I think it's got 130k miles on it. It does not roll as effortlessly anymore it seems. Like at 15mph I would not even have to press gas, it rolled easily and smoothly. Now it seems like it either lacks power of has some sort of resistance to it... have to press gas more. The regular driver claims that with busy city-only driving, he gets about 12-15 mpg with it.

It is my fathers car, and he does things to it. He lowered the idle rpm on it in his belief that it would save gas. The CV boots are torn and are crackling when making turns. He never changed the auto transmission fluid. Would any of these things make the car feel like it has less power?

We changed spark plugs to the expensive NGK ones that came with the car originally. Put in new fuel filter and air filter. Used a bunch of Techron. All that, and nothing changed. In fact, cylinder 1 misfires heavily with the new spark plugs, but doesn't when we put an old one back in (it is not new spark plugs' fault, we tried 2 of them).

Some other info: he's been running cooling system on tap water for prolly 3 years now. There is a knock sensor code, but it's been there for ages and back in the day the car worked well even with the code present. He changes engine oil/filter regularly, uses full synthetic. None of his wheels are balanced because he puts used tires on it all the time by himself. I wonder if his alignment is off too since he takes the wheels off a lot and maybe did other work around there (last alignment was done in 2006).

SO with all this info, does anyone have ideas why the car is eating a lot of gas and feeling weak?

 

would be nice to upload a video of u running the car.

 

Put the idle rpm back to normal otherwise you will overhear the engine and starve it from proper air fuel ratio. Put the idle back up at 700 rpm and your power will be back. Lowering the idle does not save gas it wastes gas becuase it's an not the right rpm.

 

Mis fire with new plugs ? How are the coil packs ?

 

Being that you guys don't seem to take care of the car all, I'm surprised you spent money on the expensive NGK plugs first... I would've check air filter and checked if the brakes were seizing first.

BTW you can get NGK coppers for a lot less - only they last for 30k miles instead of the 100k or so you get out of platinums.

 

REPLACE KNOCK SENSOR ASAP
Run premium fuel only, 4th gens perform best on Premium, even says so on the gas door.
Switch coil plugs around to see which one is misfiring and get some used one for cheap. You can find plenty of them on the org here for sale on the classifieds.
Fix/address any codes that may pop up.
Inspect transmission fluid and replace if necessary. The transmission usually won't affect the performance of the car too much but I could be wrong depending on the shape of it.
Put the proper mix of coolant/antifreeze in there.. come on... that's a no brainer..
Raise the idle back to normal. That could be also causing your knock sensor code and damaging/fouling out your plugs...


Good luck...

 

Check tire pressures. Maybe you have a sticking caliper. After a drive somewhere, walk around the car and touch each wheel. if one of them feels much warmer than the other, then you have a stuck caliper dragging the car down.



The tranny fluid may make the car sluggish because old tranny fluid in a car makes the car not want to downshift. You have to push the pedal deep into the floor and then the car abruptly downshifts. You should change the tranny fluid. DO NOT FLUSH. Drop the old fluid, replace with the same amount of fresh stuff. That should bring back some life to the tranny.

This is unusual. Maybe your FPR and fuel damper are shot, so the cylinder at the end of the fuel rail is not quite at the same fuel pressure as all the others. I would change them anyway. They are old and tired.

The problem with using water for coolant is that anti-freeze is more slippery and provides lubrication to engine parts, like your water pump. The water pump on our car is a tough job to replace. I would stick to using anti-freeze so that you replace the water pump later rather than sooner. Use the Japanese coolants like Toyota or Nissan because they contain less abrasive silicates compared to american Prestone brands etc. Make sure to use green coolant, not the orange 5 or 10 year stuff. NOT compatible.

The knock sensor code is not critical. Leave it for last and check everything else first. If you run 87 octane, then dont bother replacing the knock sensor. If u want to make the most of using premium fuel (91 octane or better) then replace it.

