My unit has recently dropped to 14.0 miles per gallon.
The car had it's transmission rebuilt last Fall.
But recently the economy has dropped to 14.00
I've checked the MAF sensor and sprayed it down, it's definitely clean.
I understand the Fuel Filter, Pump is a plausible issue as are other sensors.
I'm curious how best to DIAGNOSE the issue so I'm not replacing parts I don't need.
Can someone from this amazing group help me once again?
FYI, in cabin air filter was replaced last season as well.
Thank you.
The cabin air filter won't affect your mileage, but your engine air filter definitely could. Is it clean?
Yes air filter is clean as well. Brand new.
To diagnosis it, you need to analyze readings from live data, including STFT, LTFT, MAF reading, oxygen sensor readings,...
One question regarding the car maintenance: when did your change the spark plugs?
We changed the plugs last season, but I pulled one, it was fouled. Would that be the best place to start, I like the idea of DATA to determine the source. I could ask a local mechanic to check those...Yes?
What type of service shop would be best geared for this type of work/repair? I fortunately live amongst a plethora of service shops. The benefit of living in Detroit.
Thanks for your response.
If you have access to a good local mechanic, they usually check the data before replacing parts. Just tell them what the issue is and the symptoms you have. You can also point to them the spark plug situation to give them more information. If you also do some research, there are lots of information about the stuff you can check before taking your car to a mechanic. Here is an example:
https://autoguysland.com/why-is-my-car-getting-bad-gas-mileage-all-of-a-sudden/
Any chance you are throwing a code for the knock sensors? If you are, the transmission won't shift into overdrive and your engine will be revving high when it would normally shift. Your fuel economy will suffer. Knock sensor failure is common on these RX300s around 150k.
WOW.....That actually is a number of issues. Especially the overdrive.
I'll have them check for that.
A new twist this morning. The car, when not warmed up, is sluggish. Very sluggish. But once warmed up. Better.
Would that indicate anything else?
I have an appointment with the local mechanic tomorrow.
Ever since the transmission was redone, it has revved much higher than normal, YES, OVERDRIVE was not engaging. I was resigned to the fact that I was screwed by the fly by night transmission guy.
The mileage has just recently plummeted though. I do not have any engine codes/lights. I will seek out a technician immediately to scan it. That's a great suggestion. I'm thinking it's a costly repair though, correct?
If it is the knock sensors, expect to pay 3 to 4 hours labor. The intake manifold has to be removed. The sensors (2) are probably around $150 each from the dealer. I got mine off eBay, supposedly genuine Toyota, for a lot less.
Thank you
A quick question about KNOCK SENSOR issues....wouldn't I have a CHECK ENGINE light ?
If the OBD is working properly, the CEL (along with the VSC and Traction Control lights) should be on for a RX300 with bad knock sensors.
They are NOT on. But the transmission does not hit OVERDRIVE.
When the engine is cold, it's sluggish. When I sit at a light for a bit, it all of a sudden feels very peppy.
Fuel economy is 14.2 right now, I've got it at a service place, but they are overwhelmed with repairs at this point, I'm going to be lucky if they have a chance to scope it.
Your suggestions from this group are GREAT! Thank you everyone.
I'll share what the results are and hopefully it's a cheap fix.
(yeah, right)
Please keep us posted. Hope for the best...
So the saga continues. The put it on the scope and said everything is working fine. No check engine and all readings were within specs. Personally, I think I need to find a Scotty Kilmer style technician. Not these guys. They seemed perplexed that I would question the gas mileage and what could be causing it. WITHOUT A SENSOR or LIGHT on the dash.
Does a fuel filter cause a sensor warning or an alert of sorts?
Unfortunately no. How big was the drop in your gas mileage? Are you calculating it yourself by dividing miles driven by gallons used?
I was relying on the provided display numbers.
(I grew up with calculators, aren't those things ALWAYS right?...sarcasm)
Mental note, do my own math with next fill up.
So as I continue to attempt to diagnose this problem, I'm finally near a new tank of gas.
(I don't drive much) I did try some fuel injector additive and the MPG results jumped from 13.9 to 18.00
The thing is that it's not consistent. I start the car in the morning and allow it to run. When I leave, it's 13.9. I drive about 10 minutes to work (using cruise control, stop and go traffic....and it will get to 16.9) If I drive home, it'll stay about the same. However, if I use the peddle and brake without cruise, my mileage will tank. I'm planning on running a full tank of premium through it. Noting the mileage prior and then in 3 weeks when it's empty, again noting the mileage. But I'm curious about the wild variations from the computer led display.
I'm getting no check engine lights, the icon does work. No codes or anything. I'm planning on doing spark plugs and cleaning out the fuel injectors again with an upper engine treatment.
Looking for any additional suggestions.
Add some fuel injection cleaner into the nearly pty gas tank and then go for a highway drive for about one hour (Italian tune up).
Will do