Is it normal for ignition timing to advance upon acceleration, then after letting off the throttle it advances further, then at idle it will jump around all screwy for a second or two, then return to normal?

While my timing is jumping all screwy for a second or two the car maintains a high(1200rpm)/sputtering idle, then mellows out right after my timing locks back in. CHecked TPS, checked voltages from CAS and coils at my ECU, and checked for air leaks.

Help please, this is driving me crazy. I couldnt imagine this being normal

 

As normal a H.Rap Brown and as American as cheery pie.

What are you looking at the timing with?

 

A car-battery powered timing light. It has a hard time reading the signal tho.. it will only read it if i hold onto the timing light lead while its on the spark plug wire, or if i ground the timing light lead while its on the wire.

 

Timing advances once your above approx 1100 rpm.

When you let off the throttle and the rpms go down to idle speed it will do what you described (jump around screwy then settle down to regular idle timing).

The closer you have the idle speed to 1100 rpm the odder it will act. The 750 give or take is a normal idle speed and causes less confusion.

I watch the timing on a RTEK2.0 and have a general idea of how the timing acts from just watching. If your driving at a steady speed like 3000 rpm in fifth, the timing for Lead and Trail are about the same figure. Something like 26 or 28 degrees BTDC. Then at that speed if you stomp the pedal, the timing drops down dramatically, say into the teens. As the car accelerates and gains speed the timing advances again upwards. I suppose because the LOAD now isn't as great as before.

If I rev the engine in the driveway, then let off, the timing will advance....then drop down below the normal -5L/-20T and sort of fiddle around below those figures for a moment or two then return to the normal -5L/-20T.

I don't think you have a problem if your idle speed is well below the 1100 range at idle.

IF you have a idle just below 1100 rpm, and rev the engine and then let off, sometimes the timing will remain higer than normal -5/-20 and sit around 14degrees BTDC for sometime til the idle finally drops down below approx 1100 rpm....if it ever does drop down.

I'll have to stare at my RTEK sometime while sitting in the driveway to see if when I rev it, if the timing advances, then when I let off if it advances more before dropping down. I think that's how you stated it

Something like rev engine.......timing advances.........let off........timing advances a bit more....then timing falls down and acts screwy for a moment and returns to normal -5/-20. Yeah, Ill take a look sometime.

 

Thanks HAILERS. When my timing seems a bit screwy i see about 1200 rpm idle. Then the timing will magically stabalize, and about a second AFTER that my idle returns to the normal 800.. which leads me to believe the high idle is being caused BY the screwy timing. Maybe i have it backwards, but it just seems odd.. and sounds odd too.

Thanks for your help!

 

Heres a little more info: when i check on the L1 lead, at idle it *sometimes* fires at 3/4 inch MORE advanced from the normal 5* notch mark (sorry, i have no way to measure exactly how many degrees). my guess would be about 25*BTDC. But when the motor warms up the timing is dead accurate at the 5*ATDC... MOST of the time. Occaionally ill get a few blips from the timing light that its firing at the 3/4 inch advanced mark, and ill even get that its firing at 180* from when it is supposed to.

 

Could this be a malfunctioning CAS?