Misfiring, Or Something's Not Right With My Car.

[KrazyKong]

I'm confused as to what's wrong with my car.

I'm getting misfiring at low revs. But this is my best guess, it could in fact be something else. I have an Auto, so when I turn Overdrive OFF and have the Power Switch on, you can hardly notice it anymore.

Here's what I did. Installed a FMIC, and did the boost grounding trick. Same plugs (Bosch Plats gapped at 1.1), same coilpacks, nothing else was changed. Before I did this the car ran perfectly and as good as it's ever been. Smooth, idling nicely and no blips or hiccups when putting your foot down. Now there's definitely something off. Oh and did I mentioned my fuel mileage has gone down the toilet. I'm losing 80-100kms per half a tank! And I use BP 98 Ultimate religiously.

Do I need a SAFC? or to reset the ECU? I installed a Walbro GSS294 fuel pump in some months back, so I know it's not that.

Someone mentioned maybe gapping my plus to 0.8 so I'll give that a shot, but what's got my confused is I see others with better coilpacks and pretty much the same setup as me that run fine at 1.1.

It's odd, some days it doesn't misfire or hiccup. Other times it's doing it as soon as I accelerate, and I'm hammering it. Just pulling out of the driveway. The car still idles fine.

What have I done wrong? And what on earth happened to my great fuel mileage.

[Get EPIC]

My mileage was crappy when i had a loose clamp on an intercooler pipe so you might want to check there is no loose clamps.Other than that check the plugs.Oxygen sensor might be on the way out also.

[KrazyKong]

A few days back, I checked them all and replaced a clamp. I havn't driven much since then, so maybe that might have been a cause. But the fuel mileage is noticeably worse. I've only just replaced the plugs and O2 sensor, so it's not them. It's something directly related to the FMIC and or the grounding the boost actuator.

[Galois]

A few days back, I checked them all and replaced a clamp. I havn't driven much since then, so maybe that might have been a cause. But the fuel mileage is noticeably worse. I've only just replaced the plugs and O2 sensor, so it's not them. It's something directly related to the FMIC and or the grounding the boost actuator.

Can't imagine it being your fmic mate, not if its not leaking. Try un-grounding your boost actuator and see what that does? It is possible the extra boost is sending you into safety or r&r mode or something.

Coilpacks make a big difference apparently. Mine are waiting for me at home atm! Lol, finally to be rid of the misfiring and 5 cylinder running.

What I've done recently is disconnect the electrical wire to the boost solenoid, which gives me the 7psi actuator boost. What boost are you running? Maybe give this a go too and see if it makes your car more drivable?

Also, I read a bit into safc a while ago, I suggest you heavily look into it to make sure you buy the right aftermarket computer gear fro both now and future mods. I seem to remember safc has its limits...

[KrazyKong]

It's possible it was leaking for the first week or so. I replaced a clamp that appeared to be not holding properly so we'll see how that goes. If anything maybe this will help with the fuel mileage but the "misfiring" problem is still there.

I don't have a boost gauge installed, so am not sure of my exact boost figure. The misfiring happens often when I'm just putting around, foot barely on the pedal, and then start to accelerate. Other times when I floor it, I can feel it slipping or misfiring. But once it gets over a certain speed or rev range it's happy.

Uhh, while I wouldn't mind some new coilpacks, I don't know enough about them to know if I in fact need them, or if the money would be well spent. For all I know, mine are working just fine, any maybe they aren't

I'm going to disconnect the ground actuator wire and put it back to how it was stock for awhile. I have no other boost mods going, no T-pieces, gauges or anything. Yeah I was wondering if I need a safc, but really my car is stock apart from the fmic and boost grounding.

As for future mods, I'm pretty much done for the long foreseable future. Not unless a high flow or some other better turbo drops in my lap for peanuts.

[Galois]

Definitely try un-grounding your boost solenoid and see how it goes, if it doesn't fix it try disconnecting the boost solenoid electrical wire.

Coilpacks for you will be like $380 delivered from performance wise. These are the yellow jackets. Unlike the splitfires, they come with a 2 year warranty and they're pretty good with it. They sent birds a new coilpack before he sent them the bad one a week ago.

To get nissan ones will be like ~$190 each.

If you have the stock coilpacks you are literally waiting round for them to go wrong, not many people are running the original ones. But if they're working may as well keep them.

