Significant drop in mileage - help!

[Tyler]

@ NSXSTASY - For the record, and in my own opinion, I think you are very arrogant! "Oh goodie! Another topic where someone takes a previously level-headed discussion and comes in flaming, insulting and attacking other members for their well-intentioned posts, using words like "dumbass", "pathetic", "idiots", and "imbeciles"! Just what we need!" You like to think you know it all, but in reality you don't.

"BTW, I also let the car warm up in winter (and in summer and pretty much all the time), before I drive it." "That's a big waste of gasoline" For starters, it is not a big waste of gasoline, it does not use much actually. Secondly, it is not healthy for the car to idle more than 1-2 minutes when the car is cold. Reason being, oil pressure is low, your vehicle is not getting the proper lubrication. Start your car, let it idle for 1-2 minutes, then drive keeping it under 30 MPH until the temp gauge has raised to the middle.

Lastly, (pretty stupid question but still needed to be asked) why do you guys drive an suv if you are worried about gas mileage?

[yogi799]

Originally Posted by lion9mdx

Is the torque converter locking up correctly? .

Holy cow, are you saying this could cause a real drop? My check engine light came on 5 months ago, it is some message about torque converter stuck open (or closed) and the dealer told me to just drive, nothing to do about it really...

Indeed, the car drives like new and I've since towed a lot and taken a 4000 mile road trip with no glitches. There is no unusual RPMs, slippage, etc, I know my RPM bands very well and know that there is nothing different about how it drives in ANY gear... All is like out of factory, however freeway MPG is worse, a lot worse (not sure if only since the check engine light came on or not, the two could be completely unrelated). So do you think they may have something to do with one another?

[kalyanakrishna]

Originally Posted by nsxtasy

It sounds to me like the most probable reason for the drop is your move from a warmer climate to your first cold (or, semi-cold) winter.


That's a big waste of gasoline. And it is another possible explanation for your drop in mileage.

I never, ever let the car sit warming up. I get in, start it, and take off immediately, even in the dead of winter, driving it gently until it has a chance to warm up (which only takes a few minutes).

been doing this for a while, so that cant be the reason. Also, the warm is barely over a couple of minutes - start the car, grab the lunch bag, laptop, wear shoes, put in the car and drive off. I'd rather let it warm up idle because I have to get on to a freeway at 70mph right away.

[kalyanakrishna]

Originally Posted by Tyler

"BTW, I also let the car warm up in winter (and in summer and pretty much all the time), before I drive it." "That's a big waste of gasoline" For starters, it is not a big waste of gasoline, it does not use much actually. Secondly, it is not healthy for the car to idle more than 1-2 minutes when the car is cold. Reason being, oil pressure is low, your vehicle is not getting the proper lubrication. Start your car, let it idle for 1-2 minutes, then drive keeping it under 30 MPH until the temp gauge has raised to the middle.

Lastly, (pretty stupid question but still needed to be asked) why do you guys drive an suv if you are worried about gas mileage?

The warm up is shorter than a wait at a red light. I have to get on a freeway right away, so I like to see the temp gauge move up from cold a bit and drive it under 35 while I try to get it to a bit under 30% before I start doing 70 mph. Its been this way for a while and I think it helps esp. when the temps are below freezing.

[NewMDXOwner]

Originally Posted by yogi799

Holy cow, are you saying this could cause a real drop? My check engine light came on 5 months ago, it is some message about torque converter stuck open (or closed) and the dealer told me to just drive, nothing to do about it really...

Indeed, the car drives like new and I've since towed a lot and taken a 4000 mile road trip with no glitches. There is no unusual RPMs, slippage, etc, I know my RPM bands very well and know that there is nothing different about how it drives in ANY gear... All is like out of factory, however freeway MPG is worse, a lot worse (not sure if only since the check engine light came on or not, the two could be completely unrelated). So do you think they may have something to do with one another?

If the Torque Converter is stuck in the "Locked Up" position your car will stall at a stop light. If it is stuck and cannot lock up (after about 45mph), you will have near term issues with lower gas mileage and long term issues with overheating the transmission even though the accelerated wear on your transmission does not show up right away.

[yogi799]

Originally Posted by NewMDXOwner

If the Torque Converter is stuck in the "Locked Up" position your car will stall at a stop light. If it is stuck and cannot lock up (after about 45mph), you will have near term issues with lower gas mileage and long term issues with overheating the transmission even though the accelerated wear on your transmission does not show up right away.

I have this:

http://www.mdxers.org/forums/73-2001...-like-new.html

P0741 HONDA - Torque Converter Clutch Hydraulic Circuit Stuck Off

Read more: OBD2 - OBDII Code P0741 HONDA - Torque Converter Clutch Hydraulic Circuit Stuck Off | Engine-Codes.com

But I see no anomalies with RPMs or feel any slipping that did not exist before.
So I gather you are saying this could be the real reason for my MPG drop...

