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1.6 ignition timing
Hello,
Can anyone explain to me the reasoning behind disconnecting the throttle position sensor when adjusting ignition timing? I am wondering because my 1998 nissan sentra with the 1.6 stalls any time i unplug the throttle position sensor. It will crank up again but immediately die when the rpms drop. I want to put a used distributor on the car to try and solve an intermittent rough idle and stalling problem that gave me code 0340 (cam position sensor). I have a junkyard distributor with the cam position sensor in it but when I go to adjust the timing I can't unplug the TPS or the engine dies. Anybody else run into this? Maybe my TPS is the problem. |
#2
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Of course engine will stall when disconnecting the TPS. Where did you get the information. If the distributor is installed properly and after re-connecting the components such as plug wires, etc., and after engine start ignition timing is controlled by the computer according to Specs. If you have to adjust idle speed, refer to page 35 of Engine Control Manual. You can download the manual from this site. Manuals are in Knowledgebase section at the top menu tab.
Be sure to follow distributor removal procedures per factory service manual. |
#3
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Thanks for replying, and thanks for letting me know about the service manuals. I was originally getting my info from a Haynes manual, but the one here has much more information.
Both sources say ignition timing adjustment (if you don't have the Nissan Scan/Service tool) is to be done with a timing light and turning the distributor with the engine warm and the TPS disconnected. I ended up increasing the idle speed by turning the screw on top of the throttle body so that it would idle with the TPS disconnected and then adjusted ignition timing. After setting the ignition timing I checked the idle (no tachometer so I did it with a a bluetooth OBDII adapter and Torque lite on my phone) and surprisingly the idle was in spec: about 690 so I left it. What seems weird to me is that I increased the idle speed by quite a bit--more than a full turn of the screw--to get it to idle with the TPS disconnected, but prior to now I had never had a problem with idle being too low. I guess without a tach I might not have noticed it. Anyway I drove about 20 miles and didn't have any trouble so hopefully it was the old cam position sensor causing the problems. |
#4
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The ECM has a targeted base idle that it tries obtain by controlling the IACV-AAC valve based on inputs from various sensors. In order for it to work properly, the base idle needs to be correctly set. The ECM has a timing set mode, which is accomplished with the TPS disconnected; at the time, the base timing and idle can be properly set. Obviously, if it stalls, the base idle needs to be corrected first, if possible, and if not, it suggests that the IACV-AAC valve is faulty.
So, when you want to set timing or base idle, the first thing to do is start the engine and warm it up by running the engine at 2000 RPM for 2-minutes, then, let idle and turn the engine off. Disconnect the TPS connector, and then restart the engine. Rev the engine several times and let idle; if the engine stalls, you'll need to adjust the base idle to keep it running. Adjust the ignition timing to spec. by using a timing light and by turn the distributor, as necessary (FYI, most Nissan engines run better with an additional 2-3 degrees of advanced timing over the factory spec). Once your timing is set, recheck you base idle and adjust, as necessary. Turn off the engine and re-connect the TPS. |
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ignition, timing |
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