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Discussion Starter · #1 ·
Back to work on the Shelby. Before I go back to troubleshooting electrical, I need to set the throttle plate to the original mechanical idle setting. The books I have show the throttle body assembly, but do not specify the closed / idle throttle setting. What is that setting? Is there a measurable gap between the blade and body like in carb settings, or is it to full closed position? If there is a gap setting what is it?

Thank you.
 

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I set it with the Engine running, hot idle, at an acceptable idle speed.

This way the idle speed never drops below your desired idle speed.

If working properly, the AIS can increase cold idle speed.

Thanks
Randy
 

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Discussion Starter · #3 ·
Thanks for the info. Problem is this thing isn't running. I know the idle set screw is not to factory specs so I need to set it before I can begin troubleshooting the other issues, like high TPS voltage and idle through the roof.
 

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If you think the idle screw is suspect, back it off entirely.

I don't know of a factory setting other than it's never enough.

The AIC is essentially an electronically controlled vacuum leak.

There are some threads on cleaning/setting the AIC/IAC

I don't rely on them and set the idle manually with said screw.

Possibly you have a vacuum leak causing the roof top idle?

Thanks
Randy

 

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There is no "gap measurement" for the throttle plate, there are too many variables that will affect idle speed for that to be accurate, base idle which is idle speed with AIS closed/stepped in so the only airflow is through the throttle plate opening. Follow the instructions for getting to base idle, if incorrect make the correction to base idle.

If the car does not start/run and you feel the issue is TPS/Vacuum related...
1)What is closed throttle TPS voltage? (.30 - .90 volts at closed throttle is normal)
a)The TPS will not create a "No Start" issue unless voltage with the key on/engine cranking is above 2.50 volts, this is clear flood mode, the controller assumes that you are holding the throttle open because the engine is flooded so it will not pulse the injectors until the key on/engine cranking voltage drops below 2.50 volts.
2)Excessively high idle is going to be caused by an AIS Circuit issue or a Large Vacuum Leak.
a)The vacuum leak may/will create a No Start/Rich Running condition if vacuum to the MAP Sensor is affected.

87 L-Body with a T-1 still uses the AIS with the Planetary Gearset as shown by Randy in the above post.
If you are having AIS/TPS issues the problem may be that two (or more) wires are shorted together in the AIS/TPS harness.
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Discussion Starter · #6 ·
Hi NAJ. Thanks to you and Glhs60 for the responses. This is actually related to two threads from last year:

Erratic Idle, No Idle, High Idle. The car is possessed! and High Idle as Engine Warms. Mystery Vacuum Leak? '87 Shelby Charger T1, and probably Fault Code System Non-Op. '87 Shelby Charger T1.

I think I just need a new TPS. When I last worked on the car, looks like Sept 2021, I adjusted the idle control screw i back of the throttle body under the plastic cap. we were ruling out the high idle and high TPS voltage as tested. Then the faut code came up too. Right after I made the adjustment, the engine died. The OBD fault code system crashed again too. The engine restarted but would not idle at all.

I went back to the thing yesterday. OBD is working (at the moment) and it gives me fault codes, theyre only 11 and 55, but its working. I'd like to reset that idle adjustment screw back to the factory spec. I'm 99% sure it had never been played with until I touched it. It's been so long, I don't remember how far I changed it.

Any recommendations on setting it, or is it just start it and adjust while someone holds the throttle open?

It looks like the TPS part number was 4179849. I read elsewhere on here that that was superseded to 5227597?
So far I'm not locating a new TPS. Any idea where to get one?

