Replaced coils and plugs still reading P0300

[Lin]

Replaced cam shaft rocker arms, once everything was put back together engine started shaking and misfiring. 

 

Code P0300

Replaced sparkplugs and ignition coils. 

 

Upon initial start sounds ok for the first 20 second then starts misfiring and shaking. 

 

Code still reading P0300 

 

Check engine light is going back and forth between flashing and steady. 

 

 

Not sure where to go next with this, help is much appreciated. 

 

 

[2late4u]

more info would help at least which eng,miles and other such info? what was the problem before you worked on it? was it running okay? have you cheked yoiuring wiring to make sure something hasn't been damaged or not plugged in correctly?

[Lin]

2014 3.6 93,000 km 

Was running fine until the rocker arms started ticking. 

Changed out the rocker arms and once it was back together it was misfiring and shaking code was P0300 

 

Changed out the sparkplugs and Ignition coils, now it will idle normal for about 20 seconds then it starts misfiring and shaking. 

 

Check engine light goes from solid to blinking to solid. 

 

 

[2late4u]

someone will chime in that will be more help than me, But i do have to say you must have done something wrong considering what you say has been done,,, , might be a  while since it's the weekend. good luck and welcome to the group there will be some good advise coming soon

[5rebel9]

Depending on how the rockers were replaced, IF cams were removed and extreme attention not given to timing chain/marks alignment, that could be a possibility of not being in proper "timing".

OR as posted before of wiring not fully connected.

Edited November 5, 2022 by 5rebel9

[Lin]

Everything was marked before being removed and put back in place.  The marks were done with a paint marker so a thicker line leaving room for error. 

 

Is there a way to test that the timing is correct? 

[5rebel9]

I so not have personal knowledge or experience in performing this work. BUT from a close friend ASE master tech & shop owner) who has done these is that with the VVT system these have that it is critical to go by the book on setting timing chain/cam marks. EVERY chance that things will go "south" when using your own marks.

Only way to check is to open it back up and align the marks accordingly AND don't forget to have the crank gear in align also.

GOOD LUCK and let us know how you "make out" with this problem.

[John/Horace]

Paint marks are often used by mechanics, especially on timing belt engines. But like 5rebel is saying, there are still a series of marks on cam gears etc that should also line up when crank pulley is pointing to TDC. Off by even one tooth and timing will be out causing cylinder misfire and idle problems. There is a special kit with plastic shims for the sprockets to help keep stuff from moving during internal work. Makes the job easier to do.

 

Changing noisy rocker arms early, before the cam shafts themselves are worn. Is the right approach to car engine repairs.

[Lin]

Thanks for the reply! 

 

We did purchase the tool kit with the plastic shims to use when changing out the rocker arms.  

 

Seems like we will have to pull it apart again and start over. 

 

 

 

[Lin]

Dual overhead cams

The lines on the cam sprockets were aligned, sprockets locked with the tool kit. Chain wasn't removed from the sprockets. 

Evething was marked, sprocket, chain the only part remove was the cam shafts. Intake removed first, replaced rockers and put back in, remove exhaust cam, replace rockers. 

 

Two factory dots on the sprocket and the cam so we put everything back to our marks and also was super to line with the factory dots. 

 

Once we started up again the engine was shaking and sputtering and the exhaust smelled almost like sulfur. 

 

After that we changed out the sparkplugs and coils and it felt a little better but is still misfiring. 

[Lin]

One thing-  while trying to line up the marks on the camshafts we bypass them on first turn turning clockwise, interested of making a full turn we went counter clockwise to align. 

[5rebel9]

As my last badly spelled post said.... I have not done this job MYSELF. But By coming back counter clockwise moved any slack in the chain to the wrong side and thus probably at least a tooth off somewhere in the gears alignment. I've done many single cam timing chains and timing belts in my day, and this is why they always say rotate clockwise 2 revolutions and recheck ALL timing mark s for alignment.

[John/Horace]

I have done a chain, tensioner and wear guides on a 2.4 double over head cam GM engine a few years  ago.

Also several  timing belts on double cam V6 engines. Staying clockwise and rotating around to double check marks is always needed. Finicky and time consuming work. Some mechanics always put a new hydraulic tensioner on this style engine if they have the covers off.  Constant chain tension very critical on first start up.

[Lin]

Thanks for the replies!

So if not turning two full revolutions caused a slip, how do you suggest bringing it back to the correct timing?