2009 sonata V6 I get engine code for #6 cylinder misfire, Ive replaced the plug, the coil pack. It runs fine when its warmed up. Any other things I check/replace before I take it to repair shop?

Dear Earl,
You have not supplied me with the year, make, or model of the vehicle, but for the past (about 20) years, the most common answer to your problem in the USA would be a bad "coil pack".
This is usually a tall skinny plastic thing that makes the spark for the spark plug, and has a wire connection on the bottom to energize it.
The top of it has either a hole for the spark plug wire, or a wire that goes to the spark plug.
The number of coil packs are according to the number of cylinders/spark plugs in the engine. ( Usually 4 or 6.)
God bless your efforts.

Check Engine Light/Misfire Due to Intake Valve Locks ...

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Jeep Liberty Check Engine Light/Misfire Due to Intake Valve Locks/Valves. ...Misfire cyc 4 and random cyc misfires, changed coil packs and plugs... sounds as if rod ... Light came on again (misfire on cylinder 4) - switched coil from 4 to 2. Light ...

Jeep Liberty Questions - Cylinder Misfire code - CarGurus

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CarGurusMay 27, 2009 - #4 misfire new plugs and coil pack on #4 light came back on after 300 miles if ... How come it stopped misfiring for 2-3 months, and now is back? ... I have a 2005 Jeep Liberty 6 cylinder, engine light came on scaned the codes ...

Liberty Cylinder Misfire / Computer issue? - JeepForum.com

No, a plugged converter would cause the engine not to breathe properly. Too much back pressure would stall the engine or make it run very poorly. It would not be local to any one cylinder-all of them would be affected.

To diagnose a misfire in one cylinder, well, you start at that cylinder. It could be ignition related- the spark plug and spark plug wire for #6, possibly the ignition coil for #6 in the coil pack for the engine. (A v-6 would have 3 coils in the coil pack, one coil for 2 cylinders.) It could also be fuel related, so the fuel injector for cylinder 6 should be considered. And the last reason for a misfire is usually the most expensive repair: low compression in #6. This may be a head gasket problem, or a piston ring problem, or one of the valves for #6 may not be sealing well, causing low compression and the resultant misfire. The engine computer codes a misfire when it senses low power output from that particular cylinder. The misfire causes a lag in crankshaft rotation, and the crankshaft position sensor senses it.

wow, no engine option stated, and no DTCs.

4.0L I-6 or 4.7Liters?

WHY DO THAT FIRST. $$$$ parts first.

why not do a tune up first.

you swap in the most expensive parts first? ouch,

The PCM tells you when ckp or cmp fail, with DTC codes

so its not that. but you never posted ALL DTC errors. why not do that.?

do a real tuneup? heat (spark plugs, filters.)

if you have P030x errors,

eg: p0301 is cylinder #1 is misfiring (3 ways to do that not JUST spark)

eg: P0300, random on all cylinders. (fuel mix wrong) or never tuned up.



Misfire 101; (example P0301 DTC)

P030x codes, are all just about spark, misfire is caused by 3 things, (at least)

1: sure spark. weak. (tuneups work as does hV wires sets if no COPS) if 1 cop is bad move it to other location, does failure follow the move>???????? buy new cop boots if engine has cops.

COPS means coil over plug, so v6 has 6, v8 has 8.

coil packs have 3 coils inside for v6 and 4 for V8. called wasted spark to any tech.

2: low compression, think of your v6 (is it) as 6 engines, not 1.

3: wrong FUELING rates. including air leaks to 1 cylinder.

if engine has EGR that too, will cause gross misfiring.

so can an air leak near one intake runner, causing 1 cylinder to misfire.





why not scan it with a real scan tool that can see ALL jeep codes

then post all DTCs found. both idling and driving for 45mph or 1/2hr.

with these facts and what engine is there we can do the remaining tests.

free book



http://www.jeep4x4center.com/knowledge-base/index.htm?utm_source=cj#service







The tune up is this and filters.

do the tune up, new wires, and plugs using correct spark plugs not some bs, magic ones, use spec, plugs first. its in the manual.

then HV wire set on 4.0L,

if cops V8 , 4.7L try new boots on them. or swap them to find bad one.

the USA car V8 has coil on plugs





misfire means ONLY that this cylinder has weak COMBUSTION

its not weak spark only, that is only 1 cause of poor combustion.



post DTC\'s driving and we can fix it

the best tool is the

Innova 3160 scan tool, that is what I use on home cars.

it does all jeep codes, ALL.

i can drive , and scan and log DTCs.

and gather lots of facts on errors.

that is always the best way,

you can not fix cars today with out owning a scan tool.

unless , luckiest man on earth. (guessing)

Try swapping the coil packs around - like swap #1 with #2, and swap #6 with #5, see if the misfires MOVE with the coil packs swapped to the new cylinders or if they stay with the cylinders. If they move with the coil packs, the new coil packs are bad. If they stay with the cylinders, there's a problem with those cylinders. You DID replace that camshaft sensor, right?

Have you checked your #1 and #6 injectors?

Duplicate question

number 6 plug depends on what engine you have 6 cylinder or an 8 cylinder you need to be careful with that code it could be a plug , a plug wire , a coil pack . i had an issue with that code and it was the crankshaft sensor 38 dollars from an autoparts store dealer wanted 170.00 ! crank sensors have an adjustment on them a few thousands of an inch and yes it makes a difference ! hold it down while you tighten the bolt . hope this helps

It sounds like a misfire. Check spark plugs 5 and 6. It could be bad fuel, bad plug wire, or weak coil. Check the fuel injectors as well. Other possible causes could be an egr valve stuck open, vacuum leaks, low fuel pressure.

Replace the coil for number 3 cylinder.

P0306 is a misfire on cylinder number 6. The fact that you have oil on those plugs may or may not be causing it. The oil on the plugs is because of a leaking "internal" valve cover gasket. First thing I'd do is change the valve cover gaskets. Audi will murder you if you want them to do it (I've heard of people quoted $700 or more for this job). It's VERY easy to do. You can order the gaskets from www.ecstuning.com or www.purems.com for about $25 per side. I'd change them for sure, as they're a known issue on these cars.

Now, if your new plugs and changing the gaskets (and cleaning up of course) doesn't fix the misfire, you need to swap coil packs around and see where the code goes. The coil packs are the three parallel items on the top front center of the engine under the beauty cover. Trace the #6 wire back to see which coil pack it goes to. Then swap that pack with another pack, clear the codes, and fire up the car. See if the check engine light comes back and if so, scan the car to see what codes come up. If you still get P0306, then the failure didn't move, and the coil pack is not the issue (in your case, it's likely to be the wire, since you have new plugs and swapping coils didn't work). If the misfire moved to a different cylinder (one which is now hooked up to the coil pack that was originally firing the #6 cylinder) then that coil pack is bad and must be replaced (another known issue on the A4).