Will start just fine, but RPM idle gauge goes up and down while in park or driving. Seems to accelerate slowly, but eventually get up to speed. Also seems to effect gas mileage per tank.Plugs are fine and all connections are connected.
Check engine light has remained on (for years) with GMC technicians unable to detect problem and have passed all emissions testing required. Engine light has never effected performance.
Truck has run great execpt for that
jb
Arrange to test the vehicle with OBD-II Scanner in order to confirm exact error codes of the engine.
For the problem of RPM idle gauge goes up and down while in park or driving is due to the dirty Throttle Body which is very common in these vehicle. Throttle Body needs to be cleaned, follow the steps in the attached videos to clean it in order to fix the problem of variation in the RPM in idle position. A lot of videos are available on YouTube to fix this problem:
https://www.youtube.com/watch?v=-0OOUpoSFoA
https://www.youtube.com/watch?v=G5HNMiEcXz0
https://www.youtube.com/watch?v=df9YYULxQE8
https://www.youtube.com/watch?v=Qo4f-7HbkAc
https://www.youtube.com/watch?v=GXCirzBkde0
Check Engine light indication could be due to bad gas tank cap, change the gas cap and remove battery negative terminal for 1 hour to reset the light and then put back battery wire. Check engine light will be disappeared and will clear the error codes. Follow the steps in the attached video:
https://www.youtube.com/watch?v=5qSslj6VQCU
https://www.youtube.com/watch?v=0ANU0a9Vw5w
If it come back after couple of times of switching ON & OFF, Evaporative Emission Control System Vent Valve/Solenoid Circuit Malfunctions. It must be replaced and again reset by removing the negative terminal of battery for half an hour. Attached video shows how to replace EVAP sensor:
https://www.youtube.com/watch?v=AH00NyHb6Fc
https://www.youtube.com/watch?v=6DNExV7V5No
https://www.youtube.com/watch?v=hbFr4-DoGSQ
https://www.youtube.com/watch?v=slp--D8P0T8
Complete List of OBD Codes: Generic OBD2 (OBDII) & Manufacturer are available on:
http://www.totalcardiagnostics.com/support/Knowledgebase/Article/View/21/0/genericmanufacturer-obd2-codes-and-their-meanings
Disclaimer: PS attached videos are only for the reference purpose.
Sounds like a tps throttle position sensor or something with the circuit. This will cause fuel problem and also the RPM gauge to move up and down
In some applications a check engine light is triggered by the odometer. Requires the dealer to reset. If no ODBII faults are present, the only sensors that are subject to physical wear are the TPS(throttle position sensor) and the 02 sensor(oxygen sensor). These 2 sensors are relatively cheap and should be replaced due to age(2000). To maintain optimum performance, I do 3 things, every 30,000 miles. 1) Change the Air Filter. 2) Replace Fuel Filter and 3) Add a can of B&G44K to a full tank of fuel. The B&G is the best on the market and will condition your fuel pump and injectors. It is available only through dealerships(11.00 a can at Toyota) and should not be substituted. These 3 things are your path to cheap performance and fuel economy
SOURCE: 1999 GMC Sonoma check engine light on when gas tank full
i have had the same problem and i found that it was the fuel pump causing the problem
SOURCE: POOR GAS MILEAGE
Have you changed the fuel filter? I know it sounds weird but a plugged filter will make a truck use more gas. The computer tries to compensate for less fuel by commanding the injectors to open longer. Also a plugged filter will cause excess back pressure on the fuel pump making it loud.. Good Luck.
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mine does the same thing why does it do that?
I have the same problem with mine but it does not really seem to affect my acceleration. the check engine light has been on for about two years and still have not been able to figure out why or what code it is for.
Mine does pretty much the same thing. It seems to accel. fine, but while driving or in park I can sit in watch the rpm gauge repeatedly jump slightly, couple hundred rpms. I do think it is causing me to lose mpg to. I used to get around 300 miles from a tank, now I'm down to around 260 or so. This is only over the past year or so.
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