R34 GTT idle problem

[Danowner]

Most likely one of the thousands of posts about idle problems with an RB engine. So, my r34 has been running like a dream. I've owned it for about 4 months, and never had a single problem. Put in a boost controller myself about 2 months ago, never had a problem. In the last week, my car has decided to drop to 500RPM when warm, and at a complete stop, and in the last day, it's done the same thing, but the idle was very rough and a bit up and down. Here's a video of my car idling, ignore the engine as for some reason on camera it comes out to be extremely loud, but IRL is a lot quieter for some reason. I just wanted you to focus on the exhaust pattern, as that's what I'm referring to when I say rough idle. This morning when I cold started it, it did the rough idle thing, dropped to 500RPM, and went rough, rough rough and then stalled for the first time ever, started it up 2 seconds later and was all good, started fine no worries. I took of the cam cover to check the timing belt, but it looks like it's in very good condition. No tears or anything. Here's the video: R34 idle Problems

 

I'm in need of some feedback if possible, just some recommendations on what I should look to fix, maybe if someone has experience the same problem I'm having. Cheers heaps guys!

[GTSBoy]

It's misfiring.  Could be recent change in fuel composition (end of winter mix, start of summer mix) depending on where you are.  Could be dirty plug(s).  Could be dirty AFM.

The video showed it idling at ~1000rpm.  I assume it was still warming up.  If it's settling to 500 rpm (where it should be aiming for 650rpm) then that could be because of the miss, or it could be because the IACV is clogged enough to stop it controlling.  The IACV incorporates a wax pellet cold start valve that gives you your cold engine high revs but it will close as the coolant warms and if the IACV can't control with the stepper motor then you can lose idle revs.  I had to clean mine recently because of this.  Was dropping to (nice) idle of 400rpm.  Not satisfactory for driving though, as it can and will stall.

[Danowner]

Cheers heaps GTS boy, i did actually experience misfiring about a week or 2, took out 1 of the coils looked fine (was late and had to get somewhere), so I just put it all back together after checking 1. I was driving to 80km/hr and was in 2nd at about 5k RPM, car made what I can describe as a 2step firing noise, then kept going. That happened twice but under the same circumstances, never had a problem since. I checked the consult port for errors, and got code 55 which is 'no malfunction', so that's all clear. Just bought some throttle body cleaner, will get to all the air control valves when I get home. Really appreciate the help, and will keep this thread updated just in case anyone else has the same problem

[Danowner]

Cheers heaps GTS boy, i did actually experience misfiring about a week or 2, took out 1 of the coils looked fine (was late and had to get somewhere), so I just put it all back together after checking 1. I was driving to 80km/hr and was in 2nd at about 5k RPM, car made what I can describe as a 2step firing noise, then kept going. That happened twice but under the same circumstances, never had a problem since. I checked the consult port for errors, and got code 55 which is 'no malfunction', so that's all clear. Just bought some throttle body cleaner, will get to all the air control valves when I get home. Really appreciate the help, and will keep this thread updated just in case anyone else has the same problem.

[Danowner]

Also, just driving my car now, I'm experiencing really strong stutter when I'm upshifting, feels like turbo lag but turbo is hitting boost fine on the stock gauge. I'd explain it as stuttering but it's more of a hesitation, I'm shifting at about 5k, and it takes a good second to actually tourqe up again, and keep powering, hence why it feels like turbo lag, but yeah hitting high PSI fine

[GTSBoy]

It's missing.  if it will miss at idle it will miss worse under load.

[Danowner]

Here's an update: so I've changed the spark plugs, used electric dialect on all coil packs and cleaned all of them. It must be just a faulty coil pack. I've also cleaned the AFM sensor with some contact cleaner. Literally no change in performance. This must narrow it down to be the coils. I'm looking to get some spitfire coil packs, might as well go all out as I'll be adding heavy mods soon.

[Danowner]

Update 1,000,000: I've put spitfire coils in, literally no difference. I am lost. I have no idea what this could be now.

[Billyboy369]

I know that it’s been two years, but did you ever find out the problem, I am having the same in my 1999 R34 RB25DE NEO, have replaced the coilpacks and harness and spark plugs, have checked my AFM, and no change have put some injector cleaner in and there was a slight improvement but it’s still idling low and rough