INTAKE LEAK TEST
1DANGER
Propane is an extremely flammable liquid and vapor which may cause a flash fire. Keep it away from heat, sparks and open flame and only use it with adequate ventilation.
To prevent false readings, keep the air filter and the air box cover installed when performing the test and do not direct propane at the air box.
To make p a tester you will need a standard 14 oz. propane cylinder. And either a HD Propane Enrichment Kit HD-41417) or a standard propane burner with a valve and a 12 in. (304 mm) long-1/4 in. (6 mm) piece of diameter copper tubing OR remove the burner tip from a standard propane torch and valve assembly in which case you will use a piece of 5/16 inch copper tube of which you will flatten one end to form a nozzle and a piece of 5/16 inch ID rubber hose. You will cut the rubber hose to 18 inches long and insert the round end of the tubing into one end of the rubber tubing.
For the testing procedure you will start engine and warm it to operating temperature. THEN if you are using the HD propane tester turn the propane tester valve counterclockwise to open the bottle and aim the copper tubing nozzle toward all possible sources of leak such as fuel injectors and intake tract push valve to release propane. If you are using a homemade tester open the propane bottle valve to allow propane out to do the test and close it when you have tested a possible source of an intake leak. OR the better way would be to obtain an inline push button valve to start or stop the flow of propane. Be very careful to limit and control the emission of propane gas. The tone of the engine will change when propane enters any source of an intake leak.
You likely have P0505 set and this is the IAC. You need a special torx tool to adjust the adjustment screw because it should NOT be adjusted/fooled with. The problems with a low or high idle should be fixed and not this adjustment.
IDLE AIR CONTROL, DTC P0505
IAC Operation
The ECM controls engine idle speed by moving the IAC to open or close a passage around the throttle plate. The IAC motor has two windings and the ECM sends voltage pulses to the proper motor winding of the IAC to either cause the pintle to move in or out of the IAC a given distance for each pulse received. Idle speed is increased as the ECM retracts the pintle, allowing more air to flow through the throttle body and idle speed is decreased when the ECM extends the pintle, allowing less air to flow through the throttle body. The IAC position is measured in steps by a computer program called the H-D DIGITAL TECHNICIAN. A fully retracted pintle and open passage around throttle plate is indicated by a high number of steps and is correlated to an increased amount of air flowing through the throttle body. Conversely ZERO steps represents a fully extended pintle which is a fully extended pintle and a closed the passage around the throttle plate, which is an abnormal condition. The ECM resets the IAC each time the ignition is turned off, by sending sufficient pulses to extend the pintle and effectively close the throttle body. The reference point used by the ECM is the fully extended value in steps from which a set number of counts (steps) are then calculated by the ECM for use in setting the proper idle speed and IAC position. WARM IDLE SPEED is ECM controlled and cannot be adjusted except with Digital Technician. When the engine is stopped, the IAC pintle extends and then retracts to a fixed "Park" position for increased airflow and idle speed during the next engine start sequence. This key OFF reset procedure takes 10 seconds to perform. A special test lamp may be used to test the IAC operation. The color of the lights is not relevant to IAC operation. In NORMAL circumstances when the key is turned ON the test lights will alternately flash and then remain steady on to confirm ECM signals. When the key is turned OFF the lights should alternately flash and go out after the 10 second reset procedure. IF one or more of the lights fails to illuminate during key the ON/key OFF/key cycle a problem is indicated and there is also a remote possibility that one of the circuits is shorted to voltage. This would have been indicated by a steady light. In these circumstances with the Ignition Switch OFF, disconnect the ECM and turn the ignition ON again and probe the terminals to check for this shorted condition and fix it by repairing a faulty ECM connection or by replacing the ECM.
Diagnostic Trouble Code P0505 sets if the idle RPM is +200 or -200 from the preset idle speed and the IAC motor is at zero steps or at maximum steps for greater than 5 seconds. P0505 may occur with others for a multiple code situation and if so the other codes must be resolved first before dealing with P0505.
Engine Idle Diagnostic Tips
Engine idle speed can be adversely affected by the following:
1. an intake air leak;
2. improperly adjusted throttle stop or a misfiring cylinder;
3. leaking injectors will cause fuel imbalance and poor idle due to different air/fuel ratios in each cylinder.
(To check for leaky injectors, first remove the air cleaner and then with the throttle wide open, turn the key ON for 2 seconds and then OFF for 2 seconds five consecutive times and look fro any sign of fuel in the induction system. If there is any you will need to replace the fuel injector(s).;
4. vacuum leaks
5. contaminated fuel;
6. excessive oil in the crankcase (oil sumping);
7. TPS reading greater than 1% (possibly caused by a throttle cable misadjustment);
8. battery voltage reading of less than 9 volts;
9. a VSS greater than 0 will disable idle speed control; and
10 loss of battery power to ECM pin 31.
Wire Harness Connectors
NO. DESCRIPTION TYPE LOCATION
[78] ECM 36-Place Packard Under Right Side Cover
[87] IAC 4-Place Delphi Below Fuel Tank (Right Side
Code Description
DTC DESCRIPTION
P1353 Front cylinder no combustion
P1356 Rear cylinder no combustion
P1357 Intermittent secondary front
P1358 Intermittent secondary rear You likley have P0505 set and this is
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