Timing and TPS questions

Hi, I've got two questions.

I just finished rebuilding the engine for a friend's 1996 Bronco. It's a 351w. First question is about the 121 code that I can't rid of: "Closed throttle voltage higher or lower than expected." The voltage between green and black wires on the throttle position sensor (TPS) is ~.54 volts. Other postings say it's supposed to be somewhere between .6 and .9 v, preferably closer to .9 v. Some postings say to loosen the screws and move the sensor around to vary the voltage. First, it seems to be impossible to loosen the screws while the throttle body is attached to manifold so real time adjustment would appear challenging. Secondly, even with the screws loosened, there is very little play in the positioning. So I purchased a new TPS and replaced the old one. I get the same error code with the new one. Could I be installing it backwards? Which way do the wires go? Toward the IAC side or toward the outside of engine, like where the EGR valve is? I have the wires toward the outside. Note that I did try the old one with the wires toward the IAC and I still got the error and low measured voltage.

Second question. I have timed the engine at 10 degrees BTC with the spout on. Seems to work OK. However, all postings say to remove the spout and then do the timing. Every time I remove the spout from the distributor, the engine dies immediately. What's going here? Is this expected behavior?

Would appreciate any help. Engine actually runs really well and I'm pleased with my rebuild. Just seeing if there is upside to be had.

Rebuild pictures if interested:

https://picasaweb.google.com/106068607007984139595/Bronco

yo jandpp,

WELCOME!

The 96 DTCs should begin with a P; such as P1121

DTC 121, 122, 123, 124, 125 & DTC P0122, P0123 & P1121 in TSB 94-26-4 "...The following is a list of vehicle symptoms which have been associated with the TPS, but can also be related to other vehicle components. Check engine light, Stalls, quits, hesitation/stumble, fast idle; To minimize the replacement of good components, be advised that the following non-EEC areas may be the issue: Excessive blow-by, PCV malfunction, Vacuum leaks, Fuel pressure, Throttle sticking or linkage binding.

MANY VOLTMETERS WILL AUTOMATICALLY CHANGE RANGES WHEN MEASURING TPS OUTPUT FROM IDLE TO WOT. WHEN A VOLTMETER IS USED TO MEASURE TPS OUTPUT FROM IDLE TO WOT, THE METER SCALES OR CHANGES RANGES AUTOMATICALLY. THERE MAY BE AN ERRONEOUS METER DISPLAY UNTIL THE VOLTMETER HAS LOCKED TO THE APPROPRIATE VOLTAGE READING. THE ERRONEOUS METER DISPLAY DOES NOT REPRESENT A DEFECTIVE TPS. NOTE: IT IS RECOMMENDED THAT THE "RANGE LOCK" FEATURE ON MANY METERS BE SET FOR CHECKING TPS VOLTAGE..."

Source: by Ford @ http://content.chiltonsonline.com/TSB/displayTSBHandler.ashx?assetID=36931&key=6kAUBD5BruOJf%2f3tgozUqjXM3RdbjcQqW4sVWiE%2fp2IojfpfKqM07dr61%2bQAWHtT%2bshJrOWtEbFFvIVKQBltEWhp4KsgX3E865g3s0zA0J2WPaO8KG20YMSNxn1bNyVU1PYDJABM6vBUMr7qIKyVow%3d%3d

READ MORE

btw, Upper Case is by Ford, not me...

Voltage @ Idle should be .65 to 1.28

TPS in 96 is not adjustable.

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From my 96 Bronco Workshop Manual;

CAUTION: Slide rotary tangs into position over throttle shaft blade, then rotate throttle position sensor CLOCKWISE ONLY to installed position. Failure to install the throttle position sensor in this manner may result in excessive idle speeds on 5.0L and 5.8L.

 

On a 5.0L and 5.8L engine, position the throttle position sensor so that the pigtail points toward the idle air control valve (IAC valve)

IAC Location pic



Testing in 5.0 & 5.8; "...Symptoms of a BAD TPS: The one thing that you can definitely count on, when the TPS fails, is the Check Engine Light shining nice and bright to let you know that there's a Diagnostic Trouble Code stored in the Fuel Injection Computer. Here are some specific symptoms you'll see: 1.TPS Diagnostic Trouble Codes: (DTC’s) stored in the vehicle’s computer’s memory. Code 23: Throttle Position (TP) Circuit Performance Problem. Code 53: Throttle Position (TP) Circuit High Input. Code 63: Throttle Position (TP) Circuit Low Input. Code 121: Throttle Position (TP) Circuit Performance Problem. Code 122: Throttle Position (TP) Circuit Low Input. Code 123: Throttle Position (TP) Circuit High Input. 2.Really BAD gas mileage. 3.No power as you accelerate the vehicle. 4.Hesitation when you step on the Accelerator Pedal. There are times when the ECM (Electronic Control Module = Fuel Injection Computer) will think the TPS has failed when it hasn't. This usually happens when the ECM spits out several Diagnostic Trouble Codes at once.. and so what will save you time, money and the frustration of replacing good parts, is to test the Throttle Position Sensor..." READ MORE

