Suspect overheating causing pinging/pre-detonation sounds
 

Hi everyone, I've been trying to diagnose this for awhile and the problem still persists. The symptoms are you get that loud rattling noise on WOT at RPM's above 5000 rpm. It only happens when the car has warmed up and has been driven for some time. If it has just warmed up to operating temperature and you redline it, there is no noise. This noise is accompanied by loss of power. It comes only after driving for awhile. I have been posting in other threads regarding this noise but have come to no solution so I am opening a new one to ask for help.

The car is 07, 85000 km mileage 6sp. It is daily driven. Regular oil changes done every 4000km. Car is redlined frequently. No CELs. The CAT is not glowing underneath the car. Coils/plugs/wires changed at 74000km (relatively new). No misfires. No leaks anywhere underneath the car. No sweet smell, or white smoke from exhaust.


Things I have done to help fix it:
- BG44K can in fuel tank DID NOT FIX PROBLEM
- Coolant flush and fill with new Mazda FL-22 coolant DID NOT FIX PROBLEM
- Jumpered fans/tested cooling fan relay 1,2,3 all are working DID NOT FIX PROBLEM

1) I have been monitoring temps with Scangauge2, on cruise, the coolant temps stay between 81C and 82C. When I hit stop/go traffic, it's between 96C and 100C! (and this is with just 1st and 2nd gear, not even going above 4000rpm). I've flushed the coolant 2 weeks ago already. I live in Canada, the ambient temperatures when this happens is only around 10 - 15C. Is this normal in stop/go traffic?

2) I verified that the driver side fan works by turning on the A/C. Both fans are working. I've also noticed while idle, my idle temps fluctuate between 93 - 97C. The fan kicks on at 97C in idle, and stops when it goes to 93C. Is this normal?

Please help. I've read potential solutions:
- fuel pump going bad (but if its bad, why would it only dump less fuel when it's hotter? It should always be dumping less fuel even when cool)
- thermostat? how to tell? The cooling fans are coming on, and the heater core is working.
- Waterpump? how to tell?
- Radiator bad? how to tell?



EDIT: http://www.youtube.com/watch?v=5naJ9Eb2R1U

This was on May 10th at Mosport. A friend was behind me video-taping it. On the straight sections coming out of the apex of the corner, you can hear my raspy exhaust note, like misfires...

So no one has any new info to contribute?

There's no way in hell I'm in the only person with this issue. :(

I did this.....look at Mesg#52 it only takes a minute to do and now cooler air is entering your engine and it can be easily reversed when it's really cold. You do use prem gas....correct.


https://www.rx8club.com/series-i-do-yourself-forum-73/diy-throttle-body-bypass-mod-36389/page3/

Premium gas only Vpower91

1) Seems normal to me. I've always run those temps. I was surprised as well. It's never been a problem for me.

2) Fan 2 is set to turn on at 100c (214fsh) ... I would say you are ok.

I have used working fuel pump, water pump and t-stat

Fuel pump overheating could result in less fuel.
- Buy Fuel pressure gauge

I think a Cobb AP would help you out here. You can monitor so much more with that unit.

It's next to impossible to diagnose problems like this via the intertubz.
No offense but are you even sure of the sound you are getting?
Really is it detonation/Pre-ignition ....
That to me is the first thing.

I'm going to be home working on my car the whole week of May 23rd ... if you haven't gotten it fixed ... come on up ... we can start swapping parts.

Any other device out there that's less than a Cobb AP that can monitor AFR, fuel pressure through the OBD-II connector?

The price is cheap is you ask me.

Plus you get the MM tuning service.

Send the logs to Jeff and see if he goes WTF dude you got something wrong ... better have a look at blah blah blah.

Plus when you are all fixed up you get the sweet MM tune.

Win Win if you ask me.

Or you can send it to the dealer and tell them you have no idea what's wrong and you are going to leave it with them. .... lol < big bucks there >

[quote=Footman;3973951 fuel pressure through the OBD-II connector?[/quote]

OH Sorry BTW can't do fuel pressure via OBD-II .... well not out of the box anyway.

BHR can set you up.

I found the code for scangauge that monitors CAT temps and AFR... I tried it out. started the car and AFR was at 14.1, slowly increasing to 14.7 idling.

What should I be looking for?

Well there is no exactly about it, this why MM has his service.

At idle anything up around there is fine. 14.1-15.1

What counts is when the engine is under high load.

Under load you don't want the AFR quite that high, they should be in the low 13's to high 12's

My understanding is that it's hard to get an NA car to knock but if you are running leaning lets say 16 -18 then you might get knock.

