Rb20 Misfire

[ima_slap_joO]

Gday, over the last couple of months ive noticed a pretty bad misfire at and above 4k rpm, which it will always do. I noticed after driving for around 3 hours last week the misfire completely went away, only to come back later. I've tried changing the coilpacks which i beleived could have been the culprit though with changing 4 out to rb25 packs which were working fine prior to me receiving them, i cant get any combination of coil- on plug to eradicate my misfire. I have just removed all the coilppacks and plugs, and ive noticed 1,2,3 cyl experiencing yellow discolouration at the lowest part of the ceramic on NGK platinum plugs, less that 4000 ks old. 4,5,6 cyl plug seem in much better condition, though cyl 2 plug having experienced the worst of the lot, with the yellow looking more intense, resembling sunburn-orange at the lowest point. This leads me to believe cyl 2 must have had the worst of the misfire, with possible misses coming from 1 and 3, as those 3 coils have all had more heat delivered to the ceramic. Those coils have all been replaced, with all combinations of coil i have (10 in total) having been tried. I was running 14 psi with no issues for 3 years, and after noticing the misfire i have wound it back to the lowest possible, 12 psi, though it dosent make a difference 12, or 14. Up to 4000 rpm the car is fine, idles fine and no smoke. The issue could have originated around the time i originally changed the old plugs, which were iridiums. Anyone got any ideas to solve my misfire issue? Ta

[hnito2]

it could be the ignitor... best bet would be to buy some new splitfires, new plugs n see wat happens, if its still missing then try a new ignitor n loom....

[ORIGIN]

had the same problem with my rb20 changed plugs then it was all good

[slider_grub]

I seem to have a similar problem. After i started boosting 1 bar ( Everything else stock except im using a Blitz ECU and 1 bar external wastegate), i used to have a jerk once in a while, especially on cooler days on full throttle when the wastegate opens. Initially i thought i had a fuel shortage and took it to the dyno but the fueling was good. The tuner recommended spark plug change, so i changed from Denso irridium power (did about 30k kms) to NGK irridium BKR8. It was ok for a while but i seem to have the same problem now. This morning it was raining and even at low rpms, the judders abit on throttle.

1. Are my plugs too cold?

2. Im using an NLTC (68 degrees) thermostat, because it gets really hot here in malaysia and if im stuck in traffic with the AC on, the temperatures goes up abit adn i thought i had overheating issues. After installing a water temp meter, i noticed my temperature doesnt rise above 70 degrees on normal cruising without the AC on. Is this too low for optimum ECU fuel mapping? i.e The ECU thinks the engine is still warming up burns richer?

Thanks!

[ima_slap_joO]

Ok, i seem to have solved the issue. I ducked down to peps auto today and picked up 3 more platinum plugs, changed out the 3 discoloured plugs and tested that, and i still had the same issue. This lead me to beleive i have changed all that i could in that area, and the only other modification i could make would be to drop the gap on the plug down a bit, being 17 years old, the whole ignition system is getting tired and probably not delivering the energy to the plug that it needs to maintain spark, (changing to aftermarket coils could also help here). So i dropped the gap from 1.1 to around .8, possibly a little less. I also noticed a small crack in my breather cross pipe, linking the 2 rocker covers, which i cleaned a bit and duct taped it up best as i could. Anywho, started it up, gave it a bit and no problem, pulls to redline with no inkling of a misfire. I should probably look at swapping out and upgrading the coils though, im probably fighting a losing battle with these ones. Thanks for the help guys. Ta

[Galois]

Yeah changing spark plugs is the first step, and regapping them is the second. You might want to think about just going coppers mate, a lot of people here find platinums and iridiums don't last long enough to make the price worth it, and MANY have found they don't last much longer than coppers, if at all. I had a mate whose soarer used up iridiums in 3000km...

Glad the issue's fixed, misfires suck

[Galois]

Also you could go yellow jacket coilpacks as well, they're a good bit cheaper and come with a 2 year warranty.

Edited November 1, 2010 by Galois

[slider_grub]

Yeah i guess i should go for coppers too then. Any idea what heat range i should be looking at? Because now my NGKs are 8, according to the tuner, 8 is good, but according to everyone else, 6-7 is best. Im a little confused. I kinda suspect my coil packs might not be that good either. Any way to check this?

Btw, is my car being 'overcooled'

Also you could go yellow jacket coilpacks as well, they're a good bit cheaper and come with a 2 year warranty.

[Galois]

Maybe too cold, 5 is okay for completely stock, 6 is good with some extra boost

[slider_grub]

Oh ok thanks! Maybe ill try the 6, since im running 1 bar wastegate! If it is too cold, will it cause jerkiness on boost during cool days? I tried resetting my ECU as well yesterday, seemed smoother but still get jerk especially on gears 3-5.

