RB20 misfire problem

[AngelusRB20Freak]

I had been having a pretty nasty misfire problem for a while, just recently, I checked the coil packs, and replaced two faulty ones with Q45 coils. After that, all of the coils work perfectly, and the car is running all but perfectly. At low revs, it runs evenly, if you take it up slowly, at high revs, it runs even, the only problem is when you go full throttle, then around 8 lbs of boost it starts misfiring in a pretty ugly manner, I mean it pushes through but I'm losing a ton of power, and I'm really worried. Anyone have any ideas?

[AngelusRB20Freak]

Bump. Purdy please.

[S13 240SX]

did you check your IC pipes?

[AngelusRB20Freak]

I checked them and they're all good, no IC piping problems that I can see.

[Urnext]

I had been having a pretty nasty misfire problem for a while, just recently, I checked the coil packs, and replaced two faulty ones with Q45 coils. After that, all of the coils work perfectly, and the car is running all but perfectly. At low revs, it runs evenly, if you take it up slowly, at high revs, it runs even, the only problem is when you go full throttle, then around 8 lbs of boost it starts misfiring in a pretty ugly manner, I mean it pushes through but I'm losing a ton of power, and I'm really worried. Anyone have any ideas?

When you put the coils packs on did you throw new plugs in?

[Carl H]

could be a bad ignitor.

[AngelusRB20Freak]

No I didn't change the plugs when I replaced the coils but I changed them not too long ago, if anything a month and a half ago, think that could be a problem?And how can I test to see if its the ignitor?

[AngelusRB20Freak]

By now, Ive changed 4 of the coils, 1&2 are still old. Is it possible that the coils are crapping out only under load, and during idle they work fine? Can that happen? Cause it kinda feels like a coil, but what do I know.

[Urnext]

By now, Ive changed 4 of the coils, 1&2 are still old. Is it possible that the coils are crapping out only under load, and during idle they work fine? Can that happen? Cause it kinda feels like a coil, but what do I know.

Its definately possible under load the coil creates a lot more heat and over time that heat will break the electronic parts down unfortunatly with the rb20 were dealing with coils that could be over 15 years old. When you replaced the other coils did it make a difference? Also plugs would have been a good idea to replace mainly because you had a misfire so they are getting coated with gas that will in turn foul them out. The first signs of a plug fouling out is a misfire underload because its easier for the spark to jump somewhere other than it suppose to than it is to jump across a gas covered electrode tip. Hope this helps

[AngelusRB20Freak]

I just took out all the plugs today and they were all clean and gapped fine, so I guess they're out. How can I test the coils if they're only crapping out under load? Also, by any chance, if anyone thinks they might be able to help that is in the Miami area, please let me know.

[AngelusRB20Freak]

Update. I just unplugged coil #1( By the way, I replaced 3-6, the only old ones left were 1 & 2) and a misfire ensued, then, when I took it to high revs, the misfire worsened. I plugged it back in and unplugged #2, the misfire ensued, but, when I took it to high revs, it didn't worsen, it just stayed even. So I hypothesized that as you all told me it was a hairline crack in #2, to test this, i switched #2 and #1 and did the same testing, and the results were the same except reversed, therefore, ITS JUST A COIL! -Wipes sweat off forehead- WoOTThank you everyone for your help, I'll post again once I replace the coil.

[jdmser]

You should still replace the plugs if it's been misfiring like that.

[DriftingisLame]

No, dont replace the plugs again. If you just replaced the plugs (provided they are the correct plugs) check the gap on the plugs. If the gap is too large on the plug, under extreme pressure and heat the plug will not arc if its too far from the electrode. Do that first, since its free. If that does not help, keep messing with your coil packs, I've had about 6 coils on my motor and another motor go out, and they always seem to go out in different ways.

I've never had a problem with an ignitor, never seen one go bad. If there is a way to test it, please share..

[jdmser]

Reread the post above mine where he states that he has found the problem. Replacing plugs after you fix an ignition problem is just common sense. For the $12 it cost for a set of ngks it worth it to have zero doubts.

[matafied]

Just to add this in, and not saying that this is or isn’t the problem. I have found on my rbs that the factory 12v supply (white wire ) was not sufficient enough to supply the current needed to fire all the coil packs at high revs. I changed my coils; I changed my plugs, and then converted my ignition. still no beans, And the end result was using the factory 12v (white wire) to switch a relay which carried the larger gauge wire coming strait from the battery 12v source fixed everything! and yes changing the plugs after its been misfiring is only common sense, i cant tell you how many sets of plugs i went through! but the set of AC Delcos i have in now are by far the best yet, and they had 70K on them when i pulled them out of a 06 malibu havent let me down to date!!

[Urnext]

Just to add this in, and not saying that this is or isn’t the problem. I have found on my rbs that the factory 12v supply (white wire ) was not sufficient enough to supply the current needed to fire all the coil packs at high revs. I changed my coils; I changed my plugs, and then converted my ignition. still no beans, And the end result was using the factory 12v (white wire) to switch a relay which carried the larger gauge wire coming strait from the battery 12v source fixed everything! and yes changing the plugs after its been misfiring is only common sense, i cant tell you how many sets of plugs i went through! but the set of AC Delcos i have in now are by far the best yet, and they had 70K on them when i pulled them out of a 06 malibu havent let me down to date!!

Wow!! i thought i was the only person that did the rewire for the coils lol But like you said coils are a plus and correct gap is crucial if its just a little to wide under boost it blows out the spark and if your running more boost than stock tighten up the gap a little. Def sounds like a coil problem here but why waste your time just putting coils in when you should throw plugs in too so you know they aren't fouled from the misfiring