Last thing you should change would be the knock sensor. 2nd last thing would be the primary O2 sensors. O2 sensors get tired and dont throw check engine lights. If you've checked everything else, tire pressures,air filters, FPR, damper, tranny fluid etc, then change your primary O2s. Then if you want your car back to 100%, do the knock sensor.

 

Actually for 4th gens the platinum plugs last 60K miles. Its the 5th gens where the plats go for 100K miles. Never understood the difference, but that's what it is

 

You know what you're right. That was in the manual - neither number of which could justify Platinums against Iridium plugs that go for 120k.

 

been running cooling system on tap water for prolly 3 years now hunh??? how did you not blow a head gasket?? your lucky that thing runs at all.

 

Thanks for the input everyone! I will try to convince my dad to try the stuff you mentioned... he is stubborn unfortunately.

We had to put expensive plugs cause cheap ones worked even worse... even less power... perhaps due to low idle rpm?

Why would running on tap water blow head gasket?

 

Like the others have said, set the idle rpm back to normal. Also, using tap water wont kill your head gaskets.

 

tap water might not kill it, but i thought he was saying he used only tap water and no anti-freeze. you can buy 50/50 anti-freeze at the store ready to pour.

 

Oxygen sensors need to be replaced. Both performance and mileage suffer when they get old. Knock sensor replacement would help performance. But if you are too cheap to buy premium, don't bother replacing knock sensors. Your maf sensor could use a spray of CRC maf cleaner. For gods sake, take care of your cars. Does you father actually think he is doing himself a favor by running cars into the ground?

 

plus or 89 is just fine, premium is $4.00 right now and i never buy it. car runs great on 89, o2 sensors do make a difference but i let my knock sensor go for 3 years and did'nt notice a difference when i replaced it, it just retards the timing and gets a little better gas mileage and thats why i did mine.

 

A functioning knock sensor tells the ecu to ADVANCE the timing to get the full potential of the 93 octane you should feed it. So you feel more power and get better mileage. They will also RETARD the timing if you feed the car plus, or worse yet, regular. Your performance would suffer, as would the gas mileage. A broken knock sensor will not report higher octane. A broken one would run the same on premium or regular. Thats' why people say it makes no difference. A bad knock sensor and bad oxy sensors would make a car feel sluggish. I did replace both front oxy sensors and the knock sensors. Not at the same time. Power and mileage improved after the oxy sensors were installed, and again when I did the knock sensors.

 

never noticed a difference after i did the knock sensor nor do i notice a difference with premium. car's too old and i'm at 260,000 so i doubt at our cars age premium makes any huge difference at all. i've had my car for over 9 years and 130,000 and premium is a placebo imo, my 02c

 

Sure, Nissan says to use premium right on the gas filler door and in the owners manual. Must be a placebo... just another decal. My 96 Max certainly did have more power when I replaced the knock sensor. My Max has 190k miles and is in good repair.

 

Where are you located? Would you like to sell it? I'm about ready to buy my 4th 4th gen..

Seriously, I like to buy 4th gen Maximas with 125,000 to 150,000 miles and give them a mid-life technical refresh that usually costs me $800 to $1,000 in parts.

My Maxima mid-life refresh consists of the following DIY items in the following order:

1) New NGk/NTK O2 sensors and spark plugs
2) New Knock Sensor
3) New Valve Cover Gaskets
4) EGR Component Cleaning and Gaskets
5) New Filters
6) New Battery (if current battery is older than 3 years)
7) Gradual Transmission Fluid Change
8) New CV Joints/Axles (If Needed)
9) New Anti-sway Bar End Links with ES Poly Bushings
10) New Struts with all new strut hardware and bushings.
11) New Power Steering Rack Bellows
12) Wheel Alignment (Only MLM item I outsource)

After I complete mid-life maintenance (MLM) item #6, the car usually starts to run like new again when I fill up with 93 octane. After I complete MLM item #12 it usually runs and drives like a new car.

