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Help timing a 350

i have a 1987 chevy 350 that has a tbi and i want to check the timing on it but is say that you need to unpulg a plug and hook a wire but i don’t know which plug to pull or where to plug in the wire. also the idle is low and some time dies on me could timing couse this? thanks

You want to hook up to plug number 1. That’s the plug for the front-most cylinder (you’ll see that when you look down on the front of the engine). Old-style timing light required clipping to an extender between the #1 wire and the plug, but most all new ones are inductive, which clamp directly to the #1 spark plug wire. Do you have a manual for this that lists the appropriate timing setting and where to read it? I don’t know when GM went full electronic.

Edit-sounds like I misinterpreted what you meant by ‘plug’…

You probably need to jump one of the terminals on the data link connector (which is usually under the dashboard somewhere) in order to turn off the electronic spark control. Unfortunately, I can’t tell you exactly which terminal it is, so assuming it doesn’t say on a sticker under the hood, you’ll need to try to find it in a service manual. You can try the free ones over at .

There is a test plug on the wire harness either near the firewall or near the distributor. Pull the plug, and it disconnects a jumper to tell the ECM your in test mode. The ECM will cancel the timing advance as long as the plug is out. I wish I had a picture of it, but it’s been years since I last saw this set-up. Look for a black connector to nowhere. The connector and the plug are both black.

Ans, texases is right about the timing light. Hook it to plug #1. BAse timing should be 0 degrees TDC.

Take a jumper wire and plug into the A and B terminals of the ALDL connector under the dash. This allows the adjustment of the base ignition timing.


thanks i will try it after it stops snowing