I have a 1985 without vacuum advance. the book tells me to "On vehicles with Electronic Spark Timing (EST), it will be necessary to detach the EST connector at the distributor to cause the engine to operate in the bypass timing mode" but doesn't show a picture of the connector I need to disconnect. does anyone have a good picture of this connector ? does anyone know what the timing should be Chilton sucks it says

If the setting for the ignition timing is 5° BTDC, the spark plug must fire 5° before each piston reaches TDC. This only holds true, however, when the engine is at idle speed.

why are they saying if tell me what it should be that's why I have the book

 

Look for a single brown wire with a white stripe near the wiper motor. There is a weatherpak connector in about the same place as the wiper motor on the brown wire. Disconnect this wire here. Set your base timing. Then you will see that there has been a code 42 set (because the wire has been disconnected). Erase this code by disconnecting the negative battery cable from the battery for at least a minute.

 

I didn't see that the wire had to be disconnected and shot the timing and it was reading past the 12 degrees before. Does that tell me anything ?

 

If you check timing with the EST wire plugged in, the computer is going to automatically advance it. It is absolutely normal to see it passed the timing tab. When you unplug the EST wire, it should be at 6 degrees. If it is not, set it to 6 degrees. When you plug the wire back in the computer is going to advance it again.

 

Why do i have to disconnect the wire i thought that advance was only a factor when not at idle. Sorry im just trying to figgier out what im not understanding.

 

Welcome to the world of technology. I'm going to explain to you why it is a good idea for the computer to advance the timing at idle. Let's say something goes wrong with your engine, maybe you have a built up carbon deposit, maybe you are running really lean? If you set it to 6 degrees without the EST wire connected, when you connect it the ECM advances that timing. This is why on points and breaker type distributors with vacuum advance and stuff like that, you are used to setting the base timing a little bit higher. The ECM compensates for that lower timing by advancing it electronically. If your engine is not running right and starts to experience spark knock or pinging, the ECM can retard the timing at idle, to prevent any damage to the engine. If it cannot retard timing enough, it will set a check engine light. When you review the code and see that it is an EST code, then you will be aware that there could be a problem, and you will also audibly notice a knock. That's why it advances it, it has more control over timing.

By you unplugged that EST wire, the computer has no influence over the timing at idle, so you can set it accurately. Because if you move the distributor with the EST wire plugged in, you are going to have a really hard time setting it where you want because the ECM is going to try to advance or retard the timing to where it should be. That is why you disconnect the EST wire.

 

wow that was one of the best explanation I have heard ever.

 

You're welcome.

 

is this the wire?

 

when I was just looking for that wire I noticed this the pcv valve tube gourmet is shot. what is the actual name for this part ?

 

Yes, that is the wire. And I'm not sure the name of that part, it looks like just a vacuum hose. Pull it off and measure the hole and buy yourself a few feet of vacuum hose. It will probably be under 10 bucks. That dry rotted hose will cause a vacuum leak though. If you are experiencing other problems, that might solve it.

 

here is the link to my real problem
http://forums.corvetteforum.com/c4-t...y-highter.html

 

That could be a possibility if your timing was way off. If it was too far retarded from you trying to set it with the EST wire connected, the computer wouldn't be able to advance the timing far enough as RPMs increased, therefore holding you back by not firing at the right time! So, try setting your timing properly, and see if it still does it.

 

I haven't touched the timing yet I only read it ...I will set it tomorrow

 

I just replaced that piece on my car because it split. The original hose was glued to the metal vacuum tube. You need a 7/16" FUEL line. Oil fumes go through that hose and a heater hose will turn to mush.

 

I set my base timing to 6°. When the EST connector is connected the ECM sets the idle timing to 20°. May be different on your year, but I doubt it.

 

I just disconnected the EST connector and it was set dead on ....im back to replacing my exhaust system