New Spark Plugs

[konect]

Hi all.

Changed the plugs today in my RB20DET as they hadn't been done since august. I changed them all over using BCPR6ES gapped at 0.8 and now the car is missing on idle. It was missing before but now it is constant, before it was every now and then like most RB's do. Also noted that the plugs I pulled out were BCPR5ES 11 which were put in when I had it serviced at a mech.

Everything appears to be plugged in and I cant work it out.

Any idea what the problem is ?

Thanks.

[Busky2k]

Sounds like one of your coil packs might be playing up and since you removed/installed them, you might have aggregated the problem.

[konect]

Sounds like one of your coil packs might be playing up and since you removed/installed them, you might have aggregated the problem.

Hmmm I forgot to add that i cleaned the bottom of the coilpacks where they touch the plug. Just wiped them with electrical contact cleaner.

[Busky2k]

Have the car idling whilst its missing and pull out each coil pack 1 at a time (obviously replacing the one u just pulled out before) until you can isolate the problem cylinder..

[konect]

Yeh i thought about doing it but cbf undoing all the little bolts

will do it tomoz. Thanks mate.

[stuartlaw_78]

Mate..

It is a possibility that you have cracked one of your spark plugs when putting them in. This can happen when you use the socket over the spark plug and tilt it on an angle, therefore putting pressure on the top of the spark plug and cracking it.. check them all for small cracks... look carefully, it doesn't take much.

I had the same problem with my car and I had 3 cracked plugs... Mine was missing up higher in the rev range but just thought I'd let you know anyway, might be worth checking.

Goodluck!

[limpus]

Same thing happened to me...my car was running fine using BCPR6ES-11 (pregapped 1.1mm) plugs...then while servicing i changed them to BCPR6ES (pregapped 0.8mm) plugs...immediately after that the car developed a miss on idle...and only on idle...after 2 days...i swapped the 0.8 gapped ones back to 1.1 gapped ones and the miss went away...go back to 1.1 gapped plugs and see how you go...cheers...

[konect]

Same thing happened to me...my car was running fine using BCPR6ES-11 (pregapped 1.1mm) plugs...then while servicing i changed them to BCPR6ES (pregapped 0.8mm) plugs...immediately after that the car developed a miss on idle...and only on idle...after 2 days...i swapped the 0.8 gapped ones back to 1.1 gapped ones and the miss went away...go back to 1.1 gapped plugs and see how you go...cheers...

The old ones were still ok but guess wot...i put them in the wheelie and it got emptied today

have to put up with it for a while now i guess till i get paid. Sooooo annoyed I threw them out!

thanks for the help anyways.

[limpus]

New ones don't cost that much anyway...about $3-3.50 per plug...get another set and see how you go...its worth it if it stops the missing...

[Fixxxer]

Hey there,

This seems to be a relatively common problem with the BCPR6ES (0.8mm) plugs. I too, developed a miss at idle (not straight away but after about a week or so I had the car dyno run and I started to notice it immediately after that).

When I replaced the plugs I noticed major issues with arcing (missfiring) on the coils, but no cracks could be seen, otherwise the coils looked almost new. The BCPR6ES plugs, gapped at 0.8mm solved my major missfiring issues, but I seemed to develop this slight missing on idle (its more of a random miss than anythign repetitive).

I've learned to live with it, because I'd rather a slight miss on idle than not being able to rev the car.

Not sure if its the BCPR6ES plugs that may be the problem, or we all have similar coild problems (which seems likely). Although I can't work out why the coil would die on idle, but nowhere else in the rev range.

Fixxxer

[Konrad]

I changed to the BCPR6ES (i had BCPR7ES in there before) and noticed really no difference. I've been told by my workshop that my no.6 coil was on the way out but when i changed the plugs they all had an even amount of colour (not white, not black were orangey brown i think from octane booster or additives in BP ultimate??). The coils themselves all seemed fine on inspection (no corrosion etc..). I gave them a liberal coating of silicone spray, and sanded the graphite (i think) plug contacts on each coil.

I had a random miss at idle aswell (has always been there), i'm wondering if it could be something other than the coilpacks themselves? could it be the ignitor or something??

Oh and the miss seems to be more heat related, when the car is cold it runs perfect, but the more you drive it the stronger the miss becomes, i know that the coils do fail with heat, so the miss would be more apparent at idle for 2 reasons;

Main one: car is at lower revs, thus theres a bigger time period between when cylinders fire, so if a cylinder misses you will feel it more than higher revs where the next cylinder in the firing order will kick in much sooner (if that makes sense)

Another idea (maybe?): At idle there is nowhere for the heat from the motor to go, so it builds up causing the coil to fail, whereas when your belting down the freeway it has a nice cool breeze running over the top of the motor, i imagine there would be quite a few degrees difference in temps between idle and say 80kph in the coil area?? (especially if you've removed the coil cover)

[dangerous_daveo]

It could be the ingnitor pack thing. The cable the plugs in to that. Pull the plug back off, get some contact cleaner and clean both the plug and the socket. That should help. Mine was so badly corroded the car didnt even get spark.

[Lazy-Bastard]

Yeh i thought about doing it but cbf undoing all the little bolts

will do it tomoz. Thanks mate.

There's no need to remove the coil entirely to check, just unplug each coil from the loom, one at a time.

[konect]

Thanks for the info people.

I am gonna pull it all apart over easter and see what i can fix. Is it possible to gap 0.8 plugs UP to 1.1 or do I have to buy a new set of 1.1's ?

Also going to try gluing coilpacks as described in that thread about top end missfire. I pulled the first one out yesterday and either side of the metal bracket it had burn marks so I assume quite a bit of spark was escaping. Put some selleys all clear on it and havn't seen any signs of melting sealent yet so I think im gonna do them all.

[Fixxxer]

I might try cleaning the ingnitor connections with contact cleaner and see if that makes it go away, although the miss only seemed to develop after I changed the sparkies.

My miss happens at any time, even when cold. The miss doesn't get any worse when hot.

Fixxxer

[konect]

There's no need to remove the coil entirely to check, just unplug each coil from the loom, one at a time.

I realised this What exactly am I listening for when I unplug each one ?? When I did the first one it made no diff but 2 and 3 made it drop idle.

[PHaT MR30]

sounds like number 1 is the problem then, coil not providing enough spark at idle... could be a number of problems from a bad earth to faulty coil.

[konect]

Soooo if it makes no difference to the idle then that is the problem coil ?

I only checked the first three, will do the rest over easter as I said above. Stupid Nissan coil-on-plug ignition system

[PHaT MR30]

yup basically your disconnecting the spark, if there is no spark to disconnect its not going to make any difference.