Warpig

Hello, need your thoughts and opinions on how to fix my 1993 XJ inline 6.
Failed emissions. Slightly high CO and HC's. Hesitates when you snap throttle. Spark plugs covered in gasoline also gasoline coming out tailpipe. Smells of heavy fumes.
I have fixed all check engine lights except code 12 which will clear itself.

Any help will be a blessing thanks guys.

tjwalker

I'd concentrate on the fuel issue. Especially the spark plugs covered in gasoline. I'm surprised that you only "slightly failed" testing!!

Start with verifying fuel pressure. Must be done with a gauge. Should have 31 psi at idle. Then disconnect the vacuum line leading to the fuel pressure regulator and the pressure should jump to approximately 39 psi. BE SURE that the vacuum line leading to the fuel pressure regulator is not wet with raw fuel. If it is, that indicates a ruptured fuel pressure regulator and it must be replaced. I'd be checking this vacuum line pronto with the symptoms you describe....

Also be sure that your secondary ignition system is up-to-snuff. That means fresh Champion copper spark plugs, quality plug wires, distributor cap and rotor.

Good luck and keep us posted!

PDEM87

Also look at the vacuum line and connections to the MAP sensor for any cracks,leaks, or even plugage. If full manifold vacuum is not reaching the MAP sensor, it will run rich!

Warpig

New codes checked tonight is now giving me codes 11 and 24.
11* No crank reference signal detected during engine cranking.
24** Throttle position sensor input above maximum acceptable voltage

I have not tested with a fuel pressure gauge but I am confident the fuel pressure is good as I put on a new pump/ filter and fuel lines. Rebuilt fuel rail. Now the truck sat for some time around 1 year so clogged injectors may be a cause. I cleaned the injector nozzles with brake clean and a rag. Fuel Pressure regulator and vac line don't smell like gas. Doesn't seem the diaphragm is damaged. Cant feel much pressure on this vac line with my finger.

New cap/ rotor/ plugs/ wires/ ignition coil. Or by secondary are you referring to the under distributor cap cam sensor.

New vac line to MAP sensor. Again doesn't feel like much pressure with my finger. All vac lines I can get to have been replaced but the engine smooths out a little when rpm's are raised after the initial hesitation. I dont have a vacuum tester so cant test my MAP.

PDEM87

Sounds like your TPS may be failing. The higher the voltage output of the TPS, the richer the fuel mixture. It can be checked by back probing with a multimeter.

tjwalker

Follow the codes. The OBD system isn't perfect, but it's awfully darn good at pointing you to the offending circuit.

Start by testing your throttle position sensor for the code 24. More below.
---------------------------------------------------
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.