I do not have the experience at pushing a car to the knock limit so I'm only guessing.

Footman, I have the exact same problem. I just took my car out from winter storage, and although i couldnt get it to repeat the sound last year ( it only happened to me once) it sounds like might be back. My cat is also fried, after driving it for 30 mins, the O2 hole was redder than a stop light.

I have a spare engine, but I dont want to use my "get out of jail free" card if I dont have to.

I will gun it a few times tomorrow to see what the AFR is at high load. Are you suggesting that if my AFR is not running rich in high load/high RPM conditions, then my fuel pump is not delivering enough fuel and thus its running lean, which will generate more heat, which the engine then compensates by retarding the timings and the retarding of the timings generate that noise?

Okay, using the Scangauge and the AFR codes people have posted for the X-Gauge, I used it to watch my AFR.

On start up, it's around 14.1 - 14.7.
Once its warmed up, the idle AFR is 14.9 - 15.1

On WOT, the AFR at best is only 13.8, I never see 12 or 11.

CAT temps have never reached 1000F, stayed between 700 and 970F or so.

So these are the data. If I am not delivering sufficient fuel at WOT, can it make this noise?

Videos below and sound clips on the last one posted by others:

https://www.rx8club.com/showpost.php...5&postcount=16

https://www.rx8club.com/showpost.php...15&postcount=1

https://www.rx8club.com/showpost.php...0&postcount=21

https://www.rx8club.com/showpost.php...4&postcount=13

Dude ... it's too hard to tell much from those sound clips.

What gear did you see the 13.8 aft at and at what rpm?
A MAF reading is important as well.

If you suspect it's fuel then you either buy a fuel pressure gauge or a new fuel pump assembly or take it to a dealer.
A compression test should be in order as well.

13.8 in 2nd and 3rd gear. RPM anywhere above 5000 rpm.

MAF is good though, no idle issues, cleaned as well. I don't have a data logger so I can't get values at every point. I'll have someone sit beside me and write down numbers I see. The gauage changes values almost every second and I'm also doing the driving, so I can't be writing down numbers.

13.8 in 2nd and 3rd gear. RPM anywhere above 5000 rpm.

MAF is good though, no idle issues, cleaned as well. I don't have a data logger so I can't get values at every point. I'll have someone sit beside me and write down numbers I see. The gauage changes values almost every second and I'm also doing the driving, so I can't be writing down numbers.

Im begining to wonder if its the PCM. Its the only part no-one is touching on.
It almost sounds like the lead coils arent firing.

http://www.youtube.com/watch?v=hglAO8CEP94

this is a video of an fc with that problem, sounds very similar no?

It sounds just like that! yes!

If it isn't firing, wouldn't I get CELs for misfires?

So we are on the same page right? Almost sounds like a subaru boxter engine, lopey and gutty, like a loud burp.


I got one, but it was the first drive after a triple seafoam.

Heres the problem, it isnt really "misfiring".

My cat is shot, I need im going to get the AP midpipe so it doesnt kill my engine. When I do, i might see if i can borrow a timing light and go on some runs to see if they are/arent running.

well, I have a backup set of coils which I know are all still working. I replaced those at 74,000km. If I change the whole set, and see if the symptoms are there, then will know it's a coil issue.

But seriously, wouldn't a not firing coil cause misfires? And why are the coils not firing after an extended drive. I think we are on the wrong path here...

coils work or don't work, they don't just not work after a longer drive.

but the PCM might be the cause. Secretly its changing things all over the place, we just dont know it.

The pcm only fires the leading coils on startup, I wonder if its shorting a circut causing it to fire only the lead coils.

When things get wacky, always blame the PCM, 9/10 times its the cause

A non firing coil would produce a CEL, would it not?

Directly, no.

Indirectly, it could cause a misfire, too rich condition.... etc, but not a " your coil is fried" code

okay, how does it explain the noise happening in high rpm and now low rpm? it's firing at low rpm, but not firing at high rpm?

I just want to be sure before I start swapping parts.

That I dont know for sure.

This is what show who is the good mechnic, and who is just a parts swapper. need to find a way to test the coils while operating.

I don't have an inductive timing light.

Lol, no-one has one. Only guys who race ol' V8's do.

http://www.youtube.com/watch?v=5naJ9Eb2R1U

This was on May 10th at Mosport. A friend was behind me video-taping it. On the straight sections coming out of the apex of the corner, you can hear my raspy exhaust note, like misfires...