Maybe too cold, 5 is okay for completely stock, 6 is good with some extra boost

[Galois]

Oh ok thanks! Maybe ill try the 6, since im running 1 bar wastegate! If it is too cold, will it cause jerkiness on boost during cool days? I tried resetting my ECU as well yesterday, seemed smoother but still get jerk especially on gears 3-5.

Hang on, do you mean you're running a 1 bar actuator? On a stock turbo? Do you have a boost controller? I'm guessing ecu is stock?

One bar is pretty high for a stock turbo, it'll eventually cause the ceramic turbine wheel to delaminate under high heat and rpm. If it's running 1 bar with no boost controller, it could be a leak in the factory boost controller lines.

If the plugs are too cold they foul as incomplete combustion material to land and stick to the plugs, if they're too hot they melt and die lol.

[slider_grub]

Sorry if i didnt give enough info, Im running a 1 bar external tial 38mm wastegate. ECU is blitz access, fuel pump walbro 255 and works fuel regulator set at about 37-38 psi. It was set at the dyno because initially it was too ruch at 40 psi. So my fuelling has no problems.

The jerks come normally at full throttle on a cooler/rainy day. According to the tuner, its because the fuel mixture becomes richer, hence harder to spark. whichis why i change my 30k km old denso plugs to the ngks. But after about 10k km, the problem seems to have come back. Could the coil packs be not in optimum condition. I will also try to open up the plugs this weekend to inspect the condition. When i changed the denso plugs, to my untrained eyes, it looked perfect (no fouling or overheating).

Hang on, do you mean you're running a 1 bar actuator? On a stock turbo? Do you have a boost controller? I'm guessing ecu is stock?

One bar is pretty high for a stock turbo, it'll eventually cause the ceramic turbine wheel to delaminate under high heat and rpm. If it's running 1 bar with no boost controller, it could be a leak in the factory boost controller lines.

If the plugs are too cold they foul as incomplete combustion material to land and stick to the plugs, if they're too hot they melt and die lol.

[Galois]

If the coilpacks are stock they're probably on their way out. What year and how old is the car? It's an easy upgrade to regain some slight power loss and rev-happiness from the tired old coilpacks. I'm not sure what effect those mods would have.

Usual rule is change sparkplugs for new ones, lower the gap, then change the coilpacks. Though you could just do all three, the coils will go eventually and will need the upgrade.

[slider_grub]

Well i guess the coil packs are as old as the engine. It was taken out of an R32 and transplanted into my cefiro.

Yeah maybe ill have the plugs inspected and gapped and see how it performes. The recommended gap is 0.7mm right?

If the coilpacks are stock they're probably on their way out. What year and how old is the car? It's an easy upgrade to regain some slight power loss and rev-happiness from the tired old coilpacks. I'm not sure what effect those mods would have.

Usual rule is change sparkplugs for new ones, lower the gap, then change the coilpacks. Though you could just do all three, the coils will go eventually and will need the upgrade.

[Galois]

Usually people go to 0.8mm first as you can buy the plugs in 0.8 (ngk bcpr6es, ngk bkr6es and bosch fr7dp (those are platinums, but cost like an extra 50c per plug than the ngk coppers, and might last 6000km rather than 5000km )).

[slider_grub]

Ok thanks for the info. Was running irridiums and they are really expensive here in malaysia. Changing them every 10-15k is really painful on the wallet!

Usually people go to 0.8mm first as you can buy the plugs in 0.8 (ngk bcpr6es, ngk bkr6es and bosch fr7dp (those are platinums, but cost like an extra 50c per plug than the ngk coppers, and might last 6000km rather than 5000km )).

[eightsixboy]

I wouldn't bother using platinums, I have found that just using normal ngk's are better and are cheap as chips so you can afford to replacing them every service/6 months or whatever.

Also you cant regap iridiums, you will destroy the coating on them hence another reason why I wouldnt bother with them. Also if you start boosting it past standard you really should be running a .8 to .9 gap anyways (think the iridiums are only 1.1?).

[slider_grub]

Just want to ask, should i remove the low temp thermostat and change back to stock? BEcause im running sometimes below 70 degrees C, and im not sure if that hinders performance or fuel mapping.

[mad082]

yes put the stock temp thermostat back in. that will help.

and heat range 8 plugs are way too cold for what you are running. your problem is more than likely caused by the plugs fouling up, which is why you notice it more on cold wet days. go to a heat range 6 plug and you should notice a big improvement in how the car drives. it will idle smoother.

[slider_grub]

Thanks fro the tip bro, i shall try out copper plugs and removingt he thermostat first. And yes, my idle is quite rough once the car has warmed up and i do get some fuel smell from the exhaust. Hope the coil packs are ok. I dont wanna spend to much on this motor as im planning to swap a 25 hopefully next year.

yes put the stock temp thermostat back in. that will help.

and heat range 8 plugs are way too cold for what you are running. your problem is more than likely caused by the plugs fouling up, which is why you notice it more on cold wet days. go to a heat range 6 plug and you should notice a big improvement in how the car drives. it will idle smoother.