21 replies to this topic

[David S.]

Hi all,

I'm looking for some help with my 1.6. I run SSM and our engines are mostly stock. I just had it rebuilt with .010" over pistons and other than that it is stock. All of our cars go through a sealing process and the magic number is 107hp. Unfortunately my car only made 96hp. Our class rep and the dyno owner/operator both noticed immediately that in order to get the ignition timing where it's supposed to be (14 or 15 BTDC I think) they had to have the cam angle sensor all the way down in its adjustment slot. Their first thought was the timing belt was a tooth off. I took the covers off and everything is lined up. The mark on the crank might be 2 degrees off but I don't think it's far enough that it would cause it to be that far down on power.

I swapped the cam angle sensor but didn't have time to get it back on the dyno. I left the car at the shop and hopefully the sensor takes care of it. If not, maybe the ecu is doing something weird to the timing?

I'm sure the shop has some other ideas on what could be causing it but I was hoping somebody on here might have seen something like this before. So if any of you have seen something like this before I'd love to hear what fixed it.

Thanks,
David

[Bench Racer]

It's been a while since I've changed the cam timing belt.

Don't know your capabilities:

This could be why as you say you may be off 1 tooth and the cam angle sensor hit the end of adjusting slot. 

Step 1.

Double check to view you have 19 teeth between cam gears as shown.
https://www.bing.com...ex=6&ajaxhist=0

Step 2, if you do not have 19 teeth.

Use the Factory Shop Manual, pages B-75/B-76

See this video at approx. 2:40 time and notice in the background there are two crescent wrenches C clamped together. Better is to use two open end wrenches C clamped together.

This wrenching and clamping is required because to order to get the cam gears located correctly per the FSM the cams will be rotated slightly opening the valves to get required 19 belt teeth top center on intake cam gear to top center of exhaust cam gear.

https://www.bing.com...D3060&FORM=VIRE

[callumhay]

Something is off as u should be able to get 14-16 degrees before the rotation bottoms out. Using what was said by Bench, I would go back to the start. Make sure the cam lobes are in their correct position before you start with adjustments. You can have the right number of teeth but the lobes can still be off. Is the black plate with the marks mounted correctly? Check sprockets and dowel pin alignment, stabilize the crank bolt with a homemade or bought tool as you can inadvertently wiggle that thing ever so slightly as you are getting the belt on. The mark has to be perfectly aligned. The two wrenches on the cam lobes works, I've used two open wrenches to fit the lobes perfectly. Be careful not to mark the aluminum on the edges of the head with forceful outer retraction of the lobes.! You still need a willing assistant to clamp them if you use this method . Google Miata Mecca and Mike's technique for getting the belt on. I found that works too. Other things to look at.. make sure the cam sensor is in the correct way, meaning the rotating pin on the back has two different cut outs to match the cam and can only fit one way. The cut outs are easy to miss as they are very similar. Take the valve cover off if you need to see the cut out on the cam to match it up. Did u shave the head? Or did someone shave it and not know they shouldn't? That might affect it ...If everything was right tho u should have had more hp if head was shaved . Also on dyno was ur car warmed up? Did u do a few pulls to make sure they were repeatable? What was afr trace like? (Lean, rich or good?)Fuel pressure ok? Is Air box stock or been messed with? These things could cause low power and obviously not related to cam sensor bottoming out issue that you posted about. Finally make sure the mark you are using is the actual timing mark and that the cover with the plastic timing marks is on properly. If you start with a list and work through everything you should get there. I'm sure there are things I have missed but I think these are some valid suggestions. Finally, the I and E marks are difficult to line up perfectly, but they do need to be perfect. Look up what they should look like when it is right.

Best of luck and hope you get there

Cal

[Alberto]

This works much better than the 2 crescent wrench approach:

[callumhay]

The flyin Miata tool is great and their new design serves a handy dual purpose for the beverage of choice afterwards!

[Bench Racer]

The flyin Miata tool is great and their new design serves a handy dual purpose for the beverage of choice afterwards!

Ya But, Alberto has phase 1 cam gear Ninja tool. Phase 2 cam gear Ninja tool supports the bottled beverage.

[davew]

The FM ninja tool will hold the cams in place. But does not assure that the cams are properly timed to each other.

 

Blatant plug to follow:

 

I have the prototypes of a tool we have designed that will assure that the cams are alligned to each other properly.

 

My tool does not open bottles, that is what Miata door strikers are for!!!!