Source: by easyautodiagnostics.com http://easyautodiagnostics.com/ford_tps_4.9L_5.0L_5.8L/bad_tps_test_1.php

Replacement in a 96; "...Disconnect the TP sensor wiring harness. On 5.0L and 5.8L engines, it may be necessary to remove the throttle body. On all other engines proceed to the next step. Disconnect the wiring from the sensor. Matchmark the TP sensor and throttle body. Remove the 2 retaining screws and the sensor. On 5.0L and 5.8L engines, position the TP sensor so that the pigtail points toward the IAC valve. Secure the TP sensor to the throttle body with the retaining screws. Tighten to 18-27 inch lbs. (2-3 Nm) on 4.9L engines or 11-16 inch lbs. (1.2-1.8 Nm) on 5.0L/5.8L engines. If applicable, install the throttle body. Connect the wiring. Connect the negative battery cable..."

Source: by Chilton

============

SPOUT

Timing Adjustment in Ford EFI Engines; MIESK5 NOTE; Spark timing that is ******** from specification may increase exhaust gas temperature and shorten catalyst life. Refer to the following procedure for service details. a. Check spark timing. Check base timing with spout disconnected.

Set base timing to the specification on the vehicle emission decal.

b. Check computed timing with spout connected.

NOTE: COMPUTED TIMING IS EQUAL TO BASE TIMING PLUS 20° BTDC ± 3°.

Use the ignition key only to start the vehicle. Attaching a remote starter might disable or initiate the start mode timing after the vehicle is started..." READ MORE

Source: by Ryan M (Fireguy50) at http://oldfuelinjection.com/?p=71

For timing procedure, see:

Vehicle Emission Control Information (VECI) Decal in a 95 5.8



Source: by marnefist at SuperMotors.net

If VECI decal is not on your friend's Bronco;

Vehicle Emission Control Information (VECI) Decal; Contains Vacuum Diagram & Calibration Parts List for 88 & UP. On-Line for Free at Ford. Click "Quick Guides" in left panel; Scroll to & CLICK VECI Labels "Provides Vehicle Emission Control Information (VECI) and a related calibration parts list." Enter applicable info (need to know your Calibration number (also called catch code) from your B-pillar sticker). Vacuum Diagram is the same as the one on the core support or hood or air filter cover. Suggest Right Clicking this Hot Link & Open in New Window

Source: by Ford @ http://www.motorcraftservice.com

==

What is the New Code #?

Thanks for the quick and comprehensive reply.

I flipped the TPS around so that the wire pigtail comes out on the IAC side. I still get the 121 DTC. While I've read in other place too that this could be be something else like a vacuum leak, I don't think that makes sense in this case. The code is coming from the KOEO test, ie, engine is not running. The throttle plates are fully closed, and I'm measuring the voltage right at the sensor. And I'm getting too low a voltage. So unless there is some harness defect which is drawing down voltage, I would think that the problem is isolated to the sensor or sensor/throttle connection. I'm now thinking it might be a cheap part. I noticed that the part that I replaced was not a Ford part, looked relatively new and very much like the new part I purchased from Autozone. Possibly the Duralast version is faulty from the start.

Jim

yo,

I have a Defective Parts Listing here and...

"Duralast TPS sensors for our Bronco's went through 4 in 3 years.

by LBrdsoxfan in another Bronco forum

"So it turned out that autozone sold me a faulty TPS. I've returned it and bought a motorcraft one. No more problems so far."

JRoo 02-21-2012, in another Bronco forum

Check it for Resistance;

Unplugged TPS Resistance, Less than 4k ohms, Greater than 350 ohms (TP SIG/SIG RTN while rotating Throttle)

https://www.supermotors.net/getfile/899966/fullsize/tps-connector.jpg

The 96 DTCs should begin with a P; such as P1121

iSIs the 351w a replacement using an EEC IV PCM?

