RB25DET Sputtering Problem SOLVED

[TerminalVelocity]

So a couple months ago I picked up an RB25 powered kouki. The swap looked cleanly done but the car didn’t run quite right. When under load, the car would sputter at about 10psi or about 4,500 RPM resulting in a major loss of power. The car would also backfire under full throttle.

After much research looking through several threads on many forums, my dad and I found a couple tips that could help fix the problem. Below I’ve chronicled what we’ve done so that it will be easier for the next guy looking to fix his RB.

Step one was replacing the sparkplugs. The car came with NGK BKR7E plugs. I’m only at stock boost so we switched to NGK BKR6E plugs gapped to .028 in. These are one range hotter than the 7Es. There was an immediate improvement in the stuttering and backfiring, but they were both still present.

Next we noticed the fuel pressure without vacuum was only 20 psi. Raised that up to 38 psi without vacuum and the car was more responsive to throttle inputs and also drove more smoothly.

We did a check for vacuum leaks but didn’t find any.

I had read that the cause for our problems could be the coil packs arcing due to cracks in the casing from old age. We pulled the packs and there appeared to be some heat damage on the sides but we didn’t notice any cracks. To be safe we coated the sides and bottom of the packs in liquid electrical tape. Note: We originally tried using high quality electrical tape instead of the liquid tape. Heat caused the tape to slide out of position and the stuttering problem still persisted. I recommend anyone looking at this go straight to the liquid tape.

Next we pulled the rubber boot that goes over the spark plug (in the future referred to as the plug end) off of the coil pack body. This gave us access to the contact points that electrical signal for the spark is sent through. Using a dremel with brush tool. We cleaned up the contact point. We also did the same to the tip of the spring that goes into the plug end. The idea behind this is to just get a cleaner electrical connection. (be sure to reverse twist the springs out to remove to avoid damaging them)Before:After:

The last step was to ground the igniter chip and coil pack rail to the firewall. I had heard these could also arc, so we wanted to stabilize the voltage (zero difference in potential). Sorry we didn’t get any pics of the coil pack rail ground before putting the spark plug cover back on.

And that’s it. The car runs top notch and pulls like a beast. Hope this helps.

Basic car specs:97 kouki 5 speedSeries 1 rb25detAuto rb25 ecuStock turbo12psi boostNGK BKR6E plugs gapped at .028in.Factory timingFuel pressure 38 psi w/o vacuum

Keywords: rb25 stutter, sputter, mis, miss, backfire, misfire, under load,

[PorkChopExpress]

you get that liquid tape at the local home depot? i notice a little light show on all coils at night. i assume its normal.

[TerminalVelocity]

Yep Home Depot has it. lol you should probably take a look at your packs if you've got a light show goin on there.