truplaya22688 Posted March 25, 2006 Share Posted March 25, 2006 I have a 96 ES300 with approx. 135K on it. Runs literally like new, also just did the seafoam treatment like said in the forum and it runs even better. Only problem is gas mileage. When I first got the car with 85K i would get anywhere from 350-450 miles on a full tank depending on city or highway. This week I emptied my tank with only 200 miles! I did the plugs and wires and PCV and air filter at 105K. Is there anything I am forgetting to do? Someone told me that the O2 sensors may be giving out again but i dont think it would make that much of a difference would it? Also they were replaced at 105K with universals. I also prescanned the forum but found no new info or anyone else with the terrible MPG I am getting. Due to that I dont understand why this car is getting the gas mileage of a F-150 now. Quote Link to comment Share on other sites More sharing options...
Toysrme Posted March 25, 2006 Share Posted March 25, 2006 Sounds more like you're in a limp mode. You sure the check engine light isn't burned out? 1) Reset the ECU 2) 100,000m on an oxygen sensor is normal. Check/replace them both. I digress. I would doubt it's an injector problem, or you'd be running black smoke off whatever cylinder was dumping fuel. Quote Link to comment Share on other sites More sharing options...
truplaya22688 Posted March 25, 2006 Author Share Posted March 25, 2006 Sounds more like you're in a limp mode. You sure the check engine light isn't burned out? 1) Reset the ECU 2) 100,000m on an oxygen sensor is normal. Check/replace them both. I digress. I would doubt it's an injector problem, or you'd be running black smoke off whatever cylinder was dumping fuel. Nope Check engine light is ok, comes on before you crank and i just replaced both O2's at 105K and it now has 135K. The car also doesnt give off any smoke. Also after the seafoam the car has more power so theres no power loss either. Im lost, is it worth taking to the dealer at this point? Quote Link to comment Share on other sites More sharing options...
camlex Posted March 25, 2006 Share Posted March 25, 2006 Sounds more like you're in a limp mode. You sure the check engine light isn't burned out? 1) Reset the ECU 2) 100,000m on an oxygen sensor is normal. Check/replace them both. I digress. I would doubt it's an injector problem, or you'd be running black smoke off whatever cylinder was dumping fuel. One thing I don't understand is O2 sensor. I read here so many people had to replaced O2 Sensors. I have 186200 with original O2 sensors and getting 27-28 on Hwy. Why O2 sensors go bad? Extra fuel additive? or Bad ,Cheap Gas? After you did Seaform treatment, you getting 11MPG? Quote Link to comment Share on other sites More sharing options...
truplaya22688 Posted March 25, 2006 Author Share Posted March 25, 2006 Sounds more like you're in a limp mode. You sure the check engine light isn't burned out? 1) Reset the ECU 2) 100,000m on an oxygen sensor is normal. Check/replace them both. I digress. I would doubt it's an injector problem, or you'd be running black smoke off whatever cylinder was dumping fuel. One thing I don't understand is O2 sensor. I read here so many people had to replaced O2 Sensors. I have 186200 with original O2 sensors and getting 27-28 on Hwy. Why O2 sensors go bad? Extra fuel additive? or Bad ,Cheap Gas? After you did Seaform treatment, you getting 11MPG? Well I use regular gas from Mobil and the funny thing is that the MPG was even worse before the seafoam treatment. Before the treatment I got only 60 miles on half a tank, so on a full tank it would have been 120 miles! Something is definitly wrong, I just dont know what it is. Quote Link to comment Share on other sites More sharing options...
Lexusfreak Posted March 25, 2006 Share Posted March 25, 2006 You mentioned some of the maintenance items you replaced.....did that include a new fuel filter? What are your tire pressures set at? Quote Link to comment Share on other sites More sharing options...
truplaya22688 Posted March 25, 2006 Author Share Posted March 25, 2006 You mentioned some of the maintenance items you replaced.....did that include a new fuel filter? What are your tire pressures set at? Nope didnt do the fuel filter but would not changing it make that much of a difference? Also my tires are 205-60-R15 and are all at set at 32 PSI, which is right according to the sidewall. Quote Link to comment Share on other sites More sharing options...
blake918 Posted March 25, 2006 Share Posted March 25, 2006 I'd pull one of your plugs to see if it's fouled or not. I ran seafoam through my intake and fuel not too long ago, and immediately after the treatment, my gas mileage plummeted. I pulled the plugs and cleaned the crap off of them, and my gas mileage is back to normal. Quote Link to comment Share on other sites More sharing options...
