PART II: Walking timing mark discovered 1985 231

[Regalindisimo1985]

This thread supplements PART I thread: http://gbodyforum.com/viewtopic.php?f=19&t=44095
...by continuing to look into the mysterious "not advancing" issue I am having, but also looking into a different part of the system.

As of this day, a timing light was used to verify base timing with the distributor disconnected. At startup, I noticed the timing mark was registering at around 22*. I attempted to retard the timing by turning the distributor toward the 15* mark and noticed something strange.

The strange part about the adjustment was that as soon as I got close to the 15* mark, the timing mark would jump/walk down to the 8* degree mark. A jump of 7* degrees from the attempted adjustment at the 15* mark.

Once again, as I tried to advance the timing from 8* degrees back on up to 15*, the timing mark would jump/walk to the 22* mark.

This pattern of jumping as soon as I get close to the 15* mark is happening on a cold engine. As the engine warms up, the timing mark becomes more stable and consistent.

Engine specs:
1985 231 2 bbl CCC HEI ignition system
What is happening here? Distributor gear worn?

 

[81Regal]

If its the stock timing chain, GM used crappy nylon gears that can throw the timing off but I don't think that is the case here. Best bet would be to pull the dizzy and see if you have any excessive play in either the gear or the center shaft/bushings.

 

[Hoopty_Mike]

I was always told to time an engine when it's fully warmed up, could be as simple as that. You are also grounding the diagnostic terminal correct?

 

[Regalindisimo1985]

If its the stock timing chain, GM used crappy nylon gears that can throw the timing off but I don't think that is the case here. Best bet would be to pull the dizzy and see if you have any excessive play in either the gear or the center shaft/bushings.

Pulled the distributor and took the measurements.

Center shaft measured between 0.020-0.0225 inches of play. Took a dial indicator measurement from the top where the rotor sits and applied up and down pressure.

Excessive pressure where my fingers turned white the same measurement read between: 0.025-0.0275

I did not find any type of play coming from the gear.

What do the specifications call for?

I was always told to time an engine when it's fully warmed up, could be as simple as that. You are also grounding the diagnostic terminal correct?

Negative. I did not know I am suppose to ground the a/b ports of the diagnostic terminals....

 

[Hoopty_Mike]

Negative. I did not know I am suppose to ground the a/b ports of the diagnostic terminals....

I'm kind of a dumbass so I would be bound to unplug the wrong thing at the distributor, so I like to ground the a/b terminal instead (same result). If you're unplugging the correct connector you should be fine. I think your issue is you're not letting the car warm up first, I timed my cutlass last week and had no issues when it was fully warmed up.

 

[Regalindisimo1985]

...I timed my cutlass last week and had no issues when it was fully warmed up.

What were your readings with a cold engine?

Symptoms that I'm experiencing with this 231 engine are, (and in no specific order; as well as these occuring randomly) :
1. carburetor backfire when accelerating during cold startups (when it starts up)
2. fuel spray from top of carb at startup
3. Hard startups
4. Engine starts up at high advance readings: last noted was 22* at cold startup with distributor disconnected
5. Idle shifts high and then low: during these changes I noted timing marks were 22* when the engine idled high and down to 8* when it idled low.

 

[Hoopty_Mike]

I never had the timing light on it when it was cold, and I have no experience with timing a cold engine. Had an initial reading of 20 degrees BTDC @ 1500 rpm with the diagnostic terminal grounded, mind you this is a 307 and that was the stock base timing. Even at idle the timing stayed around 20* with the diagnostic port still grounded. When the diagnostic port wasn't grounded, my timing decreased with my decreased idle, and visa versa, like what was happening to you. Get the engine fully warmed up, shut it off, ground the diagnostic port, turn it back and and put the timing light on it. Hard starting when it's warm can be a case of too much timing, among other things. The other issues I really can't help you much with. I would recommend timing the engine back to factory specs and going off of that, along with grounding the diagnostic port instead. At least at that point you will know there's another issue in the ignition system.