I am testing the throttle position sensor on my unmodified 84. I connect my volt meter to one and three, loosen the screws and turn up and down. I get a constant voltage of .503 It does not change the voltage when moving up and down. Does it need replacement? Any other adjustments or testing procedures to perform?

 

I'm not familiar with the 84 TPS and what wires are used to measure, but if you are on the correct wires, i would say your TPS is shot.

 

Thanks,
Anyone know if these numbers mean unit needs replacement?
Can the replacement be for 85 and higher or just 82-84?

 

With the engine running if I slide to lever on the TPS sensor I see a surge of gas. Maybe my setting on the volt meter is wrong. Anyone with any suggestions?

 

Double check that you are on the correct wires, but you should see a change in voltage from close to wide open.

 

Get out your FSM and follow the procedure for checking/setting the TPS. It is really simple. I'm pretty sure you are checking the wrong wires. Also, there is no reason to loosen the screws to check the TPS operation or adjustment, only to change the adjustment.

RACE ON!!!

 

Your TPS has three wires,grey,black and dark blue.Black is ground. Grey should be a 5 volt reference. The dark blue is the pot center tap. If you measure the voltage across grey and black it should be 5 volts. The voltage across black and dark blue should be somewhere between the minimum voltage at which you adjust your TPS (closed throttle) and whatever it is supposed to read at WOT. The voltage between black(ground) and dark blue should vary between minimum (closed) and maximum (WOT) as you open and close the throttle On the 85 closed throttle is .54 volts, WOT is 4.5 volts.

The TPS emulates the accelerator pump in a carb, in addition to other functions. The shot of gas you see may be exactly correct.

 

Where exactly do you see this "surge of gas?"

 

Thanks,
I see a surge of gas coming out of both injectors.
I was testing the wrong wires. I can get the sensor to show close to .54 but only as close as .502 I cant seem to keep a good connection as it will show 000 but if I pull the multimeter connectors I can get it to read but it does not seem to reliably display the output number. I have tried two multimeters but do not seem to be able to keep a connection.

 

OK,
Here is what I get. With my multimeter set to 20 I measure A(grey) and c(black) I get 5.03v. When I measure A(grey) and B(blue) I can get up to 5.02v, moving the TPS causes the voltage to go down to 4v. 5.02v is with the TPS turned as far down as it can go and 4v is with the TPS as far up as it can go. If I push the throttle lever the voltage goes down.
Reading the previous posts it sounds like voltage should start at .5v not 5.02 and the voltage should go up pushing on the throttle not down.
Am I doing something wrong? Is my multimeter set properly? Or do these numbers mean the TPS is shot?

The issue I am trying to resolve is lets say the car has been in the garage for a couple weeks. I can hop in fire it up, drive around with no issues, car runs great. I get back home and it will not fire up. It will turn over, gets spark but the injectors do not fire. I can put in starting fluid and it will run until fluid runs out. I have to wait weeks before it will fire up the injectors after putting in more fluid. The only thing that sometimes works is if I lightly tap the gas before attempting to start.
Obviously the car is old so I already upgraded the fuel pump with new sock and new fuel filter. One IAC was making noise so I replaced both.

Any help would be appreciated. I think I narrowed it down to the TPS but I would like to be as sure as I can.

 

Anyone?

 

Doesnt sound like the TPS to me,as yousaid you can drive it around.
I can hop in fire it up, drive around with no issues, car runs great.

 

Sounds like the computer to me, or mabey the alarm.
Take out your ACC,fuze to disable the alarm.Then when & if it wont start, try disconnecting the battery for a minuet or so,then try again.

 

Thanks,
I thought if it was the alarm that the engine would not turn over.
The car will turn over but the injectors will not shoot fuel. I can hear the fuel pump. I replaced the computer several years ago.

 

Could it have anything to do with the electric fan? It has been bypassed. Also it has a broken connector to the a/c compressor.

 

I think your right that if it was the alarm it wouldnt crank. Sorry about that. But I'd go ahead & pull that fuze because it could be another module or something.
Yes on the electric fan, Ive seen them do strange things. I think no on the A/C connector.
Can you think of what you were working on before this started?
Also still try rebooting the computer by disconnecting the battery, even with a new one.
Is it a stick or auto trans?
Can you try any of this stuff tonight?
Good luck.

 

There is no connection between your fan and the ECM. Since the injectors aren't squirting on the no start, see if they are receiving the pulse from the ECM. It could be an intermittent wiring problem between the distributor and the ECM. Pull out your FSM and go to the trouble shooting charts. I can't believe it has anything to do with TPS, and yes, you must doing something wrong.

RACE ON!!!

 

Ok,
Here is the test results. I do not think I am doing it wrong but the numbers just do not add up.

First picture is 1984 TPS Top wire (a) grey to (c) black

Results: 5v (this is good)



Second picture 1984 TPS Top wire (a) grey to (b) dark blue
Results: 5v (this should read .5v not 5v)
Multimeter is set to 20 same as picture 1



Third picture is the same as second except my finger is holding the TPS lever at half way WOT



Fourth picture is the same as second and third except my finger is holding the TPS lever at WOT



Maybe you guys can make heads or tails out of these numbers?
Notice the TPS voltage drops when going to WOT
This should be the opposite, voltage should go up when going to WOT

 

I would say that you are measuring the TPS with the leads reversed AND measuring between the signal pin and +5Vdc supply to the TPS instead of between Gnd and the signal pin.

Soo, it looks like the TPS is ok as the voltage is changing from low to high moving the throttle from idle to WOT positions.

On a CFI system I really do not know what the ECM needs to see in order to fire the inectors.

BTW, when the injectors fire normally can you hear a click from them as we L98 owners can hear from our injectors?? If so, do you hear that click when cranking the engine?

When the ECM fires the injectors its driver simply grounds the line to one side of the injector. Probe one side of the injector harness to see if the voltage pulses to zero when cranking.

 

Thanks,

I do hear a click when turning the key.

I switched the leads and get the same numbers except the numbers are negative numbers.

When testing the other wire I get 5v but when sliding the TPS lever the voltage does not change so it is the ground and not the signal pin.

I believe I am testing this correctly.