Poor starting when warm
 

RX8 04 plate, 231BHP.
Just had a 60,000 service and required both O2 sensors changing because of error ( this followed both coil packs shorting ). Anyway, the car starts well from cold and drives well, BUT if after the car is well warmed up I park and switch off immediately then return within 10 minutes it fails to start 1st time. Turns over but doesn't catch. 2 or 3 attempts and it starts then and drives perfectly.

However, if when I park I allow it to idle for 60 secs then it WILL start perfectly OK.

It is almost as it there is no fuel to ignite initially. Otherwise car drives perfectly. I'm going to reset the ECU but wonder if there is anything else anyone can suggest?

Hot start issues are typically low compression. Well at least its the particular flavour of answer you will get around here for a question like that.

Get your dealer to do a compression test.

Same issue. I've been experiencing this issue since last summer. I took it in to the dealership last Aug. and they replaced my coils, wires, and plugs. The dealership also did a compression test and the results were all around mid 6's (6.4,6.3,6.5, etc.) It seemed to fix the problem for a short time. My 8 is not my daily driver. I have put 1750 mile on the car since last Aug. About 4 weeks ago I started to experience the same issue again. If I drove the car and got it up to operating temperature and then shut it off to run into 7-11 for instance and then attempted to restart it I would have a bitch of a time. I took it into the dealer last week and had a compression test done again. The results were the same as last time. However this time I am getting a new engine free of charge. The dealerships must go through the proper procedure that Mazda Usa recommends. The first step is to replace the coils, wires, and plugs when your compression is marginal. If your compression is really bad then you should get a new engine your first time around. However, if the compression is really bad you would most likely be experiencing other issues such as loss of power.

I forgot to mention my RX8 is a 2005 with 65,000 miles.

Possibly starter issue, try getting an updated version

Starter issues are more of a problem in cold weather. The symptoms he stated is definatley compression related. As I stated I had the same issues and spoke with the head mechanic at the dealership. He immediately dismissed the starter as an issue after I stated the problems I was having which are identicle to the symptoms that Paul stated in the initial post to this thread. Its not the starter based on what I'm hearing.

I agree.
I had the same issues and it was my starter.
When I performed a compression test my results were good.
My original starter was only turning at 166rpm while my upgraded starter was turning at 248rpm according to the compression test graph I generated.
While low compression should not be ruled out because its plausible, do not ignore the possibility that it can just be the starter.

You need to correct for the RPM when doing a compression test.

Dunno if your tech (or you) did this but you will get higher compression results at a higher rpm.

So a new faster starter I guess would benefit both in rotational speed and compression <shrug> Hopefully for the OP this all it is.

This is interesting: http://foxed.ca/foxed/index.php?page=rotarycalc

And this is a good read as well: http://www.blackhaloracing.com/shopm..._S01_0122.html

Select the Compression Inspection option

wcs- Not sure if your post was directed towards me... but if so, yes I know how to perform a compression test and how to normalize the values...

yup it was directed at you but was more just my out loud ramblings .... and for the benefit of the OP who is unfortunately having these issues.

I never put the two together until I started thinking about your post.

faster starter, increased compression, better starting
sounds reasonable.

Well ... good luck to the OP!

Correct; the faster spinning starter can typically overcome heat induced loss of compression.

OP, if you have an early 2005 build you may have the older, slower, starter. There was a TSB for free upgrade but now expired due to end of b-to-b warranty for the subject year (well, most of it).

I appreciate what you are all saying and I can understand the mechanics of the situation. But why if I idle for 30 to 60 seconds before switch off do I not have the problem?

This started after the service. Plugs, filter, oil which included a flush of the system. Otherwise the car performs faultlessly.

dunno, I'm having similar issues.
I'll give it a try

Poor compression! Take the car to the dealer. You most likely will get a new engine. Go to the dealer with the relevant service bulletins to show them that you know what your talking about. Mines at the dealer right now getting a new engine and my symptoms were identicle to yours.

I have the similar problem. If I go anywhere with my car at normal temps, I need to wait at least 20 minutes before I can start it on the first try. If I go back out after 10-15 minutes, it usually takes 2-3 tries before I can get it to turn over.

Also, I have been having bad idleing problems as well as problems with stalling out when A/C is on or if I come to a complete stop too fast.

Are all of these signs of compression loss? If so, what should I take to my dealer in order to show that I know what I am talking about to see if I can get a new engine?

I still have my original starter... maybe once the Ohio weather gets reasonable I will do a compression test with both starters and compare the graphs.

@Jon,
Just as an exercise in thought, they should be the same after applying the RPM correction factor, yes?

That is something I would like to verify... but from I gathered around here, some don't believe so (unless I misunderstood some of the posts I've read).

RPM correction factor? The starter is a constant speed electric motor, with the latter 2005 and on version spinning faster. I guess now I'm misunderstanding.

Mine starts within two seconds every time; hot, cold, whatever. I do also have the BHR ignition system tho'.

While you're at it also consider testing the fuel pump. In your case it looks like low compression or a bad starter (which i doubt) but the fuel pump may cause hot starting issues. There are other problem associated to fuel pump failures which you didn't report though..

I was told by the head mechanic at the dealership that even a new starter hooked up to a charger will not spin @ 250 rpm. Simply can't happen.

Basically... he is saying/asking with my original starter spinning at ~166rpm and my upgraded one spinning at ~248rpm, they will generate different compression numbers at first.
But once I plug in the correction/normalization values (250rpm), will they be the same.

OK, I see... but of course all you need is the better initial compression to start.

I have heard that bad injectors may also cause the problem. However, the head mechanic at Turnersville Mazda has been with the company for 20 years and has yet to see an issue with injectors or the fuel pump when diagnosing warm start symptoms.

Fuel pump issues cause different hot starting problems. They do occurr and are pretty common too in hot countries :)