sheab Posted March 17, 2007 Share Posted March 17, 2007 hi . peopel came back with the same problem .. 1991 ls400 about 9-10 mpg on highway+local trafic .. did the best i could took it to dealer .. they clean throttel body fuel enjectorr+system .. Fuel Filter+air filter new .. just improve about 3 mile then before .. but im still getting bad gas mile even after spending some dough !and the mechanic or dealer dont know the problem and avoiding by saying its just normal car & runs perfect -- the car drive smooth and normal .. mechanic cant even tell me whats the problem ! so im here back to you guys tell me what could be problem and issue ! so please tell me what to look for and what could be the problem thanks ! Quote Link to comment Share on other sites More sharing options...
djspawn00 Posted March 17, 2007 Share Posted March 17, 2007 try getting 93 octane gas from a different place than where you usually go... you're pulling some dodge viper mpg numbers... Quote Link to comment Share on other sites More sharing options...
93LSOwner Posted March 17, 2007 Share Posted March 17, 2007 If I recall you stated that you put 89 octane gas? Quote Link to comment Share on other sites More sharing options...
W201 sweden Posted March 19, 2007 Share Posted March 19, 2007 Sorry about the thirsty car. The fuel injection uses temperature sensors to determine the state of the engine. If the cooling water sensor breaks, it will cause the motor to run at incorrect mixture at warm engine. Ask your mechanic to measure the resistance in the sensor at cold and warm engine. Typical values are some kOhms at room temperature, and less than 100 Ohms at warm engine. Also, an incorrect knocking sensor can delay engine timing, which will reduce power and increase fuel consumption. Good luck! /Alexander from Sweden Quote Link to comment Share on other sites More sharing options...
VBdenny Posted March 20, 2007 Share Posted March 20, 2007 There are many things that can cause decreased fuel economy such as restricted exhaust, very low air pressure in the tires, dirty fuel injectors, etc. I could not imagine that any one of these would be able to cause such a drastic decrease with a clear indication of a problem such as a check engine light or sputtering. I would certainly check out the sensor that Sweden mentioned. The dealers compuer showed nothing? We recently drove to SC and averaged 26 mpg and I was going 80 or better much of the time. Quote Link to comment Share on other sites More sharing options...
sheab Posted March 20, 2007 Author Share Posted March 20, 2007 There are many things that can cause decreased fuel economy such as restricted exhaust, very low air pressure in the tires, dirty fuel injectors, etc. I could not imagine that any one of these would be able to cause such a drastic decrease with a clear indication of a problem such as a check engine light or sputtering. I would certainly check out the sensor that Sweden mentioned. The dealers compuer showed nothing? We recently drove to SC and averaged 26 mpg and I was going 80 or better much of the time. first of all i always use "93 octane gas" once i try 87 to test the car. its about 7-10 mile diffrence . 2- i clean the fuelinjection + throttel body and full fuel system at the dealer .. they test the car and told me .. the car drive normal everything is normal and everything working fine .. and my consern is -- temperature stay exactly at the middle.. and the car ideal at 600rpm . so you guys tell me how do i find my self what the roblem .. or how do i know that temperature sensor is bad or not working good--or there is incorrect knocking sensor ??? by the way there is no "check engine" light on wel it never came on ! but i notice something when i stop at the red light and then ready to go so i press gas the car seem like give it a slip and bhommmmm go .. but only on slow acc-- but if i press the gas harder the car fly .. so please help me .. thanks for all of ur great time ! Quote Link to comment Share on other sites More sharing options...
W201 sweden Posted March 20, 2007 Share Posted March 20, 2007 Like I said, let a mechanic test the temperature sensor to start with. Get the correct values, and compare it with what you've got in your car. It is a pretty quick and straightforward job. The tricky thing about fault sensors is, that they will normally not trigger the "Check engine" light. Why? Because the ECU just thinks you are driving a car that has not yet reached full running temperature - and that is not a fault in itself. ;) Please note! The temperature gauge uses a separate sensor, and may be correct in your car. /Alexander Quote Link to comment Share on other sites More sharing options...
sheab Posted March 20, 2007 Author Share Posted March 20, 2007 Like I said, let a mechanic test the temperature sensor to start with. Get the correct values, and compare it with what you've got in your car. It is a pretty quick and straightforward job. The tricky thing about fault sensors is, that they will normally not trigger the "Check engine" light. Why? Because the ECU just thinks you are driving a car that has not yet reached full running temperature - and that is not a fault in itself. ;) Please note! The temperature gauge uses a separate sensor, and may be correct in your car. /Alexander take it to the dealer or just any mechanic will do .. or is there any way that i can find it out? Quote Link to comment Share on other sites More sharing options...
W201 sweden Posted March 20, 2007 Share Posted March 20, 2007 Anyone (almost) can do it, as long as you: - have information on the sensor data, temp vs Ohm (I don't have it) - know where to find the sensor in the engine bay - can use a multi meter Good luck! :) /Alexander Quote Link to comment Share on other sites More sharing options...
wrpsuite Posted March 21, 2007 Share Posted March 21, 2007 I'm getting 18 mpg on my 94 ls w/ 186k using medium grade gas... Quote Link to comment Share on other sites More sharing options...
VBdenny Posted March 22, 2007 Share Posted March 22, 2007 Since I have never put anything but 93 in my car I do not know about how octane effects milage. I once had a Buick Electra 225 that dwindled down to 7 or 8 miles per gallon without explaination but that was only a small drop from the 12-14 it got anyway. I always found that the Lexus works better if you do accelerate a little harder off the line. I never cared for the slow-off-the-line performance. Quote Link to comment Share on other sites More sharing options...
sheab Posted March 22, 2007 Author Share Posted March 22, 2007 I'm getting 18 mpg on my 94 ls w/ 186k using medium grade gas... high way or local trafic? Anyone (almost) can do it, as long as you: - have information on the sensor data, temp vs Ohm (I don't have it) - know where to find the sensor in the engine bay - can use a multi meter Good luck! :) /Alexander i understad as i said .. i took it back to my mechanick they drove and tested which i didnt see and gave me the car and said everything fine with the car lol and charge me for me .. and said bye bye .and now im back again .. if anyone over here can help me by explaining how to troublshot the problem it will be helpful thanks once again Quote Link to comment Share on other sites More sharing options...
blake918 Posted March 22, 2007 Share Posted March 22, 2007 How old are your plugs/wires? air filter? Quote Link to comment Share on other sites More sharing options...
sheab Posted March 22, 2007 Author Share Posted March 22, 2007 How old are your plugs/wires? air filter? like 3-5 months old Quote Link to comment Share on other sites More sharing options...
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