High Fuel Consumption In Winter?

Post by **smoked-berries** » Wed Jan 04, 2023 7:12 pm

I live in Canada and it gets extremely cold here during the winters. I drive an '02 Nissan Cima JDM.

However, I did not expect fuel mileage to drop so significantly. I am currently getting about 3km/L. I have just completed regular maintenance on my car but am getting terrible fuel mileage.

Some things to note:
I don't have a block heater, so my car is subject to cold starts pretty much everyday.
I have all-season tires with 18" rims which don't have the best traction.
Oil doesn't seem to be burning, and levels look good even after 2k kms since the last change.
Most of my driving is short commutes within city limits

What could be the cause of such terrible mileage?

Post by **Q451990** » Fri Jan 06, 2023 2:27 pm

For all of us down to your south, 3 km/L = about 7 mpg. I don't know if it would explain all of it - but if your car isn't warming up to normal operating temperature that could be part of it. It's possible the seal on your thermostat has rotted away, letting coolant bypass it when it's supposed to be closed.

At least the older engines needed to warm up before the ECU would allow the fuel map to go into something called "closed loop." In the warm-up period it would run the fuel mixture at a richer ratio.

Post by **smoked-berries** » Fri Jan 06, 2023 10:43 pm

How could I verify if the the seal on the thermostat is rotten? Not sure where it is located.

EricPres · Post by **EricPres** » Sat Jan 07, 2023 10:11 am

That would only be normal if you would do just very short distances.

Post by **Rogue One** » Sat Jan 07, 2023 1:53 pm

smoked-berries wrote: ↑
Fri Jan 06, 2023 10:43 pm
How could I verify if the the seal on the thermostat is rotten? Not sure where it is located.

Does your car have the V8 4.5L VK45DD?

Post by **smoked-berries** » Sat Jan 07, 2023 5:24 pm

Yes I have a VK45DD.

Post by **Rogue One** » Sat Jan 07, 2023 8:31 pm

Infiniti Part 21200-AD201 Thermostat Assembly

Post by **Q451990** » Tue Jan 10, 2023 10:40 am

If your car has an OBD2 connection, you could also use a scan tool to monitor coolant temperature.

Post by **smoked-berries** » Wed Jan 11, 2023 11:45 am

It does an OBD connection but no OBD2 reader seems to he compatible with it since it's a JDM. I've looked for compatible JOBD models but couldn't find anything. Any suggestions as to any readers that could work with the Cima?

Post by **Ryantzer** » Wed Jan 11, 2023 12:32 pm

What does your temp gauge show?

Post by **smoked-berries** » Tue Jan 17, 2023 8:02 pm

Temp gauge for oil? It's fine, right in middle after the car is warm

Post by **Ryantzer** » Wed Jan 18, 2023 5:30 am

No, the coolant temp gauge. Is your engine getting up to operating temperature?

Post by **smoked-berries** » Thu Jan 19, 2023 12:25 pm

Post by **VStar650CL** » Thu Jan 19, 2023 1:25 pm

Make sure your IAT (Intake Air Temp) sensor isn't reading excessively cold, and try doing an IAVL (Intake Air Volume Learn) on the MAF. Either one can cause the ECM to overestimate the incoming air density or mass and make the mixture richer than necessary.

Post by **smoked-berries** » Tue Feb 07, 2023 2:06 pm

So looks like I have a small tear in the intake hose. Is there an aftermarket replacement? The OEM requires the whole assembly to be replaced which is about $600 Canadian. Any alternatives? Would this fix the high fuel consumption?

Post by **VStar650CL** » Tue Feb 07, 2023 2:19 pm

That will definitely affect performance and fuel economy. Unfortunately I don't think there's any aftermarket alternative, almost all of those bellows are OE-only. In a pinch, Flex Seal or Plasti Dip can both be used to mend small tears, but first make sure the tear didn't result from a bad motor mount allowing excessive engine movement. Dunno about Cimas specifically, but that's a very common problem on some models.

Post by **smoked-berries** » Tue Feb 07, 2023 2:55 pm

Good call! I'll check that out. I haven't seen any movement/shaking from the engine when I start her up so it's unlikely, but are there any other ways to check if motor mount is bad/rotten?

Post by **Ryantzer** » Tue Feb 07, 2023 3:18 pm

Judging by the condition of that hose and the others in your pic, I'd suggest doing a smoke test on the intake system to see if you've got any vacuum leaks.

Post by **VStar650CL** » Tue Feb 07, 2023 3:31 pm

smoked-berries wrote: ↑
Tue Feb 07, 2023 2:55 pm
Good call! I'll check that out. I haven't seen any movement/shaking from the engine when I start her up so it's unlikely, but are there any other ways to check if motor mount is bad/rotten?

No, a visual check while an assistant "rocks" the shifter D-R-D-R is the best way to spot a bad mount. +1 to @Ryantzer's suggestion for a smoke test, especially if that bellows has hardened up and lost pliability. Under those circumstances, it's a good bet that other rubber parts have lost pliability too.

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