Timbo
New member
I have a '99 Sonoma LS, extended cab, 4.3 V6 engine. I just replaced the intake manifold gasket and have three issues I'm left to sort out. The first is that my tachometer no longer works. The second is a check engine light that came on during restart. The third is a mystery vacuum line next to the ABS unit. First things first:
The tach was working fine before the repair work. I tend to be detail oriented when I do major work like this, so labeled all wires and hoses as I went, using the directions found at Handymanlyness.com (a great site if you've never looked before). Everything went back together well, but no tach on startup. I've checked the tach sending wire at the coil for juice, it is hot and sending electricity. I've yet to find the right wire in the harness or at the fuse box, so still have that left to try. Could this be a ground wire, even though no ground wires were disconnected or have been found yet?
Second and third issues: the check engine light, which I suspect is related to the third problem, an open vacuum line found connected to the "T" fitting coming from the PCV valve. The vacuum hose off the PCV is routed over to the ABS system, where it T's so that one line goes down and is connected to a hard line that then appears to enter the firewall. The other line is only about 10 inches long, and was found as I reconected the PCV vacuum line. I did not remove this line during dismantling, but might have pulled it off a fitting or broken it as I removed the PCV line. I've had no luck finding any reference to this line in my manuals, but did spot one brief comment on this forum from a few years ago that leads me to believe it might intended to connect to a vacuum reserve inside of the driver's side fender.
Is this line intended to be connected to something or just be left unplugged? It definitely pulls vacuum when the engine is running, and does affect the idle speed at idle when going from plugged to unplugged, leaving me to think it should be connected to something. I have no loss of control inside the cab with anything is typically run by vacuum, so it must have something to do with engine performance. Any ideas?
Tim C.
The tach was working fine before the repair work. I tend to be detail oriented when I do major work like this, so labeled all wires and hoses as I went, using the directions found at Handymanlyness.com (a great site if you've never looked before). Everything went back together well, but no tach on startup. I've checked the tach sending wire at the coil for juice, it is hot and sending electricity. I've yet to find the right wire in the harness or at the fuse box, so still have that left to try. Could this be a ground wire, even though no ground wires were disconnected or have been found yet?
Second and third issues: the check engine light, which I suspect is related to the third problem, an open vacuum line found connected to the "T" fitting coming from the PCV valve. The vacuum hose off the PCV is routed over to the ABS system, where it T's so that one line goes down and is connected to a hard line that then appears to enter the firewall. The other line is only about 10 inches long, and was found as I reconected the PCV vacuum line. I did not remove this line during dismantling, but might have pulled it off a fitting or broken it as I removed the PCV line. I've had no luck finding any reference to this line in my manuals, but did spot one brief comment on this forum from a few years ago that leads me to believe it might intended to connect to a vacuum reserve inside of the driver's side fender.
Is this line intended to be connected to something or just be left unplugged? It definitely pulls vacuum when the engine is running, and does affect the idle speed at idle when going from plugged to unplugged, leaving me to think it should be connected to something. I have no loss of control inside the cab with anything is typically run by vacuum, so it must have something to do with engine performance. Any ideas?
Tim C.