how do u tell if you need a new fuel pump or fuel injectors?

[Evanarc]

Sometimes My 1994 Q45 starts and the idle dies and the engine shuts off immediately. It also bucks at certain speeds, usually when coasting. On occasion I've smelled a clean gasoline odor.so far Ive changed the battery cleaned the entire fuel system at jiffy lubecleaned the fuel injectors a second timeTuned the enginereplaced the starter(seperate issue)changed all fluids imaginablereplaced major exhaust components

The only other possible malfunctions have to be in the fuel delivery; either the 8 fuel injectors or the fuel pump.

Has n e Q owner experienced a similar problem or know how I can find out what I'm dealin with??

THanx

[96Qowner]

Check one more easy thing before you go for the hard stuff - inspect and clean your MAF connectors, as well as the MAF itself:

http://www.q45.org/maf.html

An iffy MAF will cause heavy bucking on mild acceleration as well as stalling on deceleration. And we've recently discovered that the connections on the internal circuit board begin to degrade from vibration after a decade or more of use:

Fixed MAF in spare time

Repairing MAF

Clean and grease the connector real well, first.

You can check the FPCU by grounding it to high speed:

Diagnosing Q45 FPCU

You can check the injectors by testing their resistance:

http://www.q45.org/ohminjectors.html

It's doubtful that's your problem, but check 'em anyway. Ethanol is very bad for Q45 injectors.

[Q45tech]

Automobile afficionados take their vehicles to their resident expert at least every 90 days for testing and fine tuning. Average people probably don't.

The easiest way is to pay an expert on your year and model a diagnostic fee....................make sure this technican sees cars like yours every week.

That usually means the dealership or those rare specialty shops across US.

There are probably hundreds of technicans in US competent to work on your specific vehicle.

Unfortunately there are hundreds of thousand of mechanics and technicans who need to make a living and will TRY to work on anything with sometimes terrible results.

Up to you whether trying to save $20-$40 per hour for a few hours is worth the risk.

[Evanarc]

Thanks..Ill try that 2.. I thought it could be the MAF or maybe even leaks in the black plastic valve itself. I want to remove the stock air intake and put something custom in, n e way so that wouldnt be a big deal..but then what about the ocassional gas smell? I feel like theres something wrong with the fuel pump

on a side note: ne one have any advice on what i should get for an air intake? and how to make it fit?

[Jesda]

Whatever you do, AVOID oiled filters like K&N. They are BAD for Nissan MAFs.

Enjoy!

[goody90q45]

Thanks..Ill try that 2.. I thought it could be the MAF or maybe even leaks in the black plastic valve itself.

If you're talking about the long air intake tube between the MAF and throttle body then you need to seal the leaks. The MAF measures the volume (sort of) and temperature of the air flowing by and adding extra air after the MAF will cause problems.

but then what about the ocassional gas smell? I feel like theres something wrong with the fuel pump

Follow the advice posted in this thread and gound the fuel pump. Doing this will run the pump at the highest of the 3 speeds only and will at least tell you if the FPCU has gone bad. Are you hearing what sounds like a swarm of bees (dying fuel pump) in your trunk?

a side note: ne one have any advice on what i should get for an air intake? and how to make it fit?

Forget about the air intake for now. Concentrate on getting your Q running good first and then start the mods.


Modified by goody94q45 at 4:19 PM 2/1/2008

[GseaQ]

Forget about the air intake for now. Concentrate on getting your Q running good first and then screw it up later by changing the intake.

Oh-oh. Here we go again...

[superuber]

Forget about the air intake for now. Concentrate on getting your Q running good first and then screw it up later by changing the intake.

Mine's been messed up for years now!

[Evanarc]

Are you hearing what sounds like a swarm of bees (dying fuel pump) in your trunk?

dude I guess, all i kno is it sounds ****ed up and when u havent started it for like a day or 2 the engine turns over but sometimes it seems like its just not catching right.. It like almost stalls but doesnt..once u get it in drive u will find the only problem is intermittent bucking.

AS far as the intake, I feel its a lil necessary bc the black tube near the throttle body (part of the black air filter monstrosity infiniti genuses designed)IS cracked* The stock thing is already like 200 bills so why not get somethin nicer and more pleasant to look at

[Evanarc]

btw i tempoaraily sealed the black tube with super electrical tapeso i guess its not a big problem 4 now

[Woot!]

1. Check fuel pressure.2. Check FPCU3. Check MAF

I can almost guarantee you that the fuel smell is caused by a leak under the plenum. This is a very very common problem with the Q. Good luck

[elwesso]

Dont look at the MAF, dont touch the MAF, NOT EVEN FOR A SECOND until you've checked your fuel pressure...

Ive seen WAY too many people waste money and time when they say "oh MY FUEL PUMP CANT BE BAD".. Statistically speaking, more fuel pumps fail on Q than MAF. Food for thought.

Knowing what you've said, I say about 90% chance a fuel pump will fix the problem.

[96Qowner]

Hahah, Wes, the pendulum has swung all the way to the other side!

