wpgmax

I was wondering if this is common with the max. I have a 92 SE 5 spd. with 98,000 miles. When I first purchased the car this fall I was getting close to 300 miles to a tank of gas. Since it got cold up here in the depths of Canada I have noticed a sharp drop in fuel economy. (down to around 230 miles to a tank).

What should I be expecting for fuel economy on this car?

Is there a valve or something like that that probably needs to be changed due to the mileage on the car that is maybe not functioning properly for the weather conditions?

By the way it's -22 F here this morning.

Matt93SE

iTrader: (44)

it's possible that your Oxygen sensor is dead, but I wouldn't be too sure on that. it may just be due to the extreme cold. the engine has to run a much different fuel/air mix when it's that cold, and it's likely there are also a lot of additives in the fuel to keep it from freezing..

when it warms up, see how the car is doing and you can run some ECU diagnostics on it. I wouldn't bother doign it right now because I'm sure it's a PITA to try to crawl around under the dash and use a tiny screwdriver when it's this cold.

wpgmax

I saw a slight drop in mileage (Due to weather) with my 240SX but nothing this dramatic.

Jeff92se

iTrader: (82)

Well depending how long it takes to warm up, you mileage will be worse. ie.. if you take alot of short trips, you car will never get into closed loop mode and will be running the cold start program for most of the time. That will kill mileage.

wpgmax

Jeff92se,

Can you send me an e-mail. I tried to PM you but it doesn't show up as a sent message.

Thanks

Jeff92se

iTrader: (82)

Search? You have to donate $20 to search. It's worth it.

Wiking

Short trips with cold tranny, that kills mileage. Handbrake wire harness broken, frozen water in, brakes do not disconnect? Thermostat ok?

I shielded my tranny, engine bay from direct wind. See the next chain above.

wpgmax

My car is a 5 spd so the handbrake is used everytime I stop the car so I don't think it is malfunctioning. Temperature control is working very well so i don't think it's a therostat problem. I will have to get the breaks checked to see if their rubbing.

internetautomar

iTrader: (30)

my mileage also got worse when the temps dropped, but when I did my one highway run it got better mileage.
here in the states some places run a winter blend of gas, which hurts gas mileage.
and as jeff said if your trips are short (like mine are) the car never gets into closed loop mode. and mileage suffers.

Wiking

closed loop mode??? Can you tell me more what this contains?



wpgmax ---->"My car is a 5 spd"

Dunno what others say, but current synthetic motor oils surpass the gearbox oil specs from 90's so they may be used instead. I have used in my 2gen gearbox synthetic motor oil always and no real change in winter drive mileage.

wpgmax

I run synthetic oil.

I'm assuming the closed loop mode has to do with the Auto tranny?

internetautomar

iTrader: (30)

Closed loop mode is when the computer starts to only accept certain inputs, and ignore others.
it ignores the coolant temp sensor and others, in closed look mode

Matt93SE

iTrader: (44)

in more understandable terms, the car runs in open loop mode when you first start it..
that is until the engine is warmed up, which the ECU verifies by the coolant temp sensor and an internal timer logging how long the engine has been running.

During this time, the ECU ignores the oxygen sensor and only determines fuel mix by the throttle position sensor, MAF voltage, and a couple other minor factors.
It runs rich during this perios to help the engine warm up faster and to provide smoother running while the engine is cold.


once the engine is warm, it goes into closed-loop mode, where it looks at the oxygen sensor readings as well as other sensors on the engine to provide the best compromise of fuel economy and performance.

Cliff's notes:
open-loop= cold engine, low gas mileage.
closed-loop= warm engine, good gas mileage.

T93Max

hey fellas, it was cold this morning too in seatown too. my car was all iced up on the outside. i had to warm the the engine up for like ten minutes before driven. there was alot of white smoke extracted from the muffler and like before the smell of gas inside. i do noticed the drop in gas mileage too, but just not that much.

internetautomar

iTrader: (30)

Much better answer than mine.

wpgmax

So what might be keeping my car in "open loop" even when warm. Recently went on a fairly long (5 hours) drive and still had poor fuel economy.

internetautomar

iTrader: (30)

malfunctioning CTS

LvR

Just as a matter of interest for you guys.................

Here in South Africa our VG motors run an ECU with not a single O2 sensor installed as factory standard!

Matt93SE

iTrader: (44)

Sweet!! you guys have the VE there too?

internetautomar

iTrader: (30)

Matt you never realized that the o2 is really just an extra not needed item that the EPA has foisted upon us for their own gain?

bvtran

iTrader: (3)

Yes. This is normal during cold weather. Just keep in mind even during warm weather you'll still get bad gas mileage if you drive lots of short local distance, around ~6miles/day.

LvR

Yep.

