You may have your MAP sensor connected to a ported vacuum source and not full manifold vacuum. You may have a vacuum leak causing low engine vacuum to the MAP sensor. Your fuel pressure is not set properly or your fuel return line is restricted. On a TBI system your base gasket may be the wrong size or not sealed properly. On an MPFI system you may not have the vacuum line connected or a secure connection to the fuel pressure regulator; this is also a full manifold vacuum source.
You will see a recurring theme in these troubleshooting notes and that is vacuum leaks. This is the biggest cause of engines running too lean and should not be taken lightly. Fuel pressure is not coming up to proper pressure. See discussion on fuel pressure in previous paragraphs. Plugged fuel filter; make sure that your fuel tank is not contaminated.
Make sure that your distributor is powered up with an ignition 1 source. Ignition 1 provides 12v of power at all times the key is in the on or the crank position. Ensure that the relay and the ECM are receiving power from the battery and an ignition 1 source to the red and pink wires respectively. The battery wire must be connected to a battery source and the ignition wire must be to an ignition 1 source. On TBI units ensure that the crank wire is connected to the crank side of the ignition switch or the crank side of the starter solenoid.
Verify that you have set your timing properly by disconnecting the set timing connector, setting the timing to the specified value, reconnecting the connector and shutting the engine off and starting it back up before proceeding. Ensure that your plug wires are properly connected with the correct firing order. Your fuel pressure may be insufficient; see fuel pressure discussion in previous paragraphs. Verify that there are no vacuum leaks and that the MAP sensor is properly connected.
Timing is a critical issue with sags. Verify that your timing is correctly set by disconnecting the set timing connector and properly setting the timing; see #4 also. Fuel pressure is not adequate for proper operation, make sure that there is not contamination in the tank or your fuel filter is plugged. A plugged fuel filter may be an indication of a contaminated tank. Bad ground to the block, insure that the surface that you are making the connection to on the block is clean and making a positive connection. Your O2 sensor may be contaminated, bad or not properly installed in the exhaust. You may have left out some of the important specifications for the proper calibration chip to be made.
Check that the MAP sensor is properly connected to a full manifold vacuum source. Ensure that the vacuum source to your MAP sensor is free from restrictions and has a secure connection. Check for vacuum leaks, this is the most common cause. Make sure that your timing is set correctly; see #4. Fuel pressure is not adequate for proper operation. See previous paragraph for discussion on fuel pressure and proper operation. Fuel pump relay is not coming on or is faulty. On a TBI system verify that the crank wire is connected to the crank side of the ignition switch or the crank side of the starter solenoid.
Your battery and ignition wires are improperly connected. You have not provided a good ground to the fuel pump. Fuel pump relay is not connected. ECM is not properly installed and/or the chip is not properly installed.
More than likely you have a large vacuum leak, verify that your system is free from vacuum leaks. Your ignition wire is connected to a battery source and not an ignition 1 source. The engine has not come to full operating temperature as of yet. Your thermostat is inoperable or opens at too low of a temperature. You should be using at least a 180o stat. Throttle cable or throttle on the throttle body is not coming to a complete close. Throttle plate is binding in the throttle bores.
If all is set up properly with the installation of your fuel injection system you are probably getting as good of fuel economy as you are going to get. Ensure that your timing is set properly, your thermostat is in good working order and your fuel pressure is at the specified pressure. You may have other factors such as tires, brake drag or other external issue from the fuel injection system that is not working properly. Re-evaluate your driving habits and insure that you are driving in a fashion that will provide you optimum fuel economy. If you are trying to race everyone from the light chances are you will not get the fuel economy that you expect.
This is usually an indication of a vacuum leak; again make sure that you have no vacuum leaks. This could also be an indication of the wrong base ignition timing. Verify that you have set your ignition timing correctly (see #4). Your engine may also require more air going through the throttle plates at idle than it is currently set for. Here is a procedure to check this setting. Make sure your engine temperature is at full operating temperature. Jumper Pins A & B of the ALDL connector (I use a paper clip) with the key on but the engine off. This is the same thing you do when checking for engine codes and your check engine light will flash off and on. Wait about 45 seconds or until any trouble codes present have flashed through; code 12 is normal (see #14) After this then unplug your IAC valve which is on the throttle body. Remove the jumper from the ALDL, turn the key off and then start the engine. It may start hard and you might have to depress the throttle pedal a little bit to start the engine. If you have a fast idle this did not work and you may have to tape over the fresh air hole that the IAC receives it air from. If you do not have a fast idle then it is OK and you can proceed to adjust the throttle plates. Let the engine idle for a little bit and then check you idle speed. The speed should be about 550-600 in idle or about 100 rpm less than you requested for your chip. If it is lower than this you can raise the idle up or if it is above this determine if you should bring the speed down. More than likely it will always be lower. There is a little cap on the side of the throttle body by your throttle lever that has an adjustment screw under it. Remove this cap and use the screw under there to adjust your base idle speed without the IAC operational. If you have done all of this and you still have an issue we may not have received all of the proper information to build your chip.
