(djifml452fwqep55pzzk4e45))/

 

Thanks for the quick feedback. Going to drive it easy close to home for awhile until light comes back on then go from there. Hoping that the “worst” outcome will be HG replacement

@TnShooter: dealership did fuel injector, so OEM(?) Ordering heater control valve to take care of that issue.

@JudoJohn: thanks for the link for the oil analysis. I will definitely do that.

 

While an oil analysis (UOA) can be beneficial, it doesn’t diagnose a problem.
It can indicate a problem.

You will benefit more form doing UOA multiple times.
You establish a “baseline”, then monitor changes from there.

There is more than one way coolant can enter the crankcase.
Yes, the majority of those it is a head gasket. But not always.

My point is, We know there is a problem.
If you are having a mechanic do the work.
He’s SHOULD still diagnose the issue the proper way.
He’s not going to rely on the UOA alone.

If you are doing the work. You should still do a compression and leak down test.
I’d probably start be doing an exhaust gas contaminant test of the cooling system.

Basically, the cost of the UOA isn’t going to benefit you financially in this situation.
You’d be better off applying the price of the UOA to the repair bill of the current problem.


No disrespect to you at all @JudoJohn
I agree, UOA are a good thing. But they are far better for telling you the state of your engine based on a an established baseline.

Yes, they will indicate higher/lower levels of a single analysis.
But you’ll still need to find the problem.

I am just try to help the OP save all the money he can.
If it is indeed the HG, it’s going to be expensive and/or labor intensive.

Again @JudoJohn, I’m not saying your advice wrong.
I’m just saying, I don’t think it will help OP in the long run with this problem.

 

One other thing related to above:
I just read that the 3.4L V6 engine is known for intake manifold gasket leaks that could cause a misfire just as a leaking HG can.
What I read said they are made of plastic and typically fail between 50,000 and 80,000. I’m at 224K with original. Could this also cause a cylinder specific misfire? I imagine this should be replaced at same time as HG even if it is intact?

Thanks for the feedback. I don’t work on my truck but like to have as much information and understanding before I take it in for repairs.

 

Yes, they would have to be replaced at the HG change. That could also be your culprit. It could be a bit of all three.

 

IMHO, the OA is another diagnostic tool. They don't cost very much. I had a Nissan Sentra that was prone to HG failure. I used OA to see how much of whatever chemical (I don't recall exactly, but perhaps silica) would get to a certain level, so I would know it was time to replace the HG before it totally blew. In that case, it would leak ever so slightly into the cylinder, so the coolant was burned, and did not enter the oil system and give you the typical "milkshake".

 

I did not read all the posts , so if this has been covered i apologize. I have a 99 that i chased the same #5 miss. After replacing coils and plugs and coils again.........i thought theres no way its the plug wires because they were only 2 years old. Bam thats what it was.

 

I read through 90% of this. I have had a cylinder 6 misfire that was hard to chase down. Here is the order of diagnostics from free to cheap to expensive vs. Labor time and intensity of doing testing.

Swap coil pack from cylinder 5 to another cylinder. Disconnect battery to clear codes the see if code comes back and follows the coil to new cylinder. I would swap it to cylinder 1. This is because a HG leak isnt off the table yet and cylinder 3 is adjacent to 5 so if it moves to 3 with coil swap you may replace coil and issue still present cause it was really a sneaky HG leak. Swapping to cyl. 1 avoids this. If the mis dosent follow the coil then it's not your coil pack.

Plugs and wires. They are cheap and like others stated "young" wires and plugs still fail.

Compression test . You can buy decent ones ( I like otc brand) for 30 bucks. If cylinder 5 has more then a 10% difference in compression from all your other cylinders move to leak down to figure out where the compression loss is going.

Leak down will require an air compressor ( hopefully you have one so you don't need to pay a shop) I picked up my OTC leak down tester for 50 bucks. Tdc number 5 cylinder and run the test. Watch to see if it holds. Pressure. If it doesnt listen at exhaust pipe, throttle body plate, and open radiator ( while cool and running test obviously). If your leaking at throttle body you have an intake valve burnt or out of spec ( possibly intake gasket but those are harder to hear and smoke test should be run to verify). If leaking at exhaust it's an exhaust valve out of spec or burnt ( exhaust manifold gasket leak would be hard to hear as well and smoke test will also verify this). Bubbles in the radiator tell you HG leak. Usually HG leak will show the adjacent cylinder also not holding compression during compression test. So in your case both 5 and 3 would be low compared to other cylinders.

So if cylinder 3 is low on compression test I'd start expecting all other tests to point to HG.

If you still aren't sure. Smoke test. Actual smoke tests can be expensive. I personally use a cheap 10 dollar 30 watt soldering iron in a mason jar with mineral oil soaked rag and fashion up a tube system to feed into my motors vacuum system and the let it do it's thing and trace where smoke comes from. This will tell you if gaskets, manifolds, or vacuum leaks are your culprit. The down side is if it's the intake manifold the 5vz intake manifold is centered over the engine hidden under the plenum and hard to see. Good news is if you pull your intake ( might have to open throttle to keep engine running during test ) you should be able to see the intake manifold near cylinders 3 and 5.

You've already swapped an OEM fuel injector in so I didn't address that in the line up since it would now be low on my list of culprits.

If all tests don't tell you anything. Start checking wires. This is ridiculous. But only takes an hom meter. Check coil and injector wires at the connectors which is the most common place to see tear or frays in wires. The proceed ohm and resistance testing wires at connector. Throw a node light in the mix since they are cheap too. If these test good then test using alligator clamps on ohm meter or node light back at wires feeding into ecu. This is where wire testing is rediculous and tedious.

If by then you haven't found an issue...either you tested wrong somewhere or I'm at a loss.

All in all the entire testing equipment used above for all tests cost about $120 ( again assuming you already own a compressor). A mechanic in my area will average $100 bucks an hour plus test cost. So for one hour of a mechanic trying to figure it out you could have all the test equipment to do this on your own.

Hope this helps...

 

Very nice informative and well explained post