Detonation (knock)

[G-Papi]

I made it happen. After hearing of it, and being skeptical, I finally made it happen in the CX-7. My skepticism was probably fostered by my knowledge that the vehicle has a knock detector that would sense preignition, and cut power.

The chain of events is this:

1. 10 miles of expressway driving at speeds of 60 - 75 mph, and about 1/2 mile of driving after the exit.

2. Ten minutes in the pharmacy.

3. Returned to vehicle and left parking lot. At the first straight stretch, I floored it in third gear. There was a serious and loud spark knock (rattle) and a heavy cloud of grey (not blue) smoke from the exhaust pipes. (at about 4000 rpm) I immediately backed off the gas. The knock ceased (along with the smoke).

4. Easing back on the gas in 4th gear produced smooth acceleration with no knock or smoke. Heavy acceleration after that point was unable to reproduce the knock.

5. Back to the dealer I will go.

[arlsmazdaspeed]

change your plugs!!!

[G-Papi]

New car at 6k mi????

[Brian MP5T]

Shitty gas??

91 Octaine MINIMUM.

[G-Papi]

93 octane Shell

[xavier]

93 octane Shell
That was my exact situation. I was in third and I didnt even floor it. I was 1/2 throttle in third and got to about 4,000 rpms and then it started knocking. 92 octane for me all the time. I think there is a problem with the tuning and I dont think something as small as colder plugs is going to solve the problem.

[Brian MP5T]

Wow, I was totally not expecting you both to say High Test..

I also agree that the plugs are not going to solve this..

The tune is a Mazda thing so I would ask the dealer.. If many people ask the dealer, perhaps mazda will modify the map (Flash) like the MSP was in late 2003..

[xavier]

Wow, I was totally not expecting you both to say High Test..

I also agree that the plugs are not going to solve this..

The tune is a Mazda thing so I would ask the dealer.. If many people ask the dealer, perhaps mazda will modify the map (Flash) like the MSP was in late 2003..
Thats where Im starting but I have already gotten "unable to duplicate the problem". Hopefully, the flash Mazda is working on for the 6th gear 60 mph hesitation and stuttering will solve the problem. Hopefully but doubtfully.

[G-Papi]

It's more likely a turbo cooling than a tuning issue. I had one other car spark knock like that. It was an older Ford that was overheating badly.

My first response (after backing out of the gas) was to check the gauges. Temperature was where it always is - about midway.

Anyway, if I get the "can not duplicate" response, then at least I'll have the episode documented, in case it blows the hell out of one of the pistons next time.

[xavier]

It's more likely a turbo cooling than a tuning issue. I had one other car spark knock like that. It was an older Ford that was overheating badly.

My first response (after backing out of the gas) was to check the gauges. Temperature was where it always is - about midway.

Anyway, if I get the "can not duplicate" response, then at least I'll have the episode documented, in case it blows the hell out of one of the pistons next time.
I understand that it is a cooling issue but thats what tuning if for. Tuning, if done correctly, minimizes the chance of detonation by monitoring variables such as timing and temp and controlling those variables if possible to keep the liklihood of detonation to a minimum. I understand that it is impossible to eliminate the chances of knock but all it takes is one instance of knock to blow a motor (if its severe enough). Not saying your motor will blow on the first instance but it could.

[1Sleepy93]

It's the damn top mount IC that causes the problem. Heat soak it and it's no longer cooling air but heating it. The grayish cloud was unburned fuel most likely.

[xavier]

Well I got a call from the dealership that has my CX7 and they said the CEL was partially due to a loose air intake boot. Now I did remove the intake baffle but I was careful to make sure the intake was reinstalled correctly. Maybe I should have tightened the intake clamps down a bit more. Anyhow that could account for my detonation as if air was entering the intake past the maf, it would cause a lean condition which would make knock more likely. I'll assume this was user error this time. PEBSWADS error! (Problem Exists Between Steering Wheel And Driver's Seat). Anyhow, I got the PCM flash, a sensor for the auto climate control, and the oil change. They are also washing her and vaccuuming her out. Woohoo. I pick her up at 4 today

[G-Papi]

I think that the loose coupling may have accounted for your CEL. The knock appears to be another issue, I believe. I had a long talk with my service advisor yesterday, and we agreed that it's probably an intercooler issue that is a "product design" matter. It presents itself as an excellent case for a turbo timer that I wish Mazda had installed as standard equipment.

