Crap!

[Gravity]

Engine light was on for about 3 days steady earlier this week. DIdn't go away until yesterday when I washed the car. No biggie I thought...

Today I go to get on the hwy, pulling hard in second, and i get this rattling sound about the same 'speed' as the engine revving about 4500+ and the engine light blinking at me hard.

I was able to reproduce several time on the drive home. It only happens when high revving and doesn't sound like knock, it sounds like 'grind' or 'rattle'

My dealer's service dept was close when it happened, so I'm calling tomorrow to get an appointment.

Any ideas anyone? This isn't the first time i've noticed the rattle, but its the first time it's been this loud and associated with a blinking engine light (which I know is usually a Bad Thing)

Nothing major done to the engine. SRI and lightweight crankshaft pulley, and i've done a 'big three' upgrade, but always adding to existing wiring in the engine compartment. No ECU modifications at all.

 

[Racebrewer]

Odd. Have you listened with the hood open?

If you take a large screwdriver and hold the handle against your ear and touch various parts of the engine the noise will get transmitted. Obviously don't touch anything moving. It'll help locate the rattle.

Autozone (at least in the States) will read the code and let you know what it means. Than you have to figure what it means.

John

 

[Gravity]

Got an appt with my dealer tomorrow at 9am. :crosses-fingers:

 

[njaremka]

Engine light was on for about 3 days steady earlier this week. ....

really? i would have tried to pull the code immeadiately. a code reader should be a part of any shade-tree mechanics work box. especially since they are soo cheap these days.

 

[Racebrewer]

So what happened? Good? Bad?

John

 

[rchrist364]

………….? What happened? Also Autozone pulls codes and tells you what it means for free. But has your service department told you the problem yet and are they mod-friendly?

 

[Gravity]

So, my service dept is mod friendly (and my family's been buying and servicing there for years...) which is a good thing... They even bolted on my corksport torsion bar while it was up on the hoist for free...

So, it was an engine misfire code. There were two, one random code and one for cylinder 1. Based on the revs and timing I know when the codes happened and all. They pulled the plugs, and the coils, and everything looked ok... all other engine specs were good, O2 sensor, MAF, timing, firing angle etc...

They're a little stumped.. Simplest answer was a bad tank of gas, but i've filled up (from nearly empty) since and i've been able to reproduce the issue. I usually always run premium (91 or 94).

The service manager did suggest I might try pulling my SRI off and putting the stock intake back and seeing if i can get the problem to recur. He didn't know if it was causing the problem, but figured it might be a place to try. Only other thing I can think is the PCM/ECU is going funny, but otherwise we're all stumped.

Problem still occurring, mostly in 2nd gear, always at high revs, sometimes after shifting up (when the revs come back down)

(dunno)

 

[fluxpato]

I usually always run premium (91 or 94).

Why premium instead of regular? Can't too-high octane cause problems in engines not designed for it? Do you see any sort of performance/mpg increase using premium over regular?

 

[njaremka]

Why premium instead of regular? Can't too-high octane cause problems in engines not designed for it? Do you see any sort of performance/mpg increase using premium over regular?

thats a common myth that premium will ruin engines not designed for it. the only thing you are doing by running premium is throwing away money. if your engine was designed for regular, run regular.

 

[Guest20182]

thats a common myth that premium will ruin engines not designed for it. the only thing you are doing by running premium is throwing away money. if your engine was designed for regular, run regular.

^this this this. too bad people are idiots. No negative effects, just no real positive either.

 

[elfhearse]

I also "read" that using premium in regular design engines could cause addtional carbon build-up. Going from memory but it had to do with premium had a higher detonation point and the regular engines compression didn't permit full combustion of the premium, leading to more carbon buildup over time.
Does Canada have to suffer with ethanol tainted fuel too??

 

[Racebrewer]

Just a passing thought and perhaps a discussion point.

IMHO, cars are currently capable of running on a wide range of octane levels because they adjust ignition timing based upon input from a knock sensor.

If the ECU detects knock (via the knock sensor) it will retard the ignition timing, slightly reducing both gas mileage and performance. If I understand it correctly, the ECU will then start to increase timing until it senses knock and retards timing again. If correct, you want enough octane to keep it from knocking (which may not be loud enough to hear) to get the best performance..

Years ago a co-workers son plotted gas mileage and octane in a Camry over many tanks. In that case he found an increase in gas mileage with a higher octane that more than offset the higher cost.

I don't know where the M2 falls in regards to this, but at some point I'll run a few consecutive tank fulls of a higher octane and see if it makes a difference. It might come down to the individual car and the local chemical mix of gas.

