Stumble at low rpms! Too Rich? Missfire?
 

Hey guys, I installed my greddy turbo kit about 2 months ago. It's the stock kit w/a TurboXS Type S BOV running 5psi. The BOV seems to be shimmed correctly; doesn't stall anytime and still releases boost pressure. If I drive the car normally hardly getting into boost or if at all the car seems to stumble at bit. Seems to do so more when its cold. If your rev the car up sitting still there's a good amount of hesitation low rpms before the motor seems to rev smoothly like it should. In my head I thought it could be (a) retarding the motor for the kit, (b) running to rich and its bogging when not in boost, or (c) bad plugs or coil pack. I haven't heard any misfiring while driving, and I checked the plugs to see if it was running rich. The plugs look perfect. My miata has 154,000 miles..lol..but ran fine pulls 20lbs of vacuum at idle. Maybe it's some thing i'm overlooking or its a timing issue which a bipes acu would fix. I dunno?!?! Any help would be appreciated.

When was the last time you changed the plug wires?

Changed the plugs when I put on the kit but never did the wires. Would you suggest changing them? I know it won't hurt...and if so what kind would you suggest?

Miatas tend to eat wires faster than plugs, so, yes, I would suggest you do that.

IMO - NGK Blues are fine

I have Accel wires, I changed my wires and plugs as part of my pre-turbo installation install. That actually solved my hesitation and stumbling issues pre-turbo.

ditto on the NGKs

It's going to feel pretty slugish compared to stock until you hit boost because of the timing retard. That's why most people feel the cost of the Bipes is well worth it. If you arn't getting a misfire code, then it's likely just timing. You could try setting the timing to stock 10* and going for a drive. Just be careful to stay out of the boost. If it makes it feel better in the bottom in, you have identified the issue.

Yes, I ran the car for a short while at 6° before getting the Bipes, and I don't recall the car stumbling at low RPMs, though. I do, however, recall fixing a low-RPM stumble back when I first bought the car buy changing the plug wires.

Same here, but it accelerated like a turd until 3K rpm. I love having Bipes, but I think I might have wanted to go with the Greddy E-Manage sometimes.

Curious; why?!?!

Because I had the timing retarded to 6 degrees BTDC. When I got my Bipes the following week, I timed up to 10, I'll probably go to 12 when I install the intercooler.