Hello, I have an 04 MT with 91k. Recently bought. I had the spark plugs changed at 90k, as well as a new battery. I started using 91 octane at Shell gas stations off the bat and started to notice a great increase of power after a couple weeks, which is great! But, a small problem is that after I fill up at the station, I try to start the car and it cranks longer at a warm start only after each fill up. I believe i need the 2 trailing hot start plugs, and possibly new coils. Do any of you have this happen to you? Any tips? I don't want to start buying anything until I find out what it is. Thanks.

 

Filling up logically won't affect the way your 8 starts, must be a coincidence. Rotaries tends to request more ''crankin' up'' before firing up when hot. Weak coils / wires / plugs will make it worst for sure, how's your idle ? Is performance seems different from ''cold to warm'' engine temperature ? Do you have a CEL ?

 

Idle is fine, and no CEL. As far as cold to warm temp in performance, it's normal. When I recently bought it, it did have a "delayed" time turning over after the first fill up with 91 octane(which only happened once), but it was all fixed after i put a new battery in. Do you believe i have weak coils, wires, and plugs? I wanted to buy a red top battery but I simply couldn't afford it at the time I changed the old one out.

 

Well weak coils gives you occasional missfires, rough idle, lost in performance, ''about to die'' coils will give you a free ticket for the ''engine flood 101'' show lol, slowly dying catalitic converters can cause this also. Since you just got the car you can't really see a lost of power if any, or tell if your idle is worst than usual. If you think something's wrong and even knowing a wankel takes longer to fire up when hot, i'll suggest you start with new coils. Not a bad investment since our coils are know to be weak, plugs change is always a good thing since you cant tell when they were last changed, a bad cat would rob power in upper rpms and eventually a CEL, a red top battery is a waste of $ IMO unless you're looking for maximum battery life durability or have race type high voltage coils and stuff that would benefit from it. Did you test the motor for compression ?

 

Do a test - once the car is warm, switch it off for the same amount of time that it would normally take you to fill up with fuel. See if it takes the same amount of time to start. I dont think that filling it up with fuel is causing the problem. Sounds like your typical hot start issue, which would be attributed to low compression. Old plugs and coils would certainly not help.

 

The test here has been done before. It starts up just fine. It's only after fill up. I'll play around with it next time, and wait a min or more after fill up and see if it still occurs. It's not an issue with me but allowing it to keep on this trail, something else that will becoming an issue might arise.

 

I will take up on your tip on buying new coils. I have also read in other forums that they are pretty weak. As far as idle, it's beginning to be a tiny bit rough, but I did just buy it a couple months ago and I am still trying to know my car more. As far as plugs, the dude i bought the 8 from threw in new plugs, and filter. So the plugs are fine but wires should be changed as well, I presume. And no, I did not do a compression test before I bought it since I got it really cheap, but I am aware that I get great power and speed in the high rpms. I love driving this car, man.

By the by, thanks for your responses and tips! I'll start off with a good tune-up and see where that leads me!

 

They will run with failing compression, it will need to be tested at some point, only a matter of time before it won't run at all.
Who knows how long?
In the meantime, for sure change all wires plugs & coils as a set every 30k miles.
While you are doing your tuneup, pull your airbox out for easier access, change your air filter, clean your MAF sensor with MAF cleaner, clean your ESS, and before you reinstall the box, be sure their are no rubber grommets that may have fallen onto your radiator and can jam a fan.
It happened to me, but luckily I noticed it before I put it back together.
Silicone spray lube is a good idea for those grommets to help the pegs slide in without popping them out.
Then do the 20 brake stomp.
If you disconnect your battery, (you should) you'll have to reset your traction control too.
Plenty of DIYs here for guidance.

And BE SURE you don't cross your wires, label them first if you have to.
Good luck!