As it turns out, it seems that Mazda knows something - but isn't being specific in its statement. The Owners Manual has a vaguely worded (to me) statement buried on page 4-12.


After driving at freeway speeds or up a long hill, idle the engine at least 30 seconds to cool the turbo before turning off the engine. Avoid simply shutting the engine off abruptly after a long or hard drive. Damage to the turbocharger may result.

It seems to me that that kind of information should have been more prominently displayed.

Anyways, I'm scheduled to go in tomorrow morning and go out with a technician to see if we can reproduce the condition.

Man, this sucks.

[xavier]

I hope all goes well. I picked up my CX7 yesterday and I havent been able to reproduce the knock...yet (knock on wood-no pun intended)

[G-Papi]

Could not duplicate the problem. But at least it's documented if I have problems later on. No flashes due. No codes showing. According to my ECU, everything's hunkey dorey.

[Rick's CX-7]

I think that the loose coupling may have accounted for your CEL. The knock appears to be another issue, I believe. I had a long talk with my service advisor yesterday, and we agreed that it's probably an intercooler issue that is a "product design" matter. It presents itself as an excellent case for a turbo timer that I wish Mazda had installed as standard equipment.

As it turns out, it seems that Mazda knows something - but isn't being specific in its statement. The Owners Manual has a vaguely worded (to me) statement buried on page 4-12.



It seems to me that that kind of information should have been more prominently displayed.

Anyways, I'm scheduled to go in tomorrow morning and go out with a technician to see if we can reproduce the condition.

Man, this sucks.


Mazda is not referring to detonation on page 4-12, but instead, they are referring to oil coking. The oil gets so hot inside the turbo, that it can actually turn solid and block oil lines, therefore killing the turbo. That's why some serious turbo guys have turbo timers; so their car's engine stay running after they turn the key off and exit the vehicle.

I do think the mounting of the intercooler is less than desireable. You have to think like Mazda does though....packaging, simplicity and cost.

Anyway, I wanted to say hello to everyone here. I've been a very loyal GM owner for the last 14 years and it has cost me dearly. Just got rid of my 02 Camaro Z28 for a new CX-7. I had a rare coolant leak into the engine of my Camaro and the Chevy guys refused to even aknowledge it. So I traded it! I must say the CX-7, although nowhere near my 12 sec Camaro, is very fun to drive. I really like it and fit and finish is light-years from my old car.

I do miss my Z28 though!

Again, nice to be here among my fellow ricers.

JUST KIDDING GUYS!!!!!:) :)

[G-Papi]

Welcome Rick.

[G-Papi]

There's something going on, and it all has to do with heat. The oil issue is understood, but something caused that spark knock for me, and I'm down to that in my process of elimination.

[Rick's CX-7]

Thanks, G!

I wanted to ask you all; do you feel your CX-7 fall on its face in the upper RPMs? Does your CX-7 keep on pulling hard in the higher power band. Mine seems a bit weak up top, which is a bit rare for a turbo car and even more strange for a DOHC engine. Peak power is at "only" 5k RPMs, which supports my feelings. Don't you guys see that a bit odd? Why isn't this engine making peak power a bit higher up?

Shoot, my 16V V8 kept on making power after 6k RPMs. Very weird to me!

[Rick's CX-7]

Well, as you suggested, the issued my very well be the IC. That and possibly agressive tuning.
If you look at it, the IC sits on top, which is where the heat is going to go. Add to that, the plastic casing around it and now the IC is inside a pressure cooker. Mazda does channel air to it, as long as you move. Once you stop, the IC is going to get hotter and hotter.

