Timing troubles, I think? (again)

J-bird

J-bird

Member
I posted this yesterday but it seams to have disappeared! :rant:

I have been having a problem with knock retard for a long time. When I started tuning my truck it seams that it likes way less timing advance than all the other tunes form other trucks like. Under boost I can only run like 4 to 6 degrees timing advance. Something looks off!

Yesterday I noticed when checking my base timing (with the connector under the dash disconnected) that when I rev the motor the timing will advance 12 degrees, then return to 0* as the rpm returns to idle. I can set the timing at idle, but when I rev the motor to around 1500 rpm it will advance a lot!!

Is this normal??? I can't see any vacuum or mechanical advance in the distributor. What could cause this, bad distributor, stretched timing chain?

Oh yea I have replaced the entire ignition other that the distributor itself. I put in plugs, wires, coil, cap, rotor, module, and all new vacuum lines.

Has anyone seen this before?

Thanks,

Jeremy Franke
 
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J-bird

J-bird

Member
Re: Timing troubles, I think? (again)

well it's not the distributor!!

I spent this afternoon cussing at the stupid dis hold down bolt but I finally got the dis swapped out for a stock replacement. I set the timing to 0*, the revved the motor a bit and the timing jumps to over 12* advanced! it is not like it's moving with the rpm of the motor ether. It gets to a certain point and jumps, then if I rev the motor higher the advance will correspond to the rpm.

The timing will jump way advanced and the jump back to 0*!

has anyone seen this before? does this sound like a bad timing chain?

Thanks,

Jeremy Franke
 
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J-bird

J-bird

Member
Re: Timing troubles, I think? (again)

replaced the balancer about a month ago, It had slipped but I fixed that problem!
 
J-bird

J-bird

Member
Re: Timing troubles, I think? (again)

Anyone seen this before? I just wanted an opinion before I start throwing more parts at it!

Thanks
 
J-bird

J-bird

Member
Re: Timing troubles, I think? (again)

I just looked at some TunerPro log data, and some times my Spark adv. relative to TDC is way up. there are time when tunerpro reads 23038.98 degrees advance. Is this just a bug in the aldl data stream, or do I have a problem somewhere else. Could this be a bad computer?

Thanks(if anyone is actually reading this),
 
P

pinellas50

New Guy
Re: Timing troubles, I think? (again)

I just noticed mine doing this today. At idle it is at zero. When the engine revs slightly, mabey no more than 1000 rpm, the mark instantly jumps to 4 degrees. When the rpms come down it jumps down to zero. This is an intantaneous jump, not like a problem with the timing chain.

I hadn't noticed it do this before. Anyone else?
 
WyoSyclone

WyoSyclone

Active member
Re: Timing troubles, I think? (again)

I'm pretty sure this is part of the code in the ECM.... there have been a couple of threads about it, and I think there is a pretty good explanation over on the Code59 site. In other words, it's normal for the timing to jump with an increase in RPM with the tan wire disco'd. I'd go look for those threads but have to run right now...
 
turbodig

turbodig

Active member
Re: Timing troubles, I think? (again)

Timing will change, both with the wire disconnected, and without.

The ECM controls timing, so with the wire plugged in, you'll see a lot of jumping around.

With the wire disconnected, the module itself runs the timing (backup mode). Timing will move around there too, although it won't be as much.
 
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