Cold air partition installed and now running a bit crap

[Burns]

I installed a cold air partition over the weekend and took the car for its first good drive since tonight and it's not running right.

It seems to be missing intermittently at boost levels above .5 bar and is more noticeable around gear changes.

With normal gentle driving and gradually rolling on the power it seems fine but when I give it good stomp (70%+ throttle) from a steady cruse or standstill it builds boost, starts to accelerate then seems to cut ignition pop and fart a bit, shift a gear keep missing popping and farting and not making much power then pic up for a bit drop off again and so on.

I have double checked all the plugs, hoses etc but can't find anything amiss.

The only thing I can think of is that the colder air is giving a denser air fuel mix and therefore higher cylinder temps and the ignition system dose not have enough spark to ignite it.

It has always missed and popped a bit on gear changes and I have put it down to the ECU cutting ignition to protect the gear box. When I turn my Blitz DSBC off or on its lowest setting keeping boost under .5 bar it seems to run fine.

Is my reasoning on track and I just need a spark plug change and a tune or is something horrible going on?

[gatty]

coil packs?

[Jay95R33]

What type of plugs do you have and what are they gapped at ?

Long shot, but maybe reset the ECU ?

J

[Burns]

I have no idea what plugs or the gap. It's strange that it has a problem all of a sudden. The car sat undriven for a week then I installed the cold air partition over the weekend and when driving it to and from work today it was running crap.

[Jay95R33]

The denser air will make a difference, so I'd say that you were right on the edge of the problem before, now with the cold air box it's pushed it over the edge

The symptoms sound like the typical plug problems that's for sure.

Do you have access to some feeler gauges to check the plug gap ?

J

[siksII]

i am quite sure it will be your coilpacks on their way out.

you might be able to patch up the problem by gapping the plugs to 0.8 (most come as 1.1) but this wont be the real fix, which is probably to buy a new set of coilpacks, or at least check to see which coilpacks are bad and replace them.

if the coilpacks are dying, usually the car will miss when the weather is colder and/or running higher boost will make it worse, which is just as you described.

[Burns]

Well looks like I know what I will be doing next weekend then. I have a set of feeler gauges so can check and adjust the plug gaps easily enough. I also have a R33 Skyline sitting around that I can’t seem to find a buyer for so might do a coil pack swap to see if it fixes the problem.

At least I know my cold air box is effective

[Terminal]

This is the exact problem i'm having at the moment. But i think it's because of the boost level being too high. i had a diagnostics check run on my sensors because my car is running too rich, and they disovered i was only running 5psi boost. they said when they tried to up the boost the fuel cut came on, and so it couldn't be boosted past this 5psi. i don't think they adjusted the boost level below 5psi properly because i'm getting that problem at high revs at full throttle.

Again, it may have just been a coincidence when they boosted it for a short time that my coil packs went out, but i think it's a pretty big coincidence this only started happening after someone had fiddled with my boost level

i have a bleed valve by the way, the stock solenoid isn't being used

[Sydneykid]

Coil packs, everything is blamed on the poor old coil packs. I have NEVER EVER replaced a coil pack on a R32/33/34 Skyline. Old plugs, excessively gapped are 75% of the problems the other 25% is ECU R&R.

My suggestion, as always, is put some new copper NGK plugs in it and gap them to 0.8mm. If that doesn't solve the problem then chances are you have reached ECU R&R. I hit it on the Stagea at 7.5 psi, their ECU is very smart and maybe has tighter parameters than GTST's. I have seen similar on an R33 S2 Auto sedan so maybe it is the auto ECU that is programmmed to intervene earlier with R&R. If that is the case then it's time for some tuning.

[Lone]

Im with sk on this one

[Burns]

But I have an APEXI AFC II installed and tuned and I have run the same boost levels before the cold air box with no real problems. I also removed the stock boost control solenoid when fitting the partition but it was not fully plumbed in anyway unless having it unplugged in confusing the ECU.

[Sydneykid]

But I have an APEXI AFC II installed and tuned and I have run the same boost levels before the cold air box with no real problems.  I also removed the stock boost control solenoid when fitting the partition but it was not fully plumbed in anyway unless having it unplugged in confusing the ECU.

I tested the solenoid unplugged confusing ECU theory, it makes no difference. Which is logical as there are only 2 wires to the solenoid, one is earth and the other has 0 or 12 volts depending on high or low boost from the ECU. No signal (such as "I'm not connected") is possible.

My first guess remains plugs. Second guess would be wiring disturbed, eg; check the AFM plug, they are a bugger, look OK but if not clicked in place cause issues. Dirt on the hot wire from the work around the AFM, maybe? What else is around the working area, leaking intercooler pipework, perhaps?

I never rely on "it was working yesterday, so it must be OK today" logic. An example, I put a new set of plugs in one day 2 months ago (not NGK) and the car ran fine. Drove it from the machine shop to the workshop (about 10 ks') still fine. Drove it onto the dyno, tied it down and it started to miss like a bustard. Pulled the plugs out and one had a loose electrode, you could turn it with your fingers. This was a $40 Bosch German spark plug. It was working 5 minutes ago, but it wasn't OK now.

[Burns]

Thanks for the ideas guys. I will go over it and double check all the connections and plumbing to make sure nothing is loose or leaking.

It is a bit strange that it runs fine under all load conditions except for when boosting above .5 - .6 bar but if I roll on the throttle gently and let boost slowly build it can run ok at higher boost levels.

It sounds like I might be up for a new set of Plugs. Any idea what I should be paying for them?

[Jay95R33]

Yep, that's normal. The break down (miss) will generally happen around the peak torque high load figure for the engine.

The more you explain it the more I'm thinking it's the plugs.

J

[Sydneykid]

Thanks for the ideas guys. I will go over it and double check all the connections and plumbing to make sure nothing is loose or leaking.  

It is a bit strange that it runs fine under all load conditions except for when boosting above .5 - .6 bar but if I roll on the throttle gently and let boost slowly build it can run ok at higher boost levels.

It sounds like I might be up for a new set of Plugs.  Any idea what I should be paying for them?

$3.00 each, max:cheers:

[CoolPC]

That's a tad cheap for sparkplugs, don't u think

[Sydneykid]

That's a tad cheap for sparkplugs, don't u think

Nope, that's what copper NGK's cost. Copper is a much better conductor of electricity than iridium or platinum, and I want the best spark possible. I change my own spark plugs, so I don't care that iridium or platinum plugs last longer. They are only used so the vehicle manufacturers can have longer service intervals. I change my plugs regularly and at ~$20 a set it's no big deal.

[Burns]

So what spark plugs should I use?

The NGK web site has the following listed for the non NEO RB25DET

Spark Plug Part No.

Recommended Plug PFR5G-11

Iridium Option BKR5EIX-11

But BKR6E-11 and BCPR7ES have both been named as the best plugs to use on here.

[BensDR30]

The PFR5G-11's are a Platinum plug and over $20 each (I've just fitted a set to my car). The BCP's will certainly be a cheaper option.

[Sydneykid]

I use BCPR6ES-8 for normal use, maybe BCPR7ES-8 for sustained high speed or track use;

B: Indicates 14mm thread diameter in the cylinder head.

C: Hex size 5/8"

P: Projected insulator type

R: Resistor type

1-9: Indicates temperature (1 Hottest - 9 coldest)

E: Indicates 19mm thread reach (approx 3/4")

S: Standard (copper) 2.6mmø center electrode

-8: Gap 0.8mm (0.032")

If you can't get -8 then you will have to adjust the gap to 0.8 mm before you fit the plugs.