DVerdeyen

iTrader: (1)

Okay, so before I get flammed, I'm simply asking for other opinions before I go throwing money at a Mazda dealer or a rebuild.

About two months ago, I was having trouble with hot starts RARELY. Typically after a fill up. It would take ~1-1.5seconds to start, the rare bad occasion a full 2.5 seconds. Typical reasons obv.. Compression, coils, plugs... so on.

I checked out my coils a month ago.. They were bad (white dots/thumb print looks) so I went ahead and changed coils/plugs/wires. Great!

So lately, cold starts are fine. 1-1.5 seconds as usual. I've noticed once or twice at school that when starting from a cold start, the coolant light would flash for a couple seconds as the car started and the rpms would shoot to 3k and as it warmed up go back down, coolant light would go back off.

Last night, after filling up had another pretty rough hot start. 2.5 seconds which seemed as if it barely wanted to start and for the first time coolant light flashed while hot. Lasted about 3-4 seconds and went back off.

When hot, I have also notice at lights that the cars rpms stay ~1k, but will dip to around 850rpm and the car shakes. Can definitely see it in the hood, but it quickly goes back to 1k.

I have also had only once (recently), where I have pulled up to a light and the rpms dipped so low the car died, however fired back up as if nothing ever happened.

After researching, I've seen that this is most likely compression. Possible vacuum leak. Not coils/plugs/wires since those are done. I've also seen where it could be the coolant seals since the coolant light is flashing when starting.

So with the shaking, I would assume vacuum leak possibly. Hot starts I would assume compression.

However the kicker for me is that when on the roads with three other Rx8s, I seem to have the most power. If we line up and take off from lets say, 30mph I seem to have no problem with inching forward slightly. (all of our cars having equal mods to exhaust only) So if all the cars were equal and I was displaying good power through all gears and rpms wouldn't that show healthy compression??

I'm lost with all of this and before I go spending money trying to figure all of this out I ask for some other opinions/things to look for to help me out. Would seafoaming the engine help any? I just started reading up on it and began to wonder if that would help find any vacuum leaks.

Thanks Guys!

RIWWP

iTrader: (2)

Your coils may have been failing, but the white spots can occur with good coils, and may not occur with bad coils. Mazda sent all dealers a notice to tell them to stop using the white marks to diagnose coil health.
See http://farm8.staticflickr.com/7014/6...590da245_z.jpg

Have you adjusted your idle speed in a map change? If stock maps, 850rpm is where it should be, the 1k indicates something is wrong.




Disconnect your battery, clean your MAF, reconnect the battery, let the car idle warm and then sit there idling for a few minutes before driving. See if the problem continues. I'm leaning toward a fuel trim problem, which might be due to a vacuum leak or MAF fouling.

If the problems persist, get an OBD2 bluetooth adapter and take a look at fuel trims (long and short) and MAF while at a hot idle. If you see +5% or more combined LTFT + STFT and under 5g/s of MAF then you have a vacuum leak you will need to locate.

DVerdeyen

iTrader: (1)

I purchased the car with 58k miles. I'm now at 78k and by the looks of the previous owner, it did not look as if he would take the time to change them. I see what you're saying with the spots. One coil did have, as described, that white circle. So I assumed when changing them that the one was still good. The other three looked much worse. Much more white and the little spots that people describe as misfires.


I had a Cobb AP and changed it to the Stage 1 tune. Then sold the Cobb after returning it to the factory tune. Besides that I have never changed the mapping.

I cleaned the battery terminals when I noticed the white acid on one terminal. Both are now clean and tight. MAF was just cleaned, that was my first assumption, Ill go back and redo that.

Vacuum leak is very possible. I've played with the intake switching back and forth from AEM to stock. Not too sure where to look however. Which is why I was curious if the seafoam would help me locate one.

Buddy has one I'll see if his measures that. I'll get back to you with the results.

Appreciate your suggestions. Would these cause the coolant light to display? I don't think so but you have more experience with it than I do.

RIWWP

iTrader: (2)

The coolant light bit is odd. It isn't any triggered logic through the ECU, it is one of the few sensors that is literally a simple circuit between the float and the gauge cluster. To diagnose that, you may want to pop the hood and watch the coolant bottle (if the engine is cold, you can even try to watch the float with the bottle cap off, you have a minute or so of warmup time before you will have to cap it). See if there is anything odd going on with the coolant in the bottle. If it becomes foamy all of the sudden, or there is a significant level drop, then you probably have a problem with the cooling system somewhere. If there isn't anything visual, the sensor just drops within the coolant briefly, then it might be just a failing sensor. However i've never heard of a failing float sensor only sinking on startup. If the float and coolant level don't change much at all, then it would point at something electrically wrong, perhaps the wiring is damaged and the extra cranking vibation is momentarily shorting or breaking the connection, triggering the light to flicker.

I'm not aware of any condition in which the coolant level light will flash, that capability just isn't in the circuitry.

I'm assuming you are applying the right name to the light
https://www.rx8club.com/attachments/...ng-lights1-jpg



The battery disconnect was mainly to prompt a clearing of the fuel trims, to wipe out any potential swing they may have picked up while the MAF was dirty, or from a persistant vacuum leak.

DVerdeyen

iTrader: (1)

I'll disconnect the battery, clean the maf, and try and locate the Bluetooth device. I may try and take a video of the coolant and the engine on startup. I have also just noticed the black thing, can't remember the name sorry, towards the top left of the engine, making lots of noise during startup.

Posted From RX8Club.com Android App

RIWWP

iTrader: (2)

That's the air pump, useful only if you still have a cat installed, and only ever activated just after cold startup. Will never affect anything else other than cat life.

DVerdeyen

iTrader: (1)

No cat so I suppose no worries there.

Posted From RX8Club.com Android App

RIWWP

iTrader: (2)

You can unplug it safely if you want, though it will cause a CEL if not blocked in a flash.

CRAZ8

I was seeing a coolant light briefly on cold start ups. We found a small crack in the radiator.
The rad was replaced and never had a problem since.

DVerdeyen

iTrader: (1)

Where did you find your crack? Bottom?

Posted From RX8Club.com Android App

CRAZ8

It was actually at the top, middle

Nadrealista

you might have very slow coolant leak.when car is hot system is pressurized and might leak into rotor chamber giving you hard start, but that should always be the case not only after putting gas into the car.....

DVerdeyen

iTrader: (1)

The only time I see the light come on is once in a while when starting, (bit more frequently lately but still random) or when I'm pushing it fairly hard on the highway typically only when behind another car at 90+. Also, this only began to happen when I put the stock airbox back in and would never happen when I had the AEM in.

DVerdeyen

iTrader: (1)

Plus I see no white smoke as if it was coolant burning or any color unusual at that.

Posted From RX8Club.com Android App

DVerdeyen

iTrader: (1)

Checked my codes. Only one was for the O2 on the cat. Just reset everything with the battery being unplugged. Will see if that changes anything.

Posted From RX8Club.com Android App