Timing Troubles
October 25th, 2017, 1:54 AM
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Timing Troubles
First some background, I'm working on my sister's 1992 S10 Blazer, it's the model with the 4.3L MFI/CPI fuel injected Vortec V6, engine VIN W. Before she bought it used about a year ago (for $400), it had a rough life and I've spent about 40 hours over the last four days undoing 25 years of neglect. One of the problems it had was leaking fuel pressure lines inside the intake manifold plenum causing a rich condition. Surprisingly, the pressure regulator was OK.
The screw holding them in stripped out, so to get the lines out I had to take the intake manifold completely off. Of course to do that you have to take the distributor out. I didn't label the spark plug wires or mark the position of the distributor before taking it out, since I was in a rush and planned on setting the timing later anyway. After some trial and error I seem to have gotten the plug wires on the right way (http://onyxphoto.net/images/wires.jpg) but it's pretty obvious the timing is off.
The problem that I'm having is that I'm getting conflicting information on what to do to set the timing. The timing where it runs best looks like this:
Where theoretically it should look like this:
This is because the Electronic Spark Timing kicks in whenever the engine hits 400 RPM and the computer advances or retards the spark.To set the timing you need to turn EST off, and that's where things get weird. I have the Haynes manual, and it says to consult the VECI label, which this vehicle is missing. According to the internet, you're supposed to unplug the "timing wire" a tan and black wire which I believe I've found hiding under the dash near the ECM:
Unplugging this wire had no effect on the timing. I've also been told that grounding a pin on the ALDL, supposedly the second one from the right in the top row will kill the EST circuit:
This also has no effect on the timing. What is going on here? I might have the wrong pinout. The one in the Haynes manual looks like this:
A: Ground
B: Diagnostic terminal
C: AIR (I don't know what that means)
D: Check engine light (MIL)
E: Serial data
F: TCC
G: Fuel pump
H: Brake sense speed input
M: Serial data
Mine doesn't have pins D, C, or G, and it has a pin to the right of the H pin that isn't even in the pinout. Incidentally, my scan tool, an Innova 3120 gives me a communication error when I plug it in. I also can't get the ECM to flash out trouble codes with the "SERVICE ENGINE SOON" light. When I ground pin B and turn the ignition switch on, the light just stays on.
This leaves me with a lot of questions, like what is the right pinout for this connector? Can I just unplug the EST module instead, or will that damage something? Is the EST module itself bad? Is there something wrong with the ECM? Any info would be welcome.
The screw holding them in stripped out, so to get the lines out I had to take the intake manifold completely off. Of course to do that you have to take the distributor out. I didn't label the spark plug wires or mark the position of the distributor before taking it out, since I was in a rush and planned on setting the timing later anyway. After some trial and error I seem to have gotten the plug wires on the right way (http://onyxphoto.net/images/wires.jpg) but it's pretty obvious the timing is off.
The problem that I'm having is that I'm getting conflicting information on what to do to set the timing. The timing where it runs best looks like this:
Where theoretically it should look like this:
This is because the Electronic Spark Timing kicks in whenever the engine hits 400 RPM and the computer advances or retards the spark.To set the timing you need to turn EST off, and that's where things get weird. I have the Haynes manual, and it says to consult the VECI label, which this vehicle is missing. According to the internet, you're supposed to unplug the "timing wire" a tan and black wire which I believe I've found hiding under the dash near the ECM:
Unplugging this wire had no effect on the timing. I've also been told that grounding a pin on the ALDL, supposedly the second one from the right in the top row will kill the EST circuit:
This also has no effect on the timing. What is going on here? I might have the wrong pinout. The one in the Haynes manual looks like this:
A: Ground
B: Diagnostic terminal
C: AIR (I don't know what that means)
D: Check engine light (MIL)
E: Serial data
F: TCC
G: Fuel pump
H: Brake sense speed input
M: Serial data
Mine doesn't have pins D, C, or G, and it has a pin to the right of the H pin that isn't even in the pinout. Incidentally, my scan tool, an Innova 3120 gives me a communication error when I plug it in. I also can't get the ECM to flash out trouble codes with the "SERVICE ENGINE SOON" light. When I ground pin B and turn the ignition switch on, the light just stays on.
This leaves me with a lot of questions, like what is the right pinout for this connector? Can I just unplug the EST module instead, or will that damage something? Is the EST module itself bad? Is there something wrong with the ECM? Any info would be welcome.
