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TPS Cause Misfire?

krieter

NAXJA Forum User
Location
PA
Vehicle Info

2000 Jeep Cherokee Sport 4x4 4.0 Distributorless Auto 152000

Been chasing the cause of a misfire on #1 cylinder had the occasional misfire on #3 and #4 but one time occurrence. TPS codes just showed up today after i unplugged the sensor and plugged it back in, after injector swap. Here is what I have done so far...

New Plugs
New Coil Pack
New Injector #1
Compression Test #1 80-90 psi
Compression Test #3 80-90 psi

Codes:
P0201 Injector 1 Control Circuit
P0123 Throttle Position Sensor Voltage High
P0301 Cylinder 1 Misfire Detected
P0122 Throttle Position Sensor Voltage Low

Any thoughts would be appreciated, bout to go switch 1 and 2 injectors to see if problem moves to #2 cylinder if that's the case got a bad injector.
 
Update...

Switched 1 and 2 injectors still have #1 misfire and control circuit (P0301, P0201) also TPS codes have gone down to just one P0123 Voltage High.

So am I just chasing an electrical issues? Wiring? Checked the immediate wiring near the injectors and connectors don't see any damage to it, no cracks, frays, splits, or rub through.

And again can the TPS send a faulty signal and cause the misfire? :dunno:
 
Test the TPS. Inspect/test the wire plug and wire harness. Seems to me the compression numbers are low, what are the numbers for the other cylinders ?


TPS failure may have one or more of these Physical Symptoms:

1) The engine loses power and is stalling.

2) The engine will idle, but may die as soon as you press the gas pedal. When driving, it seems as if all power is gone.

3) Sometimes it feels as if the transmission is failed or isn't shifting properly, if at all. If you quickly jump on the gas you might be able to get the transmission to shift, but it won’t shift properly by itself. Shifting manually, the transmission goes through all the gears.

NOTE: The throttle position sensor is also DIRECTLY involved with transmission shifting characteristics. The TPS function should be verified early in the troubleshooting process, when a transmission issue is suspected.

TPS TEST

The TPS is mounted on the throttle body. The TPS is a variable resistor that provides the Powertrain Control Module (PCM) with an input signal (voltage) that represents throttle blade position. The sensor is connected to the throttle blade shaft. As the
position of the throttle blade changes, the resistance of the TPS changes. Along with inputs from other sensors, the PCM uses the TPS input to determine current engine operating conditions. In response to engine operating conditions, the PCM will adjust fuel injector pulse width and ignition timing.

The PCM supplies approximately 5 volts to the TPS. The TPS output voltage (input signal to the PCM) represents the throttle blade position. The PCM receives an input signal voltage from the TPS. It is best to use an analog meter (not digital) to see if the transition from idle to WOT is smooth with no dead spots. With your meter set for volts, put the black probe on a good ground like your negative battery terminal. With the key on, engine not running, test with the red probe of your meter (install a paper clip into the back of the plug of the TPS) to see which wire has the 5volts. This will vary in an approximate range of from .25 volts at minimum throttle opening (idle), to 4.8 volts at WOT wide open throttle.

Perform the test procedure again and wiggle and/or tap on the TPS while you watch the meter. If you notice any flat spots or abrupt changes in the meter readings, replace the TPS.

The TPS is sensitive to heat, moisture, and vibration, leading to the failure of some units. The sensor is a sealed unit and cannot be repaired only replaced. A TPS may fail gradually leading to a number of symptoms which can include one or more of the following:

-Poor idle control: The TPS is used by the ECU to determine if the throttle is closed and the car should be using the Idle Air Control Valve exclusively for idle control. A fault TPS sensor can confuse the ECU causing the idle to be erratic or "hunting".

- High Idle Speed: The TPS may report faulty values causing the engine idle speed to be increased above normal. This is normally found in conjunction witha slow engine return to idle speed symptom.

Cheap crappy "Lifetime Warranty" parts are often out of specification or even failed right out of the box. Many times they have a short service life before they fail. Always buy top quality replacement parts and genuine Jeep sensors.
 
No lose in power or shifting problems to speak of. Didn't get the TPS code till today after I unplugged it for a second just out of curiosity to see what would happen. Not sure if knocked some dirt lose or just confused the PCM. But will test it all the same. Not really sure if this is the cause for misfire as it has been going on for weeks now and TPS only today.

Unfortunately I do not have psi readings for cylinders 2,4,5,6. Only tested 1 and 3. Will test the others asap and let you know. As far as testing compression any specific way i need to do it? Cause I let the motor turn a couple of times and got 125psi reading on #1, but saw it came up in increments so I tried my best to test it with one stroke which landed me between 75-100 psi did about 7 tests all different readings. Advice?

Also side note read in another thread a similar thing as I am experiencing with mine. Mil will flash and I guess go into a "limp" mode where tach will top out at 2800 as if its hit a limiter and serious lose of power like I'm running on 3 or 4 cylinders. When this happens throw it in neutral, shut off, start up, and she runs fine. Also if I do a hard reset (disconnect and ground positive battery lead) mil goes off and she runs like new for anywhere between 10-50 miles or half hour or so. Thoughts? Advice?

Realize I may sound like I am contradicting myself here with my previous statement of no lose of power but this is temporary where as the TPS would be constant correct?

Totally of subject but bought a U-Scan scanner that works off smartphone and bluetooth anyone have and your opinion of them?
 
I have a dumb phone, but other people report that the Bluetooth scanners work well.

Limp mode, and hard resets suggest to me ,faulty data from weak or failing sensors, and/or wiring issues to the sensors.

Compression test results should be about 120 psi to 150 psi, with a maximum variation between cylinders of 30 psi.
 
But am I right in letting the engine spin a couple of times or should I take the very first pressure reading?
 
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