rumbling/hesitation until boost or high RPMs after changing plugs

[Frostedbutts]

I changed my plugs today and when the car started it ran fine. I drove about 10 minutes and then parked at a friend's house, 30 minutes later I started the car and now it is having a strange issue. When it's anywhere from idle to 3k rpm it sounds almost like a motorcycle or a subaru, the exhaust noise is like a rumble.

Then when it gets into boost or high RPMs it pulls hard and the rumble immediately goes away.

Did my coils **** the bed? I feel like the coils would be worse up top so I'm curious to hear what someone thinks I should check.

I pulled the spark cover off and all the coils packs are plugged in, and the ground is tight. I was thinking of moving that sad ground spot to the block and see if that improves it? Any other ideas?

[Skym]

Sounds like it is intermittently running on 5 cylinders. Can be coilpacks or ignition module (sometimes coilpack loom when it goes hard).

When coil packs fail they make the engine miss intermittently. Coilpacks leak on the seal between both halfs of coilpack, just under the mounting bracket (both sides of coilpack) which creates grey tracking marks.

Usually the coil packs, sparkplugs, coilpack loom are replaced every 100,000kms under normal road use. Ignition module is not long after (could be 40,000kms or more, depending on how the car is driven, used), so worth replacing the whole ignition system.

Coilpacks fail alot earlier under track or drag use where the tuners push the limit's with the dwell settings on ECU to get more spark.

Coilpacks usually fail due to age (lots of hot, cold cycles which makes the plastic brittle and cracks), wrong sparkplug gap (don't regap to 0.8mm from stock 1.1.mm), wrong heat range. The stock 1.1mm gap creates a miss at higher rpm (damages at least 2x coilpacks, the rest fail later on one by one) due to weak ignition system, higher boost level, hence why have to regap to 0.8mm.

One upgrade is the LS V8 coilpacks (truck version with heatsink) with custom loom to suit (look at ebay or coilpack conversion thread on here for the loom). They provide more spark than stock ignition system.

[Frostedbutts]

Sounds like it is intermittently running on 5 cylinders. Can be coilpacks or ignition module (sometimes coilpack loom when it goes hard).

When coil packs fail they make the engine miss intermittently. Coilpacks leak on the seal between both halfs of coilpack, just under the mounting bracket (both sides of coilpack) which creates grey tracking marks.

Usually the coil packs, sparkplugs, coilpack loom are replaced every 100,000kms under normal road use. Ignition module is not long after (could be 40,000kms or more, depending on how the car is driven, used), so worth replacing the whole ignition system.

Coilpacks fail alot earlier under track or drag use where the tuners push the limit's with the dwell settings on ECU to get more spark.

Coilpacks usually fail due to age (lots of hot, cold cycles which makes the plastic brittle and cracks), wrong sparkplug gap (don't regap to 0.8mm from stock 1.1.mm), wrong heat range. The stock 1.1mm gap creates a miss at higher rpm (damages at least 2x coilpacks, the rest fail later on one by one) due to weak ignition system, higher boost level, hence why have to regap to 0.8mm.

One upgrade is the LS V8 coilpacks (truck version with heatsink) with custom loom to suit (look at ebay or coilpack conversion thread on here for the loom). They provide more spark than stock ignition system.

That's what I was thinking of doing, however after reading more into it I'd need to change the dwell time for those coilpacks and I'm on the stock ECU. I'd hate to shell out $400 for the splitfires just because I can't do that. Is changing the dwell time really necessary?

[Skym]

That's what I was thinking of doing, however after reading more into it I'd need to change the dwell time for those coilpacks and I'm on the stock ECU. I'd hate to shell out $400 for the splitfires just because I can't do that. Is changing the dwell time really necessary?

Supposedly it's not necessary until pushing over 20psi. At least that's what I can remember someone said on here with RB25DET.

But you are meant to match dwell settings to coilpacks installed. Splitfires are said to handle more dwell, but some tuners have found that stock coilpacks handle it better on GTR's.

