Engine/Trans noise woes. Miata gurus hellp?

[xjdesertfox]

UPDATE!

I have figured out the issue(s).

1) My cam sensor adjustment bolt went missing... my sensor was loose and adjusting itself as I would drive.
2) Either the person who did the belt last lined up the cam gears wrong, or the timing belt slipped, but I'm 2 teeth off on the intake side.

We discovered this today as we were doing a leakdown test on the car putting the cylinder to TDC.

So with that said, All of you guys were right. A Timing job done right will solve my issues, the detonation is purely from timing being off.

Heres a video of the miss my car is making due to the timing being off two teeth, for future reference in the community.

[WASABI]

Glad to hear you found the culprits. So you must have been getting horrible lack of power too? I'm in to see the video of it all fixed and running right!

-Jim

P.S. While you are playing with the CAS, don't forget to change the o-ring.

[— kung fu jesus —]

Awesome!

I would treat any repairs the previous owner did as suspect.

[xjdesertfox]

Definitely, I thought my headaches from the previous owner were gone when I replaced my speedo cable that was held together with duct tape and replaced an alternator tensioner that the previous owner felt didn't need to be there.

[xjdesertfox]

Well. The saga continues. I sat down and rotated my motor with a socket. And it doesnt seem like my timing is off. Can anybody figure this out?

Heres the timing mark locations. 2nd picture is after 720* rotation.




I noticed when rotating my motor that air was coming out of here. Is this right?


Did a compression and leak down.

Compression results all dry, little change when wet.
#1 140psi
#2 150psi
#3 150pis
#4 135pis

Leakdown:

All 4 cylinders are leaking 25-40%. I cannot even fathom how this is possible. Air is coming from the intake side. No air from dipstick or exhaust side. No air coming through coolant.

Im guessing that somehow all my intake valves are fubar'd and I need a top end rebuild?

[— kung fu jesus —]

bad seals or guides maybe.

[xjdesertfox]

Bringing this back up. Thought I had solved the issue with a new water pump, but maybe not...

So, I did the TB/WP/Seals/coolant hoses.

Engine had not been pinging in the longest time. The motor has a "Hot ping" where if I turn on my A/C or flog the piss out of my motor in hot weather, it will ping under load.

Im guessing my engine is running hot, but I cant figure out why.

A few theories.

1) I've flushed my radiator multiple times, It STILL has a ton of corossion in it. Maybe my heat exchanger cant keep up anymore?
2) My thermostat is a non-OEM 195* T-stat, maybe its bad and not opening when it should?
3) Im running BKR5EIX-11 NGK plugs. Maybe I should go 1 Step cooler? But that doesnt make sense, why would I need to run a cooler plug than factory.
4) I do have carbon deposits on my pistons, but nothing bad. But maybe I should De-carb the pistons?

[xjdesertfox]

Also, Forgot to mention. This problem is apparent with timing set to 10-11 degrees BTDC. With timing at 14-16 degrees BTDC the pinging stops.

[— kung fu jesus —]

Weird. I'm trying to think this one out.

[xjdesertfox]

Also ran another leakdown test and compression test with my own tools.


#1 162psi
#2 175psi
#3 175psi
#4 165psi

~8-15% leakage from each cylinder, sounds like its coming from the intake side.

Previous tests were done with some OTC branded tools at a shop. Apparently my moroso leakdown tester and actron compression tester disagree with the shop's tools.

[Kage]

I don't mean to necromance a thread, but I've been fighting what sounds like the same noise (or pretty damn similar) that cropped up in your first video for about the past year. Did you ever manage to track it down and fix it? Or is it still making the noise after all the work you've done to it?

Thanks!

[Hyper]

Think outside box.

I once had this problem and after thinking and thinking I realize that timing was off. Why? I simply ask, then researched and learned that all 90--95.5 crank pulley are defective. The pulley itself is defective as you think the timing is right when is not. You see the damping part of the early crank pulleys wear out or so it order to set the timing properly remove the lower plastic cover and compare the TDC at the crankshaft pulley with the camshafts. If the timing mark at the crank wheel (where the timing belt moves the crankshaft) is off then crank pulley slipped and you must stamp a new mark in the crank pulley. Mazda corrected that issue in the later 1.8 models by adding a crank sensor and wheel at the crank pulley.

I am not saying that this could be your problem but looking at your two different compression test the problem seems to lie there. Flying Miata wrote an article on this for the early mazdas. Thanks to them I figured out the issue with my ride when I had the NA.

[— kung fu jesus —]

I'm just writing a few thoughts after re-reading this thread.

Hyper does make a good point. the rubber on the damper of the crank pulley does age and harden, so it could lead to slipping timing.
That said, you could replace the pulley with a new (or newer/fresher)one. If you did the timing belt, did you check the or replace the woodruff key? It is possible for the rounded keyway to happen on these motors, like the early b6 motors, if it was installed incorrectly.

You mention you saw carbon deposits on the pistons? If you are leaking air out the intake mani, I would suspect carbon buildup on the valves too. The carbon deposits on the pistons on in the combustion chamber can lead to detonation. Think of those carbon deposits like pieces of charcoal in a bbq grill. They start to heat up and glow. Now think of those hot pieces of carbon in the combustion chamber like ignition sources for your fuel. they can lead to pre-detonation before the piston is ready, causing knock.

Based on the pictures you posted, particularly the idler pulley, it seems this car sat a lot in a previous life. I wouldn't doubt is was neglected and no very well maintained. Aside from boreospoping the combustion chambers, pulling the head to check for carbon build up would be my inclination to solve the issue. The lazy way to maybe start to correct the issue would be sea-foaming the engine and running a fuel additive to try to beak up the carbon deposits. YMMV.