Mechanics.....I need your input

[NightRiderQ45]

Hey! My sister has a '03 I30 and she is having problems right now. I know this is a Q45 forum, but I just wanted to get some thoughts from loyal Q45 lovers before I jumped to the next forum. I used her car this past weekend and it drove perfectly. She called me yesterday and said that her car started off with a bad idle. The idle would raise to 2krpm by itself and then lower to where it would barely stay on. At this time I asked her if her service engine light was on and she told me no. She then called me back and said that it came on and the problems got worse. She said when she press the gas to accelerate, she would hear a rattling noise. Then the car just turned off. The car wouldn't start for her again. It would turn, but would catch fire.

I'm thinking that it has to be bad gas that might cause the valves to rattle or the fuel injectors are clogged up. I told her to put Chevron Techron in and fill her tank but the car would start to even get to that point. She drives the car a lot on 1/4 tank and I've told her many times not to do that because the system sucks up trash once the fuel level is that low. I don't even let my Q get below 1/2! I feel bad because I came to visit her this past weekend and I used her car, and it's ironic how it goes bad as soon as I leave. Any input would be greatly appreciated.

[Q45tech]

The first thing one does with an OBD2 car is plug in a scanner and read the codes!

[NightRiderQ45]

The first thing one does with an OBD2 car is plug in a scanner and read the codes!

Yes, I understand that. That would solve everything and it wouldn't be a need for me to post; but like I stated earlier, the car will not start at this point. As of right now, I think that she would have to get her car towed to the mechanic. I might have to clarify my post, but I wanted input from mechanics as to what they think the problem is. Thanks!

[maxnix]

The car doesn't have to be started to read codes.

Never tow, always flat bed.

[Q45tech]

Unlikely that the problem is a mechanical part that is broken so the last thing you need is a MECHANIC.

A TECHNICAN however usually diagnoses electronic problems which are the usual failure mode.

The Infiniti Power train warranty is 6 years 70,000 mile. If still in warranty Infiniti will send flatbed. [if out of gas or bad battery they will charge you....other than that their nickel].

I assume you have tested battery and tried a PROPER jump start.

[NightRiderQ45]

The car doesn't have to be started to read codes.

Never tow, always flat bed.

Thanks for the input!! I will tell her not to tow, just flat bed the car. Thanks for that info also Q45tech!

[Unnatural1]

She drives the car a lot on 1/4 tank and I've told her many times not to do that because the system sucks up trash once the fuel level is that low. I don't even let my Q get below 1/2!

Why do people keep perpetuating this myth? You are not running around with 'trash' in the bottom of your fuel tank. The fuel pump's input port is always at the LOWEST point in a fuel tank. It's there so it will not be starved of fuel. If there was any 'trash' in the fuel tank it would settle to the bottom and would also be the first to get pulled in. Fortunately, there is a filter on the input of the fuel pump to catch any particles in the fuel that would damage the pump. On top of that, there is usually a downstream fuel filter to catch even smaller particles to protect the rest of the fuel system.

You don't want to run your tank dry because the fuel pump is kept cool by the fuel in the tank. But, even with the fuel gauge showing EMPTY, there is still a built in reserve of usually a few gallons of fuel. So there is no need to keep filling up at 1/2 a tank (or even a 1/4 if you don't want to).
Modified by Unnatural1 at 9:18 PM 5/1/2007

[maxnix]

So there is no need to keep filling up at 1/2 a tank (or even a 1/4 if you don't want to).

You are incorrect about the Q45 pumpas it is not completely submerged much under ¼ tank, so pump cooling is optimized only at levels greater than ¼ tank.

[Unnatural1]

This is why manufacturers build in a fuel reserve. Even at empty there is enough fuel remaining to do the job and keep the fuel pump cool. It may not be completely submerged but it's more than adequate.

The Q's fuel tank holds about 22-23 gal. How much fuel do you normally fill it with...about 18-19 gal.? That's where mine stops. That leaves about 4 gals. minus whatever space is displaced by the air at the top of a fuel tank.

[maxnix]

Most on this board fill it at ¼ full, or 16.5 gallons.

