changing ignition timing

[thebannister8]

hi i'm new to timing my 1989 gmc sierra 5.7 litre tbi...the manual doesn't specify for my year what to do...what i mean is that they mention other years and displacements and then proceed to explain what to do...i don't know if that applies to my year...it says to bypass the electronic spark timing (est)...do i have that on an 89...if i do have est will the timing read different with the timing light with or without bypassing it...i also can't find where to clear the computer codes...i'd appreciate the help...thank you

 

[DRAGGIN95]

Hello, yes you have to unplug you est wire, and yes your timing would read much different it the wire weren't unhooked. The process is as follows, first start truck let it run until it reaches normal operating temp, then shut the truck off and remove the black plastic power connection center cover on the passenger side firewall, there will be a single wire with connector underneath that cover it's tanw blk unplug it, that wire is the est wire. Next loosen the distributor hold down bolt it should be either 14mm or 9/16 I have seen both on these truck's, that will allow the dist. to turn. Next hook up a timing light and clip on your clip on lead to the number one plug wire, if you don't know it is the first cylinder on the driver's side front of the engine. Now it's time to start the truck back up, you will notice a lower idle rpm, now you can adjust the distributor until you get it set at 0 degree's BTDC. Then you can shut off your truck retighten the hold down bolt without moving the dist., then reconnect the est wire and put the cover back on. The timing should then be complete. On these truck's from 88-95 if you want to reset the computer and clear your codes unhook your battery for at least 30 seconds. Also the service engine soon light should be on while the est wire is unplugged that is normal it will go out after the wire is reconnected.

 

[thebannister8]

hi...thanks for the great information...i took the cover off and i saw what looked like 2 modulers with a number of wires coming out of each...the one on the right has 4 or 5 wires and one of them is tan with a black stripe...i then noticed to the right a large wire loom that still gets covered by the cover...in that wire loom is another tan with black stripe wire...that one has what looks like a factory connector in the middle of it...do i unplug the connector or the one from the moduler...thanks

 

[darren250r]

The est wire is alone. Its not part of a connector with multiple wires. You unplug the connector that is inline with the wire. Do a search for est if you're still having trouble to try and find a pic.

 

[woody80z28]

My EST wire was behind the dash near the ECM, but I've read they can be in the engine bay near the heater hoses too.

 

[Marcos]

My est wire is next to my blower motor, inside the cab.

 

[DRAGGIN95]

88-early 94 were under the hood. and late 94 and 95 are inside beside the blower motor.

 

[thebannister8]

thank you for the information

 

[FullBlowncustoms]

Hello, yes you have to unplug you est wire, and yes your timing would read much different it the wire weren't unhooked. The process is as follows, first start truck let it run until it reaches normal operating temp, then shut the truck off and remove the black plastic power connection center cover on the passenger side firewall, there will be a single wire with connector underneath that cover it's tanw blk unplug it, that wire is the est wire. Next loosen the distributor hold down bolt it should be either 14mm or 9/16 I have seen both on these truck's, that will allow the dist. to turn. Next hook up a timing light and clip on your clip on lead to the number one plug wire, if you don't know it is the first cylinder on the driver's side front of the engine. Now it's time to start the truck back up, you will notice a lower idle rpm, now you can adjust the distributor until you get it set at 0 degree's BTDC. Then you can shut off your truck retighten the hold down bolt without moving the dist., then reconnect the est wire and put the cover back on. The timing should then be complete. On these truck's from 88-95 if you want to reset the computer and clear your codes unhook your battery for at least 30 seconds. Also the service engine soon light should be on while the est wire is unplugged that is normal it will go out after the wire is reconnected.

Hello, I am new here. I understand this is a old post. I am installing a new billet distributor in a 89 TBI 350, What I am wondering is..... If I disconnect battery, puter be reset to factory specs. BUT if I advance the timing to 4 degrees instead of the factory 0 degrees, will the puter know and compensate for it to still run nice at 4 degrees advanced giving a bit more bottom end? Or will it only recognize the factory 0 degrees? Thank You

 

[PlayingWithTBI]

BUT if I advance the timing to 4 degrees instead of the factory 0 degrees, will the puter know and compensate for it to still run nice at 4 degrees advanced giving a bit more bottom end?

Nope. it doesn't get any feedback where the Spark Advance is unless you tell it in the .bin. You'll get SA based on it's tables plus 4°. Some people have done that, you'll just have to play with what advance (with EST wire disconnected) is best for your application.