Hello all,

So I have a 2006 RX8 with 133.000 km more or less, no CAT, I did a rebuild at 120.000km (2 years ago), changed battery too.

Changed Plugs, Coils, Wires 3.000km ago and the starter too. And at that time I did a compression test with those results: 556 585 528 and 490 457 554

I use 20w50 idemitsu oil and premix sometimes.

Last month I left the car at Mazda for a clutch issue, and when I went to get her back I noticed a slower cold start from usual. I though that she needed some revs so I did it, took her for a long run, since the temps were still quite mild.

And so I left her at the garage for a week because of temp drops reaching 5C, and since it was raining all week.

After going back to her and turning the car on, it did but was slower at doing so and the RPM didn't go close to 2000 at first...
Here video:


So I checked the next day coolant and oil levels, but both were ok, i added premix oil, to help it run smoother, i did a small run but everything was ok, it would reach 9k rpm and had no idle issues, no hot start issues.

So I left the car and decided to use her the next day, here video:


As you can see it got better, so i decided to use her for a third day, here video:


Even better than the second, so I also decided to do a bit of hot starts, and most of them were like this:


So I though that the issue was resolved and left the car again for 1 week, but when I went to turn her on, it gave me the same cold start as the first one (outside temps around 2C)


and strange enough it has a hammer sound under car and you can hear it well at the exhaust:


The car idles, at 800 rpm with a small variation of 50rpm, the maf is at 6g/s, no white smoke or blue one, no hot start issues, no drop in power, it reaches 9k rpm.

What do you think it could be ? Is it the engine or did the Mazda dealers forgot something or didn't attack it well ?

 

What unit are the compression numbers in?

Revving over 2000 on a cold start sounds weird. I don't think it's supposed to do that. Even in the dead of Canadian winter mine would go to 2000 maaaaybe. Usually 1500ish.

Are there any mods on the car?

See if you can localize the hammer sound, figure out what part of the car it's coming from . Something loose in the exhaust? Engine? Belts/pulleys? Does the sound change with rpm?

 

compression in kpa

yeah it feels like it is dying if i don’t rev a bit, at the last video you can hear a metal sound or something like that, but it only does it for first 5 sec and then goes back to normal…

no particular mods, only a bigger radiator, and a stronger starter 13 teeth, coil, wires, plugs are NGK.

the hammer sound feels like it is coming from under the car, like around the gearbox and engine, you can hear it well at the exhaust tho…

you can’t hear it from under the hood or near the front wheels…

the sound goes away if i press gas pedal, even a little gas is enough… the sound is present only on idle.

belts and pulleys don’t seem to be moving, as for exhaust i doubt they would take it down, so either Mazda reattached the Gear box badly or I dunno…

 

That's failing compression numbers though.

 

yes, so is it because of low compression ? But if so why doesn’t this happen with hot starts, but only with cold ones ?

also i noticed that if the car sits for one week, it will have a bad start (like in the last video) but if i use her daily there will be no bad cold starts…

 

If a coolant seal is compromised, coolant will seep into the combustion chamber whike the car sits and result in hard cold starts. Are you losing coolant or does the overflow bottle bubble while the car runs?

Why you're not having hot start issues with that compression I don't know, but suspect thr compression tester is lying. low 500s shouldn't be driveable.
Was the rebuild done by someone who knows what they're doing?

 

Well the dude who did the rebuild was an "expert"... at least that's what others said...

As for coolant, i'm checking it before driving, but it doesn't go down, as for bubbles, i'll have to do a test.

Anyway, today I turned her on and it was much better than yesterday, i'm sure that if i use her tomorrow too, it would be even better....

Which is crazy, I never had this in the last 4 years (not even before i did the rebuild), but yeah in the last 4 years the temps outside weren't as cold, the min was 10C but right now it's 1C

Here's a video from today:

 

Does the dude provide a warranty? Cuz uh. You might need it

 

He did for first 6 months, but it has been 2 years already...

 

Hi Loki, so after some runs, the car got better at cold starts, the hot starts are still ok like in the video...

But... today I took the car for a run since temps got better (10C now) and it had an acceleration issue, it would rev in gear but with little hicc-ups, but when I tried to rev her at idle, it did so without any issues...

After doing it i turned her off and on and had a CELL on, code P0661 which is connected to solenoid issue, actually i had this for quite some time, but it never was this strong, mostly it would do a small hicc-up between 5000 and 6000 rpm and I never had a code, at least since i had the rebuild...

Anyway I've checked here but found not much so i want to ask you, Could the bad solenoid be the issue of those hard cold starts ?

 

Google search - RX8Club - P0661=

https://www.rx8club.com/series-i-tec...-p0661-213679/

 

Yeah i did read it, but it didn't answer my question...

Which is in the comment above

 

Yes, your issues can be related to the P0661.




From Bladecutter in the linked thread;

 

Who did the compression test and with what tester? What was the engine temp when it was done? Which spark plug holes did they use? What rpm?............Compression test is a clear indication whether the engine is good, but if done incorrectly there is no point.

Have you checked the solenoid vacuum lines or plugs? Perhaps they have been swapped and your valves are being open at lower rpm instead of the cold start Secondary air pump system.

I believe the plugs should be Blue, White, Black.....although the vac diagram uses blue, red, green.

 

Thanks, I wanted to know if it could be related, i'll check everything but for sure I will change one or all of them, since they don't cost a lot.

 

It was the mechanic who knows about rotaries and does rebuilds, He used the Rotary Compression Tester the orange one.... as for temps I dunno, i wasn't there when he did it, neither spark plug holes. Rpm was 250, at least what he told me.

I will check the lines slowly, will update with new info, hope it resolves the hard cold start issue.

Thanks.

 

.

 

Update, it was the solenoid, 2 out of 3 i had to change for low voltage... also strange but the compression numbers this time went up....

from 556 585 528 and 490 457 554
to 617 597 583 and 515 654 654

it was done by the same mechanic with the same tester and same rpm (250)....