If drag or racetrack you shift to a proper CDI, coilpack setup from Motec and fit a Motec ECU at the same time. But like with most things, it's all how much you have to spend.

[Frostedbutts]

Well, with that in mind it looks like it might be time for some LS2 coilpacks.

I pulled the coilpacks again and applied grease to the base of them like it is suggested. I also noticed that some of the little springs in the coil packs were a little loose, so I pushed them back into the spots and they seemed to sit better in there (or so I think). I read some posts that there is supposed to be a "piece of carbon" inside, all my coilpacks were just the metal spring.

Then I tested the coilpacks and I am getting 1.1 ohms or resistance on each, which is out of spec.

I put everything back together in there and it's still not running on all cylinders, same issue. I still find it hard to believe that in just changing my plugs my coilpacks decided to stop firing - is there anything I should check before dropping a few hundred on new coilpacks?

[Skym]

When tested the coilpacks on my car, used a coilpack testing machine where you can see the spark output. Two coilpacks showed low spark output and the rest looked ok.

Missing can be caused by injector playing up (usually on high km engine), injector loom, coilpack loom, coilpacks, ignition module, o2 sensor making engine run lean (lean missfire at idle), blocked fuel filter (lean missfire).

Airleak just behind one or both MAF's which makes the engine stutter (similar to failing coilpack). You then tighten the intake hose clamps on the MAF's and look for cracks in rubber intake piping after the MAF's.

Sometimes a intake airleak before MAF can make it hit the boost cut alot earlier on ECU and would happen around 3000rpm+. It's due to using clamp onto adaptor type of airfilters. Usually the fix is to buy Apexi airfilters that bolt onto the MAF's with a gasket inbetween them (supplied with the airfilters).

Spring with piece on end is series 1 coilpack (around 1989-1991) and series 2 coilpack has just the spring (around 1991-1993).

[RixR32]

Which plugs did you use?
I replaced mine with the NGK BKR7E that several people said worked well, and had this issue shortly after. Thinking it couldn't be my new plugs I chased the problem replacing other things. Changed plugs back to new BCPR6EIX, (.8 gap) & ran great again and ever since.

[Frostedbutts]

Which plugs did you use?
I replaced mine with the NGK BKR7E that several people said worked well, and had this issue shortly after. Thinking it couldn't be my new plugs I chased the problem replacing other things. Changed plugs back to new BCPR6EIX, (.8 gap) & ran great again and ever since.

I replaced them with those plugs - after looking around online I'm seeing the same thing you are where some people are having issues with them. I'm going to put the old plugs back in (even though they're toast) to see if I still have the same issue.

[Frostedbutts]

It looks like I found the real issue upon further inspection. This is what my coil harness looked like on cylinder #4 (or 3 depending on which way you count?)



And this is what that spark plug looked like:



This is what the other plugs and harness connectors look like normally:








Those two broken center tabs are obviously making it so that the coil isn't firing. Does anyone have a suggestion on fixing this? Or am I going to have to buy an entirely new harness to fix it?

[steveo1502]

The harness is cheap from wiring specialties, or switch to lq9 coils, make your own harness, and get rid of the ignitor

[Skym]

Count from front of engine to back of engine. Engine fires 1st cylinder first, closest to CAS that's mounted on front of exhaust cam.

It looks like the coilpack loom needs to be replaced. Be aware that the stock coilpack loom cylinder numbers / stickers fall off, so best to remove those.

But can pop the back of the plug (should be tabs that clips on) and replace the plug itself (from another coilpack loom or supplier of coilpack plugs).

[Frostedbutts]

I found the clips on WiringSpecialties but they're $12 shipped and would take 5 business days, normally I'd be inclined to wait but I'm going to go to a junkyard tomorrow to pick up some LS2 coils anyway. I'm going to stop and see if I can find a Sentra or G20 with the SR20DE that still has the coil pack loom in place, since the clips are the exact same. I'll just clip the connector and then solder it up while I wait on my harness to be built.

Thanks for the help!

[Skym]

You're welcome.