Tristan Bull

I have a problem which I think may be caused by fouled spark plugs. When I remove the plugs they are black. It's my understanding that black means a rich condition, brown is normal, and white usually means lean. My general syptoms are hard hot starting, usually a high or inconsistent idle when warm(1200rpm or so, opposed to constant 850rpm when cold), bucking during deceleration, hesitation during cruise or light acceleration, sluggish acceleration at lower rpms. The car seems to run fine at high rpm though.

I rebuilt the engine about 2k miles ago, and have had the problems since before the rebuild. Things I've done to try to fix it are: replace the TPS with a better used unit and readjust, install new ground wires and clean factory ground locations, replace spark plug wires and fuel filter(6k miles ago), clean injectors @ RC Engineering(2k miles ago), replace spark plugs(last was w/ NGK B9EGVs approx. 300 miles ago), check for vacuum leaks w/ WD40 and a little starting fluid(though I'm kind of afraid of starting fluid on a hot engine), replaced engine/tranny mounts w/ Mazdaspeed hardened mounts(done 2k miles ago w/ rebuild, thought it might help the bucking).

Things I've done with might attribute to the problem: Removed emissions, Porting w / Judge Ito's large street port template, and slightly ported exhaust, Greddy PE catback w/ downpipe/midpipe, added Crane Cams Hi-6(with no noticeable effect to the problem).

I bought this car w/ a siezed engine and I rebuilt the engine. It wasn't rebuilt right(our first time on a rotary), so it was tore down and we did it again. I decided to go ahead and port it this time. It seems to run a lot better overall now. When the engine is cold, it starts every time and runs almost perfect. These problems really start to show themselves when it's warm. I'm wondering if it's possible that the engine would be running rich and fouling the plugs. When I first put the new plugs it it seemed to run a lot better for a few days, but by the end of the week it was back to it's old self. It's strange, because I would think it would be running a tad lean if anything. But there's no indication that that is the case. Anyway, my point is that I'm not sure how many of these problems were present before I got the car, since I never got to drive it until after the rebuild and I ripped out the emissions equipment at the same time.

Icemark

why are you using 9's on the leadings if you are expereincing fouling???

Go back to 7's, the 9's might not be staying hot enough to burn properlly.

And the correct plugs are BUR7EQ for the leading, not B9EGV which are not even designed for a rotary motor, but rather it is a gold plug for mopeds (yeah, I know some people like it, I can't figure out why... it burns out earliy and has a funky flame/burn propigation if not indexed).

Tristan Bull

Well, I had the stock BUR9EQ/BUR7EQ plugs in previously and they were black w/ carbon buildup when I pulled them. I decided to try the B9EGV plugs, because I had read on one of the other forums that people had good luck with them and they are cheap(like $12 for the 4 I believe), so I figured it was worth a shot. 9 was the heat rating recommended for mild turbo engines. If you think that the plugs are my problem, then I will pick up a new set of factory plugs. But I just felt there was more to it than that, because I seemingly trashed a set of stock plugs and now the b9EGVs shortly after.

Icemark

were you getting detonation/pre-ignition that you switched to a colder plug?

I think your driveability issues are more related to the plugs... did you index the B9EGV's???

What are you using for lube in the gas, stock MOP or pre-mix... I'd probably also check my ratios.

And in your first post you mentioned checking for leaks with WD-40 and starting fluid. I would be radically more afraid of spraying WD-40 on a hot engine and it flash exploding in a fireball then i would with starting fluid. WD-40 is the spawn and spearm of the devil and has no place in automotive applications.

Tristan Bull

I was getting what I thought was an ignition breakup at higher loads/rpm. Acceleration was not smooth. It seems better now, that I have done the other things to try to fix the problem. The exception is that I still have all the low RPM driveability issues. I didn't index the B9EGV's. I guess I should have? To what distance?

I'm using the stock MOP for now. I have the adapter to run 2-stroke through it from rotary aviation. I was going to do that, and then premix a bit when I go to the track/strip/auto-x.

Well I thought WD40 would be better, since it seems to come out in a little stream whereas starting fluid comes out in a spray. But I was unaware that WD was that much more flamable. Thank you for that bit of info. I'm glad I didn't catch fire. :-O

Icemark

sure sounds like the 9's are too cold for your application

Tristan Bull

Hmmm... Well I suppose I will try some stock plugs again. It can't hurt. The hesitation and hot starting issue was occuring with the stock plugs before I replaced them as well though.

Thank you for your help btw, Icemark.

Icemark

My other concern would have been the MOP, but since you are running the stock one, I doubt that too much oil is being injected... I would just look at the plugs.

You may also consider a CDI system, like a Mallory or MSD. I was having major spark break up from about 6K up, but adding a CDI solved that. Now the spark stays clean until about 7.5k. Draw back is that the plugs tend to die earliy. I was only getting 3k miles on standard NGK coppers, but since going to Iridiums on the leadings, have gone almost double that with no signs or wear.

Tristan Bull

I have the Crane Cams Hi-6 CDI box. I will try new plugs though. Which Iridium plugs are you using in the leading? I'm guessing the plugs for the RX-8. If they are $30, then I would expect them to last 4x as long as the stock ones in order for me to pay the hefty price tag.

Icemark

Denso IRE01-27 for leadings

Tristan Bull

Great thanks. I'll try to get my lazy *** out of bed early enough before work tomorrow so that I can pick up the plugs, and hopefully that will fix my problem. If that's all it is, I'll be kicking myself in the ***, but also eternally grateful. I can see now how the plugs could create this problem though, since they're fine until it's been running for a few min. and then I guess they're probably getting fouled up.

Tristan Bull

I had to order the Denso plugs because Autozone didn't stock them anywhere locally. So I finally got to install them today. I used the IRE01-27 for leading and standard NGK BUR9EQ for trailing. The car seems more powerful, like it did when I first put in new plugs last time. However, the hesitation is still there. It doesn't seem quite as bad, but it's still present.

Over the past few days, I've used my multimeter to monitor AFM, TPS, and O2 sensor while driving and all 3 seem to check out okay. So it seems that I'm back to where I started again?

I also did a compression test today. Compression came to 75psi on both rotors. I still don't want to believe that this is a compression problem. Compression is consistent over all 3 faces on both rotors. It just seems highly unlikely to me that I would have poor compression across the board. I would like to find a way to check cranking RPM, but I don't know how without the Mazda compression tester. Anybody know?

Icemark

On the compression, you are testing with WOT and the engine warm... right?

Tristan Bull

That's correct.