My advice is to not hammer it after prolonged idling, heavy city traffic and short periods of shut down.
I guess you speed freaks are going to have to wait until a front mounted IC comes out.

[xavier]

Thanks, G!

I wanted to ask you all; do you feel your CX-7 fall on its face in the upper RPMs? Does your CX-7 keep on pulling hard in the higher power band. Mine seems a bit weak up top, which is a bit rare for a turbo car and even more strange for a DOHC engine. Peak power is at "only" 5k RPMs, which supports my feelings. Don't you guys see that a bit odd? Why isn't this engine making peak power a bit higher up?

Shoot, my 16V V8 kept on making power after 6k RPMs. Very weird to me!
Id bet thats due to the downpipe and exhaust. Speed6 owners are reporting quite a bit when changing the DP

[ssinstaller]

The motor falls off at the top end because the turbo is too small to hold the stock boost levels to redline.
http://www.trueppc.com/gallery2/d/102685-1/k04-2516psi.jpg
(picture was borrowed from this thread: http://forum.***************/index.php?showtopic=62162&st=180#0)

[1Sleepy93]

Damn links are always getting masked. :(

[Zoom49]

I too have had an occational severe knock issue. This only seems to happen
when crusing at 20 mph and giving to motor gas (1/2 throttle) to accelerate. If you back off the gas everything is ok. Have tried several brands of premimum (91) sold here in Calif to no avail. Does the ECU flash help with this issue? Ours is an early build and we have not had the ECU or transmission software update. Thanks for any help.

[CX-7owner]

I too have had an occational severe knock issue. This only seems to happen
when crusing at 20 mph and giving to motor gas (1/2 throttle) to accelerate. If you back off the gas everything is ok. Have tried several brands of premimum (91) sold here in Calif to no avail. Does the ECU flash help with this issue? Ours is an early build and we have not had the ECU or transmission software update. Thanks for any help.

(confused)GET THE UPDATESSS! It might help with the knock!

[Rick's CX-7]

Papi,

Did you have the tranny in auto or manual mode?

[cx7pos]

Yes our cars knocks like a little @$@#$... I have been monitoring the Knock Retard PID from the OBD2 against boost. Most of the time the car starts to pull timing from about 3500RPM around 13-15psi, and than if the condition is right, it will pull timing again at 4700rpm if it reaches 13-14psi (anywhere from 1.5 to 5 degrees)

I am waiting for some Torco mix to arrive, and will start to see at what Octane will it stop (if it ever will). Since I live in Cali, we only have 91oct 98% of the time.

[1Sleepy93]

Yes our cars knocks like a little @$@#$... I have been monitoring the Knock Retard PID from the OBD2 against boost. Most of the time the car starts to pull timing from about 3500RPM around 13-15psi, and than if the condition is right, it will pull timing again at 4700rpm if it reaches 13-14psi (anywhere from 1.5 to 5 degrees)

I am waiting for some Torco mix to arrive, and will start to see at what Octane will it stop (if it ever will). Since I live in Cali, we only have 91oct 98% of the time.

Can you read the charge air temp on your reader? I'm curious how warm the air is after the IC.

[cx7pos]

unforunately, there is no stock sensor/sender post IC... it's obvious too, if you look at the exit of the IC it comes to the part where the BOV sits, than it goes in to the rubber hose, and than down to the TB.

HOWEVER! I am waiting for a air temp gauge to come in, as soon as I get that I can tell what air temp is going in to the TB.

I will post some data when I have the parts and after a good long log.


One good thing though... the EGT at running cruise 65mph freeway speed is about 1300F, and WOT won't go beyond 1800F. :) oh did I mention the knock retard??? LMAO

[G-Papi]

I cured my knock and my lag at the same time. I traded the ^$#&ed thing!

[civic si hb]

Just curious guys why knock with the CX-7? When i haven't heard much of anything with the MS3 or MS6 and knock?

