Timing On 1988 Gmc Truck

[PattiS72]

I need to know why when I unplug the wire at the firewall to set timing it shuts the engine off? And also, how bad will my fuel economy be without running the o2 senser?

 

Thanks for any and all help!

[ChevyTech77]

Probably because your fuel mixture is two rich or lean (due to the missing 02 sensor) or your balancer's outer ring has spun putting your timing mark in the wrong place.

[PattiS72]

Thanks Chevy Tech77!

[redvett]

When the O2 sensor is not working the ECM uses fuel & timing tables to keep the engine running safely without destroying it self, retarded timing and a rick A/F mixture will result. Fuel economy and performance will be compromised.

[93gmc$$]

I need to know why when I unplug the wire at the firewall to set timing it shuts the engine off? And also, how bad will my fuel economy be without running the o2 senser?

 

Thanks for any and all help!

 

 

To set the BASIC timing do this:

1. Disconnect the SET TIMING wire.

 

2. Find #1 TDC

 

3. Adjust Distributor to #1, tighten hold down bolt

 

4. Start engine, check timing with timing light, adjust distributor if req'd to 0 deg TDC (look for mark on crank pulley)

 

4a. Run at idle for a couple of minutes

 

5. Shut down engine

 

6. Connect SET TIMING wire

6a. (the book says clear the ECM codes by disconnecting the battery for a minute--probably don't have to do this)

 

7. Start the engine, run at idle for a couple of minutes, drive the vehicle at moderate power settings with accel and decel cycles to idle

 

Should be good-to-go

 

(and yes, the bad 02 sensor will cause other problems)