Matt, I hope this helps. It is the only picture containing the area in question I could find, and I have Cliff Ruggles book on the Rochester Q Jet to thank. Thank you Cliff, and I hope that you do not mind my using this picture for assistance. Ray
Larry, Look on page 99 of the book. It describes the setting of the tip-in, and shows the area in question directly above the accel pump arm. I have tried to scan and crop this image, but the details are lost as a result. Is there any way you can put this picture up in this thread? Thanks for the help. Ray
Perfect, thanks guys. I should have no problems finding that now now if only Napa would give me my parts...grrr
Thanks again for all the help, I was able to spot the plug and if/when my parts come in today I should be able to install the new TPS (using the putty knife trick) and drill out that plug to adjust TPS. Thanks
One more thing; be sure that the idle speed, timing and mixtures are all correct, as they will all affect the throttle position, and therefore the TPS adjustment. As mentioned earlier, you will likely want a 6 cyl dwell meter, as this tool is ESSENTIAL for the adjustments to the carb, and to assure that the computer is working. If the dwell is pegged one way or the other, the engine won't run properly. One more thing; the 307 engine was notorious for eating the cannister purge metering valve, causing a full rich mixture off-idle, which can cause the surging and bogging you are experiencing. Just a heads-up. Let us know... Ray
Ok, I got the new TPS. Finally put it in right...pulled the plug on the adjusting screw... and I couldn't find a damned thing to use to turn the screw. I went to napa and they sold me a "GM Carb Adjusting kit" which didn't fit... Anyone have any ideas what I could use to turn this? short of ordering something. If not, I'll just go ahead and order the kit that was linked on page one. Also, I didn't adjust the idle, timing, or mixtures at all so they should still be all correct (right?) All i've done is pull off the top of the carb and replace the TPS, then replace the top of the carb. Is there any way some of that other stuff could have got messed up in the process? And how can I check the cannister purge metering valve? sorry for so many questions, I'm not experienced with working on carbs, but unfortunately neither are any of the mechanics around here
One of two things is happening here, if the reading is really .04 volts. Either the meter is not being connected properly, or the computer is not generating the 5 volts needed to drive the sensors correctly. Carefully check the following sensors for voltage: the MAP sensor, which will have both a three wire connector, and a vacuum hose connected, the coolant temp sensor, which will likely be in the intake, adjacent to the upper hose, and may have only one wire going to it, and the air temp sensor, probably located in the air cleaner, and will likely have only one wire going to it. Does the yellow check engine light illuminate with the key on engine off? Knowing the answer to these or some of these questions will help me help you. I was an electronics instructor for more than one automotive school before retiring, and will be glad to help. Ray
The computer is sending 5 volts to the TPS, I checked that out with the bottom pin in the 3-pin connector. I will try to find those other sensors and do a voltage check on them today. Yes, the check engine light comes on when the key is turned to "run" but the engine isn't started. It also does come on at some points while I'm driving. Another thing, not sure if you could help with this part or not, but the BRAKE light is now on and my brakes are a lot less responsive than they were. Also, the park brake will not go all the way down. DO you think that's related? just started happening in the midst of this.
As far as the brakes go, I would pull off both rear drums and do an inspection. I think the problem will be apparent. Have you checked the fluid level in the master?
If the TPS has indeed 5 volts applied, I suspect that the meter was not connected correctly. Were you checking between the middle wire and ground? For the record, the same ground used for the applied voltage check can be used for the signal voltage check. Your reading, with all correct should be very close to .5 volts. Much over 1 volt will confuse the ECM, and likely set a code. With respect to the brakes, there are two things that will illuminate the brake light. One is the parking brake, which is likely the reason the brakes feel different. With the parking brake applied, even slightly, the position of the brake shoes in the rear axle will affect the "feel" of the service brake pedal. The other may be that the master cylinder may be sensing a pressure difference in the braking system, causing the switch in the master cylinder to go to ground, illuminating the light. Try disconnecting the wire to the master cylinder connector, and see if the light goes out. If it does, the issue is with the pressure difference in the master cylinder or the switch. The switch, however, will not affect the "feel" of the brakes. If the light stays on, the issue is either one of a ground on that circuit, which, again, will not affect the "feel" of the brakes, or it is one of the parking brake switch. If, for some reason, for example, the brake cable has stretched, the pedal will not completely return to the released position, and the switch on the bracket will not open. Since you are experiencing an issue of the brakes themselves, not just the light, I suspect a braking issue lighting the light, and the problem is not electrical. First, let's find out which switch is lighting the light using the above procedure, and go from there. Let us know... Ray
Ray, I was using the engine as a ground when checking TPS voltage. Should I have used the middle pin?
Matt, The middle pin is the one used by the computer to determine the position of the sensor. Was the connector connected to the sensor when you were checking it? The TPS is essentially a variable resistor, or better, a resistor wire wrapped in a coil. One side is the supply voltage, which, here is a 5 volt voltage supplied by the computer. The other end wire is the ground. Anything between these two points is a voltage somewhere between ground and 5 volts. The third, or middle wire is essentially a contact sweeping the distance between these two points, and is connected to the throttle using the plunger driven by the accelerator pump. As the throttle moves, this plunger responds by driving the plunger down, against a spring, which, as the throttle closes, pushes the plunger back up. At idle, for example, the plunger is close to the top, where it sends a signal close to .5 volts back to the computer. If the throttle is open, or nearly so, the signal is close to 4.5 volts. This voltage constantly changes, providing the computer three things. One is the position of the throttle, open, closed, or somewhere in between. The second tidbit of information is the direction of the throttle movement. Is it opening, closing, or steady? The third tidbit is the speed of the movement. Is it opening quickly, closing quickly, or steady? The extremes, either 5 volts, or ground are reserved for troubleshooting. If, for example, the computer sees 5 volts, it will set a code for an open ground circuit. If it sees no voltage, it will set a code for no supply voltage, or an open sensor circuit. The connector must be connected to the sensor for the "voltage divider, as it is called, to work. If the connector was connected, and you saw the .04 volts, either the sensor is defective, or the circuit for the middle wire was grounded. Let me know... Ray
The middle wire will be the signal return to the computer. The outside two wires will be the supply voltage, and ground. Rather than attempt to describe the connectors, wire colors, etc, it is easier to simply say that. When I taught classes, the question of which wire was what always confused the students, and, in many cases, technical info was inconsistent as well. We will, therefore, do it the easy way. The outside two wires will supply the circuit with the necessary bias, or the application of voltage. If, when using a digital voltmeter, you will get a reading of either 5 volts, or -5 volts. If you get the -5 volts, it simply means that the leads need to be reversed. When you get the 5 volt reading, the red lead is the supply voltage wire, and the black is the ground. When checking the return, or signal voltage, do not move the black lead from the ground. Simply move the red lead to the middle wire, looking for the signal. If you are careful, you can back probe the connector with it connected to the TPS. This was perfectly acceptable to GM, though they requested care in this approach, as damaging the connector was possible. Their recommended approach was to use a special "bed of nails" connector, but I found that this approach had its share or issues as well. Let's go from there... Ray