[CX-7owner]

Low grade fuels, some of these CX-7 owners(few, very few) think its OK for anything below 91, but for others its just the places they're filling up.

[Zoom49]

Just curious guys why knock with the CX-7? When i haven't heard much of anything with the MS3 or MS6 and knock?
Maybe it has to due with the automatic transmission and engine load of heavier vehicle

[Rick's CX-7]

I cured my knock and my lag at the same time. I traded the ^$#&ed thing!


What did you get?

[1Sleepy93]

Just curious guys why knock with the CX-7? When i haven't heard much of anything with the MS3 or MS6 and knock?

Could be our smaller turbo too.

[G-Papi]

I got a Mazda6s Grand Touring Automatic 5door. Bright Island Blue and tan leather interior. The only one with that combination I could find on the east coast that had the navigation system.

I had previously owned an '04 6s GT ~ Now everything is back in the right place.

BTW ~ The knock I got with the CX was a random - unanticipated event with loads of heavy blue smoke. It had nothing to do with octane. You could floor it, get that knock - back off - floor it again, and it would run like a top.

[Rick's CX-7]

I got a Mazda6s Grand Touring Automatic 5door. Bright Island Blue and tan leather interior. The only one with that combination I could find on the east coast that had the navigation system.

I had previously owned an '04 6s GT ~ Now everything is back in the right place.

BTW ~ The knock I got with the CX was a random - unanticipated event with loads of heavy blue smoke. It had nothing to do with octane. You could floor it, get that knock - back off - floor it again, and it would run like a top.

Nothing to do with octane.....roger that!

Good luck with the new ride!

[Zoom49]

BTW ~ The knock I got with the CX was a random - unanticipated event It had nothing to do with octane. You could floor it, get that knock - back off - floor it again, and it would run like a top.

I still have this occational knock, and I too dont believe mine is related to octane. I have only used Premium (91 in Calif) and have tried several different stations and brands of gas. The ECU and TCM reprograms were recently done and had no effect. I also don't think it is related to heat soak as it happens even when the car has been driven for up to thirty minutes. Maybe it has to do with the IMRC valve? Any ideas, dealer just says "can't duplicate the problem" and as it only happens two to three times a week I am stumped.

[altaski]

I developed a knock or miss also under high load acceleration. It began after I changed spark plugs at 60k miles. The factory plugs are FoMoCo and the insulator is 1 7/16" long. The Denso Iridium plugs I replaced them with are 1 3/8" long insulators. 1/16" shorter. Since the contact in the plug boot is rigid and not springy, I thought this plug length difference could cause a small gap or just not good contact with the top of the plug. Then under high load conditions when it takes more energy to jump a gap, the miss occurs. I am going to try going back to factory plugs soon and will let you know. I also got a code P300 which is multi cylinder misfire. There has also been several, like 6 part number supercisions on the coil pack/plug boot combo but Mazda dealer can't explain if any resulted in a change in design of the contact from coil to plug. ie the spring like contact.

[wannabe]

i know of several guys in the speed3/6 world that streched the spring in the pack to help with exactly what you are saying. i haven't personally, so i can't speak to effectiveness, but from what i've read its a viable option...

[altaski]

I was wondering if anyone with a 2009-2011 CX-7 that has taken your spark plugs out has noticed what type of contact is in the plug boot? Whether it is a spring looking thing or something else?

The 2007 CX-7 has a spring looking thing. There has been about 6 part number supercisions since. I can't seem to get a dealer to call the parts center to find out about the new part number, what type of contact it has. So without actually buying one for $98 I can't find out unless one of you helpful CX-7 owners can tell me.

Please help.

[mazdaspeedfx]

I had the same thing happening.The dealer had to replace the timing sensor and it has not happened in over 10k miles.I had it at another dealer in Aberdeen Md and they kept it for a week and did NOT fix it. I took it to Belair Md. and they fixed it on the first try.