Same hot start issue here, and I still couldn't figure out why.
If you guys can, that would be great. :)
Here's what I've done:

-new starter, 2007 2kw
-new battery
-new fuel pump-DW200 and cleaned fuel filter.
-new set of coils, wires and plugs 2 month ago.
-compression test shows high 80s on first rotor and low 90s on second rotor, 250 rpm. (before seaform)
-Seaformed the rotors via LIM.

Yet, i'm still having hot starting problem.
Fyi, NO stalling issue at red light, oil change every 3k miles.
Cat will be the next thing i'm gonna look into as Charles mentioned in the first few posts.....
Thought about fuel injectors, but the car idles and runs fine.

id usually say its your compression.
But you say its good; but readings seem weird; usually each rotor has 3 different ratio readings with a total of between 5:1 and 9.8:1 make sure its a rotary compression tester.
piston testers do not work.

upgrade your ignition system again. If it doesn't work at last youll have extras for next tune up date.
coils,
plugs,
wires.

even though u might have recently upgraded.
Id say one is not operating correctly.

RockAuto Parts Catalog is pretty cheap parts.

Another thing i might add is make sure your plugs are tight; there are torque specs on them which i cannot recall right now.

That's new to me....:SHOCKED:

lol, jk.
Yes, 3 numbers for each rotor.
First rotor around the high 80s, second rotor around the low 90s.

Gonna rule out the ignition, had the BHR before this set. Same issue.

with my 04 rx8 was it was running ok up until a month a go i stalled it then it wouldnt restart when hot then when cranking it was firing it was like a car out of fuel and it still does it now if stalled or stopped when hot ok cold starting and if its hot it will bump start straight away at less than 5mph and about 6 foot if that
also there is a sensor near the secondary air pump that had a vacuum hose on and some idiot has cut it and i do not know where the other end goes help please

Hi guys, hope u can give me some advice

I have an 04 car with a weird hot start problem. Whenever i park the car and come back it doesnt want to start. This is a partuculary anoying problem when filling it up, so i usually just let the car running or press the gas pedal to the floor to cut off the fuel supply, crank the engine for about 5s then let go of the pedal and continue cranking unil the car starts-about 10s after. However a while ago i gave the car to my mom for a test drive and the car stalled/died because she dropped the clutch too fast. I tought that it would be a problem to start the car up again because it was quite hot however that was not the case. I just crancked the engine and the car started imediately.

So my question is do u think it has a low compression problem? (i tought that was the problem for sure but im not so sure now because it starts just fine when u turn it off and start it on again. It takes lets say about a minute before the start up problem becomes apparent)

i had the Mazda dealership check the plugs and they said they were fine, but they couldnt do a compresion test because they dont have a rotary tester, and the only dealership that has it is a good 2h drive from my town, so i dont really want to spend the time and money to drive there. (i tried to arrange for me to drop the car there and wait while they do the test, but they started complicating things and i dont really trust them to do a good job)

So do u have any advice to what the problem could be and what could i do to try and fix it?

Any help is much appreciated, tnx :D

Fuel pump, compression or probably both.

Tnx for the quick reply :D

I hope it's just the fuel pump, because the car only has 45,000 miles on it, and it was driven like it should be driven :D but it is quite thirsty, i could never get it much above 15mpg, also i doesnt have a catalic converter

starting problem. and low compression
 

Hey all. I have 2004 rx8 low compression, it starts fine when I first start it in the morning but after I go to where ever I want turn it off and after 15 mind or less it takes too long to start. But I noticed when the car angels up like parked on a hill it starts fine. What's that could be please help.thanks

There's your problem. As rotary engines heat up compression decreases, when starting hot the compression is at it's lowest. There is no way to fix this problem other than an engine rebuild or a remanufactured engine.

low compression
 

How much it should cost me for any of it? Can I do it my self?

Rebuild/replace your engine. I added some to the above post to make it less vague.

mines the same wont start when hot but fine when started lots of power and engine runs sweet i have changed plugs coils leads starter to uprated one done everything and still no better still got hot start even added special oil treatment so confused what to do next cars up for sale now dont want to put any more money into it now owes me to much the cars a rubbish worst car i have ever had

Alton,

Im going to assume you did not do any research on the RX8 before you purchased it. If you had, you would have gotten a proper compression test done before hand. Your experience would have been much better.

