Missfire Under Light Load

[Pal]

Hey Guys,

got a bit of a problem with the car as stated. I done a service last week (oil and plugs) and after that i picked up a slight misfire under light load (cruising) was ok under heavy acceleration. I changed the plugs again thinking it was a bad plug but still done it. went to cotteslow yesterday and has gotten alot worse now with it actually dropping a cylinder now and again and staying like that for a few minutes and then instantly coming good for a little while.

seems to happen when just coming off boost. I have read maybe i have a bad earth and the obvious coil pack gone (getting tested on Tuesday). Anyone had this problem?

I have used the search and alot of stuff rambles on about maybe fixing it but never seems to get to the problem.

Eric

[WARLORD BAS]

what plugs did you use? if you can provide part number that would be great.

[Pal]

the normal bkr6e coppers. at .8 gap. running about 14 to 15 psi boost on highflow turbo. these were the same as i used previous with no problems

[PROXIMITY]

All the rubber booots and springs were intact with no splits ? checked all coil connections ?

I wrap my coil boots with electrical tape this has always helped me alot.

Clean your cooler out, over long periods of time or with high crankcase breathing oil will reside in bottom of cooler, once heated it mists up when under load helping to drop spark/ cylinder.

[Stinky Rooster]

coil pack harness getting old and brittle mebbe? Probably just a simple earth leak, and when you changed out the plugs a second time you made it worse. I would throw a multimeter across the whole harness and check the resistance before anything else.

[Pal]

checking the harness and coils tomorrow, the harness is looking a bit ratty with a couple of exposed wires that i can see. wire at the fitting on the earth lead is looking a bit corroded. will rectify these tomorrow. cooler is fairly new so i don't think that is the problem. coils look in reasonable condition, can see any cracks in the boots or on the coil itself, doesn't mean that they are good though. picking up a set of proven coil packs on Monday to try out

[Pal]

Just run the car in my garage with all the lights turned off so it was pitch black and got the coil pack cover off. There are small sparks under about 4 coils at idle and come and go as the revs build. I would say from this that my coils are stuffed.

[XRATED]

Your obviously loosing alot of spark energy.

Take your coils out, clean the boots and replace any cracked boots. Wrap the boots in electrical tape or loom tape. Then spray silicone over them. Make shure the springs are in good nick and stretched out a little, also sake shure the the little black contacts at the ends are clean and square.

J.

[Pal]

have just ordered a set of yellow jacket coil packs. hope that fixes it. will do temp repair to coils to get car going for now. thanks for help guys

[rexrxr]

have just ordered a set of yellow jacket coil packs. hope that fixes it. will do temp repair to coils to get car going for now. thanks for help guys

sounds like definitly a coil pack 2 to is on thyre way out. if you washed the engine bay down recently that could be it too ive had this prob before getting moisture in the coil packs

and therefore missing try blowing the coilpacks out with compressed air b4 throwing more money around

[jonesl]

I have the same problem, If you find out what the problem is let me know =)

[Beer Baron]

well if it's only missing under light load and is fine under heavy acceleration then I'd be looking towards the 02 sensor. the symptoms you describe are textbook 02 sensor failure.

[Pal]

would this cause a minor miss or or make your car sound like a wrx. mine will have a major miss making it sound like a wrex for a minute or so and then drop back to a minor miss. the engine bay was lightly washed down but i have done exactly the same thing before with no problems. i know what to wet and what not to wet.

silastic and taped my coils today, fitted them and went for a drive. was good for a few minutes them the bad miss come back as soon as the car warmed up. what are the symptoms of a ignitor pack failing

[STATUS]

bkr6e are a bit shorter than the BCPR plugs that should be in there which can also make coil pack issues worse.

[Pal]

so what is the full code for best plug for a rb25det with 15 psi of boost. there are so many different ideas going around

[Beer Baron]

BCPR6ES with 0.9mm gap. or BCPR7ES is one range colder if you like.

[Pal]

thanks guys, have ordered a set and will put them in when i get my coils

[Pal]

fitted new yellow jacket coils and the bcpr7es spark plugs and went for a drive and is still misfiring and still sounding like a wrex. Very annoying as it will run very good then just drop out and start misfiring then it will stop as quick as it started. will look at the igniter amplifier now. anyone no where to get one and how much??? $400 bux later and still the same checked under the bonnet with all the lights off and still getting alot of lights flickering from under the new coils, not sure if this is normal.

[ezy_09s]

Sounds like a problem i had a while back & i found a bad connection at the plug of the afm.

I would check the ignitor also.

Edited March 13, 2010 by ezy_09s

[Pal]

ok, done some more investigating and i found out that No 5 cylinder is not firing sometimes ( pulled coil plug and noise didn't change), swapped coils and still not firing on 5. listened to injector a can here it clicking away so that is ok. now swinging towards maybe a sticky valve. don't think it would be burnt as comes good then crap again.