Question about advance in a 1981
Thread Starter
Heel & Toe
Joined: Oct 2018
Posts: 22
Likes: 1
Question about advance in a 1981
Hello all,
I just finished replacing the camshaft in my 1981. Everything went smoothly, except I'm running into some possible issues with ignition timing.
I disconnected the 4 plug wire from the dizzy to the ecm and set the timing to 10 degrees, and the engine idles smoothly. However, when I plug the wire back in, the engine starts to runn worse and the timing jumps up to ~16 degrees and hops around that mark. It bogs down a bit when I plug the connector in.
Is this normal? Or could this indicate an issue with what the ECM is telling the distributor to do?
What kind of advance should I be seeing with the ecm plugged in?
I can only assume it would be a poor idea to drive with it disconnected.
Any advice or knowledge would be extremely appreciated. I want to bring this car home!
Thanks!
I just finished replacing the camshaft in my 1981. Everything went smoothly, except I'm running into some possible issues with ignition timing.
I disconnected the 4 plug wire from the dizzy to the ecm and set the timing to 10 degrees, and the engine idles smoothly. However, when I plug the wire back in, the engine starts to runn worse and the timing jumps up to ~16 degrees and hops around that mark. It bogs down a bit when I plug the connector in.
Is this normal? Or could this indicate an issue with what the ECM is telling the distributor to do?
What kind of advance should I be seeing with the ecm plugged in?
I can only assume it would be a poor idea to drive with it disconnected.
Any advice or knowledge would be extremely appreciated. I want to bring this car home!
Thanks!
Drifting
Joined: Aug 2019
Posts: 1,511
Likes: 498
Normal operation, computer will put it where it wants it . After you set base timing shut back off and plug in the harness and go for a drive and if it drives good leave it alone . A 1980 distributor and carb is the best fix , 81 carbs have a TPS switch that works off the accelerator pump lever and electronic metering rods that get stuck and are slow to move even when they’re not stuck.
TPS and MAP sensor are big players in the factory ECM for deciding timing
TPS and MAP sensor are big players in the factory ECM for deciding timing
Thread Starter
Heel & Toe
Joined: Oct 2018
Posts: 22
Likes: 1
map
rpm
carb dwell
throt pos sensor.
new cams idle vac is what?
rpm
carb dwell
throt pos sensor.
new cams idle vac is what?
I'm sorry, but I'm unsure what carb dwell is. Nothing was changed on the carb.
I haven't tried anything with the tps, could that lead to the issue I'm seeing?
New cam is an oe stock replacement. I had worn lobes, and wanted to keep everything stock.
Team Owner
Joined: Jan 2007
Posts: 53,648
Likes: 878
From: Southern Cal Ca
St. Jude Donor '22
check idle vacuum
carb dwell s/b 30 deg measured with dwell meter set on 6 cyl
hot lead to green pigtail and black lead to ground.
car hot, closed loop.
recheck all your wires and vac hoses.
carb dwell s/b 30 deg measured with dwell meter set on 6 cyl
hot lead to green pigtail and black lead to ground.
car hot, closed loop.
recheck all your wires and vac hoses.
