A new issue developed the other day. it occurs most obviously when i'm cruising at highway speed and I need to step on the gas a little to accelerate or climb a hill. The Tahoe starts bucking and missing unless it downshifts. I'm suspecting that it's time to replace the fuel filter but I'm not sure. the Air cleaner is relatively new as is the ignition system. I have not recently (or ever) cleaned the fuel system or throttle body and the truck has 220,000 miles. Any and all suggestions are appreciated.
95 tahoe bucking in top gear
- Thread starter arowsom
- Start date
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SunlitComet
OBS Jedi-Do Good
when you give it gas again depress the brake enough to make the brake light come on. If it stops something is amiss with the converter lock up system. The most frequent failure of it is the brake switch above the pedal. It is not you fuel filter I don't think. You could also have some work ignition parts causing a misfire. Perform the procedure below and post what coded come up.
ALDL Connector (Located Underdash)
READING DIAGNOSTIC TROUBLE CODES:
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.
DIAGNOSTIC MODE:
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:
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.
ALDL Connector (Located Underdash)
READING DIAGNOSTIC TROUBLE CODES:
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.
DIAGNOSTIC MODE:
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.
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retorq
Full Access Member
Mine did that when the TPS was bad, only did it when it was past 3/4 throttle ...
raptorforme93
Full Access Member
My tahoe did this twice before I changed the plugs wires and dizzy. It has never done it since that was all replaced
Thanks for your responses. I have not been able to get the service engine light on so i have not had any codes. I did notice the other day however that it only happens when the engine is warm. I can step on the gas with no hesitation, missing or bucking when it's cold. EGR seems to be working fine. All ignition parts except the plugs and coil are less than a year old. Exhaust is new from the block back as of early April. Throttle position sensor reads a smooth curve on an ohm-meter. O2 sensor, Fuel Filter and Fuel Pump are original. Mileage is 222,000. Because it runs fine cold I'm guessing that it has something to do with the emissions control system but I'm not sure how to start troubleshooting. Any help out there is appreciated!
SunlitComet
OBS Jedi-Do Good
Well original O2 sensors are certainly not helping. However I don't think it is your primary problems. Made time to clean your injectors yet?
SunlitComet
OBS Jedi-Do Good
there is a better method but it might be costly and that is straight injection int to the fuel supply line of tbi. Check with local shops on price aor dump a bunch of techron in your tank.
JonnyTahoe
Full Access Member
I can tell you its NOT the EGR. The fuel Filter should of been the First thing you replaced. You just said it was the Original. Plugs and wires second, Hello, "Tune-up 101". Sunlit has some great advise but before you get Crazy Tecno tune the thing up with common sense cheap items that should of been done the first week you owned the vehicle.
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