John

 

[Racebrewer]

Hi Gravity,

I haven't taken a close look at the ignition system on the M2 myself, but if you keep getting the same code (mis-fire on #1), I'd try swapping coil pack and spark plugs between no#1 and some other cylinder and see if the problem moves with it. Code Readers have gotten cheaper and pay for themselves quickly.

Or, you could put a new spark plug in the mis-firing chamber as a start. Did anyone actually look at the plug for color, etc?

If the problem stays with the same cylinder, I'd then try swapping injectors and / or doing a leak down test.

Keep us posted.

John

 

[Gravity]

I have indeed seen both a noticeable performance increase (Likely due to the ECU advancing the timing to burn the higher octane fuel) and a measured milage increase by running high octane fuel in the car. (Based on the trip computer readings)

The guys at my dealership did pull all the plugs and tested the coil. They said the gaps were fine, plugs were clean and coil tested fine. I didn't think of injectors, would that show up on a code? When we looked at fuel/air mixture and such all the stats looked fine at the time the codes were thrown.

Hi Gravity,

I haven't taken a close look at the ignition system on the M2 myself, but if you keep getting the same code (mis-fire on #1), I'd try swapping coil pack and spark plugs between no#1 and some other cylinder and see if the problem moves with it. Code Readers have gotten cheaper and pay for themselves quickly.

Or, you could put a new spark plug in the mis-firing chamber as a start. Did anyone actually look at the plug for color, etc?

If the problem stays with the same cylinder, I'd then try swapping injectors and / or doing a leak down test.

Keep us posted.

John

 

[njaremka]

wow...

the ONLY thing octane does to gasoline is increase its resistance to predetonation from compression. it fires and explodes exactly the same once the spark plug fires. also, contrary to popular belief, modern ecu's do NOT advance timing when higher grade fuel is used UNLESS the engine ecu was tuned for the higher grade fuel. if the ecu was tuned for 87, it will get no more power running 91+. if the ecu was tuned for 91+ and you run 87, you will get a reduction in power until you return to 91+ fuel.

you guys have to learn what to believe when researching on the internetz. not everything is true.

 

[Racebrewer]

" the ONLY thing octane does to gasoline is increase its resistance to predetonation from compression. it fires and explodes exactly the same once the spark plug fires. also, contrary to popular beliefmodern ecu's do NOT advance timing when higher grade fuel is used UNLESS the engine ecu was tuned for the higher grade fuel. if the ecu was tuned for 87, it will get no more power running 91+. if the ecu was tuned for 91+ and you run 87, you will get a reduction in power until you return to 91+ fuel.

you guys have to learn what to believe when researching on the internetz. not everything is true."

100% correct. However, they do retard with knock though and that is issue. Knock is caused by more heat and load than the gas can withstand. The ECU backs the timing down until the knock goes away and then advances it back. When you go to "Bob's House of Gas" do you really think you're getting the advertised octane? It may actually have been 87 at one point in its life, but that may have been many, many weeks ago before the light aromatics evaporated.

Knock is going to be influenced by weather, actual octane of the gas, load on the engine, etc, etc. The knock sensor will feel it before you do and back off the timing.

Last month I drove the 86 year old father-in-law's Civic (no knock sensor). I thought the poor thing was going to blow up it was knocking so bad. It had been fed the cheapest gas my FIL could find for a couple years.

" when researching on the internetz. not everything is true" Again, you are 100% correct. So why not test it yourself and see if it makes a difference in your car? Three tank fulls of high octane are going to add about $6.00 total to your gas bill. If your gas mileage increases by 5%, you break even. If not you can be a "voice of experience and truth" and say it didn't work for you when you tested it, otherwise you are just repeating what you read on the internet.

John

 

[fluxpato]

So if the engine's knocking with 87, then using a higher octane should stop knocking, right? Is there any way short of using a ScanGauge to tell whether the engine's knocking? What sort of decrease in fuel economy would be present in an engine with retarded timing/knock vs one running without any knock/normal timing?

 

[Racebrewer]

Take a look at Ultragauge for a cheaper alternative.

Probably just a small percentage. The differences ain't gonna be much at all.

John

 

[Racebrewer]

Hey Gravity,

Regarding the rattle, take a look at:

http://www.mazdas247.com/forum/showthread.php?123799823-Corksport-SRI-and-check-engine-light

Look in the last few posts. This may be your noise.

John

 

[Gravity]

Update: Spoke with Corksport yesterday regarding the crankshaft pulley, and they advised that I should remove it and put the stock one back until they remanufacture the new corrected batch.

My dealership replaced the stock pulley today and the noise is gone and I can't get the misfire to happen again. An inspection of the Corksport part does reveal that the timing wheel is loose and rattling on the pulley. Has this solved the issue? We'll have to wait and see now!