Hi, I've been working on this for a while and am really stumped. This all started as a routine thermostat replacement. I ended up breaking off one of the housing bolts so I decided to remove the intake manifold and use a Heli-coil so I could use the same intake. That all went well and I got everything back on without any issues. I got it started late at night and it was running really well but I hadn't timed it yet. The next day I decided to set the timing with the light. It still was running good at this point. I unhook the ESC and set the timing without issue. I start it again this time with the ESC plugged back in expecting it to be running great. Instead, it wont idle down and is surging and hunting all over the place. The only thing I did was set the timing. It idles between 1400-1600 rpm back and forth. As it surges it sounds like it just drops off/misses and then picks back up. Almost like the advance keeps bouncing back and forth? The vacuum is about 21 at 1200 rpm when i mess with the timing to get it to idle down that far. I've plugged all the vacuum lines too. It seems like it could me a vacuum leak but it's weird that it would happen all of the sudden right and all I did to it was set the timing. I'm all out of ideas and could really use some help. Thanks in advance.

 

Also, I forgot to say that it still idles high, but doesn't surge really at all when I unplug the ESC. So idk if that has something to do it. Thanks.

 

Anybody have any input? Could the intake manifold have developed a leak all of the sudden or does this sound like an ignition problem? I wanna get it fixed as soon as possible but don't want to redo the manifold gasket again if it isn't bad nor buy more unnecessary parts. I've tried spraying around the manifold and other vacuum hoses but it doesn't change the idle at all.

 

To me it sounds like you might have goofed on the timing. Try starting completely over, from step one.

https://www.thirdgen.org/forums/tech...e-old-lg4.html

 

Ya, I've re-done the timing. When I first threw it together and timed it by ear it was running great. Once I unplugged the ECS connector to time it, it was still running like it normally would, but once I plugged it back in it started doing the surging idle and wouldn't idle down like it used too. The vacuum does seem kind of low, but the surging doesn't happen when I unplug the ESC, it runs fine but not great since there is no advance.

 

Now I have another problem. After doing some more tuning it seemed like it was running better. I plug in the ESC so I have advance and it isn't advancing at all. The timing light shows its still at 0*. On top of the that, the check engine light is still on even when it's plugged in. I go to check the code by jumping the terminals and the engine light just stays on and wont flash. No solenoids are clicking either. I then noticed that the mixture control solenoid doesn't even click like it does normally when the not in diagnostic mode. The engine runs though so the distributor is getting power. It almost seems like the ECU is bad. I just replaced it a couple months ago with a unit from the local junkyard and it was running great. Perhaps this one took a turn for the worst too. Any opinions from anybody?