From the way it sounds, you also have a low compression engine.


When healthy, there is nothing like a Rotary screaming down the road.

If you have any questions or concerns, the forum and Mods/Staff are always here to help.

Travis

Have you gotten a rotary compression test.

Hot-Start Issues.
 

Okay, Ive been having a hot start issue as well. Had a misfire the other day so I ordered the BHR ignition system, plugs, wires, coils, and will be installing them tomorrow. Could that fix the hot start issue?

Also, The engine has just been rebuilt and im about 600 miles into the freshly rebuilt engine. (Is there some type of break-in period for the rebuilt engine to build compression?).

And I also have read that it could also be that I may need to replace the starter. Since the engine was just rebuilt I havent gotten a compression test done. But i'm not sure, just trying to figure out the issue. Any help?

Check your fuel pump and engine compression.

Hi - I too have a 2004 Rx8, with warm starting issue
Compression just checked, and according to a local RX8 specialist mechanic, readings are ok & shouldnt be the problem (I can't quote the readings, sorry)
New more powerful starter motor installed
New coils
New sparkplugs
Engine 'de-carboned' (whatever that means)
New battery
Car has only done 78,000 km

Lots of $ spent =>No improvement

I spotted a reference to an oil additive Mazda RX8 hot start problem quickly cured with 400mls Ametech | eBay

Is this a credible solution? otherwise what else should I look at. Mechanic is out of ideas.

That sounds like the right steps. What about plug wires?


I would not trust that stuff.

Go to the mechanic and get your specific test results. IT should be 3 pressures per a rotor and an rpm.

If he does not have it in that format then I would not consider him a real specialist. Do you mind telling us who it was and where you are?

Hi , compression readings were: Front rotor 65, 67, 71 Rear rotor 75, 70, 71, at cranking speed (270 rpm).
Mechanic advised other RX8s with lower compression start fine.

I further understand the fuel pump was ok and, and spark plug leads have also been replaced. All sensors and electronic diagnostics come back fine as well.

Mechanic was Steve Sinclair, of R.E. Sinclair Ltd Christchurch, New Zealand http://www.resinclair.co.nz/services.html

The other well regarded RX8 specialist in town is Al Marsh of Al Marsh Automotve, who has also looked at it and equally drawn a blank

You do realize those numbers are Really low right?

A rotary specialist told you it was fine?

Converted to kg/cm2 your looking at low 4's and 5's...

That motors done..

I'm assuming it was done with a rotary specific tester.
Travis

Your engine is dead.

Period. End of story.

Any who tells you different is selling something.

https://www.rx8club.com/attachments/...sion_chart.png

If those are 6.5, 6.7, and 7.1 it is just below the line. If it is PSI then it is completely dead. I'm guessing Since you're in New Zealand it might not be PSI.

Every engine is different. just because they've had vehicles work before this one might not. Or they could have been milking you for money.

^^This


Travis

Unless he was using very old equipment, I don't think we would use PSI here in NZ.

I just spotted that cranking speed is 250, not 270 rpm (https://www.rx8club.com/series-i-tec...-speed-229691/), which on that chart puts me in a slighly better spot.

Both those mechanics indicated my readings are at the 'low end of normal' and nothing to particularly worry about for a few years yet (given my moderate use).
My motor that has done only 78,000 Km (48,000 miles) The last guy described another RX8 he just worked on that was still fine after 200,000 Km (120,000 miles) on original engine.

If the engine is dead already, then I am royally scr@wed!
Car checked out as mechanically fine (apparently) a year and a half ago, cost me $11K to buy and would now cost me another $9K for engine rebuild.

sorry to hijack
 

im having a simlar issue cars performance is perfect go like crazy but has a hot start issue

no loss of power until 4thj gear and only higher end rpms engine gets to temp really fast im talking 1/8 of a mile if that and the temp needle is half way from clap cold in the morning english weather

wont start when hot but will bump off straight away and has full power until 4th gear high rpms but u open the bonnet and the heat hits u like a brick

new coils plugs leads throttle body

suggestions please