The ideal 4th gen MLM candidate will be a 95 to 98 model that I purchase for $1,500 to $1,800 dollars. Adding $1,000 to cover MLM will produce a fun to drive car that will easily yield another 100,000 to 150,000 of enjoyable miles.

 

CS AR has the right idea. The original poster has a relatively low mileage car with a few problems. The original posters father believes in running old cars into the ground "to save money". CS AR looks at things the way I do.... How many miles would be left in the car once some issues are taken care of? Usually quite a few. Some money, usually less than a grand, and good skills can result in a car that can be driven 5-10 years reliably. Now THATS saving money.

 

Man, IDK bro. I just ran a tank of 87 through my car after nothing but premium for the life of it (previous owner only used premium as do I). I was very curious to the theory as I've only used premium for my 15+ years driving.

My car with 65k felt absolutely sluggish as it gets. Even my wife noticed it sputtering. And if she noticed something other than a new smelly tree, it was real.

 

When i changed the ks on my 98, i wasnt counting on noticing a difference but i was surprised because I did actually feel the difference in low rpm power like when i was goin up hills on the highway at a steady speed and this was a highway that i drive all the time and noticed a little "lag" before i changed the ks...plus i allways burn premium...well at least 91..just because that was all the original owners burned...

 

It says premium on the gas door and everywhere else. I put premium in my lawnmower dude and everything else that uses gasoline.

 

. i will admit that back then there was no corn being blended into our gas and premium is probably a better option if you really want good performance. im my max, i won't use lower than 89 or plus.

 

My maxima on the gas tank cap says "unleaded gas only" and thats 87 here. been using that since then. i had used 89 before, didnt notice too much difference.. probably slightly

 

Extremely impressed! I live in Orange County, bought it for $1100 (95 Maxima) and 1850 for the 97 Infiniti. I am still milling over your list, very helpful... give me a moment..

 

I appreciate everything on the list, problem is there is no profit if I go that far, I do hear a noise that is probably the anti-sway bay bushings now that you mention it on both the Maxima and Ininiti. The Maxima gets a hiccup now and again and we are thinking it is the egr after replacing plugs and coils with little improvement. I am going to test the coolant temp sensors, I think they should read about 2000 ohms cold and decrease from there to about 350 ohm at operating temp.

 

I agree. I'm the same way. I figure to only costs an extra couple bucks per tank, why not?

I like things feeling responsive and smooth. That's why I have always used premium. Not to mention, all my prior vehicles would ping like my Duramax if I didn't use it.

Plus ain't bad either though.

 

I have another Japanese car company vehicle with a 3.5L V6 that I bought new in 2006. At ~112,000 miles I installed new set of NGK Iridium plugs that were the same as the ones that came with it new. I saw no change in mileage or performance that someone would expect from new plugs. I realized it needed new O2 sensors because I could see a decrease in mileage compared to when it had under 60,000 miles.

Since a new set of NTK/NGK O2 sensors for that vehicle from a good discount source cost over $400, I procrastinated and put off the purchase.

Finally my mileage dropped to roughly 13 MPG around town. When I put in new O2 sensors mileage and performance jumped back to levels I remembered when it was new. That was when I saw performance the gains I expected from new plugs.

Many members buy O2 sensors from rockauto.com and

Nissan OEM parts from courtesynissan.com

Depending on order size you can get a similar price as Rock auto without paying shipping charges from AdvanceAuto when you use a discount code like TRT41 or HUGE50 for up to $50 off an online order. I usually split up my AA orders to get 40% off using TRT41 with the minimum purchase amount. Then use other coupon codes for 30% off for smaller orders.

I like to order from AA online then pickup the parts at my local store. They usually have my order sitting on the counter and ready for pickup within 15 minutes after ordering online, so I don't have to wait for them to look up a part when I get there.