miatex

Hello to all! Recently my car has been showing some knocking... I thought it was a bad tank of gas, but since I have a timing gun, I decided to check it...

I could not find the timing marks to be nowhere near where they were supposed to be... I then removed the #1 plug, and checked my TDC, with the dipstick, and confirmed my timing marks have definitely moved... I put a dot of whiteout where the TDC was and checked the timing...

It was actually high, but just trying to figure out how much:
Question #1: The end of the scale is 20deg right? If so, that were my timing was! I used the LINK to reduce it by 5 degrees and drive easily to avoid knocking...

I got home and tried to adjust the timing back to the 10deg, but found impossible (so far) to loosen the CAS bolt... The car has been garaged since (2 days)

Question #2: If my pulley is slipping, other than moving the timing marks around, is also responsible for the ignition advance?

Question #3: How can this be fixed?

Thanks!!

miatex

fastivab6tg25mr

what motor and what ecu are you running?

if you have an adjustable cas the pulley cant change timing. it just has marks so you can check it. my crank pulley on my BP+T moves alot also. the only way to keep the timing marks from moving is with a new pulley that hasnt separated yet. ive been driving with mine moving around for about a year with no ill effects so i assume its harmless.

curly

iTrader: (25)

pulley can change timing, or at least how it's read, by slipping. Check your main bolt torque, it can loosen, even on the long crank nose cranks. I believe fastiva is refering to a pulley slipping on the rubber vibration dampner. Not sure I've ever heard of that happening on our engines, but I have heard of crank and pulley damage due to a loosened crank bolt.

Savington

iTrader: (31)

I've seen it. Take off the plastic covers and use the notch on the oil pump/crank gear to determine actual TDC. Then see how far off the balancer is. If it's off, I would strongly recommend replacing it - the rubber bond has broken and there's not really a whole lot holding it together at that point.

Having said that, if the timing marks slip, but the main alignment mark that indexes to the arrow on the oil pump housing is still correct, that will not change the actual timing that the motor reads. The timing is based off the CAS which is up on the exhaust cam, so that balancer could come off entirely and the car would still run fine.

Bryce

iTrader: (24)

I once set my timing without knowing my harmonic damper had slipped. It ended up being 15+ degrees retarded and made flames.

hornetball

iTrader: (4)

We need to know engine year. Several changes through the years, short nose, long nose, CAS on intake cam, CAS on exhaust cam, etc.

In any case, sounds to me like you've earned yourself a TB/WP job to get in there and make sure everything's right.

soviet

iTrader: (10)

did you actually lock the timing to 10*? Because without locking the timing, 20* at idle is normal.

Ben

iTrader: (33)

A slipping damper will not affect your base timing, but will affect how you read your base timing. If you set your base timing off marks that are not accurate, then your base timing is not accurate.

I'd recommend replacing the pulley immediately with a new one. It's unfortunately not an uncommon problem, so I would not get a used pulley. Last I looked, you could get a new pulley from Mazda Motorsports for the $120 range or so (from memory).

miatex

Soviet, you rise a very important point, that I did not think about before...

I have a 93, I don't know if it is Long nose or Short nose (How can I figure this out), my ECU is a Full LINK from FM, the car is Turboed, and the timing I am reading now is not from the marks, but from the new whiteout point I made after determining TDC with the dipstick....

Now, how do I LOCK the timing to 10degrees?

Thanks!

miatex

curly

iTrader: (25)

Stock you jump two terminals under the diagnostic port with a paper clip. MS you set base timing to -10* and adjust from there. Not sure about a link.

miatex

Read the instructions, and followed them, I was actually 10deg above the recommendation!!! No wonder I had knock, thank God that the traffic jams here are everywhere and I hardly ever see boost...I think that saved my engine.

I reset the timing back to 10deg, and did a run... I saw some noise but no knock...

Thanks for the help!

miatex

DJ_Sixty

I have been searching and I find this topic closer to what I've been seeing in my car.
I have a 1600 NA and my last trackday I notice some knock.
I also notice a small drop in EGT temperature witch lead me to thinking that my ignition was a bit advanced.
I check with the light and I was right. I was 14-15 deg instead of 10.
I check TDC with the dipstick and all is good.
I set the timing to 10 again and test the car, and no knock and EGT's back to normal.

Now the question I need some help:
Is it possible for the CAS or camshaft, or anything to slip?

The CAS was tight and the screw well fixed.
In 4 years I owe this car, this is the second time this happens.
Last time I had this problem it was me that did the timing adjust to make sure it was on 10deg.
I have a FM Link ECU just like miatex, and it always runs fine.
I leave 3deg margin to knock in my ign tune just to be safe.

Any idea?

Thanks!

Savington

iTrader: (31)

Timing belt may have skipped a tooth, or the balancer marks are rotating. Both are easy to check.

DJ_Sixty

The balancer marks are in TDC when the piston is at TDC.
About the intake cam, how many deg is one tooth?

Thanks

EDIT: The car runs normal now, and feels it's fast as always.

fooger03

iTrader: (2)

360 / number of teeth on cam gear = degrees per tooth in cam gear

180 / number of teeth on crank gear = degrees per tooth in cam gear

DJ_Sixty

OK So 46 teeth on intake cam is 7.826º
The CAS was advanced 5º or a bit less so it shouldn't be it.
Do you know if the miata runs different with one tooth advanced in the intake cam?
It should loose power and gain torque. I didn't feel nothing.
In one friend car (not a miata) that happen and the idle become irregular and you feel the car had trouble reaching max rpm.
About 3 years ago the my miata didn't start and it was 3 teeth off, never understood why that happend. After setting the belt properly and check the tensioner, one year and many trackdays after, I had knock, like now, and the car was 8!!Deg advanced. I re set the timing to 10º and it was runing fine until some weeks ago.
The EGTs that time also where lower and then back to normal after re set to 10º, just like now!
Is it possible for the CAS to loose it's possition even if the screw is well tight?
I don't see what more can it be...
Can I doble check the intake cam is well set without taking the valve cover?
I don't belive that's the case, but all it's possible now.

hustler

iTrader: (6)

Supermiata damper crew is clearly meeting in another thread, lol.

fooger03

iTrader: (2)

Coincidence? You Decide.

OP, did you perform work on the front of the engine or on the ECU within a reasonable time of you discovering the problem in either case?

-------------------begin separate thought-------------------

If your timing has mysteriously changed on your post-1991 automobile while your damper hasn't delaminated, your timing belt hasn't slipped, and your CAS was reasonably tight, then we obviously aren't discussing an NA Miata...

DJ_Sixty

No work perform on the engine or ECU.
If back then one tooth did advance, and now another as well, then the car would be too much out of timing (7.8º * 2) to work well don't you think?
But lets assume that it skip one tooth some years ago and I'm running out of timing.
That doen't explain the 4-5Deg advance I was seeing a week ago, neither the EGT's right?

Even Miatex discovered that is car was 10º advanced, but unless he advanced the ignition too much because of the old pulley misleading (I never had that problem), he too found his car out of timing without doing nothing. (I'm guessing a bit)
It appears that he only checked the timing after he had knock, and then discover that the damper pulley was delaminated.
For what I know that doesn't change the timing on a NA.
He found the TDC and only after doing a new mark, he saw the ignition was 10º off.

DJ_Sixty

That's the reason I'm here asking for help.

For me it's really strange, and I don't understand.

I'm seeing that no one had this problem, but I will NOT disregard the intake cam timing just to be 100% sure!