Engine timing question

[mc-ca]

I hope this is not a dumb question but - I just took my 91 NSX in for a smog check - It failed because the timing was measured at 39 degrees. The spec to pass the smog check was 15 degrees +/- 2 degrees. The smog check techs could not believe that it was so far out - the motor passed all the emission checks. They checked it with two timing guns with the same results. I'm taking it to the Acura dealer where they do all my servicing on Friday.

My questions are: can the timing be that far off? If it really is that far off can it damage the motor?

The car did pass a smog check 18 months ago so the timing had to be ok at that time. I had the timing belt replaced about 12 months ago by my Acura dealer.

 

[nis350]

I hope this is not a dumb question but - I just took my 91 NSX in for a smog check - It failed because the timing was measured at 39 degrees. The spec to pass the smog check was 15 degrees +/- 2 degrees. The smog check techs could not believe that it was so far out - the motor passed all the emission checks. They checked it with two timing guns with the same results. I'm taking it to the Acura dealer where they do all my servicing on Friday.

My questions are: can the timing be that far off? If it really is that far off can it damage the motor?

The car did pass a smog check 18 months ago so the timing had to be ok at that time. I had the timing belt replaced about 12 months ago by my Acura dealer.

maybe the TB was not lined up properly, but still, I would think that you would feel the difference in performance or maybe even rough idling etc...

 

[Briank]

39 degrees is really far off. The only thing I can think of is they used the blue mark instead of the white mark things could be way off. The blue mark is where you tension the timing belt.

 

[nis350]

39 degrees is really far off. The only thing I can think of is they used the blue mark instead of the white mark things could be way off. The blue mark is where you tension the timing belt.

wouldn't the car runs like crap with the timing so far off? 39 degrees at idle can be disasterous at 6000 rpm.

 

[mc-ca]

It runs fine all the way to 8000 rpm. It even had very low emmission readings. I'll find out tomorrow - I hope.

 

[Steve]

How did they measure the timing?
I think that some lights show an error on our cars.

 

[nis350]

It runs fine all the way to 8000 rpm. It even had very low emmission readings. I'll find out tomorrow - I hope. [/QUOte

I've heard that advancing the timing provide some minor boost in acceleration, but from 15 to 39, it is just a bit much. Does your idle RPM remain the same and smoothly? I still think that the TP probably was not lined up probably for this false reading.

My tech. told me that the car would run fine even when it is off a notch or two, but it shows up when you try to time it.

 

[Yellow Rose]

Everything Is Fine

The spec for the NSX engine at idle is +/- 15° BTDC.

At steady-state cruising on the street, much like the emissions test roller dyno, the timing for the NSX engine is approximately 39° BTDC.

A naturally aspirated NSX under wide-open-throttle will have timing in the mid to mid-upper 20's° BTDC.

If they are failing you at 39° BTDC on the roller dyno, they DO NOT know what they are doing.

By the way, to the point of pre-detonation, advancing the timing will usually result in cleaner emissions. For them to not recognize this telsl me that they REALLY DO NOT know what they are doing. Run. Fast.

 

[mc-ca]

The timing test was done at idle with a hand held timing light that had a led readout that read +39. They also used a second timing light with exactly the same readout. The car runs smooth at idle, starts the first time...

 

[mc-ca]

Mystery solved - the smog shop must have connected the timing light up wrong. The dealer measured it in spec at 15 degrees. I should have taken it to the dealer directly for the smog check. I did not think the dealer had smog check capability.

 

[Tom239]

Different timing lights can give different results with an NSX.

I have seen this first-hand, and it's also discussed in this thread here on Prime.

 

[mc-ca]

Thats exactly what happened to me. THe Smog shop used a digital timing light and the Acura dealer used a basic one and just looked at the red notch on the timing pully. The white one is 0 degrees the red one is the spec at 15 degrees.

This should be in a Faq.