TIMING BELT / TIMING HELP!!!

[BCR42Y]

Hi All,

I hope some fo you can shed some light on this subject and help me....

After a long day i have managed to finish changing the belt & water pump on the MX5 and get it all back together.

All good your thinking?

Well not really, i started it, and it started fine, let it warm up, got rid of the bubbles in the radiator and then decided I will take it for a drive.

Pulled out of my driveway, and thats about as far as i got.

As soon as i put some load on it, it just pinged its head off, cautiously i turned it off and pushed it back in the garage, i have blown pistons before in turbo charged cars, so i dont feel like rebuilding a engine.

Now, i was very careful putting the new belt on, i made sure the crank was at the correct mark and that the cams were held at the right positions before the belt went on, and it all looked right when i turned it over a couple of times, the tension on the belt felt ok as well.

My question here is, in the event it skipped a tooth, would the car still idle fine and then when load was put on it start pinging? i am guessing that the timing has been advanced hence the pinging?

Is there anyway of adjusting the timing manually on the 1.8 motors (96 model mx5)?

Could the computer be playing up? or could the airflow meter be playing up?

I am going to pull the covers off and have another go at the belt tomorrow night, is there any tips you can offer me, or something that i may need to look out for??

Any help is greatly appreciated.

Sorry for the long winded post, but its been a very very very long day, as i have never worked intimately on a twin cam motor it has been a real learning curve for me.

Thank you

Halil.

[Wuey]

The engine will start but will stop immediately if the AFM is not connected or damaged after removing the connection by undoing the two screws rather than the clip.

Did you count 19 teeth between the cams? The computer is unlikely to play up from a timing belt job.

See this excellent pictorial link:

http://www.villacorte.com/miata/timing_belt/

[BCR42Y]

Hi Wuey,

I didnt count the teeth between the cams, i will look at that tomorrow night when i have it in pieces again.

I disconnected the AFM at the clip and the battery was disconnected? I hope i havent done anything wrong there.

Is there anything else i should look out for anyone?

Regards Halil.

[JBT]

To cause all the pinging:

1. Your ignition timing was way out before you changed the belt; or
2. You have the cam timing out by a tooth or two.

Before you pull the cam cover, check the ignition timing (yes it is adjustable on the NA) but don't change it.
There are two timing marks on the 1800 pulley. As you look at the engine from the front, the left mark should be on 10 degrees before TDC and the right mark should be on 0 degrees. If it is off the scale (about 20 degrees BTDC) then you have the exhaust cam (and maybe the intake cam too) incorrectly timed.

All the above assumes that you have not moved the CAS at any stage of the belt change procedure.

The belt can't \"jump\" a tooth unless it was incorrectly tensioned (by a lot). There should be about 10mm deflection of the belt available between the cam sprockets if the thing is set up correctly.

[Astroboysoup]

last time i did a belt change the intake cam was off by a tooth advancing the timing by 7 degrees per tooth.

this is on a 1.6

[JBT]

CAS on the 1.8 is on the exhaust cam.

[CT]

The trick with the cams is to make sure the lobes are parallel to the ground both pointing to the outside of the engine, ie intake pointing left and exhaust cam pointing right. As long as you are at TDC zero degrees with piston number 1, and there are 19 free teeth on the belt between the cam gears - the belt and cams will be fine every time.

[BCR42Y]

Thank you for all the tips, i have just finished it and it is all good now.

I counted the teeth, and i had 21 teeth between the timing marks on the cams.

That fixed and the belt tensioned and its running fine.

Thank you all again for your help!