1987 Fiero GT 5 speed manual

I wanted to check the timing on my car, so I did all the procedures, with jumping the diagnostics and such. Anyway, with the timing light on both 1 and 4 spark plugs, i could not see the timing mark in the harmonic balancer. I went to check it without the diagnostics jumped, which i then saw the timing mark around 12 degrees.

So i think my harmonic balancer timing mark is off. Is there anyway I can put a mark on the balancer in the correct position?

Also, while in diagnostics mode I had to have a friend keep on the gas so it wouldnt die, and the headers started glowing red hot, dont know if these are issues.

Your ignition timing is probably way off. I suspect not only has the outer ring of your harmonic balancer/damper spun, but it was probably already out of position the last time someone timed the ignition.

Yes, you can mark your balancer with a new line (when you've found TDC of cylinder #1)... but if your balancer is loose... how long is the outer ring going to stay in place while you do the timing? One minute? One second? Besides, ignition timing aside, your balancer needs to be... balanced... and if it's spun, it isn't.

The only real solution is to get a replacement harmonic balancer. There are several threads here where people have made recommendations as to sourcing one.

[EDIT] Temporarily ignore what I posted above. It's possible that the last time someone timed the ignition on this engine, the jumper simply wasn't in place. The timing will be far too retarded. Time the engine with the jumper in place, and advance the distributor (turn counter-clockwise) until you get the recommended advance. Report back with your results.

quote Originally posted by Xenoblast: I went to check it without the diagnostics jumped, which i then saw the timing mark around 12 degrees.

It would still be a good idea to double-check that the balancer hasn't spun. Make sure the wider groove lines up with 0° when cylinder #1 is at TDC. The original balancers are all at least 33 years old... and they don't last forever!

[This message has been edited by Patrick (edited 03-24-2021).]

I checked the TDC on with it at 0, it seems like cylinder 1 is indeed at TDC so I don't think the balancer has slipped, so thats good.

I just wanted to confirm that my mark is on the right place, so heres a pic:


If the timing is indeed this wrong, would it cause any damage? Ive driven it over 1500 miles like this.

Here's an image of a known good Fiero harmonic balancer. It's a little difficult to tell because of the angle, but it looks like the wide #1 groove and the keyway are close to same location relative to each other as your balancer. However, I suspect your balancer is a bit off.



I'd say the wider groove of your balancer should be closer to where the arrow is pointing. If it was me, I'd use a thin wooden dowel or a straw in the spark plug hole of #1 cylinder just to make sure that TDC indeed lines up with 0° on the scale.

quote Originally posted by Xenoblast: If the timing is indeed this wrong, would it cause any damage? Ive driven it over 1500 miles like this.

With the ignition timing being way too far retarded, you've probably done no more harm to the engine than perhaps carboning up the heads... although it might also have been detrimental to the catalytic converter.

Time the ignition the right way (with the ALDL jumper) and report back how it runs.

[This message has been edited by Patrick (edited 03-24-2021).]

I've been following this thread with interest and it raises a few questions for me.

1) How does a harmonic balancer slip if it is keyed to the crank with a key?
2) How likely is this to happen?
3) What type of key is used? Formed on the shaft? Woodruff? Rectangular? Square?
4) Would a simple set screw on the bolt prevent the key from coming out or slipping?

Just curious to know.

[This message has been edited by Mike in Sydney (edited 03-24-2021).]

quote Originally posted by Mike in Sydney: How does a harmonic balancer slip if it is keyed to the crank with a key?

Mike, you're not paying close enough attention. I've mentioned "outer ring" in regards to the balancer twice already in this thread.

There is a rubber spacer between the outer ring and the hub. You can see it in both images above and in the image below. The rubber breaks down over time. This then allows the outer ring to slip and spin on the hub. The timing marks are therefore thrown off, and the balancer is no longer balanced for the engine.

This is what the balancer on my '86 GT looked like years ago, before I replaced it.

[This message has been edited by Patrick (edited 03-24-2021).]

Never had this issue pop up but it seems like rather than replace it, it wouldn't be too hard to separate the wheel and replace the worn out rubber with some sort of bonding agent like urethane and bond it back together in the correct alignment.

Thanks, Patrick. Sometimes the obvious escapes me.

I forget who it was, so maybe it was Patrick? Someone here on the forum had a car where the outer ring would continue to spin for some period of time (a few seconds maybe) after the engine was shut off. Now THAT'S a slipped ring!

quote Originally posted by css9450: ...maybe it was Patrick?

No, that wasn't me... but I recall the post!

I should have said this yesterday but Im gonna do it later today, I have to wait until my friends done with school so that he can help me. I will keep you all updated.

quote Originally posted by css9450: I forget who it was, so maybe it was Patrick? Someone here on the forum had a car where the outer ring would continue to spin for some period of time (a few seconds maybe) after the engine was shut off. Now THAT'S a slipped ring!

I'm Patrick and that happened to me! Although I don't recall posting about it on here. It was pretty strange. An odd vibration while the engine was running, and then a Z-Z-Z-Z-Z-Z noise as the ring continued to spin after shutting off the engine.

Pertaining to the original post, here is a good tutorial on finding TRUE top dead center in any engine. If you verify that it has indeed slipped, it's a good idea to replace it, because as mentioned, it will continue to slip, and eventually come apart as happened to me.

https://www.youtube.com/watch?v=2Yh2ZpKHkq4

quote Originally posted by PatrickTRoof: I'm Patrick and that happened to me!

...

quote Originally posted by Patrick: Report back with your results.

I timed it, with 10 degrees on both 1 & 4. On the guides they tell you the average of both cylinders should equal out to 10 so I assume that works, but let me know if otherwise.

First thing I noticed is that the car idled in diagnostics mode.

There suprisingly was no real power gains with it normally running, but it does idle a lot smoother.

The timing before was so bad that at idle running normally, the ignition timing mark was at around 2 degrees advanced.

[This message has been edited by Xenoblast (edited 03-25-2021).]

Thanks for reporting in. It's good to hear back when an issue is positively resolved.

I happened to come across the following image in an old thread. This is the eventual outcome when the harmonic balancer hub and outer ring decide to go their separate ways!