RB25 Miss at Idle & a little through the rev band

[jakeoster]

Hey guys,

 

Im running an RB25DET S2 on stock boost (7 psi) and when the engine is idling and occasionally through the rev band I'm getting a misfire. It misfires quite a bit while idling. I'm running the recommended NGK plugs gapped at .28 in. as recommended. It seems like it happens more often when the weather is colder. I've read that the coil packs seem to have an issue arcing out, but I have heard many different opinions on that. I have heard that some people wrap them up in tape and use some sort of epoxy, but I have also heard that that can make them run too hot and cause problems with them getting overheating and it doesn't last long. I have also read that grounding them some how can help. What do you guys think? Id rather not buy new ones if I dont have to...

 

Thanks in advance.

[motoman]

I looked in the fsm that i have downloaded. It says that when you have misfiring during idle. To Check three areas. The first being to check the ignition system by real time diagnosis. Second Check the condition of the Crank Angle sensor in real time. Thirdly to check the condition of the spark plug. I don't think there is any problem there.

 

Under acceleration check the signal system(Ignition signal, crank angle signal,air flow meter signal) for an instantaneous break. I'm guessing the want you to see if the sensor is bad and that the signal is cutting out. Check the spark plug gap. Which you already said yours are set to .28 so they should be fine. Check for any leak from high tension cable. Check if the ignition coil power supply is lowered. Lastly it says to check if fail safe mode is not set due to a detonation sensor error.

 

That is what the FSM said for poor idle and driveablility for ignition misfire.

 

Do you know if your throwing any codes?

[rayaapp2]

All 6 of my S2 coil packs were arcing with only 82K miles on them. I tried the liquid tape solution, and it helped moderately, but did not solve the problem. I bought the Super Spark coils from Raw Brokerage. I have 35K miles on those now and Im still happy with those.

 

Do not bother with Platinum of Iridium plugs. Its either the weak coils or possibly the composition of our fuel(which affects resistance across the gap) that causes the misfire... Ad a small amount of surface area

Try plain (no vspark or anything special) copper core plugs of the same heat range and gap of between .037-.041"and youll be fine. If you turn up the boost then worry about the heat range.

 

Easiest way to check you coils I found was this.

 

warm your engine up to operating temp and get the heat soak on. Have a spray bottle ready with plain water. I found it best to have the coil cover off and to do this at night after a hot run down the freeway. Pull into a place where you can turn your light source off, but not yet! Leave the engine running. Pop your hood. Listen for any sounds coming from the coils any time you hear a misfire. I could hear the coil arc over to the coil rail! After you take the time to listen for that misfire get your spray bottle ready. Turn your any lights off. VERY lightly Mist the coils. If you spray heavy amounts of water you will CAUSE your own misfire. You will have to look closely around the coils to see any arcs as they will be faint. Since the coils are not under load you have to force them to arc or simulate a load by creating an easier path to ground. The arcing tends to happen through almost invisible cracks in the coil housings. You will be able to verify by looking for the heat scoring around where the arcs are coming out of once you look at it again in the light. Those arcing coil packs can be addressed by trying those fixes you probably read about. After several used sets of 6... I had 3 known good coils... So I bought a set of after market ones.

 

You are also using fuel that is probably a bit lower grade than what the engine was designed to run? I notice a slight mis sometimes when I fill up with cheaper mixes of premium(valero vs chevron).

 

Hope that helps

Edited September 11, 2011 by rayaapp2

[mr jdm]

Pull your fuel pump fuse, start the car.

 

Let it die.

 

Take each coil out while somebody is cranking and see if you have spark.

 

I would think you have a MAF issue before an ignition issue if your misfiring.

[jakeoster]

Pull your fuel pump fuse, start the car.

 

Let it die.

 

Take each coil out while somebody is cranking and see if you have spark.

 

I would think you have a MAF issue before an ignition issue if your misfiring.

 

When it's dark I can see some sparking from the coilpacks.

 

Also with the Power FC hooked up I can see that I'm getting ~1300mV at about 1200rpm idle from the MAF and the Power FC FAQ page recommends that you get a stable 1100mV. Would this constitute a problem with the MAF?

Edited September 11, 2011 by jakeoster

[rayaapp2]

Pull your fuel pump fuse, start the car.

 

Let it die.

 

Take each coil out while somebody is cranking and see if you have spark.

 

I would think you have a MAF issue before an ignition issue if your misfiring.

 

It seems that this pops up once every 6 months. A word of caution:

 

DO NOT FIRE THE COILS WITHOUT A SUFFICIENT GROUND! Ignition coil damage can result!!! COP coils have thinner coils and more of them esp in a turbo car. These thin coils of wire can easily burn open when the ground has no where to go! POOF smoke does not go back in.

[rayaapp2]

When it's dark I can see some sparking from the coilpacks.

 

Also with the Power FC hooked up I can see that I'm getting ~1300mV at about 1200rpm idle from the MAF and the Power FC FAQ page recommends that you get a stable 1100mV. Would this constitute a problem with the MAF?

 

One problem at a time.

I have not seen the FSM as far as the MAF goes. 1200 RPM idle is a bit high. I believe you are looking for a 'stable(as in within a 2 or 3 rpm)' 750-850 rpm with all accessories off. The PFC has some cool idle stabilizing features for electrical system loading. If the FSM tells you to check the MAF at 1200 RPM Im not going to contest that, but as far as an idle goes thats high.

