coilpack failing?

**evolution23** · 06-19-2011, 01:48 PM

Edit: Found a loose ground right above my turbo, does anyone know where it is supposed to go? I connected it to one of the allen bolts that hold the [24 valve] cover.

Alright so after messing with the coilpacks/wiring etc just all the electrical.. i am starting to wonder if its fuel. When the car starts missing for more than just a couple seconds, i get a strong fuel smell and when the cylinder picks up again, usually get a back fire. I am starting to wonder if i have an injector sticking open? Also somewhere by the intake plenum, sounds like under it by the injectors, when i turn on the power to the car i hear a faint kind of hum/hiss while the system is priming, it lasts for about 5 seconds then the sounds fades. While starting the car i can hear the miss, and while the car is running down under the intake plenum i can hear like a ticking/knocking sort of sound. Almost sounds like electrical sparking. Every time it makes the ticking/sparking sound the engine idle drops and has what sounds like a misfire. I will have a video up shortly, the first hiss while the system primes can barely be heard, theres a louder hiss for a second then the faint faint hiss can barely be heard after. Once the engine starts the ticking/knocking is fairly noticeable. Can anyone tell me if this sounds normal or if it sounds like the cause of my random misfires and cylinder shutting down while driving. And if its the cause of this, is it an injector?

**andy66** · 06-19-2011, 11:45 PM

What happened with my engine ( from the post you referenced ) was i ended up buying new coil packs and a new set of wires. One of my coils was on ots way out and would randomly make the car missfire and run like ****. Sounds like you have the same issue. I figured that taking the coil pack cover off was a good preventable measure to avoid having this happem again. Whe it's on it keep it pretty warm underneath it makes the plastic on the coil harnesses pretty brittle. I cant imagine all that heat under there can be very good for the coils either. Then again i live in thw okanaga. And it gets pretty hot here in the summer. Id suggest testing your coils to see if you can isolate which coil(s) is failing , and check your coil wires to see if the yellow plastic on the inside of the harness is cracked and not letting the three little tabs in there line up properly. Just my 0.02 as maybe where to start.

**evolution23** · 06-20-2011, 12:19 AM

I thought the cover would be better cause it would keep any unwanted debris away from the coilpacks and any moisture that may get up there but i never thought about it keeping heat in. I was going to get a new wiring harness to start as its probably the cheapest thing to start with. Then if the problem still persists i was going to change the coils, then if both dont fix it, i was thinking that silver box on the back of the engine that the coil harness connects to (not sure what its called). Anyways though, im assuming its one of those 3 things. My best guess is a coilpack because when it runs like that, it randomly runs fine for a second then goes back to running like crap but it could be the wiring harness, ill check the yellow plastic inside cause maybe tiny bumps in the road make the difference. Anyways ill start with checking the harness, then probably buy some yellowjacket and new harness.

Originally Posted by andy66

What happened with my engine ( from the post you referenced ) was i ended up buying new coil packs and a new set of wires. One of my coils was on ots way out and would randomly make the car missfire and run like ****. Sounds like you have the same issue. I figured that taking the coil pack cover off was a good preventable measure to avoid having this happem again. Whe it's on it keep it pretty warm underneath it makes the plastic on the coil harnesses pretty brittle. I cant imagine all that heat under there can be very good for the coils either. Then again i live in thw okanaga. And it gets pretty hot here in the summer. Id suggest testing your coils to see if you can isolate which coil(s) is failing , and check your coil wires to see if the yellow plastic on the inside of the harness is cracked and not letting the three little tabs in there line up properly. Just my 0.02 as maybe where to start.

**caliber676** · 06-20-2011, 01:28 AM

For what your time and money is worth, its probably better to take it to a place that has a labscope and a good technician to use it. There are so many variables that can cause the car to misfire. The ignitor, coilpacks, plugs, harness, ecu are all probable causes, not to mention the MAFS. I alway say its better to get it right the first time than replace parts till its fixed. Ignition system problems are rather finicky systems and problems in the circuits are best found on a labscope that can pick up finite waveform patterns that cause problems. Its one thing to resistance test a coilpack and pull them to test if one isnt firing, but you cant exactly pick up a poor coil condenser oscillation on a secondary circuit ignition waveform. And since the transistors are housed in the ignitor pack, it becomes harder to tell whether the problem is the coilpack or ignitor circuit.