If your fuel pump is real noisy you may not have isolated it from the body or the frame real well. Isolation brackets were provided with your fuel pump. If these are properly installed it should isolate any radiated noise from the pump. If this is insufficient you may need to isolate it more with some rubber grommets. We have also diagnosed noisy fuel pumps with fuel return lines being too small. By stepping up the size of the return line you may eliminate fuel pump noise after the other items have been addressed.
Your check engine light should illuminate when you turn the key to the on position for a bulb check. If this does not come on it is possible that it is not receiving 12 volts to the one side of the bulb. The wire provide that comes from the ECM provides a ground circuit for the light. You will need to provide a 12 volt ignition source to the other side of the light. Check to ensure that you have 12 volts on one side of the light and that the light is functional. If the light is functional and you have verified that you have 12 volts provided to one side of the light then the ECM is not operating. Ensure that the fuse for the ECM is OK. If the fuse is OK insure that you are receiving 12 volts to the ECM where indicated (see wiring diagram provided) If you are not receiving 12 volts to the ECM something in the vehicle’s power circuit is not connected properly. If 12 volts is available at the proper cavities of the ECM please check that you have a proper ground circuit to the engine block. When all of these steps have been taken the ECM may not be working properly, please contact us for further diagnosis.
A constant rapid flashing check engine light indicates that you have a fault in the ECM and it is operating in back up or limp home mode. Make sure that the calibration chip is in the ECM and there are no bent pins on the chip. If the chip is properly installed and there are no bent pins the ECM or the chip is faulty and needs to be replaced or repaired.
A check engine light indicates a hard fault with your fuel injection system. Ensure that all of your sensors are connected, you have a good ground and that no wires are pinched. Also insure no vacuum leaks and that your MAP sensor is connected to a full manifold vacuum source. If all of these steps indicate a proper installation and no issues you will need to read the codes from the memory area of the ECM. If you have a scan tool this is very easy. If you do not have a scan tool you can use your check engine light to output the fault codes. Below you will find this procedure along with a definition of all the different fault codes that can be output.
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To Display Trouble Codes:
Run a wire (I use a paper clip that is in a Ã¢â‚¬Å“UÃ¢â‚¬?) from Pin A to Pin B with the ignition on but the engine not running. The “Check Engine ” light will flash in the following sequence: flash, pause, flash-flash, long pause flash, pause, flash-flash, long pause flash, pause, flash-flash, long pause. This is a code “12” which will always be there. After this series of flashes and pauses any stored trouble codes will now flash. If you do not see the “12” flash three times, your diagnostic circuit is defective.
Some vehicles will display stored trouble codes, then “12” again, followed by energizing “most system controlled relays.” The fuel pump relay will not energize. The idle air control valve will fully extend to enable checking minimum idle speed.
CLEARING THE TROUBLE CODES
Turn the keyswitch to the off position. To clear any trouble codes, disconnect the battery for 30 seconds or unplug the connectors to the ECM. If this is done at the battery, and your car stereo is equipped and programmed with a four digit pin code, you may have to re-enter that as well to use your stereo again. A better place to remove power is at the fuse.
12. No reference pulses to Electronic Control Module (ECM). You will get this code when checking for codes because the engine is not running.
13. Oxygen sensor signal stays lean during warm engine cruise, your O2 sensor could be unplugged.
14. High temperature indicated at engine coolant temp. sensor. Sensor could be unplugged
15. Low temperature indicated at engine coolant temp. sensor
21. High voltage at throttle positon sensor. Sensor could be unplugged.
22. Low voltage at throttle positon sensor
23. Low temperature at manifold air temperature sensor
24. Circuit fault in vehicle speed sensor
25. High temperature at manifold air temperature sensor
29. Fault in 4th gear switch
32. Fault in exhaust gas recirculation valve diagnostic switch
33. High voltage (low vacuum) at MAP sensor.
34. Low voltage (high vacuum) at MAP sensor.
41. Cylinder select error
42. Fault at electronic spark timing circuit (sets when timing is set also, clear code and verify that it does not return.)
43. Low voltage at electronic spark timing circuit
44. Oxygen sensor lean
45. Oxygen sensor rich
46. Fault at vehicle anti-theft system
51. PROM error
52. Low voltage at oil temperature sensor
53. High voltage at battery
54. Low voltage at fuel pump OR Low voltage at Fuel pump relay
55. Problem at Electronic Control Module (ECM) – ECM failure OR Serial bus error
62. High voltage at oil temperature sensor