 

Again 1 problem at a time starting with the basics. Fix the spark issue first. If you can visably see the sparking from the coil packs to anything you have an issue to address!

As I hinted above under load the problem is amplified. As you compress air/fuel resistance between the plug gap rises. Under load the resistance spikes. This is why you see a lot of folks with this issue hit a wall at a certain rpm under load. Its just becomes easier for the spark to get to ground through the coil insulation rather than over the plug gap. Anyway, you can try the liquid electrical tape or epoxy, but I would not expect that to fix it. A lot a digging and you will find that NAPA can order the OE coils from a place in the US, but they are around 119 ea.. You will have to look around for aftermarket options. Do some serious research. Not all the aftermarket coils are better than the stock ones.

 

Once you have a solid rpm, set your idle up. You may have to adjust your idle air bypass screw as well. Follow the FSM for that setting and if your using the PFC you should be able to ignore the part where it asks you to set the ECU into base mode. Double check your TPS at idle so it doesnt hunt(use the FSM for the readings which I believe are pin 2&3 .4ohms idle to 5ohms at WOT). Once that is all setup check your MAF as per the FSM and diag from there.

[jakeoster]

I went ahead and ordered the Raw Brokerage Super Spark coilpacks. Considering getting a tune done within the next week or so.

 

Considered LS2 coilpacks but I decided against it as I didn't want to add to my already growing list of stuff to do. I want to actually reverse the trend and spend more time driving the car instead of wrenching on it haha.

 

I'll let you guys know how they work out.

 

Also! Does anyone know what too do about the computer relay or something? I'm not very good with electrical and the issue is my Power FC won't save data to memory. I've read it's due to a lack of a relay or something along those lines.

[rayaapp2]

Relays?

 

There is a keep alive wire that needs battery 12V.

What data is it not saving? The tune?

 

I am fairly satisfied with those coils.

[jakeoster]

Yea, it's kinda funky. I set my rev limiter to 6000 from 6600 as a test and when I power off the car and restart it, the rev limiter goes back to 6600

 

From the Power FC FAQ;

 

"Any changes made to settings on the Apexi PowerFC are written in memory and then commited to NVRAM when the car is powered off. When the PowerFC detects power loss to IGN it saves its state into NVRAM. This usually takes around 1 second. Once this is complete the unit is safe to be powered off (happens automatically). If your car has had an engine swap it is possible and likely that the standard ECCS wiring has been altered or is not the same as factory. This may mean that when the IGN is turned off the PowerFC doesn't have time to save its changes. This results in any changes made to be 'lost' when the power is off. Below is a diagram on how it should be wired in with the ECCS relay. The diagram is suited for the RB26 ECU so if you have a different version look up your corresponding ECU's diagram for the matching wires."

Edited September 13, 2011 by jakeoster

[motoman]

There should be a constant 12v to your ecu. For a series 2 ecu it should be pin number 58. It is a White/black wire. I'm not sure what it is for a series 1 ecu if that's what harness you have. I'm pretty sure they are the same though.

[rayaapp2]

There should be a constant 12v to your ecu. For a series 2 ecu it should be pin number 58. It is a White/black wire. I'm not sure what it is for a series 1 ecu if that's what harness you have. I'm pretty sure they are the same though.

 

I would tend to concur. However I cannot dismiss his stated quote. There are reasons why the electrical systems were designed as they were. If you deleted a relay or something you should really think about re-installing it as it was in the donor car. If for nothing else that to know your not gonna burn up your ECU if you end up with an over-current situation... ie when you are getting or giving a jump start. You would not be happy with a fried ECU. Trust me thats not fun and the stock wire harness has its own inherit flaws that you do not need to pile more issues on. The BEST example being the fuel pump circuit and inductive fly back issues with the relay. I found that out the hard way.

 

In other words you should only be altering the wiring into a non-stock configuration IF you are absolutely positive that your making an improvement. I would highly recommend you consult an electrical engineer as well. If you know who is who on the forum here you will know who to ask. There are more than a few.

 

S1 diagram. I was able to extrapolate what I needed from this diagram for my S2 setup.

[motoman]

This is the schematic that I'm working off of. It show the power that goes to pin 58 is bypassing the eccs relay.

 

[jakeoster]

Ill take a look at it, thanks for the help guys.

[motoman]

Did the new coils help with your misfire issues?

[jakeoster]

Did the new coils help with your misfire issues?

 

Yeah, made a huge difference. It still has some small random misfires at idle but I think that will be tuned out on the Power FC. Very satisfied with the difference.

[jakeoster]

I ended up having the tuner sort out the non-saving on the Power Fc because I sort of lost my confidence to mess with electrical surrounding the ecu after I fried one ecu in the past. There was numerous issues with the swap that he addressed. Ranging from tach not working, cracked comp housing on the turbo, and an issue that kept VCT from activating. The turbo wouldn't really make boost past 1 or 2 psi only when I was really flogging it, if I wasn't then it was mostly in vacuum. It made weird noises when making boost and seemed a bit flat in hind sight in addition to taking a long time to build boost.. I figured the internals of the turbo were out but I didn't think it would be a cracked comp housing. He says the internals of it appear to be fine. I should have the car back later this week.

 

What's funny is I thought the car was pretty fast and it wasn't even making boost, running rich due to the MAF not reading the right volume of air due to the crack in the comp housing, and no variable cam timing.

Edited September 26, 2011 by jakeoster