Misfiring RB20

[Salar]

Hey guys,

I know this topic has been covered many times, but I have found my case a bit more confusing. I did some research and tests before making this thread.

so it all pretty much started this morning when I was going to school. Car started fine ran normally when cold, however after a few kms - or 15 mins- of driving, engine started to misfire in lower RPMs like 1500-2500. Ran almost normal past 3000 RPM, full throttle, boosted good and all. But whenever stopped at red lights or started to move it ran like crap. almost sounds like a flat-4 subaru engine.

This is when it gets interesting, on this saturday I tried to swap my stock GTS-T fuel pump that has never been out, for a 1990 GTR's. But since the connections and screws were really old and tight on the GTS-T pump I decided to let it go and didn't end up swapping it. I put it back, and went for a drive on saturday night. I noticed car was misfiring in lower RPMs just a couple times for maybe 3-5 seconds. And I must mention my car has never done this before, not at least in the last 15 months. So on my way back home I decided to give it some gas to see if it comes back, but it didnt and car ran normal.

Then on Sunday, I went to get my Nistune board installed and get it tuned. That was a drive from North Van all the way to tsawwassen, did the drive with no problems. The tune is just a base remapping and I didn't do it. On Monday not much driving involved but as far as I recall, the misfiring didnt happen.

SO today afternoon I decided to have a look at my spark plugs, just the first couple cylinders and they didn't look that bad. I replaced them in the sept 2010, that was probably 6K ago. while at it also did a coil pack check just for the first cylinder though, and the coilpack was fine. I suppose when the car ran normal under full boost after 3-4K RPM the coil packs shouldn't be the problem.

I am just not sure about the ECU and tune I am on right now. Could that possibly be the problem?

Thank you for reading


car spec


RB20DET

Garrett GT2871 Turbo

3" turbo back exhaust - no cat

Apexi power intake

running on stock boost and GTS-T injectores

stock ecu with Nistune board

[Nismo_line]

try swapping out the fuel pump and change the plugs again

[nelsonmxmarc]

Check all the plugs then let us know..

Theres a flag raised when you see uprated turbo and stock fuel system, as well as neglect to tune.

Ultimately, boosting it will yield a lean condition - guaranteed. This could have potentially caused some blow by, which you'll normally see at idle since its pretty docile and there is a baseline we can grasp (ie. 1100 rpm ALL the time..). Anyways, check ALL spark plugs and let us know how they look..

Other issues to address;

1. Ignitor when hot tends to fail, if it's on its way out. So 15 min warm up may prompt this
2. Same for coilpacks. When warm, fail, if they're on the outs.
3. wiring on the fuel pump is not proper - bad ground or signal wire maybe.
4. Lean condition - bad air leak = 16+ afr = LEAN = mimics a misfire

If you have an AFR gauge, it's a good place to start!

[Salar]

checked the wires and coils today, didnt see anything wrong. replaced the spark plugs and now it's running normal again. I hope it won't come back when the car is warmer.
I thought the spark plugs should be good since they don't have much miles on them, but they were black.

Thanks guys for your help.

[nelsonmxmarc]

Rich condition wont heal itself! :P Have it tuned and you'll see a world of difference!

[TheyKilledKenny]

If it runs fine when its cold then starts to run like crap when its hot it could be a coil. If you have a small crack in one, it would seem fine when cold because the crack is small, once it heats up that crack gets bigger and could lead to the problems your having.

[Salar]

i drove the car tonight after doing the plugs and it seemed fine, but that was like 10-15 mins. i guess i'll find out tomorrow if the coils are failing.

Rich condition wont heal itself! :P Have it tuned and you'll see a world of difference!

yeah next step to install afr and a tune.

[Fast_Gts-t]

I have the same problem with my gtst it might be the spark plug what do you guys use for the rb20det? I'll try to search on the forum later...

[BenOswald]

How can you be sure your coilpacks are fine? This problem sounds verry similar to what I dealt with a few years back, the culprit was the coilpacks. They had no red dust on them and appeared to be in good shape. It took me 4 months to finally believe that was the problem and buy new oem ones. Car ran great after that.

[Salar]

you can do a test on your coilpacks. run the engine at idle and pull out each coilpack and see if it sparks and makes the engine run bad, if it does then the coilpack is good. it seems coilpacks last about 120K.

I have the same problem with my gtst it might be the spark plug what do you guys use for the rb20det? I'll try to search on the forum later...

i just bought BCPR7ES. i used to have BKR7E and they didn't last very long.

[BenOswald]

That is a way of testing (I did this test when I was trouble shootin this problem) however, if the problem is intermittent, which it sounds like it is, there is a good chance that doing that test will not show any problems with the coilpacks. My advice, replace your coilpacks with new ones, you won't loose anything, you'll gain peace of mind. IMO.

[Salar]

good point, do the Nissan dealers carry them?

[nelsonmxmarc]

The proper way to test them is to check the resistance the produce. Take the pos/neg terminal on the coilpack (its marked at the plug side) and test the resistance. I'm not 100% sure but i think that if the value exceeds .9 ohms you're in red. Anything below, your coilpacks are in good shape.

The reason to upgrade to yellowjackets and other brands of coilpack is that they produce less resistance than stock.

[Fast_Gts-t]

you can do a test on your coilpacks. run the engine at idle and pull out each coilpack and see if it sparks and makes the engine run bad, if it does then the coilpack is good. it seems coilpacks last about 120K.



i just bought BCPR7ES. i used to have BKR7E and they didn't last very long.

is there a big difference between the 2 spark plug? I need to change the plugs badly!

ty

[Salar]

right now i can't really tell you. my car runs rich and i need a tune badly.