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Tim's Auto Repair
Tim's Auto Repair, mechanic
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Experience:  Have owned a repair shop for 25 yrs.
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Chevrolet K1500 4x4: I just tuned up my 1994 chevy silverado

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I just tuned up my 1994 chevy silverado 5.7 tbi and now it is loading up on fuel I replaced the aic valve and no change. my engine light comes on and goes off reguarly. the truck went from 17 to 6 mpg. in two days any answers would be great.
are you saying the engine seems to get too much fuel and is flooding the engine?
sense the engine light does come on,,,,can you give me the trouble codes?
tell me all you can
Customer: replied 4 years ago.

I don't have a code reader and the shops around me say they can only read 1996 and up. I can crank engine it acts like it's flooded. when driving at 40 or above it smooths out with a miss every ow and then ,but stopping and starts are almost impossable. after the tune up it ran fine for 3days and now not so great

there are a couple of things that could cause this..
1-the ect[egine coolant tempeture sensor
2- the map sensor..
you need to get the trouble codes to see if the codes point to one of these,,,i will show you haw to scan this one without a scanner
1994 Chevy Truck K 1500 Truck 4WD V8-350 5.7L
Coolant Temperature Sensor/Switch (For Computer) Locations, Components: Engine Coolant Temperature (ECT) Sensor
Engine Coolant Temperature Sensor

The Engine Coolant Temperature (ECT) Sensor is located on the intake manifold next to the thermostat housing.

1994 Chevy Truck K 1500 Truck 4WD V8-350 5.7L
Manifold Pressure/Vacuum Sensor Locations, Components: Engine Control Module - ECM
MAP Sensor Location

The Manifold Absolute Pressure (MAP) Sensor is located on a bracket, mounted to the intake manifold, on the passenger side rear.

1994 Chevy Truck K 1500 Truck 4WD V8-350 5.7L
Computers and Control Systems Testing and Inspection, Reading and Clearing Diagnostic Trouble Codes: Reading Diagnostic Trouble Codes, Without Scan Tool
ALDL Connector (Located Underdash)

The means of communicating with the control module is the Data Link Connector (DLC) located under the instrument panel and is sometimes covered by a plastic cover labeled "DIAGNOSTIC CONNECTOR". The DLC is used in the assembly plant to receive engine information to determine proper operation before it leaves the plant. The Diagnostic Trouble Codes (DTC's) stored in the control module memory can be displayed by counting the number of flashes of the Malfunction Indicator Lamp (MIL) (Service Engine Soon) when the diagnostic terminal of the DLC is grounded. The DLC terminal "B" (diagnostic terminal) is the second terminal from the right of the DLC top row. The terminal is most easily grounded by connecting it to terminal "A" (internal control module ground), which is located to the right of terminal "B" on the top row of the DLC.

When terminals "A" and "B" have been connected, the ignition switch must be turned to the "ON" position with the engine NOT operating. The MIL (Service Engine Soon) should flash DTC 12 three times consecutively. This would be the following flash sequence: One flash, pause, two flashes, long pause, one flash, pause, two flashes, long pause, one flash, pause, two flashes. DTC 12 indicates that the control module diagnostic system is operating properly. If DTC 12 is NOT indicated, a fault is present within the diagnostic system itself, and should be addressed by consulting the appropriate diagnostic chart.

Following the output of DTC 12, the MIL will indicate any DTC three times consecutively. However if no other codes are present will continue to repeat DTC 12. If more than one diagnostic trouble code has been stored in the control module memory, the DTC's will be displayed from the lowest to the highest with each DTC being displayed three times.

When the diagnostic terminal is grounded with the ignition "ON" and the engine "OFF", the system will enter the diagnostic mode. In this mode, the control module will:

- Display a Diagnostic Trouble Code (DTC) 12 by flashing the Malfunction Indicator Lamp (MIL) "Service Engine Soon" (indicating that the system is operating properly).

- Display any stored DTC's by flashing the Malfunction Indicator Lamp (MIL) "Service Engine Soon". Each DTC will be flashed three times, then DTC will be flashed again.

- Energize all control module controlled relays and solenoids except the fuel pump relay. This allows checking circuits which may be difficult to energize without driving the vehicle and being under particular operating conditions.

- Move the Idle Air Control (IAC) valve to its fully extended position on most models, blocking the idle air passage. This is useful in checking the minimum idle speed.

If the diagnostic terminal is grounded with the engine running, the system will enter the "Field Service" mode.

In this mode, the MIL "SERVICE ENGINE SOON" light will indicate whether the system is in OPEN or CLOSED LOOP operation.

If the system is in OPEN LOOP operation, the light will flash approximately two and one-half times per second.

CLOSED LOOP operation is indicated by the light flashing approximately once per second. Also, in "CLOSED LOOP" the light will stay "OFF" most of the time if the system is running lean. It will stay "ON" most of the time if the system is running rich.

While the system is in the "Field Service" mode, new codes cannot be stored in the control module and the "CLOSED LOOP" timer is bypassed.

Customer: replied 4 years ago.

I tried to connect the a-b terminals and got no reaction from service engine light ,just stayed on no flashes

this is strange
check all fuses,,but,,your problem may be the computer itself,,these obd1 computers cost around $80+- at your local parts store...
Customer: replied 4 years ago.

I hate to keep on with the questions but if the ect still works the gauge would it still have a chance of being bad

the ect doesnt work the only gos to the computer,,the gage works of the sender in the cylinder head

Customer: replied 4 years ago.

hey Tim I think we have found the problem the ect connectionis not clipping tightly on the probes could that be it and should I replace it

yes,,this could cause the problem..make sure you fix it to where it gets a good connection...if you must replace it,,these cost less than $20+- at your local parts store
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Customer: replied 4 years ago.

Tim thanks so very much for your help you are the man expect a high praise. Thank you John Paschall

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