All this about coilpacks and spark and boost would be more meaningful if it was a problem at higher rpm, having the same problem at low rpm sounds weird. Does the car vibrate? One of the spark plugs may not be firing at all for some reason...

[KrazyKong]

It's hit or miss. Sometimes it runs ok, other times I notice the "problem" more. Now if I have the Power switch on, and Overdrive OFF, the problem seems to almost all go away. It's still there, but not as noticeable.

Since I installed a FMIC that was pulled from another car and am using the original hoses, I guess I should source some new ones just to be sure. As far as the coilpacks go, I'm just not sure that's the issue right now.

Let's put it this way, before I installed the FMIC and did the boost solenoid grounding, the car ran like gold. It ran very very smoothly, no problems anywhere with idling, misfiring or anything.

So by doing these 2 things, FMIC, boost grounding, I now have a problem. That doesn't mean to say they are the problem. It's possible the extra boost and denser air from the FMIC is causing something else to freakout.

I wish one of you guys, could just jump in, take it for a spin and then go ahh!!!! that's your problem right there.

So for arguments sake, I'm going to undo the boost grounding and put it back to stock. Then the only thing changed will be the FMIC. I'll get some new hoses to be sure there are no leaks. I have my old set of spark plugs I can gap to 0.8 if things get that far, but again I just don't feel my gap or coilpacks are the things giving me grief.

[Galois]

It's hit or miss. Sometimes it runs ok, other times I notice the "problem" more. Now if I have the Power switch on, and Overdrive OFF, the problem seems to almost all go away. It's still there, but not as noticeable.

Since I installed a FMIC that was pulled from another car and am using the original hoses, I guess I should source some new ones just to be sure. As far as the coilpacks go, I'm just not sure that's the issue right now.

Let's put it this way, before I installed the FMIC and did the boost solenoid grounding, the car ran like gold. It ran very very smoothly, no problems anywhere with idling, misfiring or anything.

So by doing these 2 things, FMIC, boost grounding, I now have a problem. That doesn't mean to say they are the problem. It's possible the extra boost and denser air from the FMIC is causing something else to freakout.

I wish one of you guys, could just jump in, take it for a spin and then go ahh!!!! that's your problem right there.

So for arguments sake, I'm going to undo the boost grounding and put it back to stock. Then the only thing changed will be the FMIC. I'll get some new hoses to be sure there are no leaks. I have my old set of spark plugs I can gap to 0.8 if things get that far, but again I just don't feel my gap or coilpacks are the things giving me grief.

That does sound weird. Let us know when you to some testing, it'll be interesting to see.

[KrazyKong]

Could I be running over 10psi? I guess I'll have to get a gauge to know for sure. I remember reading on here that the ecu, solenoid? or something in a stock R33 doesn't like going past 10psi. So with boost grounding and a nice FMIC, it's possible I'm peaking over 10psi right? Could that then be causing my issues?

[Rolls]

I reckon adding the FMIC and grounding the boost solenoid coupled with plug gap too big and old coils is your issue. Reason being the FMIC cools the intake charge so denser air = more fuel, boost upgrade also means the computer is going into the very rich parts of the map to try and stop you killing the motor (safety feature from factory). Now more fuel means the spark is more likely to be blown out, if you have a big gap (1.1) and old coil packs that aren't giving the best spark all the above could cause these issues.

What I would suggest is first putting the boost back to standard, then gap plugs down to 0.8, then new coils. If this still hasn't fixed your problem then it looks like a remap/nistune is on the cards, they can pull the fuel out from 4.5k onwards which saps power and can cause rich misfires with bad spark.

Personally I would get the remap first and have the cash ready to get new coils if needed, as the remap might mask the bad spark problem as they can pull enough fuel out to stop it missing, if the spark is bad enough then both new coils and getting it tuned should fix your problem right up, not to mention you can run 10-12psi and you will get more power and better economy.

Now you say it is missing at low revs, I am assuming this is the typical 5k misfire that every second thread on this forum is about? Personally I got the misfire around 3k on partial throttle and at 5.5k on WOT, coils and a tune fixed the problem completely as the ECU was pushing enough fuel to drop the AFR to 9:1 blowing the spark out.

edit: I don't think the power button has anything to do with it, you are probably overthinking it, unless of course it happens at a specific rpm and using different revs/load tends to make it occur more often, but you should be able to reach any load/rpm in standard shift mode as well.