amf1932 Posted March 25, 2006 Share Posted March 25, 2006 This might sound silly, but did you check whether the car rolls freely? What I mean is, are the brakes dragging due to a stuck caliper, or the emergency brake not releasing fully.......and did you check your tire inflation? And finally, you're sure that the gas tank is not leaking? Sometimes a leaky gas tank will leak only when you're on the road, so you can't see the leak when the car is parked. Quote Link to comment Share on other sites More sharing options...
takeaflyingleap Posted March 25, 2006 Share Posted March 25, 2006 Sounds like limp mode to me too. I have had an O2 sensor give out on me in less than 20k mi. I have even had brand new ones that were bad from the factory. Just because there new doesnt mean anything. I would also check to see if the brakes are binding. If it's none of those start from the bottom up. Air filter, plugs, fuel filter, fuel injectors, fuel pressure regulator, fuel leak... you get the idea. Neil Quote Link to comment Share on other sites More sharing options...
truplaya22688 Posted March 26, 2006 Author Share Posted March 26, 2006 Sounds like limp mode to me too. I have had an O2 sensor give out on me in less than 20k mi. I have even had brand new ones that were bad from the factory. Just because there new doesnt mean anything. I would also check to see if the brakes are binding. If it's none of those start from the bottom up. Air filter, plugs, fuel filter, fuel injectors, fuel pressure regulator, fuel leak... you get the idea. Neil Update - just realized that there are 3 O2 sensors, :whistles: I only changed two in the engine bay and i was told today that there is one behind the catylic converter, which i did not know about and probably is the original one with 135K. So as of now I am going to clean out my plugs and wires and change that O2 sensor and hope for the best. Thanks for everyones help. Quote Link to comment Share on other sites More sharing options...
monarch Posted March 26, 2006 Share Posted March 26, 2006 Changing the post cat sensor won't help your gas mileage. Only the pre cat sensors are important for mileage. My guess is you've got a serious fuel system fault that's causing way too much fuel to enter the combustion chamber or a serious ignition system fault that's causing an ignition miss on one or more cylinders. Pull the plugs to help gain some clues. Quote Link to comment Share on other sites More sharing options...
Toysrme Posted March 26, 2006 Share Posted March 26, 2006 camlex, barring something odd - as an o2 sensor ages two things happen. 1 they respond slower 2 they read progressively less voltage (Lean) so the management runs progressively richer. Even when they still output about the right voltage signal, they can still be slow to read etc. I still think it's more like a limp mode. On my 3vz-fe when I was installing my smt-6 I had to run across town before I was finished. Long story short, there were ignition signal problems I wasn't able to sort out, but the engine would crank & run in the bad limp mode so I went anyway. I got sub 50 miles to a 1/2 tank. (Maybe 40-45 it's been a few years) Make sure you have all your gears avalible too you. 1-4. Both a limp mode, and warm-up programming will lock-out overdrive on the transmission. Make sure it shifts into O/D & check the coolant sensors too. (Still check those o2 sensors). Check the plugs like they said. It could be contributing, bad spark isn't going to be the **sole** cause for that bad of mileage IMO. The ECU is still squirting the same fuel (less) regardless if it's burning or not. Quote Link to comment Share on other sites More sharing options...
truplaya22688 Posted March 29, 2006 Author Share Posted March 29, 2006 camlex, barring something odd - as an o2 sensor ages two things happen. 1 they respond slower 2 they read progressively less voltage (Lean) so the management runs progressively richer. Even when they still output about the right voltage signal, they can still be slow to read etc. I still think it's more like a limp mode. On my 3vz-fe when I was installing my smt-6 I had to run across town before I was finished. Long story short, there were ignition signal problems I wasn't able to sort out, but the engine would crank & run in the bad limp mode so I went anyway. I got sub 50 miles to a 1/2 tank. (Maybe 40-45 it's been a few years) Make sure you have all your gears avalible too you. 1-4. Both a limp mode, and warm-up programming will lock-out overdrive on the transmission. Make sure it shifts into O/D & check the coolant sensors too. (Still check those o2 sensors). Check the plugs like they said. It could be contributing, bad spark isn't going to be the **sole** cause for that bad of mileage IMO. The ECU is still squirting the same fuel (less) regardless if it's burning or not. Just a question, if it was in limp mode would it loose any power? Because the car has more power then ever now after the seafoam treatment. Also I checked today and all 4 gears are working and so is the O/D. Also checked all the plugs and wires and they are fine, cleaned them out anyway with the seafoam spray. Where would the coolant sensors be? I'll check those next, if those arent it then i have no choice but to take it to a mechanic. :( Quote Link to comment Share on other sites More sharing options...
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