My 1992 has started having some of these problems. I've got an automatic with the 5.8. When I'm sitting at the drive thru or someplace it gradually starts idling higher. Shifts hard between all gears, and sometimes can't find 4th gear. It will also sometimes stall out if I'm traveling down a dirt road at an idle. None of these symptoms are consistent. Sometimes she runs great. I pulled trouble codes and the only ones that came up were 122, 123. Is it pretty certain that my TPS Sensor is failing?

Yo texmatlock,

Welcome!

Yes the TPS Needs to be tested. Also loom for connector or wiring issues @ & to the TPS.

I will break my reply into multiple posts due to some unknown restrictions here.

DTC 121, 122, 123, 124, 125 in TSB 94-26-4 "...The following is a list of vehicle symptoms which have been associated with the TPS, but can also be related to other vehicle components. Check engine light, Stalls, quits, hesitation/stumble, fast idle; To minimize the replacement of good components, be advised that the following non-EEC areas may be the issue: Excessive blow-by, PCV malfunction, Vacuum leaks, Fuel pressure, Throttle sticking or linkage binding. MANY VOLTMETERS WILL AUTOMATICALLY CHANGE RANGES WHEN MEASURING TPS OUTPUT FROM IDLE TO WOT. WHEN A VOLTMETER IS USED TO MEASURE TPS OUTPUT FROM IDLE TO WOT, THE METER SCALES OR CHANGES RANGES AUTOMATICALLY. THERE MAY BE AN ERRONEOUS METER DISPLAY UNTIL THE VOLTMETER HAS LOCKED TO THE APPROPRIATE VOLTAGE READING. THE ERRONEOUS METER DISPLAY DOES NOT REPRESENT A DEFECTIVE TPS. NOTE: IT IS RECOMMENDED THAT THE "RANGE LOCK" FEATURE ON MANY METERS BE SET FOR CHECKING TPS VOLTAGE..." upper case is by Ford. Source: by Ford

... The TPS is a three wire sensor that measures the throttle plate opening and its rate of change. This sensor is a variable resistor, also called a potentiometer, that is directly linked to the throttle plate shaft. The TPS outputs a voltage directly proportional to the throttle opening. As the accelerator is depressed the throttle plate opens and the TPS voltage increases. The TPS assists the PCM in determining transmission shift points, converter lock-up and along with the MAP and MAF sensor are main PCM indicators of acceleration and load. In other words, the PCM looks at these sensors to calculate engine operation upon acceleration. Let me preface by saying I do not believe that most Ford TPS Sensors require adjustment unless you have played with your Throttle Plate Set ***** or have a performance application. The procedure is not mentioned in any late model Ford Factory or Engine/Emissions-Diagnosis Manual that I have seen. In other words, Adjustable TPS Sensors may be applicable to older vehicle applications. In late model vehicles, the TPS Sensor is "self calibrating". If you require an Adjustable TPS you must set it just below 1v, ideally between 0.96v-0.98v. This is because the PCM is programmed to observe the TPS Signal Voltage in three modes: TPS Modes Idle Mode - Less than 1v Part Throttle Mode - Greater than 1v WOT Mode - Greater than 3.7v (Breakpoint is +2.7v) The 0.96v-0.98v. setting has been determined to be optimal as it minimizes time delay between Closed Throttle and Part Throttle which increases performance. This is where performance TPS Adjustment Settings Instructions are directed and many mistakenly think it is all inclusive. The shop modification of drilling out the ***** holes for additional adjustment is directed at people that use the incorrect TPS or cannot achieve the setting parameters due to intentional Throttle Body variences. On the other hand, EEC-IV Broncos use a Non-Adjustable TPS. Each time the key is turned on the PCM reads the Closed Throttle TPS voltage and places it in KAM memory as TPREL PID (or Ratch) Voltage. Ratch Voltage then becomes the baseline for Idle where the PCM assumes 0% Throttle Opening. The PCM is programmed for a voltage stairstep, (or Ratch), to Part Throttle and Wide Open Throttle (WOT) values. These stairstep values are based on the initial Closed Throttle readings and are determined each time the ignition key activates the PCM and TPS. Ratch Values Closed Throttle - Initial Voltage Setting Part Throttle - +0.02v above Closed Throttle Wide Open Throttle - +2.71v above Closed Throttle Even though the PCM determines Ratch Voltage with key on, there are different initial vehicle specifications for TPS Settings. This is to ensure that your TPS can operate within the full range of it's mechanical/electrical capability (In the case of my 1990 5.8L Bronco, this range is 0.34v-4.84v between 0-85 degrees rotation). As long as your initial TPS settings are within the factory specified range, such as listed below, your TPS will be correct. TPS Settings 1990 Bronco 4.9L - 0.73v to 1.22v 1990 Bronco 5.0L - 0.73v to 1.22v 1990 Bronco 5.8L - 0.73v to 1.22v 1995 Bronco 4.9L - 0.65v to 1.28v 1995 Bronco 5.0L - 0.65v to 1.28v 1995 Bronco 5.8L - 0.65v to 1.28v In either case, the PCM generally operates in Open loop on cold Start-up, Closed-Loop on warm idle/low-load cruising and Open-Loop during WOT. Open-Loop refers to shutting down the EGR, ignoring O2, ECT, ACT Sensor Input and relying upon programmed fuel maps. The TPS is advising the PCM through throttle modes when to go into Open or Close Loop Operations. And, as the TPS is an electrical/mechanical device, the TPS Sensor can wear out by developing dead spots which cause idle problems or hesitation usually in the most used lower range. Finally, Curb Idle and Fast Idle are controlled by the PCM and IAC and are not adjustable. This means adjusting your Throttle Plate Set ***** from the factory calibration will not allow the IAC to effectively control the rpm. This also changes the Throttle Plate position potentially causing it to stick in the bore and it alters the TPS settings by either telling the PCM that you are always at Part Throttle or pushing it outside of setting specification. The Throttle Body Return ***** adjusts the Throttle Plate for Minimum Air Rate, which is the minimum amount of air required to maintain idle with the IAC unplugged. Plug the IAC in and the PCM is in control of your Idle within it's programmed parameters. This means that you should not have to touch the Throttle Plate Set ***** unless someone has played with it or if you have a performance application which is tuned for a higher Idle air flow. That is where you must adjust your TPS back to factory settings to compensate for the change in Throttle Plate position. As the Minimum Air Rate, Engine Load, TPS Sensor and the IAC are very closely linked, they must all work together to maintain a good idle. Idle problems can be caused by a myriad of other issues which should always be looked at first. These include ignition, fuel, spark, EGR, vacuum and PCV to name a few. After these are ruled out, the KOEO TPS Harness may be tested for Reference Voltage, the KOEO TPS Voltage may be back probed for baseline setting and a smooth increase thoughout the Throttle rotation and the unplugged TPS Sensor may be tested for Resistance also throughout the Throttle rotation. KOEO TPS Testing

