94 q fuel injectors

[Dinkydow]

I just purchased a 94Q. The prior owner, although he took real good care of it, had to replace 4 fuel injectors, one of them twice. This was done one at a time. There is now 52k on it. I have been told it is the gas. I live in Minn and the prior owner in Nevada. The question I have is would it be a good idea to use 87 ocatne versus 91 and then put in a can of the octane booster?? The reason I ask is Everyone I know has cars that take 87 octance and have never had any fuel injector problems, this includes my prior cars. Thanks for help!! Wayne

[AZhitman]

Wayne - Welcome to NICO!!! Congrats on your low-mileage 94, it's a GREAT car!

You should NEVER run less than Premium fuel in your Q. Octane has ABSOLUTELY NOTHING to do with the injector problems on our cars, they become damaged/clogged due to impurities in the fuel and a condition called "cold soak" (?) created by short drives wherein the engine doesn't reach operating temp and varnish deposits accumulate on the injector nozzle (I know I butchered this explanation but you guys can fill in the details).

Bottom line: Our Q's go through fuel injectors. It's part of owning a Q45. It is critical to change your fuel filter periodically AND to run a quality 91+ octane fuel. Most of us also use a product called BG 44K as a detergent additive (it's the same chemical that Chevron calls "Techron" but in a highly concentrated form. Use a bottle in the tank at every oil change for best results. Fortunately, your car has probably seen the last tank of oxygenated fuel (which excerbates injetor failure) since it's no longer living in NV. A good injector flush and a thorough plenum and throttle body cleaning would be a great idea now, and have your local dealer check the power balance to ensure all current injectors are in good shape.

Commercially-available octane boosters are a waste of money as they generally are insufficient to increase octane by more than a point, and it's expensive to boot.

The people you refer to who only used 87 octane, but supposedly "never had fuel injector problems", were because those were "pedestrian" common vehicles (non-performance) where you wouldn't notice a bad injector anyway. Those cars aren't manufactured to the precision tolerances and engineered to the "ragged-edge" of maximum performance like your Q.

She's a sensitive, finicky, picky, lady, but also well worth the extra care.

Hope I answered your questions - Take care and enjoy the forums.

[Dinkydow]

Thanks alot for your Info and help. Unfortunatly minn uses oxygonated 01 octane to. I would appreciate your feed back on one more thing. I picked my car up in Las Vegas and frove back to Minn, Everything ran great until my last moring out. I started it and back into the Motel to get my bags, when I came out the Q had stopped running, It restarted fine but when I put it in drive and tried to move it would barely move, it acted like it was either gettiing to much or not enough gas, it wasn't blowing any smoke so I am guessing not enough, finally I got it to go 10 MPR, then 20 etc so finally I got it up to 50mph and that was it, when I come to a hill it would slow down to 30 or so. If I tried to step on the gas to much it would bough down, as soon as I let off the gas it would come back. Finally I stopped at a mall, came back in one hour or so and it ran just like new. The prior owner gave me all his maintenance records, he took it into the Ifininiti garage in Vegas for everything, including oil changes, anyway I see where 6000k ago the same thing happened to him. He called Infiniti, they towed the Q in. and by the time the mechanic got to it they said it ran fine and couldn't duplicate the problem.. Does this sound familiar at aLL?? Any suggestions or ideas will be greatly appreciated!!!!! Thanks again Wayne

[Dinkydow]

I mistyped I meant 91 octane Wayne

[DAEDALUS]

Sounds like a bad connection somewhere (intermittent) and the symptoms sometimes are due to a bad mass-airflow sensor (MAF) connector. Raise the hood, look for the little square box at the front of the large air hose, just beind the airbox. Jiggle the harness connector attaching the harness to the box, and push it on firmly. Make sure it still has the metal wire clip securing it onWelcome to NICO.

[Dinkydow]

Hello DAEDALUS, Thank you for the input, I will check that out!! Wayne

[Q45tech]

The fuel pressure should always be checked along with the volume [or make sure that the pressure is correct at 6,000 rpm WOT on the street not in the shop]..............because the pump and 3 speed controller can be intermittent due to the solder melting under load and resolidifying at idle, low speed.Because the current flow at idle is 1/3 that of WOT !