When I first came to the NICO Forums with my bucking problem, everyone had been concentrating on the fuel pump and FPCU and filter, and anything else related to the fuel delivery path. They were just starting to realize that the MAF can cause those systems. So I replaced my fuel pump, swapped in a good used FPCU, replaced the fuel filter - no fix. Then I cleaned my MAF ... success.

For the next few years, we've steered people to the MAF, and you're right, we seldom stress the actual fuel path anymore. It's just that a MAF cleaning is virtually free - just a couple bucks for the cleaner.

[maxnix]

True, but I am with Wes as MAF sensors may wear out eventually, but seldom are in need of cleaning unless aftermarket filters are used or AFCI is extended for too long.

The MAF connector is much more likely to have problems.

If anyone still thinks their K&N is a viable option and OEM filters are not good, I can email them an acrobat file of the filter test to which Q45tech linked a while ago. In short, save your money and replace OEM annually. Your car will perform better and last longer.

[NightRiderQ45]

True, but I am with Wes as MAF sensors may wear out eventually, but seldom are in need of cleaning unless aftermarket filters are used or AFCI is extended for too long.

The MAF connector is much more likely to have problems.

If anyone still thinks their K&N is a viable option and OEM filters are not good, I can email them an acrobat file of the filter test to which Q45tech linked a while ago. In short, save your money and replace OEM annually. Your car will perform better and last longer.

I would love to view that! Knowledge is pricele ss

[Evanarc]

whats the best way to fix this? is there a temp solution or should i just get a new fuel pump

[Magnum PI]

I would go to car-parts.com and locate a good MAF first. I did the fuel pump pressure test, but replaced the fuel pump and FP control module anyway. Alot of work pulling out the rear seat and getting the new pump in correctly. It still bucked intermittently. Replaced the MAF and voila! That was a 10 minute job.

[goody90q45]

whats the best way to fix this? is there a temp solution or should i just get a new fuel pump

Evan we're all trying to help you get your Q running well but you're not letting us know that you've done any of the self-checks that we've suggested other than taping up the intake tube. You may well find that you need a new fuel pump, and a FPCU, and the MAF is shot, and the MAF plug is corroded beyond repair and 3 injectors are dead but before you start throwing $$ at parts do the checks that have been suggested to you in this thread. You might find that you own a gem in the rough that only needed to have corrosion remove from one connector. Sorry to lecture.

[Rex]

If you smell fuel, check under the plenum and see if you've got anything collecting under there.

[Evanarc]

The MAF is fine its beautiful I cleaned it perfect and retaped the throttle body intake valve with good heat resistant tape

so its not an intake problem its gota be fuel delivery.

Theres still a fuel smell in the cabin, butI dont see any build up under the plenum

Read my new post its a refined thread

[Mint Q45A]

Fuel smell = fuel leak.You may want to check for any potential leaky injectors - here is some info

zerothread?id=298955

[Q45tech]

The rubber rear 2 hoses on the fuel rail leak on EVERY Q [90-96] standard common repair every 7-10 years depending on fuel composition. Just like KS and coolant hoses....................combo work is the norm along with valve cover leaks.

[Haitian_King]

Forget about the air intake for now. Concentrate on getting your Q running good first and then start the mods. Modified by goody94q45 at 4:19 PM 2/1/2008

The veracity of this statement is of unimaginable profundity.

Heed it.

[Rex]

One other thing that comes to mind is if the fuel pump was replaced without replacing the O-ring. You'll have fuel smell from the tank, that will come right into the cabin. But will be stronger in the trunk.

[Haitian_King]

The MAF is fine its beautiful I cleaned it perfect and retaped the throttle body intake valve with good heat resistant tape

so its not an intake problem its gota be fuel delivery.

Theres still a fuel smell in the cabin, butI dont see any build up under the plenum

Read my new post its a refined thread

You mind taking a picture of the pins in your MAF connector? How crazy would it be that your problems could solved by "re-crimping" your connector pins. It's at least worth a shot. I'd definitely go with all the easy tests before I started tossing money at the wrong thing.

But that's just me.

[Haitian_King]

True, but I am with Wes as MAF sensors may wear out eventually, but seldom are in need of cleaning unless aftermarket filters are used or AFCI is extended for too long.

The MAF connector is much more likely to have problems.

If anyone still thinks their K&N is a viable option and OEM filters are not good, I can email them an acrobat file of the filter test to which Q45tech linked a while ago. In short, save your money and replace OEM annually. Your car will perform better and last longer.

I don't like to say that OEM isn't good. Anyone who says that they're bad is being a little economical with the truth. K&N and other after-market parts give some gains and change engine noise while sacrificing long-term reliablility.

I don't want to say that the aftermarket filters will destroy your engine. In fact, it's quite possible that the decrease in engine protection could be quite minimal.

I guess it all comes down to personal preference. If you want your car to sound different and get the slight acceleration improvement at the cost of replacing the filter more frequently, then go for it.

II don't think that K&N would be as big as they are if they sold products that were real car killers. One would assume that the BBB would have caught wind of that.