1987 base timing mode issue

[Jpk707]

Hello, I've got a 87 ford ranger I'm having trouble with. When putting it in base timing mode the idle surges.
I've probed out my map sensor it responds correctly, replaced my iac, hunted for vac leaks any found have been fixed. Fuel pressure is good.
Doing koeo and koer test return only 11 11s
Parts replaced a few years ago: iac, map, egr, egr solenoid manifold, tfi, pip. Any thoughts? Thank you!

 

[tomw]

If you are removing the jumper plug to set the base to 10 degrees BTDC, and have a surging idle, I would check the timing and set it to 10BTDC, and shut down the engine. Replace the shorting plug, and see how the idle is then.
An alternative would be to use a timing light to check the stability of the timing with the shorting plug removed. If the timing jiggles around, you likely have a worn distributor, or gears, or the aux shaft may be wobbly. If the timing is steady with the plug out, then the surging is not timing related, but more likely rpm related.
tom