Non-resistor plug issue? (NGK #4554)

[e30kid89]

So, I finally got my m52 turbo back in one piece and took er' out to do some shakedown driving and make sure everything is good for the year. One change I made was switching/try out the cooler NGK R5671A-8s since I had decided the least amount of boost I'm running would be 14psi. I have them gapped to a tight .020" but In boost/spool-up till 5.5/6k rpms the car hesitates/breaks up then and 5.5/6k it rips again smoothly and pulls hard to redline. Here's an example. 5th, cruising around 60mph...floor it...spool...full boost...hesitates...hesitates...feels weak till 6kish then BAM pulls hard like "normal." The AF's are all over the place when it is hesitating which looks like it is a misfire. Days before I put the car away for winter I had put down ~530whp on the dyno without any ign trouble using current hardware minus the plugs, I had been running BKR7Es since I had first ran my built motor. Can it possibly be an issue with the plugs being non-resistor? Sure feels like it, but i'm open to suggestions.

[mcoupemindy]

Don't know that this will help, but I'd suggest opening the gap up a bit and giving it a shot. They might be a bit cold for the pressure you are running. Additionally, I've noticed that those plugs are a bit more sensitive to rich misfire - which means you might be dumping a bit much fuel at those spots and the plugs are simply misfiring.

[5mall5nail5]

So, I finally got my m52 turbo back in one piece and took er' out to do some shakedown driving and make sure everything is good for the year. One change I made was switching/try out the cooler NGK R5671A-8s since I had decided the least amount of boost I'm running would be 14psi. I have them gapped to a tight .020" but In boost/spool-up till 5.5/6k rpms the car hesitates/breaks up then and 5.5/6k it rips again smoothly and pulls hard to redline. Here's an example. 5th, cruising around 60mph...floor it...spool...full boost...hesitates...hesitates...feels weak till 6kish then BAM pulls hard like "normal." The AF's are all over the place when it is hesitating which looks like it is a misfire. Days before I put the car away for winter I had put down ~530whp on the dyno without any ign trouble using current hardware minus the plugs, I had been running BKR7Es since I had first ran my built motor. Can it possibly be an issue with the plugs being non-resistor? Sure feels like it, but i'm open to suggestions.

Yep. Check your coil pack boot resistance and coil condition. The non-resistor plugs cause EFI/RFI. A break up like that is exactly what happens. The resistor in your spark plug helps arrest some of the flyback/noise dumped into the ground plane and such. Your ECU is likely getting whacked out. If you dump BKR7E's back in and it works, it's a resistance issue. I had the same thing happen when running GM coil packs on my car + non-resistor plugs. I would get breaking up/ECU resets at like 5000 RPM. Put BKR7E's back in and no issues. Today, I can run non-resistor plugs but I have brand new coils and boots on my car. I am also not running the factory ECU and have shielded my harness better.

[e30kid89]

Don't know that this will help, but I'd suggest opening the gap up a bit and giving it a shot. They might be a bit cold for the pressure you are running. Additionally, I've noticed that those plugs are a bit more sensitive to rich misfire - which means you might be dumping a bit much fuel at those spots and the plugs are simply misfiring.

Thanks for the suggestion. If ii were to choose sides my tune is currently on the rich side (11.0af in boost on pump) so that may be possibility too. may pick up a set of 7s as well to test out since I JUST threw out the set that was in the motor.

[5mall5nail5]

Thanks for the suggestion. If ii were to choose sides my tune is currently on the rich side (11.0af in boost on pump) so that may be possibility too. may pick up a set of 7s as well to test out since I JUST threw out the set that was in the motor.

11.0 is not rich enough to cause drown-out misfires. I would grab a set of resistor plugs to swap in and do a back to back test. I did this exact same thing a few years ago and identified the issue. Like I said, with new coils and boots, I have no issues today.

[NOTORIOUS VR]

I don't see why you should run anything colder then a 7 IMO... Go back to the proven BKR7E... unless you're cracking 600whp I don't see the need to go colder (I am assuming 7's are already 2 steps colder then OE) at least from personal experience with many different motors and the 7E plugs.

[e30kid89]

Yep. Check your coil pack boot resistance and coil condition. The non-resistor plugs cause EFI/RFI. A break up like that is exactly what happens. The resistor in your spark plug helps arrest some of the flyback/noise dumped into the ground plane and such. Your ECU is likely getting whacked out. If you dump BKR7E's back in and it works, it's a resistance issue. I had the same thing happen when running GM coil packs on my car + non-resistor plugs. I would get breaking up/ECU resets at like 5000 RPM. Put BKR7E's back in and no issues. Today, I can run non-resistor plugs but I have brand new coils and boots on my car. I am also not running the factory ECU and have shielded my harness better.

I'm on a "good" set of coils and boots - not brand new...and on the stock DME/ostrich 2.0 so yeah totally makes sense I agree. Gonna go run out to grab some 7s right now, hopefully I can install and test before It rains today. Shoulda just got a new set of 7E's but whatevs.

Thanks everyone for chiming in!

[e30kid89]

So I swapped in the 7s, much much better but the issue is still faintly there in the longer gears/more load (tiny bit in 3rd, and there in 4th and 5th). I'll be checking out my coils/boots next. So werid the ignition would break up until 5.5/6k then be perfect. I'd assume it would be bad to redline. Any other things I can check out?

[mcoupemindy]

So I swapped in the 7s, much much better but the issue is still faintly there in the longer gears/more load (tiny bit in 3rd, and there in 4th and 5th). I'll be checking out my coils/boots next. So werid the ignition would break up until 5.5/6k then be perfect. I'd assume it would be bad to redline. Any other things I can check out?

Not really weird at all. Where you are misfiring is purely in the torque band - and that's where most misfires happen.

[5mall5nail5]

Not really weird at all. Where you are misfiring is purely in the torque band - and that's where most misfires happen.

What makes it tough too is that when the torque peak occurs, its also the hardest time for the spark to jump the gap - its the time you also see electrical issues, etc.

[e30kid89]

I'm actually glad to hear that...I'm sure the schricks don't help either, they are a new addition this year as well. Car pulls really hard once the gremlins let me have fun. I know of a couple sets of coils I can swap with friends so I'll try that next.

[Heineken M3T]

I use #4554's and every time I started to get a miss fire under boost, it was a coil going bad.

Got tired of it happening and replaced all 6 coils, and haven't had a misfire problem in 5,000+ miles.

But my misfire would start at boost, and continue past 6,000 rpm

[e30kid89]

How about 1k ohm boots vs the 1.8k? Does that matter? I have been using a set of 1k boots since were known to be more desirable for FI...considering getting a set of new boots before I go for the coils.

[MikeE36]

I run the 4554s at .018" with no problems, but I do have fresh coils/boots.

Mike

[rpm620]

Yes they will rich misfire

[e30kid89]

So I broke out the multimeter earlier tonight.

Tested the boots, most read this (bosch 1k boots):



One boot had a bit more out of the 5



Onto the coils...my 5 bremi coils all read this:



And the one bosch coil I have read the following:




How do these numbers look? I know the bentley spec is 0.4-0.8ohms with a +/20% I think. I have my eyes on getting new coils/boots but it would be easier knowing these coils weren't 100% so I can justify it a bit more.

[mcoupemindy]

If you are mixing coil packs, that's a no-no on these engines. Many have had problems doing that just n/a.