[David S.]

Thanks, everybody. I'm almost positive the timing belt is on correctly. Although with as many headaches as I have been having with this car I may buy the Flyin' Miata tool just so I can get the beers down quicker haha.

Is there anything that would make the computer pull timing? I know other cars have knock sensors but the Miata doesn't. I'm used to working on newer stuff and am a sucker for OBD2.

[David S.]

I posted at the same time as Dave. I guess I don't need the tool after all if I can use the door striker to open my beers.

[Bench Racer]

David, this info is from David (Bench Race) and maybe David (Dave) will comment. Shooting from the hip. Info for Component Description page F-10, Troubleshooting Guide page F-12 and Dechoke Control System page F-124. Dechoke Control System shows input signals to ECU for output to injectors. All of the sensor devises values can be checked out per the Factory Shop Manual.

 

When the engine is at idle with correct RPM, is the idle smooth or rough. A couple ways to identify is watch the engine motion or watch the shift lever, flopping around would be called rough. Timing issues is one item to cause rough idle.

 

Early on with my 1990 I struggled through some sensor/electrical issues.

[OctaneNation]

I had a similar issue. My car was down on power so I checked the ignition timing and it was advanced ~15* from my normal running spot. Cam sensor was tight. Put another sensor on and it seemed to adjust to the same timing when adjusted to the same spot (using an external scribe line as reference). Cam timing is fine... What could cause ignition timing to jump like this in the first place??

[David S.]

I had a similar issue. My car was down on power so I checked the ignition timing and it was advanced ~15* from my normal running spot. Cam sensor was tight. Put another sensor on and it seemed to adjust to the same timing when adjusted to the same spot (using an external scribe line as reference). Cam timing is fine... What could cause ignition timing to jump like this in the first place??

Hmm. So are you still having the problem or did you figure it out? How much power was it down?

[davew]

Remember this is a 1.6 and not that smart of an ECU. Timing on this car is 99% dependent on mechanical installation. I would still bet that the cam timing is off. Do not go by the ignition timing marks. Use only the notch behind the crank pulley to line the timing belt  up. The balancers have been known to spin and be inaccurate.

 

Inside an NA cam sensor is a trigger wheel. The trigger wheel is attached to the shaft by a "D" shaped notch behind the little screw. I have seen the "D" wear and cause the timing to be off. Doubtfull if you have tried a known good sensor.

 

Check the "D" in the sensor since it is easier. Then pull everything apart to check the timing belt properly. Then think about electrons

 

Dave

[David S.]

David, this info is from David (Bench Race) and maybe David (Dave) will comment. Shooting from the hip. Info for Component Description page F-10, Troubleshooting Guide page F-12 and Dechoke Control System page F-124. Dechoke Control System shows input signals to ECU for output to injectors. All of the sensor devises values can be checked out per the Factory Shop Manual.

When the engine is at idle with correct RPM, is the idle smooth or rough. A couple ways to identify is watch the engine motion or watch the shift lever, flopping around would be called rough. Timing issues is one item to cause rough idle.

Early on with my 1990 I struggled through some sensor/electrical issues.

Haha thanks, David. I'll take a look and see if anything will make it pull timing.

[Bench Racer]

IMHJ, better video timing belt install. See time 14:45.

 

https://www.bing.com...32959&FORM=VIRE

[Steve Scheifler]

+1 for cam timing. Unless you've done it before, it is very easy to mistake right for wrong and vice-versa. When lining up the teeth to the back plate, focus on the inner-most edge of the tooth that nearly touches the back plate. If your perspective is off just a bit the nearer end of the tooth will appear to shift. You might also use a phone camera to get a shot from directly straight on.

If it really isn't that, is this an old short-nose crank? Did someone not get the pulley and key installed correctly so the pulley has rotated relative to the crank?

[OctaneNation]

Hmm. So are you still having the problem or did you figure it out? How much power was it down?

 

Checked it yesterday. Both cams were advanced 1 tooth... Not sure exactly when or how it happened but cam belt and tensioner were replaced ~1 year ago.

[Jim Venable]

Dave W,

 

On March 28 you referenced a prototype tool to properly align the cams. Has this tool become a reality or still in the development stage?

 

Thanks,

 

Jim Venable

[davew]

In concept it worked great. I made it out of aluminum and it needs to be steel. Waiting for machinist to make a steel version. Hope to have first one by early next week.