[NightRiderQ45]

So there is no need to keep filling up at 1/2 a tank (or even a 1/4 if you don't want to).

Modified by Unnatural1 at 9:18 PM 5/1/2007

Well, I'm speaking from experience as far as "trash" being in the tank. Before I purchased my Y33, I owned a J30. I used to drive the car to 1/4 all of the time and even sometimes until I see the light come one. That finally caught up with me because my start started to drive awful. Took the car to the mechanic and they said that my injectors were clogged up because of that driving habit. That's why I tell her not to drive her car with that little of gas in. Plus, the more gas that's in, it's better for the fuel pump. That's why I fill up my car when it gets to 1/2 tank because I don't want to wait until it 1/4 and pay a lot just to fill it up.

I found out what the problem was Q45Tech. The codes said that the idle air control sensor was bad. I'm just going to have the one on the car cleaned of the carbon deposits before purchasing a new one

[DrewQ45]

You are right in most of what you say, indeed, the fuel inlet port does have a little filter bag and it does sit at the bottom, so running the tank low is not a danger. However, there is some sediment that collects at the bottom of the tank over the years. I have seen it for myself when pulling fuel pumps. This is why the filter bag is there in the first place. Sometimes people drop gas pump handles on the ground, put it back in place and the next person gets the dirt, or the station's gas tank/tankers are contaminated... who knows.

The peak danger exists for those who keep their car running while fueling since the fuel is being vigorously mixed at that time...but again, the filter bag should take care it, I just don't believe in bombarding it with particles when avoidable.

...Drew...

[Q45tech]

Measure the running fuel temperature inside tank and in fuel rails and you will see why it is advantageous to keep the tank as full as possible especially in Summer.

[StarPD]

Measure the running fuel temperature inside tank and in fuel rails and you will see why it is advantageous to keep the tank as full as possible especially in Summer.

I routinely ran my '94 Q45t down to empty. At 105k miles, the FP was on its last legs before I traded it. My tech advised me to never let the fuel level get below 1/2 tank especially in the summer, and especially if I would be regularly making hard turns, which was the norm for me.

I no longer let my tank get below 1/2.

Hopefully, my 2005 Q45 FP will last a little longer.

BTW, does anyone have any feedback on F50 fuel pumps? Are they the same as on G50s? Are they also subject to needing replacement at around 100k or so?

I remember the mech FPs on American V-8s that could be replaced for around $15 and 1/2 hour's work tops. $1500 at the dealer for a G50 FP is pricey, and I'm no longer able to play mechanic like I used to.

[Q45tech]

The newer systems are returnless and higher pressure so they pump less fuel per mile.In theory they should last longer unless made cheaper to take advantage of reduced demand.

Why would any company waste resources designing things to last longer than 100k?

[StarPD]

The newer systems are returnless and higher pressure so they pump less fuel per mile.In theory they should last longer unless made cheaper to take advantage of reduced demand.

Why would any company waste resources designing things to last longer than 100k?

Thanks.

I dunno.Maybe so loyal customers don't have to expect to need a $1500 replacement when the car hits 100k?But then, maybe not.

Infiniti sure gives no customer expense consideration to replacement of other items, like spark plugs, valve cover gaskets, and on F50s, headlight bulbs. Perhaps we shouldn't expect any better.

[Q45tech]

Because historically the average new car buyer dumps the car before the warranty expires.

What does the factory care about something way in the future that might affect resale a tiny bit, which is never in the minds of most new car buyers.

People who PLAN on keeping cars beyond 100k should have an entirely different enhanced rigorous maintenace schedule.

People who buy old MB and Top BMW KNOW to demand all records and analyse the potential purchases.

These things seem lost on 2nd and 3rd buyers of Infiniti and Lexus.

Failure to attend the month long "how to buy a USED LUX CAR" course.

[carnal_c30]

maybe a maf sensor problem, i dont quite understand the last sentence the car "would catch fire" but if the car is starting has the CEL light and keeps dying it could be the MAF

[maxnix]

However, there is some sediment that collects at the bottom of the tank over the years. ...

When wise owners pull the tank and steam clean it (if it is not corroded) and likewise the fuel lines from the tank to the injectors. Even just a film. Doesn't have to be chunks.