It was hot, flying down the freeway ac blasting

Hill comes up, 70 wasn't enough with the winds to keep up to speed so i gave er some gas, hit near 5k and I hear this sound like the dash is vibrating but it got worse and changed to a metal like sound, kinda like different sounding pistong engine ping. The more rpms the louder the sound, I couldnt past 6k, maybe if I kept holding it but it had no power and I thought it was just gonna POP!

It kept doing it for along time that day till I turned off the car and started driving back 100miles it was fine the rest of the way

Any ideas? I thought I was gonna loose a seal It hasnt ever done that nor is it atm, just curious what that is

 

If it drives fine when you dont have it loaded up, you may have had some detonaiton. Did it seem like someone was smashing on your engine with a large hammer? lol

Or was it just backfiring maybe?

 

Um

I know what back firing is, I'm sure a 8 yr old would lol?

It was like metal pop corn.

pop pop enough to shake the dash, the rpms SLOWLY climbed to 5.5k, dash shook like I was going 110mph, then 6k it was like **** is it gonna blow, then I let off as I could not tell what was doing that sound, I know it was the engine dead middle, plus I could not accelerate, I was only going about 80-85, normally I can hit 100-110 pretty easy from 80ish even with the automatic, now I mean I was VERY confused and scared, it felt slow as if it was on one rotor

I do think my engine has low comp tho, unless 90F temps compared to 80F have much of a HP difference, whenever its hot outside like above 90 my car runs slow as hell. I'm pretty sure low comp wouldnt cause detonation or pop corn metal sound.

I did think it was detonating, I did advance my timing but not near enough to even require hire octane gas it runs crappy like the stock timing with 89 octane (no power till 4k or so) plus it wasnt advanced much, and its been advanced for maybe a year now and I've never herd that sound.

I think my grandmas mustang pings, she thinks thats what it is, its only when you push the gas a certain amount near a certain rpm bout 3k or so depening on the situation, sounded just like that knock/ping sorta but like thousands of metal pieces (popcorn) were flying into the exhaust

Summary
Flying metal, in exhaust, pop pop pop, no power

Hopefully somone had this or knows rotaries enough to let me get a idea of what to check, I have some horrible feeling my engine is gonna blow on me, esp with the check engine light going on and off, but if the code was stored the light would stay on, it doesnt. If i push the throttle or keep driving it goes off, car runs the same (And no the check eng light was NOT on while this poping was occurring)

 

Does sound like detonation. Is your car NA or turbo?

Maybe some bad fuel, maybe you advanced the timing too much, not enough fuel going in (filter, dirty fuel injectors), spark issues (switched plug wires).

The above is what comes to mind going from more to less likely.

Maybe you were lugging the engine a bit (accelerator to the floor, too low RPM's, too high a gear, engine load high). When I go full throttle, I do it gradually, letting RPM's climb smoothly.

 

NA automatic

No this was the auto downshifting (I couldnt keep speed after I noticed it doing this thus I was so freaked out, felt like I only had half the power) stepped on the gas downshifted to about 5k ish maybe 4.8k as I hit 5.2 or so then boom it started the popcorn sound, it'd only happen then, I got to my friends town got him, poped the hood nothing odd let it get some fresh air and when I went back I took it to 8k and no prob, running like normal :|

nah the timings not advanced much at all, I spent hours trying to figure out how to adjust it without a timing light, its been a year, if it was adjusted much at all it'd run better at 89 octane (me and my dad played with different octanes it runs the same as it always had stock)

Fuel was fine as I didnt fill the tank after getting my friend, didnt change a filter or injectors after

Spark plugs havent been changed in 5k miles, if only mazda didnt put the damn ac lines in the way I would of removed them the other day and taken a look, bad plugs would cause detonation? If only autoshops didnt charge so much, I hate reaching down there in that tight space -_-

thanks

 

Check it with a light. I used to have an n/a automatic, thers no reason to run anything higher than 87. It could have run fine at that timing setting for a while until intake temps heated up or you got some poor quality gas.

Should be checkin on your plugs every couple weeks if its your daily driver. Get yourself some brake cleaner and freshen em up every once in a while if you dont want to replace them.

 

I've had this problem happen to me as well. I'm running a 1987 TII (stick shift), and it's quite the frightening experience when that happens. I've so far just been keeping RPMs lower and not driving quite as fast until I can figure it out. I have also noticed that when the noise occurs, if you have your hand sitting on the shifter, then it feels like the shifter's going to snap off in your hand (jerks around in time with the pinging sounds). Not sure if any of this information is helpful, but hopefully it can help pinpoint the problem.

If anyone has any information on the definite cause of this, then it would be greatly appreciated.

 

Possibly broken bits of the transmission spinning around where they shouldn't?

*edit* or is the wafer in your cat broken up and trying to come out?

 

just pull a plug one at a time on each rotor and turn it over...really if its a seal and it was that bad you will be able to tell which one doesnt sound like the others

 

Yep the auto wouldnt transfer the vibs as much as a manual so thats probably the same, my dash was literally vibrating more and more even making the idiot cluster black thing start popping out (idk why it never stays down anyways )

No idea how to check it with a light know any shops that may do that?