LvR

Not so sure its that bad an item to have included in a closed loop fuel/ignition management system if fuel economy is important - personally would actually have loved at least one to have been included on my VG - think it can actually compensate for out of calibration injectors/coolant temp sensors/MAFs/TPSs - ie - anything that makes the stock mapping of timing/mixture go wonky.

internetautomar

iTrader: (30)

sorry, but I'd rather tune without it. and have a default open loop configuration that is mapped for my use.

LvR

Thats the problem with an ECU controlled "anything" - very little about the actual specific engineering design parameters is actually known and controllable without incurring huge expenses - the result is that our motors are of the "either OK or not" flavor Ito "tuning" - really not much you can bugger around with to improve matters while using stock maps.............

I am sure you would have to agree that the stock ignition/injection maps on these motors are not bad at all and is most likely pretty good - I am quite impressed with my auto V6 showing better open road performance and economy and comfort when compared to a noisy and vibrating and intensely irritating 1600 Golf thats in an equally well-maintained condition.

While I can see the presence of an O2 sensor would insert yet another component in the "closed" loop for both ignition and mixture, the KS basically performs that function on my motor without a O2 sensor present - but only when things go wrong - its therefore not completely an "open loop system" .................... oh and there is feedback from the temp sensor too

internetautomar

iTrader: (30)

Megasquirt.
Problem solved

LvR

...................Sure - but as I said .......... Mega-expenses

Also once you go that route, you couldn't really give a flying pig's fig about the presence or not of a O2 sensor - no?


Later - Well after reading a bit about how Megasquirt goes about the business of causing things to explode it would seem you are not getting your open loop thing done going that route .................

internetautomar

iTrader: (30)

Megasquirt is actually WAY more cost effective than replacing your ECU, it's about $200 for the base setup and you can fully tune it from your laptop.

I looked into for another pet project car of mine, but that may just end up with a carb.

EDIT: you can through the software work without the o2, now admittedly the system will function over a broader range eith greater tunability if it is installed vs being omitted.

jwmaxse

iTrader: (1)

There's several reasons for a decrease in gas mileage in the winter:

-Driving in the snow and spinning your tires alot
-Letting your car sit and idle to warm up for extended periods of time
-Like these guys said, different fuel mixtures in the winter
-Possibly lower tire pressure from the cold

It might just be a combination of alot of these things, that is a pretty big difference in gas mileage though, I hope you figure it out.

eric93SE

iTrader: (1)

Hey LvR, do you have any car jacking problems there. I saw that LETHAL anti-carjacking methods are allowed (a.k.a. flame thrower).



back on the subject, if you live in sub-sub-zero temps, you can block off some of the radiator, especially when doing short driving. Just remember to remove it when the weathers warms up.

LvR

With a Maxima? - cant remember ever seeing any getting jacked here. Now BMWs, Golfs and Toyotas - totally different story!

"Allowed" does not make it legal - you kill somebody you're screwed - you burn somebody and he takes you to court chances are you will get screwed too.

Flame throwers are the exception I guess - but then again I have never been around a lot of jackings to see what happens.

eric93SE

iTrader: (1)

Yeah thats true, the 3rd gen max is definitly not desirable car for thieves.

I saw a movie the other day where this guy gets car-jacked at gun point, and I'm thinking to my self how easy it would be to setup a stun gun with electrodes attached to the seat, and a second remote to actuate it , how nice it would be to kick the c r a p outta that guy

Tarzan

If that is really a t° issue and not just something that has started by coincidence when Winter came, I would imagine that a certain moving part in the fuel or air supply systems is stuck when it is cold outside. Do you happen to smell gas in the ducts by any chance? BTW this is not really a cold winter this time, eh?

Wiking

Good points.

Driving in the snow and spinning your tires alot
---> gas pedal ctrl = drivers personal "problem"

Letting your car sit and idle to warm up for extended periods of time
---> soot buildup plus very hot intake channels warming slow incoming air =less oxygen weight per cubic measure. But... this is same in the summer...

One countering =compensating point is the cold air temp: in winter everyone has "intercooler effect" maximized, more oxygen to burn.

Coarse, studded traction winter tires grow consumption some 5-10% be it cold or not, but otherwise, if one thinks only the after warmup situation, the total consumption should be quite the same as in summer. That is if u build up your engine bay shielded...

During warmup period, tranny needs extra power to turn around.

eric93SE

iTrader: (1)

well, one thing that the 4th gen changed was it added an ambient temp sensor (in the intake stack I believe). Our MAFS need to measure how much air is comming in, but the temperature of that air greatly effects its operation, it does not have a correction for temperature like the 4th gen. This is why we run richer in the winter, the MAFS misreads and tells the ecu that there is a lot of air comming in, mean while its just very very cold air.

wpgmax

No fuel smells at all. I don't know what it's been like in Brampton but it has been between - 30 and -40 with the windchill since a couple of weeks before xmas here in Winnipeg. Currently it's -39. (for you Americans thats -38.2 F)