Change Your Plugs After Buying an FD
 

I bought my FD in May and got around to changing the plugs and wires this past Saturday. Car would smoke a little on start up while cold (blue smoke) and idle kind of rough when it was below 70* outside. While changing the wires a few just slipped off without any effort and 1 plug was soaked with fuel and was rusted on one side and another had a worn electrode. After changing there is no more smoking and the idle is nice and smooth. Here are pictures of the two bad plugs. From the service records it looked like only 2 plugs were changed, those looked relatively fine, the other 2 not so much.

https://cimg4.ibsrv.net/gimg/www.rx7...4634e24f82.jpg
https://cimg5.ibsrv.net/gimg/www.rx7...ddfe3f43cc.jpg

Also, before I changed the plugs and wires I was getting a hesitation around 1800-1900rpms. I was hoping it would go away but it hasn't. Any idea what it could be? It is not the infamous 3k hesitation as I still have that. :(

Yeah those plugs are REALLY worn. The FD is hard on spark plugs, this is something that needs to be changed more often than a conventional car. Probably every 10,000-15,000 miles.

The 1800 RPM hesitation - in general, rotaries don't have much low-end torque, I never drive below 2000 RPM. Below 2k it gets really awkward and jerky, that's the nature of the engine.

Dale

The official US maintenance schedule calls for plugs to be replaced every 24 months/30,000 miles. I think 24 months may be too soon, but 30,000 miles is way too long to go.

I was lazy and ignored the time criterion altogether and only tracked the mileage. Here's what mine looked like after being in the car for only 13,000 miles.


Fronts:
https://cimg2.ibsrv.net/gimg/www.rx7...fc74b0c8f0.jpg

Rears:
https://cimg5.ibsrv.net/gimg/www.rx7...0507893901.jpg

Pull and clean every winter, if the electrode is worn replace. I don't subscribe to plugs being a 'set it and forget it' for X number of miles.

I only notice it when speeding up from a stop. Other than that I’m not below 2k ever. I won’t worry about it. Also after changing the plugs, finally burning through the tank of gas that came with it and putting in new 93, and hitting red line a few times, again it runs so much better. I missed this car so much and I’m glad to have another.

I replace them every 2 years, and usually less than 2000 miles per year.

Ed it

How fast plugs wear really depends on driving, amount of boost, etc. Lots of factors. When in doubt, change plugs.

FYI, Advance Auto Parts typically stocks RX-7 spark plugs - the little one 2 miles from my house has them in stock. They also do online ordering for in-store pickup and, with 2 seconds of Googling, they typically have a 20% off coupon for online orders. Order, get 20% off, and go pick them up at the store. If you sign up for their rewards program you will CONSTANTLY get $5 off coupons that are also fantastic.

Dale

That is exactly what I did haha

So the cold idle issue is still present. If it is below 70* outside when starting the idle is rough. It sounds like it’s missing.There is some blueish smoke also and today some of it looked a little whitish. Once it is warmed up the idle is steady and no more smoke. Videos are below. Maybe I'm overthinking it. These were the compression numbers in April before i bought the car. Rotor 1: 8.9, 6.9, 9.5 and rotor 2: 8.0, 7.8, 7.8. The guy didn't drive it much so I don't know if there was carbon build up. After I redlined it a few times it ran better to me. I changed the oil to 20w50, new spark plugs and NGK wires. I have a ceramic coated downpipe waiting to go in but I want to get this figured out before I start changing parts.

Here is the initial cold start

Cold Idle. Smoke goes away after it warms up

Warm start and short idle

Idle smoke
 

White "smoke" just looks like normal condensation burning off.

I did have issues with idle quality and blue smoke when i bought my fd previous owner had normal banjos in place of omp oil injectors caused a lumpy idle

Honestly it all sounds pretty good…and normal. It starts quickly both cold and hot, idle drops and smooths as I would expect. IIRC cold start idle was always a little lumpy on the stock ECU on mine too, but your tach is steady.
A little initial blue smoke wouldn’t bother me either…a little leak from the OMP injectors, maybe just a little getting by the control rings. But I don’t think that’s unusual at all either. And I agree, a bit of steam from condensation burning off. It’s likely if you watched other piston cars cold start you’d see something similar. :dunno:

Thanks guys. It’s not as pronounced here as it wasn’t that cold. When it does it the pops are very noticeable and sometimes the car will shake along with them. I have a new fuel filter to put in and I don’t know if the coils are original or were replaced at all. The fuel system is new Mazda oem. They change everything under the hood for it. I have a PFC here for the future but I don’t think installing it stock or with just a downpipe is necessary or will fix this problem although it would give me more readings which would be nice.