Do you premix? If you don't premix, try premixing and see if it ceases. If the noise goes away and you notice no power loss, then it can be an oil injection problem (maybe due to poor oil injection). How is your oil consumption? If you burn little/no oil at all, then you can have some injectors clogged or something in the omp going bad... and this can cause 1) rattling and loss of power and 2) bad engine in the long term...

Try premixing atleast 200cc/8oz and see if it solves. Then you know it's a matter of oil injection.

If you are already premixing and you still have that problem, then you probably will need a new engine sooner or later :-/

I've never premixed since I've owned the car. The car was bought brand new. Only used Shell V-power 91. Oil changed every 4000km. The coils/plugs/wires changed 10,000km ago. No CEL misfires.

Oil does get consumed, so I don't think it's the injectors. On that track day, I was on the track for only about 20 minutes, spending time mostly between 5000 - 9000 rpm, and I used the first 1/4 mark on the oil dipstick.

Recently put in 1 can of BG44K, I've never used that before, should I put a 2nd can to clean it some more?

Might the behavior of the electronics change when heated?

I'm chasing a similar problem. Car is fine when cold, but faint raspy noise and slight loss of power above 3-4,000 rpm after driving it awhile.

Going to change coils and plugs and see.

Now that's not true.

Coils can and do exhibit issues only when hot, when the windings inside are starting to fail. I've seen this countless times in other applications.

BC.

That's not true, either.
I think I have 4 of the buggers.

One here in Colorado.
One at my sister's place in NYC.
And two up in Canada at my parent's house.

And I've never owned a V-8.

They are great tools for chasing down misfires and bad coils, however.

BC.

I have one too. The only thing I can think of to use it for anymore is to track down a misfire.

Most of the video clips you link to are mine, rotary specialist says it sounds like pinking but it isn't.

Check your SSV and VDI valves - do they have play in them both radially and axially - i.e. can you move the shafts up and down or in and out? The SSV valve on mine is quite loose and curently the prime suspect. Makes quite a clatter if you move it about.

I didn't see this post linked anywhere...I think this is possibly what you are dealing with? Or maybe it is along the same lines?

https://www.rx8club.com/series-i-trouble-shooting-95/noise-loss-power-202296/

I had almost the exact same symptoms. I bought 2 cans of seafoam. I used one like the directions on here direct you to do.

https://www.rx8club.com/showthread.p...ht=seafoam+diy

Then I put a whole can of seafoam in the gas-tank for the next fill-up.

I noticed an improvement the next day. I have since traveled about 1,000 miles and I just get a few hints of the rasp, but mostly they go away after driving it a while. I also had my coolant flushed after the seafoam. I don't know if that helped, but it definitely didn't hurt...and I'm at 90,000 miles on the original engine.

Does anyone know the terminals on the coil and what it is assigned to, and what firing voltage is required?

I want to take the set out, manually hook each set up to 12V battery, then apply the firing voltage to the 3rd terminal and see the jump on the sparkplug.

I figure this is one true way to test it.

I will try to check the SSV and VDI actuators. I'm trying to do it without dismantling too many things because doing that might introduce other problems putting it back together.

Chances are, I can't get to the engine parts when they are hot. If this is heat related (because the symptoms occur after extended drive), and it is indeed the SSV/VDI actuators, there is no way I could tell because with heat things expand and contract when cold. Thus when its cold while I check it, there maybe no play or anything wrong at all.

Can a small leak right at the MAF sensor cause these conditions? I just looked carefully at the MAF sensor and discovered that one of the screws no longer has thread biting onto the plastic intake tube. Seems the thread on the plastic is done. Anyway to fix this without having to buy a new intake box?

It's not the SSV and VDI actuators you need to check, it's the valves themselves in the intake manifold. You can check them hot or cold without getting burned.

How to check the valves? Do I have to take off the plastic intake (black assembly) to get at it? THat's a bitch to check!

I also replaced the 6 x 1/2 metal screws that were stripping the plastic intake housing with 6 x 3/4 metal screws and now the seal is TIGHT!

Footman, there are 2 you can easily check.

Stand by the passenger side tire. put your right hand under the black plastic intake. youll feel actuator, kinda hamburger shaped. feel around to the end of the rod, and there should be a little flappy thing you can push on.

The 2nd one is close to it, theres a hole in the large mass of wires, you have to poke your hand in there pretty deep, but its the same deal.


Mine were a bit sticky, but I seafoamed and moved them till they were all good again. They should push and spring back with great ease, there should require next to no effect to move them.

The secondary shutter valve on mine may well be fuggered, I don't think movement and noise like this is normal. It opens and closes ok, but is loose as hell:

http://www.youtube.com/watch?v=UahOn-XS_m4