Rb25de Neo / Misfiring On Cold/cool Starts, No Issue Once Engine Is Normal Tempt

[kresot9]

Hey all

I can't take it anymore with the issue and its time for DIY and learn and save $$$. I drive a r34 4door rb25de neo manual

Firstly i would like to say last year before the end of November i bought new spark plugs and had them replaced because the rocket cover gasket needed to be replace so might as well change of the spark plugs as well. With this change the car has been running perfectly without a beat until last week.

I have been noticing the car was causing some issues after roughly 10-15minutes of driving from cold start, it was coughing and losing power, it took a bit to notice but then become a lot more noticeable during cold starts and honestly felt like it was misfiring. After some time driving and the tempt reaches normal the engine runs smoothly and no misfire at all.

So here it is, I would like to know how can i go on and diagnose the problem and try and fix it, without having the diagnostic tools and electronics.

From reading through different posts, the most common places to check are the spark plugs and the coil packs, that is all i know.

I do not own a lot of tools as well if it comes down to having something really specific to fix it. (I do have a torque wrench lol)

Edited February 5, 2016 by kresot9

[89CAL]

First of all: Rocket covers...... no. Just no. They are ROCKER covers when the car has a rocker setup. RB25's run OHC with no rocker setup, so they are actually just cam covers

What spark plugs did you use? Have you tried having a look at the cold start valve? Is it plugged in and getting power? Are the lines to it OK etc?

If it runs 100% when warm then it has to be something that is only operating on cold start (like the cold start valve, i think the AAC will also be more active at cold start)

[kresot9]

my bad, it wasn't intentional just finger slipped the R and T are close

With spark plugs i got these ones 'Iridium Option BKR5EIX-11' which was from 'http://www.sau.com.au/forums/topic/32825-na-skyline-spark-plug-numbers/'

Silly questions, where and how do i check the cold start valve and the plugs, also it runs 100% when warm even driving it for 45mins it was good, the AAC? if you do not mind explaining also

thanks

[admS15]

Pull the plugs out and have a look at the colour of them. Brown is good, black means they're fouling and white means they're getting too hot. Check cold start valves as mentioned. Next thing to look at would be coil packs.

[kresot9]

With the cold start valves what should i look for exactly? Smells, discoloration, marks? Also any possibly way to explain how i would go and remove it?

[Wordsmith]

Have you got an error code? There's a thread somewhere which shows you how to read the error code using just a safety pin with the fuse box.

[KiwiRS4T]

Unlikely to be plugs or coils.

Could be the ecu temp sensor. If you look where the top hose meets the block you will see two temp sensors. One has one wire (that's for your temp gauge) and the other has two wires - that's the one that goes to the ecu. I don't know of any easy way to test it but they are not too expensive to replace if you get one from an auto parts shop or auto electrician rather than Nissan.

But before you do that (if you are poor) you could try cleaning the AAC valve. This is a fiddly job but it doesn't cost any money. There at least two tutorials on how to do it.

Here's one (don't know if it applies to the Neo but you'll soon find out:

http://www.sau.com.au/forums/topic/110431-diy-aac-valve-cleaning-idle-reset/

[kresot9]

i bought myself some new coil packs but im a bit edgey with the caution they are stating after installing the split fire 008 coil packs

That the ignition timing may be needed to be done due to the increase of ignition energy and it will also cause a loud knocking sound.

Anyone else seen this on their installation papers before and should i need to worry?

[admS15]

i bought myself some new coil packs but im a bit edgey with the caution they are stating after installing the split fire 008 coil packs

That the ignition timing may be needed to be done due to the increase of ignition energy and it will also cause a loud knocking sound.

Anyone else seen this on their installation papers before and should i need to worry?

Don't stress. Just put them in. They won't change anything. I suppose they have to make them sound superior somehow lol.

[kresot9]

Well its really odd, because if it was something serious more people would of posted about it...

[Hadouken]

Therefore not serious at all because no one posts about it

[89CAL]

You are not altering Ignition timing by installing new coilpacks. There is a chance that the poor coilpacks have had an increased dwell time. But the car would not have been tuned on crap coilpacks so putting new ones in should just make it as good as it was when it was tuned

If its on stock ECU, nothing at all to worry about. Change the coilpacks, do an ECU reset and all should be well

[kresot9]

reset ecu like with shortening the fuse with like pins

Like how this guide states?

http://www.skylineowners.com/forum/21-tuning-technical-questions/11461-how-reset-read-fault-codes.html

[kresot9]

Well thanks everyone, i did the job and definitely saved some money doing it my self, the test drive seemed good without any weird sounds or disturbances in the power so will see how it goes for the weekend.

Thanks all!