cdsm25

Have a problem with my 94 auto 4wd. After it gets good and warm, if i apply the gas it gets stumbly. This will happen in park or drive and will clear after about 1/3 throttle or letting off. It feels like the engine going under load as the rpms fall slightly. It feels like timing is being pull. Checked tps voltage, new fuel filter, cap, rotor, plugs. no codes other then 21. Any ideas??

cdsm25

Sorry code 41 not 21

tjwalker

*Code 41 is almost always a failing alternator. What is the output of the charging system? With a good system, you should have between 13.5 and 14.0 volts at idle. Can and should be verified with a meter at the battery.

*Wouldn't be a bad idea to verify your fuel pressure. With a gauge, which can be rented inexpensively from many parts stores. For a 94, you should have 31 psi at idle. Then disconnect the vacuum line leading to the fuel pressure regulator (be sure that line is pulling good vacuum and isn't wet with fuel) and the pressure should jump to approximately 39 psi.

cdsm25

Its running right at 14.0v and I checked fuel pressure earlier this week it was right at 32/39. I just took it out and it is real bad at idle in gear. Taking off from a light is spits and sputters then bam full power..?? it starts again around lock up. I seems like its the first 10% of the tps is messed up. What should be the voltage at zero throttle? its at .66 v

Bustedback

I suspect a bad TPS.

cdsm25

What should the voltage be?

cdsm25

FOUND IT!!!!!!! I disconnected the cam angle sensor or the plug on the distributor and the problem stopped. I thought it was a timing issue to begin with but had talked myself into everything else. Can these CAS be cleaned or do I need a new distributor?

tjwalker

The throttle position sensor is connected to the throttle shaft on the throttle body. It sends throttle valve angle information to the PCM. The PCM uses this information to determine how much fuel the engine needs. The TPS is really just a simple potentiometer with one end connected to 5 volts from the PCM and the other to ground. A third wire is connected to the PCM. As you move the accelerator pedal with your foot, the output of the TPS changes. At a closed throttle position, the output of the TPS is low, about a half a volt. As the throttle valve opens, the output increases so that, at wide open throttle, the output voltage should be above 3.9 volts. Testing can be performed with an electrical meter. Analog meter is best. You are looking for a smooth sweep of voltage throughout the entire throttle band. While slowly opening and closing the throttle, take note to the movement of the voltmeter needle. There should be a direct relationship between the needle motion to the motion of the throttle. If at anytime the needle moves abruptly or inconsistently with the movement of the throttle, the TPS is bad

You should have 5 volts going into the TPS. At idle, TPS output voltage must be greater than 200 millivolts. At wide open throttle (WOT), TPS output voltage must be less than 4.8 volts.. The best is 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 5 volts. One of the other wires should show .26V (or so). The other wire will be the ground and should show no voltage. Move the throttle and look for smooth meter response up to the 4.49 at WOT.

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: -

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

• 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 with a slow engine return to idle speed symptom.
• Slow engine return to idle: A failing TPS can report the minimum throttle position values incorrectly which can stop the engine entering idle mode when the throttle is closed. Normally when the throttle is closed the engine fuel injectors will be deactivated until a defined engine RPM speed is reached and the engine brought smoothly to idle speed. When failing a TPS will not report the throttle closed and fueling will continue causing the engine to return to idle very slowly.
• Engine Hesitation on Throttle Application: The TPS is also used by the ECU to determine if the driver has applied the throttle quicker than the Manifold Air Pressure sensor can read. The fueling is adjusted accordingly to cope with the sudden increase in air volume, however a faulty sensor can cause the ECU to ignore this data and the engine will "hesitate" when applying the throttle. In extreme cases with the engine at idle, a sudden application of full throttle can stall the engine.
• Engine Misfire: A fault TPS can report values outside the denied acceptable range causing the ECU to incorrectly fuel the engine. This is noticeable as a slight misfire and can trigger the misfire detection software and/or Malfunction Indicator Lamp (MIL) light on the dashboard. Extreme cases can cause excessing misfires resulting in one or more cylinders being shut down to prevent engine and catalytic converter damage.

cdsm25

Thank you for the details! Its most appreciated. Last night in a complete frustrated state I decided to look at only timing sensor and found if I unplug the distributor or cam angle sensor it completely stopped. Now it did feel like it had a curve so to speak but the problems stopped. Hopefully I can scratch up some dough and get a new one today. Thanks again for your info, it will be saved and used in the future.

Chris

cdsm25

UPDATE: Today I wire a switch to the power wire of the Cam Angle Sensor so I can start it up and then shut it down to get what seems to be a fixed timing. Oh I tried to clean it and it made it worse. I cant believe I'm 29yo and cant afford (well till payday) and 50 buck distributor, guess thats what I get for going back to college lol. Its working so just an update if your in a pinch!

Bustedback

You don't need a new distributor, you only need the cam sensor.