[lion9mdx]

Originally Posted by yogi799

Holy cow, are you saying this could cause a real drop?

Yes, if it's not locking up, you'll have a noticeable drop. (The locking torque converter is the biggest reason that automatic transmissions now have similar fuel economy to manual transmissions.)

I know you said you know your RPM situation really well, but this code just seems like too much of a coincidence not to be the explanation here.

[dc1225]

Originally Posted by nsxtasy

In addition to the suggestions mentioned above, you might want to also check the items mentioned in this recent discussion:

Worried about freeway fuel consumption recently. Getting 16 MPG...


FWIW, the mileage on my well-maintained gently-driven 2004 is about what yours is now - 14-16 around town and 20 on long-distance trips. I've never gotten anywhere close to your earlier 19/20 in the city or 23-26 on the highway. So I can't explain why you would have been getting such high mileage earlier; what you're getting now seems normal to me.

Ditto nsx. I get 14.3 city, 16-17 hwy. pretty consistently. Anyone gets above that has nothing to complain about.

[NewMDXOwner]

Originally Posted by yogi799

I have this:

http://www.mdxers.org/forums/73-2001...-like-new.html

P0741 HONDA - Torque Converter Clutch Hydraulic Circuit Stuck Off

Read more: OBD2 - OBDII Code P0741 HONDA - Torque Converter Clutch Hydraulic Circuit Stuck Off | Engine-Codes.com

But I see no anomalies with RPMs or feel any slipping that did not exist before.
So I gather you are saying this could be the real reason for my MPG drop...

The Torque Converter has nothing to do with slipping in your transmission, at least not until the extra heat wears away your clutch plates, but that will take a lot of miles. By itself, whether or not it locks up, you won't feel slipping.

One way to know is that, above about 45 mph, you should feel a very very very slight jolt as the Torque Converter locks up. It feels as if you have an extra gear. With that said, it is so hard to count the gears now that transmissions have so many gears that it goes through!

Another way is by the quote of the link you provided: "When the accelerator pedal is depressed (less than 2/8) in lock-up condition, the engine speed should not change abruptly. If there is a big jump in engine speed, there is no lock-up."

[dons04mdx]

Originally Posted by kalyanakrishna

Not to my knowledge. We changed timing belt around then (along with some other work). What would be the symptoms of an unadjusted valve?

I'm not a expert, just a good googler.

Intake and exhaust valves that are not adjusted to open and close at the proper times degrade an engine's ability to make maximum power. Intake valves control when and for how long fuel is allowed into the combustion chamber, and must be synchronized with the speed of the pistons to allow the maximum amount of mixture into the engine. Exhaust valves perform a similar function, except their purpose is to allow burnt gases to leave the engine. If the valves aren't adjusted correctly, the engine will not burn fuel at maximum efficiency. Power and mileage then dramatically decrease.

Read more: What Are the Problems Caused by Bad Valve Adjustment? | eHow.com What Are the Problems Caused by Bad Valve Adjustment? | eHow.com

From extensive reading on this and another Acura forum it seems that the valve adjustment is one of the most often overlooked maintenance items and it causes a lot of seemingly random problems: bad gas mileage, random misfires, poor idle, etc. I'd get it done if I were you.

[kalyanakrishna]

Originally Posted by dons04mdx

I'm not a expert, just a good googler.

From extensive reading on this and another Acura forum it seems that the valve adjustment is one of the most often overlooked maintenance items and it causes a lot of seemingly random problems: bad gas mileage, random misfires, poor idle, etc. I'd get it done if I were you.

Thanks, I will look for how to do it.

[kalyanakrishna]

Took it to the shop today. He said EGR looks fine. So, back to square one.

[dons04mdx]

Originally Posted by kalyanakrishna

Took it to the shop today. He said EGR looks fine. So, back to square one.

Why not have him do the valve adjustment too? Or are you going to do that yourself?

[kalyanakrishna]

Originally Posted by dons04mdx

Why not have him do the valve adjustment too? Or are you going to do that yourself?

I am going to have to do that, he did todays as a courtesy. Oil change is coming up, so I will ask him to do the check then.

Yeah, I'm not qualified to do any DIY engine stuff on my car. Pollen filiter, that I can do.

BTW, maybe this is a weather / gas issue. On the current tank, I am back up to 18-19. However, let me report back once I am at least half way through the tank.

[kalyanakrishna]

I wanted to close on this thread.

Since my last post, I did see the mileage return back to its usual mid 19's. I am not sure if the earlier drop was due to bad gas, needed air filter replacement, weather conditions or what not.

A few times I was able to see High 22's as well.

Thank you all for your responses.