Its all to take in, but the ignition system is a complex system, and with a good technician who can diagnose with a labscope and interpret waveforms, your going to spend a lot less time/hassle in the shop and a lot more time driving, as well as a lot less money on parts replacing

**evolution23** · 06-20-2011, 06:01 PM

Alright so the car is starting to do this a lot now. i will hear random misfires now and then and soon after the car will run like crap. when its running like this i can smell fuel really badly inside the car so im certain its got to do with loss of spark to 1 cylinder. Its hard to get the car to keep running like this while at a stand still but ill keep trying and see if i can narrow down which cylinder it is. I got cylinders 1,2,5 unplugged and i could hear the engine drop but by the time i went to unplug cyl 4 it started running fine again. I have also noticed that it seems to do this a lot more while going uphill and while just cruising, if i give the car some gas it stumbles for a bit then gets going. runs fine while boosting but as soon as i let off it runs like crap again. it can switch from running great to running like crap and vise versa instantly so im wondering can a coil work then not work instantly? i have been told if its a plug it wont switch on and off like that, it could be the wire coming in contact then losing contact. it could also be the ECU?? ill try to figure out which cylinder but its hard to keep it running like that while not moving.. any help is appreciated.

**galwin** · 06-20-2011, 10:53 PM

A good way to isolate which coil pack is not working is by disconnecting the harness of each coil pack with the car running and see which one of the 6 you pull sounds different from the rest. If they are working, the engine will bog down a bit, the one that doesn't work won't make a difference. And that's the one you replace.

I ended up removing my cover, replacing the faulty coil pack and then cut slots in the cover before reinstalling it.

The other thing I would do is pull the spark plugs and check the gaps and sand down the contacts.

**andy66** · 06-20-2011, 11:15 PM

Ya there's the issue with it keeping unwanted debris out which is always a plus, but I have a fully metal nismo cover ( i dont know if its the same on a standard skyline but on my nismo its all metal ). My whole problem started after running the car hard for a a good portion of the day at an event an then had it randomly run like poop after sitting at a stop light. Definitely sounds like you have the same problem i had. Check your coils and inspect your wires and plugs. More then likely that's your problem right there. Leaving your coil cover on is totally up to you though. It never even occurred to me that leaving the cover on would cause a coil to fail due to heat.

Anyone else have the same issue from leaving the coil cover on ? Do most of you guys leave it off or on ? Any thoughts / suggestions ?

**evolution23** · 06-21-2011, 01:39 AM

yeah i took it off this morning and to my surprise, the car started doing this. i checked the yellow plastic inside the clips, it looks good but when i unplugged one i had a tiny chunk of plastic fall out so im thinking the wiring will need replaced, also i have another set of coilpacks here, i have no idea if they are good or not but im throwing them in tomorrow and will see how it goes. iv been trying to jump under the hood and unplug coilpacks while its doing this but by the time i get to the engine, it starts running fine. it really only does this when driving, it will sometimes do this while at rest but its really hard to catch it cause the only times it runs like crap while stopped is at intersections. ill keep trying, hopefully i can get it. if not im going to try an get a scanner hooked up so i can watch each cylinder and see which ones missing. hopefully i figure it out soon, moving and need the car to make a 4 hour trip in a couple weeks!

**caliber676** · 06-21-2011, 02:58 AM

A bad ignitor can also cause this. Besides the resistance test, you'd need to swap it out with a known good unit and test drive it.

**DarkCaporaL** · 06-21-2011, 07:56 AM

I once had a gremlin misfire a couple years back that would come and go each time I drove the car, tapping the gas would make it stop. I cleaned my MAF, cleaned my plugs, checked for vaccum leaks (couldn't find any), undid the intake piping plenum side, checked the ECU for codes, reset it, tried octane booster/fuel injection cleaner, then the problem went away.

Mind you a couple months later I changed my coilpacks, so I'll never know exactly what caused it.

Pretty sure the ECU was pulling timing since it wouldn't boost to 1 bar...may have just been a case of bad fuel, who knows.