2007 Kia Grand Carnival 3.8 VQ Auto Misfire P0300 and P0302

1331 Views 54 Replies 6 Participants Last post by bopbo, 4 d ago

axtigin36

Discussion Starter · 2 mo ago

Hi all,
Hoping someone can help.
I'm having issues with my car, its only been with me for a month. Its got less than 200,000kms on it.
Recently while driving, the car started misfiring and trouble codes P0300 and P0302 came up.

I tried checking it myself by replacing the spark plugs and moving the injectors and coils around.
The P0300 and P0302 code stayed on after swapping coils, injectors and plugs around.
I replaced the fuel pump and no change.
Brought it to a mechanic nearby who blamed the leaking valve covers and replaced it.
After replacement, misfire stayed and codes are still the same.
We have plans this Easter but looks like we wont be going.
Thinking about bringing it to Kia due to Easter coming up, they are fully booked until mid April.
Any suggestions or ideas would help.

Thanks in advance.

1 - 20 of 55 Posts

leo42.2875

· #2 · 2 mo ago

You need to diagnose not change parts or a mechanic that guesses, that just cost you $$$

You indicate a miss fire on #2, that could be spark, fuel and mechanical..

axtigin36

Discussion Starter · #3 · 2 mo ago

leo42.2875 said:
You need to diagnose not change parts or a mechanic that guesses, that just cost you $$$

You indicate a miss fire on #2, that could be spark, fuel and mechanical..

Hi leo,

yes, that is correct. as for my previous investigation stated above, i replaced the plugs as im sure it hasnt been done before and swapped the coils around. that told me that there is nothing wrong with the coils and plugs and injectors. i also tested coil number 2 with a spark plug installed to visually check for spark and there was.
Today, i tried to run new wiring for the injector and coil up to the main wiring harness going to the battery side. this still did not fix the issue.

i brought it to the mechanic as i was expecting a more intensive fault finding they did perform a compression test and it showed that all cylinders were close to each other. they had the car for 3 days until they gave up.
I'm planning to bring it to Kia as they probably know more about it than any other mechanic or me.

any other suggestions are welcome.

leo42.2875

· #4 · 2 mo ago

You need to get a scope on the vehicle, and drill down on the issue.

A diagnostician would be preferable over a mechanic..

Rob22315

· #5 · 2 mo ago

axtigin36 said:
Hi all,
Hoping someone can help.
I'm having issues with my car, its only been with me for a month. Its got less than 200,000kms on it.
Recently while driving, the car started misfiring and trouble codes P0300 and P0302 came up.

I tried checking it myself by replacing the spark plugs and moving the injectors and coils around.
The P0300 and P0302 code stayed on after swapping coils, injectors and plugs around.
I replaced the fuel pump and no change.
Brought it to a mechanic nearby who blamed the leaking valve covers and replaced it.
After replacement, misfire stayed and codes are still the same.
We have plans this Easter but looks like we wont be going.
Thinking about bringing it to Kia due to Easter coming up, they are fully booked until mid April.
Any suggestions or ideas would help.

Thanks in advance.

Those valve cover gaskets leak quite often. The front leak tends to destroy alternators. It won’t solve your misfire problem but it wasn’t a waste of money.

Rob22315

· #6 · 2 mo ago

axtigin36 said:
Hi leo,

yes, that is correct. as for my previous investigation stated above, i replaced the plugs as im sure it hasnt been done before and swapped the coils around. that told me that there is nothing wrong with the coils and plugs and injectors. i also tested coil number 2 with a spark plug installed to visually check for spark and there was.
Today, i tried to run new wiring for the injector and coil up to the main wiring harness going to the battery side. this still did not fix the issue.

i brought it to the mechanic as i was expecting a more intensive fault finding they did perform a compression test and it showed that all cylinders were close to each other. they had the car for 3 days until they gave up.
I'm planning to bring it to Kia as they probably know more about it than any other mechanic or me.

any other suggestions are welcome.

Did you clear the codes before swapping? Just double checking the obvious.

Trackerrrr

· #7 · 2 mo ago

Have your mechanic do a relative compression test with a scope. You may have a valve hanging open on the offending cylinder.

axtigin36

Discussion Starter · #8 · 2 mo ago

leo42.2875 said:
You need to get a scope on the vehicle, and drill down on the issue.

A diagnostician would be preferable over a mechanic..

Thanks Leo. Ive checked the car over for blown fuses and cabling that could have been melted or shorting. so far nothing so its booked with Kia and wont be looked at til the 19th of April.

axtigin36

Discussion Starter · #9 · 2 mo ago

Rob22315 said:
Those valve cover gaskets leak quite often. The front leak tends to destroy alternators. It won’t solve your misfire problem but it wasn’t a waste of money.

Yes, I knew it wont. It was leaking quite badly so i just had it replaced to save the alternator. Cant DIY anything at the moment because of a broken hand. It was also a good test for that workshop, atleast I know I wont be coming back there in case of emergencies.

Reactions: 1

axtigin36

Discussion Starter · #10 · 2 mo ago

Rob22315 said:
Did you clear the codes before swapping? Just double checking the obvious.

Yep, cleared the codes before hand and the battery removed. Still no luck.

Reactions: 1

axtigin36

Discussion Starter · #11 · 2 mo ago

Trackerrrr said:
Have your mechanic do a relative compression test with a scope. You may have a valve hanging open on the offending cylinder.

