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99 gmc 4x4, truck is mechanicly taken care of, problem is if i trump on the gas the truck will hesitate, motor sounds muffled, pinging noise like bad gas, shifting is held back. If I ease into to it, to go faster, it works fine. Great accelleration, smooth, shifts nice. I have changed: plugs, wires, TPS, MAP, MASS, intake gasket, fuel filter, air filter, had the injectors cleaned and tested, fuel pressure is good, changed all O2 sensors. What could this be????
1999 GMC DENALI-when I shift into passing gear it kicks down but it won't "power through" the gear and shift-thought catalytic converters were bad-replaced y pipe and 2 or the 4 02 sensors still no good. No power on take off towing or hills
Will replacing the throttle position sensor and the MAP sensor lower my hydrocarbonsWill replacing the throttle position sensor and the MAP sensor lower my hydrocarbons
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It could be electric fuel pump stall. The pump isn't pumping fuel fast enough. This model may have a inline fuel filter before the fuel pump as well that might need replacing.
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Sounds like the fuel pressure regulator in your EFI (carburator). Sorenson make a rebuild kit complete with gaskets, screens and regulator for around $30.
The code is a cylinder misfire in cylinder #4-it could be a bad coil, bad sparkplug wire, bad sparkplug, a problem with the fuel injector, or a mechanical internal problem like a valve in #4 not seating properly. With that cylinder not running at optimum, you will experience hesitation.
If not taken care of, yes, it will cause further problems. Gas mileage will suffer, unburnt gas may wash into your oil sump, emissions will be high, the catalytic converter may get damaged through contamination, oxygen sensors may become contaminated and need replacing- the list goes on. Do have it checked-it might be a simple fix, but it should be taken care of.
sometimes the plugs for the selonoids under the truck get wet and voids connections, you can check power at fuses and switch then down on actuators for the 4x4. My 90 has a floor shifter and if this is yours also then i'd check the linkage under truck for proper operation and shifting. My 03 yukon xl has the push button type on dash and everytime i get the truck washed at the car wash my 4x4 wont work for a day or two, as the plugs under truck get wet and shorts connections. I"m to lazy and it really doesnt bother me at the moment to climb under and dry and seal them so they are water tight.
Check TPS for smooth and linear electrical response over the entire range of motion. If the response is jumpy or erratic at all, replace TPS. Thank you for using fixya and good luck.
REPLACE THE IGNITION COIL, THE PLUG WIRES AND INSTALL IRIDIUM PLUGS, IT,LL RUN LIKE NEW AND YOUR WALLET WILL BE HAPPY BECAUSE OF DRASTICALLY INCREASED GAS MILEAGE!
i know the camp verde hill of which you speak , last vehicle in the shop with that same scenario , after doing everything possible including a catalyst check , as we could not duplicate the problem , we replaced fuel pump at owners request and next trip he confirmed it was a fix .
It could be electric fuel pump stall. The pump isn't pumping fuel fast enough. This model may have a inline fuel filter before the fuel pump as well that might need replacing.
Will replacing the throttle position sensor and the MAP sensor lower my hydrocarbons
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