KOEO TPS Reference Voltage - 5v (VREF/SIG RTN)

KOEO TPS Signal Voltage - <1v to <4.8v (TP SIG/SIG RTN while rotating Throttle)

Unplugged TPS Resistance - <4k ohms/>350 ohms (TP SIG/VREF while rotating Throttle)

Yo T,

Part 2;

1988-1991 TPS Wire Colors
VREF - Orange/White
TP SIG - Dark Green/Light Green
SIG RTN - Black/White (My 1990 is actually Red/Gray)


1992-1996 TPS Wire Colors
VREF - Brown/White
TP SIG - Gray/White
SIG RTN -Gray/Red


Motorcraft TPS Wire Colors
VREF - Orange
TP SIG - Green
SIG RTN - Black







For more information, see this link:Throttle Position Sensor Testing, Replacement and Adjustmentl!

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Was the Transmission Control Indicator Light (TCIL) ( overdrive on-off LED ON shifter... stalk blinking?

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Here are some wiring diagrams (partial, 86 through 96) and Technical Service Bulletins, (80 through 96) @ http://www.revbase.com/BBBMotor/Wd

Yo T,

parts 3,

See  my vacuum leak test in post #20 @ http://broncozone.com/topic/23994-90-58l-getting-continuous-code-33-and-running-code-44/?p=125535

Quick check is to get a vacuum gauge; Normal Engine Vacuum at Idle is 15-22 in and holding steady;

 and if not, read this Vacuum Gauge Diagnosis by Ford @ http://www.diesel-da...tj/stj30013.htm

Yo T,

parts 3,

See  my vacuum leak test in post #20 @ http://broncozone.com/topic/23994-90-58l-getting-continuous-code-33-and-running-code-44/?p=125535

Quick check is to get a vacuum gauge; Normal Engine Vacuum at Idle is 15-22 in and holding steady;

 and if not, read this Vacuum Gauge Diagnosis by Ford @ http://www.diesel-da...tj/stj30013.htm

Lots of good info. Thanks

miesk5 You called it. Thanks for the help. $50 part, and an hour of my time is all it cost me. Replaced the TPS sensor and she's back to running like a champ. After I swapped it out and did a quick disconnect / reconnect at the battery she dropped to an idle at about 700 RPM and stayed steady. Shifting as it should and running out perfect.

Yo Tex,

Great & yw!