Ive gone and booked it with a Kia dealership, I will ask them to check that as well. Hopefully if there are any ECU updates, they can perform that as well.

axtigin36

Discussion Starter · #12 · 2 mo ago

So today, just removed the Bank2 valve cover to inspect if the valves are stuck. So far all intake valves and exhaust at bank 2 are moving and not getting stuck open. So good to know that this engine doesnt need valve clearances. I will try to remove the intake tomorrow and check and clean those OCV.

Does anyone recommend an engine flush for these? Never used one as I just change the oil more frequently in my other car if I see the engine dirty. The inside has some sludge and varnish. This has only got 190,000kms and the service history is on point. What could cause the sludge?

leo42.2875

· #13 · 2 mo ago

axtigin36 said:
The inside has some sludge and varnish. This has only got 190,000kms and the service history is on point. What could cause the sludge?

Short drives, not long enough to burn of any moisure contamination and too long between oil changes.

ron1004

· #14 · 2 mo ago

axtigin36 said:
I'm having issues with my car, its only been with me for a month. Its got less than 200,000kms on it.

axtigin36 said:
The inside has some sludge and varnish. This has only got 190,000kms and the service history is on point. What could cause the sludge?

What makes you so confident that the service history is good, considering you've not had it long?

Thinking about bringing it to Kia due to Easter coming up, they are fully booked until mid April.

That would be a wise move seeing as the "mechanic" you've been using lacks diagnostic skills.

Sludge with varnish is an indication that low grade oil was used and extended operation between oil changes.
If it was sludge only it could be a result of the engine never reaching the correct operating temperature.

There's high risks doing an engine flush, but you might make the call on doing so based on "what you got to lose".
If a flush chemical is used you would need to do very frequent oil and oil filter changes until its clean.

blog.amsoil.com

Engine Flush: Is It Good or Bad for Your Engine? (Plus See How To Do It)

An engine flush will improve engine performance in most cases, but you may want to skip it with old, high-mileage engines. Find out more here.

blog.amsoil.com

If you suspect your vehicle falls into this camp, leave well enough alone and skip the engine flush.
It’s probably not worth trying to revive an engine in such poor condition without first fixing the bad seals or other defects.
In effect, you’re choosing your problem: either sludge and deposits robbing performance or, if you clean the engine, the seals showing their true condition.

axtigin36

Discussion Starter · #15 · 2 mo ago

ron1004 said:
What makes you so confident that the service history is good, considering you've not had it long?

That would be a wise move seeing as the "mechanic" you've been using lacks diagnostic skills.

Sludge with varnish is an indication that low grade oil was used and extended operation between oil changes.
If it was sludge only it could be a result of the engine never reaching the correct operating temperature.

There's high risks doing an engine flush, but you might make the call on doing so based on "what you got to lose".
If a flush chemical is used you would need to do very frequent oil and oil filter changes until its clean.

Engine Flush: Is It Good or Bad for Your Engine? (Plus See How To Do It)

An engine flush will improve engine performance in most cases, but you may want to skip it with old, high-mileage engines. Find out more here.

blog.amsoil.com

Yeah, im actually thinking i shouldnt trust the service history by the dealer as i have experienced it with a company car where they tell you they did all those things but in reality, they didnt.

It was recommended by the locals and the easiest for me to access plus they had pretty good google reviews so I gave them a shot.

Regarding the oil flush, I've only done it once with a high mileage engine and the valve seals started leaking. Could be because the sludge was actually blocking the oil leaks or just a coincidence.
Im going to opt out this time for now.

I'll post an update tomorrow.

Hope everyone had a good Easter weekend.

axtigin36

Discussion Starter · #16 · 2 mo ago

Update..
1. Removed the intake today.
2. Checked all spark plugs from Bank 1.
3. Checked both OCVs. (OCV from Bank 2 is missing the filter!!!! Looked in the hole and obviously its not there.
Where can it go? Can this be the cause of misfire at Cylinder2?

Put everything back together and the misfire is still there at cylinder 2 and the P0300.
Im close to buying a used wiring loom to eliminate wiring as the cause.

can this be a faulty ECU?

thanks all!

hope everyone had a great weekend.

See less See more

leo42.2875

· #17 · 2 mo ago

Done replace the harness until proven faulty.. Do you have the experience and equipment to start tests at the ECU

bopbo

· #18 · 2 mo ago

The missing filter may have been removed to fix the problem of the filter falling apart and lodging in the valve, the fact it is missing is a minor concern, but would not cause misfiring only. If the valve had a problem you would gat a CVVT correlation code as well as misfire on the whole bank.
Have you checked the compression on that bank?

axtigin36

Discussion Starter · #19 · 2 mo ago

leo42.2875 said:
Done replace the harness until proven faulty.. Do you have the experience and equipment to start tests at the ECU

Hi Leo,
Noted. When I jumpered the wiring at first nothing really changed anyway. When i unplug the injector and coils, i get different codes so that rules out the wiring harness i guess.

I don't unfortunately. Looks like its up to the dealer next week.

axtigin36

Discussion Starter · #20 · 2 mo ago

bopbo said:
The missing filter may have been removed to fix the problem of the filter falling apart and lodging in the valve, the fact it is missing is a minor concern, but would not cause misfiring only. If the valve had a problem you would gat a CVVT correlation code as well as misfire on the whole bank.
Have you checked the compression on that bank?

Hopefully thats the case. When i tested the OCV, it was moving freely. The only code im getting is a conistent P0300 and P0302. The mechanic did and they said its all close together. I dont have a compression tester with me. I might invest one.

1 - 20 of 55 Posts