2003 GS300 High negative fuel trim, no power, bad mpg
07-01-18, 03:48 PM
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2003 GS300 High negative fuel trim, no power, bad mpg
Hey guys, first post for my wife's GS300. I need help on chasing down an issue. Her car is running very poorly and rich with no CEL. The LTFT is around -20% idle, -24% light gas, -18% WOT. The car feels like a small 4 banger. A bunch of noise but very bogged down. It is feels horrible to drive. She is also getting around 10-12 mpg. Background: 197K on the car today. Sparkplugs, O2 sensors, timing belt all replaced around 160k. MAF just replaced this weekend, no change in performance. I have reset the ECU many times for fuel trims to return to 0% and they jump right back once the O2 sensors start reading. I have induced a vacuum leak and the LTFT shift to +3% at idle, -14% light gas, and -6% WOT. I think it has to do something with the fueling. I don't want to just throw parts at it. I was going to check the fuel pressure at the rail but didn't see a way to do that. I also think this has been a long time issue and has lead to clogged cats. I however want to fix the issue first and then work on the cats if the car still feels bogged down. Also we have ran about two bottles of fuel system cleaner over the last few tanks. Those seemed to help a little with smoothness but the car is still a dog.
Is there a way to easily check fuel pressure?
Any help would be greatly appreciated. Thanks
Is there a way to easily check fuel pressure?
Any help would be greatly appreciated. Thanks
07-01-18, 09:44 PM
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Thanks for the advice. I will look over all the hoses again. Also I have always thought vacuum leaks cause a lean condition. I was able to better my LTFT when I removed a cap on the intake manifold.
07-02-18, 06:18 PM
#5
Yes get your injectors leak tested and also while you got them off clean them using the ultrasonic method.
Also check the fuel pressure by taking the main union bolt off the rail (see attachment). The fuel pressure regulator in the tank could be bad.
Also check the fuel pressure by taking the main union bolt off the rail (see attachment). The fuel pressure regulator in the tank could be bad.
Last edited by vijayn; 07-02-18 at 06:21 PM.
07-03-18, 08:34 PM
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Very helpful. Thank you! If I get a chance to check it out I will report back.
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skytechja
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