Edited September 16, 2010 by Rolls

[Jay11]

From my research into this if its at lower revs then its generally something to do with the fuel system?

Maybe check your fuel filter and make sure the walbro pump is working properly.

But depends what low revs you're talking about?

If you still have stock coilpacks you'll be looking at changing them soon anyway if you're doing modds, coz they would be getting on now.

Edited September 16, 2010 by jaylon

[Galois]

Now you say it is missing at low revs, I am assuming this is the typical 5k misfire that every second thread on this forum is about? Personally I got the misfire around 3k on partial throttle and at 5.5k on WOT, coils and a tune fixed the problem completely as the ECU was pushing enough fuel to drop the AFR to 9:1 blowing the spark out.

I had similar: various mises up to 3k, then from 4k onwards missing on wot.

9:1 wow that's low.

My car seems to run 14psi fine when the stock boost solenoid is plugged in (I unplugged it to save turbo, and im due for a clutch change so the extra boost is making it a nightmare), do you think it's had a tune or has an aftermarket ecu? Not really sure how to tell...

[KrazyKong]

My rev counter has been broken and continually seeks for a year now. By low revs I mean barely even touching the throttle. I've pulled out of my driveway and was not even doing 20km and it did it's little hiccuping.

If I'm looking at Nistune and coilpacks and who knows what else, then I'll most likely just put the stock SMIC back in. I don't have thousands of dollars to spend and from all accounts others have done what I have without any issues.

The best I can do an afford right now is to gap the plugs at 0.8, but then again I wouldn't be getting blowouts at 20kms either. And of course take the ground boosting off.

If anyone lives on the Gold Coast and knows a thing or too about Skylines and all the things discussed, I'd love to meet up with you, and you can take my car for a spin and see what it's actually doing.

[Rolls]

Is it blowing clouds of black smoke? If not it could possibly be a fueling issue or faulty cas/afm.

Can you get hold of a consult cable and check for error codes?

[Galois]

My rev counter has been broken and continually seeks for a year now. By low revs I mean barely even touching the throttle. I've pulled out of my driveway and was not even doing 20km and it did it's little hiccuping.

If I'm looking at Nistune and coilpacks and who knows what else, then I'll most likely just put the stock SMIC back in. I don't have thousands of dollars to spend and from all accounts others have done what I have without any issues.

The best I can do an afford right now is to gap the plugs at 0.8, but then again I wouldn't be getting blowouts at 20kms either. And of course take the ground boosting off.

If anyone lives on the Gold Coast and knows a thing or too about Skylines and all the things discussed, I'd love to meet up with you, and you can take my car for a spin and see what it's actually doing.

Hey mate, so you don't have a boost gauge in your cabin?

I think, but am unsure, but isn't nistune only for r34s? Or am i all confused? I haven't really got into the aftermarket ecu stuff yet... To get coilpacks it'll be about $380 delivered express. And you can get bosch fr7dp's (6 for $44 at repco, check they have them in stock though), which are plat and gapped to 0.8 mm, saves damaging the platinum on the plug.

Definitely un-ground the boost, it might be the easiest solution. I'd keep the fmic for a bit, just saves you the pain of removing it to find it wasn't the problem.

Good luck

[Galois]

Is it blowing clouds of black smoke? If not it could possibly be a fueling issue or faulty cas/afm.

Can you get hold of a consult cable and check for error codes?

or try this for free

http://www.skylinesaustralia.com/forums/Re...de-t266512.html

[Rolls]

You can get nistune modules for every skyline bar the R33 as it uses a difficult to modify CPU/eeprom

However you can use the ECU out of an R32 or Z32 300zx to run your rb25 if you want. Problem is you need to use an eboost or msd switch to control the VCT if you go the r32 rb20 computer.

or try this for free

http://www.skylinesaustralia.com/forums/Re...de-t266512.html

Yeah that also works, just have to do it a few times to make sure you get the codes right.

[Galois]

You can get nistune modules for every skyline bar the R33 as it uses a difficult to modify CPU/eeprom

However you can use the ECU out of an R32 or Z32 300zx to run your rb25 if you want. Problem is you need to use an eboost or msd switch to control the VCT if you go the r32 rb20 computer.

Yeah that also works, just have to do it a few times to make sure you get the codes right.

Ahh ok, cheers for clearing it up.

The codes flash on a loop. It's really easy and you can reset the ecu afterwards which is good to do every now and then. Might just help your misfire problem too.