Wait, the day got hotter but on the way back I kept putting on the heater full blast and i wasnt getting it as hot, the intake temps should of been atleast 5-10f higher then when it did the popping, so I still highly doubt it was timing

Edit

I think I mentioned my check eng light goes on and off randomly, if the code was stored it'd stay on though right? So anyways will the ecu know if the OMP goes kaput? (s5)

 

To set the timing with a timing light, your going to get one of the timing lights from autozone/discount/napa/wherever and hook 1 wire to your trailing/leading coil wire and adjust it checking it with the front pulley. When you point the light at it, depending on trailing or leading, the mark on the main front pulley, you will either see red or yellow. If its the red mark (trailing), set it for 20 degrees ATDC (after top dead center. You can't set it with a standard POS timing light as its only use to doing piston which adjusts the timing the wrong way.). If you see a yellow mark (leading), set it for 5 degrees.

Long story short, look at the pic I posted. You'll realize that the 29.99 special timing gun from discount auto crap won't do it as you can't go 20 degrees ATDC, only like 5. Make sure you get one that will do it correctly.

Also, yes, the car will put itself in limp mode if the electrical part of the OMP goes out. If its a S4 OMP, it has a metal rod (mechanical OMP) which is much more reliable than the S5.

 

Just set the timing manually, I had a timing issue, set it with a light and it was still way off ( Definately my fault) but I found it you set it this way it is much easier and accurate.

There is a little yellow mark on the Eshaft pulley closest to the front cover. Line this mark up with the little pin on the front cover above the pulleys.

Take out the CAS and line up the marks on the gear and housing.

In order to keep the marks lined up when you re install the CAS take off the top cover (two screws) and hold the gear with your fingers so it doesnt move around when you install it.

Bam, timing is set

 

metal pop corn is the beautiful sound of detonation

 

eh I would but I didnt move it near enough to affect anything

Must of either been crappy as hell gas, really hot as hell intake temps (Which wouldnt make sense as my intake will pull hot air in a tlow speeds from the rad, yet I was going 70ish and it was doing it more and more

I believe ya guys as slpin said its detonation, I'm so lucky it didn't blow I was letting it do that for mins, I bet my rotors are going to look like **** when I rebuild

 

I've always heard that just one ping will kill a rotary, but after stabbing my CAS wrong and sending her knocking for a good 5 seconds under load, she held together just fine.

Prolly a different story under boost, lol.

 

i also had a similar problem under load, mine is consistent though. every time you apply power, i guess metal popcorn is a good way to describe it....

my car is under boost, is it a really bad idea to adjust timing myself?

 

Have you changed saprk plugs recently? I know when I first had my car, I changed the plugs
and accidently mixed up the trailing and leading plugs, and when the car was under load it
had these exact symptoms.

 

eyeballing it yes, I guess as stated above you can return it to stock timing, I'm not going to touch my timing I already know its good enough, maybe it was detonating.. the intake temps may have been near 100F that day.... I ran 89 the other day it makes crazy power past 5k and runs cruddy below 3k, so I'd say my timing is inbetween, I'll just have to remember to throw in 89 when its a hot hot hot day

RX-7tII88, nay.

I always do the plugs 1 by one anyways, I did however recently clean them, they needa be replaced.

 

I have a question for clarification. Are you running a turbo or are you N/A?

I ask because I spoke with my Engine Electrical professor today regarding this issue.we came up with the possibility that, since the popping noise is a form of detonation (at least it is in my case) which means that the plugs are sparking when there is no need to do so. Or rather when the engine is still in the midst of it's compressions stroke.

Now, since I'm running a turbo, it's possible that (since I'm pushing 13psi as opposed to the stock 5.5psi) there is so much air in the engine under load that when it compresses, the temperature is high enough that it ignites the fuel without needing the spark. This causes the spark to become wasted, but fire anyway. This makes that popping noise.

As for how to fix the issue, I'm not 100% sure yet. But if you're running a turbo, I would suggest turning down the pressure a bit to see if that aids the issue, or worsens it. Also, if you have the option, see if you can re-tune the engine to run under that sort of compression despite it being expensive as all get-out.

Hopefully this helps.

 

Damn, you might really be onto something here!

 

that is a pretty good theory about the whole turbo thing. i do have a turbo with a boost controller, i didn't notice the popping sound getting any worse after i turned up the boos though.

Another thing that i did actually try was disconnecting the trailing plug wires. This decreases power slightly but the sound is completely gone, it revs to 7000 no problem at all.. just buring a little more fuel.

I tried turning the boost up higher while i'm not running the trailing plug as well, but that doesn't change it, the sound is still not there... running it like this is probably pretty bad for emissions though,

 

LOL! why would you turn the boost UP if the engine is detonating? hahaha...Your trailing wires might be mixed up. Their positions are relative to the rotor housing position. T1 (coil closer to the front of the car) goes on the front rotor.

 

I heard a similar noise like this on my old motor at 6krpm or above and it turns out my exhaust insert was busted on one of the pins so it just rattled around and the diffusers broke off and shot out the exhaust on the rear rotor.

 

I suddenly feel smarter for not continuously running my engine while knocking... although it should be common sense. If it sounds / feels like someone is rapping on your engine with a huge hammer and the car is shuddering, its prolly not good to keep running it like that.

You can put on all the band aids you want, but its best to just correct the problem so your not bothered with that troublesome noise. Oh, it also might save your engine.

As for the exhaust insert, that is something I hadn't thought of. That could do a number on your cats / mufflers if you got em. It doesn't take much to get em out.