Thanks
 

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Screw adjustment screw in enough to get the car to start 1200 rpms is fine. Now remove hose from brake booster slowly which will cause the rpms to jump to about 3000. The ais should close. Placing a finger over the ais passage way on top of the TB with the elbow removed will tell you it's the ais is closed or not. One closed unplug it. Now hook hose back up and adjust idle screw to 900 rpms and turn car off. Plug ais motor back in, disconnect battery to clear codes and you should be good
 

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Discussion Starter · #9 ·
What is closed throttle TPS voltage?
Here's the info the last time I worked on it. August 2021. It showed high and that day I got a fault code for high tps output shortly before everything crashed.
TPS Cold, ignition on, engine off. Closed= 1.163v WOT= 4.15v
TPS Cold, engine running poorly described above at 500 rpm Closed= 1.156v
TPS Hot engine running at idle after 25 minutes and rpm up to 900 Closed= 1.156v
Here's where everything crashed. With volt meter still back probed to TPS, I took rpm to 2500. TPS was 1.4v. When I released the throttle, idle dropped to 760 then after a minute, the engine died. Now it won't idle. I checked for codes. Remember there had been none before. After the engine died, I got Code 24 and Code 52. The volt meter was still plugged into the TPS.
 

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Discussion Starter · #10 ·
Screw adjustment screw in enough to get the car to start 1200 rpms is fine. Now remove hose from brake booster slowly which will cause the rpms to jump to about 3000. The ais should close. Placing a finger over the ais passage way on top of the TB with the elbow removed will tell you it's the ais is closed or not. One closed unplug it. Now hook hose back up and adjust idle screw to 900 rpms and turn car off. Plug ais motor back in, disconnect battery to clear codes and you should be good
Got it. Thank you. On the Base Idle Setting, which I did prior to turning in that setting screw, the AIS and TPS are on the same 5 wire connector. Unplug AIS and TPS is unplugged too. I wonder if that may have led to the high TPS output reading after I plugged it back in.
 

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If you had the TPS/AIS unplugged and the key on that will set a Code 24 since the circuit is open.

Backprobe the TPS Signal and Signal Return Lines with a Digital Voltmeter.
With the Key On/Engine Off (KOEO) turn the base idle adjustment screw until the TPS voltage is between .30 volts and .90 volts.
Now attempt to start the car.
Will the car start and run?
If No...
Are the spark plugs fouled and is the oil fuel diluted?

If you feel you need a new TPS...


 

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Discussion Starter · #13 ·
Hello all. i bought a TPS that lasted about 30 minutes, No voltage readings, Zero volts, and codes 24 and 52, Lots of unburnt gas smoke.
Questions:
On base idle vacuum leak Idle controller set, the plug is 5 wire and controls the tps too. When I unplug the ais power. does that need to be done separately from the tps wires somehow?

Is there an electrical issue known that will fry a tps?

While it lasted, I had to reset the idle screw every few minutes. Hot idle was generally good at 900, but shut down and restart was 500 rpm until I gassed it a bit.

Any ideas?

Thanks
 

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Amperage "Fries" circuits, Amperage is the actual flow of electricity, Voltage is only the pressure differential between + and - that causes electricity (amperage) to flow.
If your TPS fried it indicates excessive amperage in the circuit, the question then becomes, where did the excessive amperage come from, normally this is caused by a short circuit allowing amperage to flow directly to ground without any resistance or a short to voltage from another circuit.
Did you place the TPS/AIS wires in the wrong spot in the connector?
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The TPS has 3 wires...
OR/WT - 5 Volt Reference From LM Blue Connector Cavity 1
OR/DB - TPS Signal Line Back To LM Blue Connector Cavity 21
BK/LB - Signal Return (Ground) to the LM Red Connector Cavity 25

Once you have verified the wires are in the correct spots in the 6 way connector, unplug the 6 way connector, with the key on/engine off you should have 5 volts present on the OR/WT wire.
You should have less than 5 ohms continuity from the BK/LB wire to ground.
With the 6 way connector plugged in and a normally functioning TPS you should have between .30 and .90 volts at closed throttle on the OR/DB wire.
Be sure the Main Controller Ground is securely connected.
Schematic Rectangle Slope Font Parallel


As far as running Black Rich and Code 52 (Rich Exhaust Indication) assuming you did not damage a circuit in the LM or PM, Black Rich is not going to be caused by either the TPS or AIS, however, if you lost the 5 volt reference to the MAP Sensor, or CTS (on earlier vehicles) that will create a Black Rich condition.
Black Rich can also be caused by High Fuel Pressure, Leaking/Shorted Injector(s),Leaking FPR, Loss of Vacuum to the MAP Sensor, CTS out of Range (Earlier vehicles only).
 
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