7mge lopes at idle after changing ignition timing to 10 with check connector bridged

[sfoster84]

Hello this is my first post.

I have an 87 Supra 7mge/a340e with sport package.
I pulled the cylinder head to have my machinist adjust all 24 valves by cutting the valve tips slightly to bring the clearances back to spec. He also milled the head and ground all the valve seats. Before I pulled it the car idled fine. I had did a slight rebuild on the motor as the bottom required no machine work but did not have the money to have my machinist work on the head at the time.

I used a fel-pro head gasket with arp head studs torqued to 90 ft. When I set ignition timing I have the check connector bridged and move the distributor to 10 on the timing cover the car starts to lope from 1300-1800. If I place the timing back on zero the lope goes away but idles at 1100. I have checked the timing multiple times and it is dead on tbc. I have found the ISC valve to not be functioning anymore and I can unplug it while the vehicle is running and there is no change in idle. It also does not click when I turn off the car.

I am looking to see why the car would lope only when I start moving timing towards the 10 mark. The pressure regulator towards the firewall also needs new crush washers so it has a slight leak of fuel, but I do not see that amount of fuel loss to produce such predictable results.

[cre]

RPM fluctuates due to timing changes as the point at which the fuel is reaching it's peak expansion varies drastically with just a couple degrees. Tweak it too much either way to compensate for an idle issue and you put other components at risk when the loads increase.

Try cleaning or replace the ISC. Make sure your spark plugs are not fouled, plug wires are firmly connected, vacuum lines all run properly, and make sure the mechanical timing is 100% correct.