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engine miss firing after plug and wire change... please help

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Jun 16, 2016, 6:27 PM

Post #1 of 3 (826 views)
engine miss firing after plug and wire change... please help Sign In

I have an 04 Hyundai xg350.3.5l 6 cyl. 160k miles. Need to get it registered and can't do so without it passing an inspection. I've had this car for a year and it's always drove great. I have a check engine light so I take it over to autozone have them do their test. He tells me I have a small emission leak, something about gas cap... but cap seems fine. I figured I'd change the wires just as regular maintenance,also in hopes of squashing that check engine light. First of all I changed the spark plugs i'd say about half a year ago. didn't mess with the wires at that time. So I get from autozone a duralast wireset for my vehicle, since they had them in stock and didn't feel like waiting for a package. At that time they didn't mention it's required to have the duralast ignition coil boots with it. Also in my mind I was like nahhh to getting new coils and figured itd still be good with the old ones. After the first wire change car misfired. I double, triple, even quad checked the make sure I have the wires in the correct order. After that I was think why the heck would it do that. so I did the process again and put my old plug wires back on. Still misfiring....... So i'm thinking like what the heck is going on. Today I went back to autozone and told them about it thinking I might have the wrong wires for my car...and they said oh you need the required coil packs for those wires. So I just say screw it and buy all new spark plugs ( bosh double plat or whatever) got those coils I needed for that wireset. i do the whole job today those wires, igniton coils, and plugs. still misfiring...... WHy the heck is this such a pain in the butt? Swear it takes 2+ hours for the job because i have to get the intake out before i can reach the plugs. Have had to take that intake off 4 times in the past couple weeks.
Anyways, uhhh the firing order autozone gives me is

rear of car
front of car
2-5 1-4 3-6
that's correct right?

Guys any help would be appreciated been out of a car for 2 weeks because of it. car functioned fine intil i put those new wire sets.
Really angry because i feel like it shouldn't be this difficult to change some plugs and wires.

Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Jun 17, 2016, 2:19 AM

Post #2 of 3 (817 views)
Re: engine miss firing after plug and wire change... please help Sign In

This could be more trouble than you had now.
First: Parts outlets, Autozone included are there to sell parts and not necessarily know "Jack" about more than what their system tells you what fits at all not what is right, really needed, best or mandatory. Their "free" code readings are nice of them but you really should just want the code not what it tells them to sell you.

By now another code reading is going to be wrong as it's misfiring so more would show than whatever emissions code it had now lost info and yes just a fuel cap can set a code not tell you to replace a part (gas cap) but on the list - could just be loose, leak in a neck or hose?
OK - So you take an engine that was running fine and now doesn't after replacing wires and then installing the wrong spark plugs as this should without looking insist on having NGK OE spark plugs only. Their own site list the Bosch plug you mentioned as OE and can't verify that on my own but possible? What came out - brand and part #?

Now it would be important to know what the plugs you took out looked like and from which cylinder they came from. This and wires you do ONE at a time so there's no chance to lose firing order and even with multiple checks could have that messed up. Their site shows what you posted for firing order and positions but also said this has a distributor so mentioned it turns clockwise. It may be incorrect info - the best reason to leave no chance to mix it up from when it was known correct to begin with.

So, know that all the things done to even get at this stuff is work and you disturb numerous things plus just handling high voltage (secondary ignition items) new, in transporting, removal and installation they are sensitive to being handled at all.

This has all been touched by you - the old now new back to old partly to solve a problem it didn't have till you touched it so just common sense says you need to test everything you touched and still have whatever issue causing an emissions code to find when it isn't miss firing.

A bit lost for you where to start now. I think I'd be plain looking for a stray spark arcing if you can see it at all new or old parts now in it. Re- verify your firing order thru another means if any chance that's wrong if it takes buying the software for this specific car and engine. Another here may verify with other than info I found which you may be going by that is notoriously wrong.

That's it - recheck everything you touched. It didn't have this problem before so that's the clue to work with for now,


kev2 profile image

Jun 17, 2016, 6:27 AM

Post #3 of 3 (810 views)
Re: engine miss firing after plug and wire change... please help Sign In

first the firing order you posted is correct. the cylinder pairs are also correct.
Start with a scan - get the codes and post them someone will advise... do not purchase anything until diagnosed.
then as colleague posted double check your work - bosch is NOT a recommended brand.

"WHy the heck is this such a pain in the butt?" no longer DIYer friendly.

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