Situation: cold crank [pump high speed for 10-15 seconds, solder gets soft but works because the circuit board is cold, cruise along, then accelerate solder melts as pump speeds up, car dies due to low fuel, wait an hour, car cranks as solder has reformed, cycle repeats till controller burns out completely.

The problem is the pump is drawing too much current at each step but the controller can survive as long as you don't accelerate [and immediately double the current requirements].

The pump fuse won't blow as the abnormal current is just below the time current blow point ---- fuses come in 5, 10 or 15 not 8.937 and the ambient temperature plays a roll in time to blow.......plus blowing a fuse on acceleration could get you a head on with a semi.

We get cars towed in all the time where they crank perfectly when they arrive..........either pump, controller , or they were flooded by a driver who doesn't understand not to do a cold crank and less than a 5 minute warm up move.

In cold weather {below 40F coolant] the Q must always run at least 5 minutes to get out of the cold startup cycle. You would be amazed at how many tows this is over a winter!!!!!!!!!!!!!!!!!!!!

[Q45tech]

Instead of an extra cold start injector the Q fires all injectors simultaneously for a few seconds during cranking, then goes double rich until the coolant starts to warm. In cold weather a situation [like cold cranking and immediately driving from the street into driveway and or garage and shutting the car off will result in a burst of fuel from all injectors because the ecu thinks the car is dying and tries to save the shut down. Flooding the cylinders, later [the next morning] the cold start cycle begins again but then there is double the fuel amount and the car gets flooded and won't start!

Flooring the throttle on crank tells the ecu the car is flooded and cut off the injectors to clear the gasoline! Simple but no one tells the car buyer especially used......happens on used car lots too when they cold move a Q and don't know the secret!

IT can take 1-2 minutes of cranking with throttle floored to clear a really bad flood situation......what ever you do don't lift the throttle till it cranks or the ecu will dump more fuel making it impossible without a jump as the battery may get exhausted.

We have seen some so bad from the owner doing who knows what that the plugs must be changed and the cylinders blown out with compressed air and the oil changed immediately!

[Dinkydow]

Hello, I thank you for taking the time to answer my question! In the explanation you gave which is the most likely problem, the fuel pump or the controller? My Q has 52K on it and I don't drive it in the winter for 2 reasons 1. I live in northern minn and you need 4 wheel drive, and 2 I don't want to get salt on it. Anyway this spring I want to survice the transmission, should I just drain and refill or take it to an Infiniti dealer, 400 miles away, and have it drained and have a new screen put in? What do you recommend for rear differential oil, transmission oil, power steering oil, regular or symthetic?? Someone had mentioned to me to have the ac oil chaged?? I have never heard of that before, is the oil in the freon? Also I am afraid Iam not to smart what is the plenum? How do I know if it and the throttle body need to be cleaned? Is it something I can do? What plugs do you recomend? Is that something I can do? Thank you so much for you time and help!! Wayne [email protected]

[AZhitman]

Hoo boy. Wayne, you may want to take some time and read some of the old posts (better plan on most of a day).

Quick answers: Drain and refill trans yourself (twice), clean or replace filter (cheap at dealer) and use Mobil 1 synthetic. All synthetic fluid swaps are smart. Good idea to have AC system purged/recharged (oil is in the charge). Plenum is the big silver "spider" on top of engine (also called an intake manifold for us old-school guys). The TB needs cleaning, period, all of them do. NGK plugs ONLY! (cheaper at sparkplugs.com) Plugs are a huge PIA to replace, but someone here can walk you through it.

All in all, it might be a good idea to have the plenum pulled, replace ALL under-plenum rubber hoses (they crack), replace plugs, and clean the TB and plenum thoroughly. Many small jobs that can be consolidated to save on labor costs.

[DAEDALUS]

Fuel pumps usually go first...the current draw goes up and eventually the controller goes bad too. In this case Q45tech is saying the solder on the controller is suspect. I think if you're still seeing the problem, then you will need to hook up a fuel pressure gauge to the car and just leave it on until the problem happens and you can read the pressure. I'm not sure how to read the volume. Tuck the gauge away in a safe spot and make sure all the hoses are secured without any leaks. Or you can run fuel hose up to the windshield so you can read the gauge while driving.

[Dinkydow]

Thankyou very much for info and the time you took to answer all my questions. I really do appreciate it!!! Waybe [email protected]