96 q cuts out while driving for a sec./ hesitation quick rpm drop

[bigal8627]

im having a problem with my q suddenly while driving the car would hesitate but not miss a complete stall for a sec then resume like normal. its very hard to duplicate at a specific driving condition. eg: load has no effect, speed has no effect or rpm range.only under normall acceleration before it started acting up... istarted the car and it ran for a sec then shut off it did it one more time and then ran fine for a few min then had a hard time keepin it running. i did the self diagnostics and found a code 34 the knock sensor problem.. heres my take let me know what you guys think.... it is not a miss all the cylinders are hitting fine it is an even cut out of the engine very sharp not a sputter which makes me kind of rule the fuel pump out IMO im thinking it may be the knock sensor but i dont want to do it if it isnt the problem yet.one more thing happened recently i had water leaking in from the windshield on the passsenger side but i pulled the ecm and had no damage or corrosion. anny suggestions on where to start. I am a mechanic ... wanted to turn to the infiniti pros first!

[Q45tech]

Begin with the MAF and CAS connectors [intermitents], try a substitute MAF.

IF MAF: Ocassionally necessary to carefully resolder the [4 + 4] circuit board pads that lead to connector and sensor.

10 year old knock sensors [temperature induced housing cracks] are all done by now..............usual to replace both and harness simultaneously.

Over the years we have replaced hundreds of KS on old Q.

[96Qowner]

Yeah, it's almost certainly the MAF. Wiggle the MAF connector while it's running, inspect and clean the contacts ...

Here's a great thread on the subject, showing all the possibilities that people go through:

zer...age=2

It's the MAF or its connectors.
Modified by 96Qowner at 11:06 AM 5/8/2007

[bigal8627]

i would like to comment on some news about the issue . when i picked up the car it was stumbling intermittently and had very little gas . i went to the gas staion and barely made it there. i filled up 7 gallons of super then drove it home and it ran better but still intermittently i drove it yesterday and it is getting better today it drove pretty good but still have a weak feeling to the car. i thinkitys comming from the knock sensors retarding the timming.

[maxnix]

Well, you have OBD II so get it scanned.

Without a maintenance history (fuel pump, fuel filter, intake path cleaning?) tough for us to tell as many things could be causing that behavior.


Modified by maxnix at 8:24 PM 5/8/2007

[qsiguy]

Can knock sensors be intermittant? One of mine is bad and I bypassed it with a 560K ohm resistor while t-shooting my emission failure. If it's possible for them to be intermittant wouldn't that cause a sputter or something when the timing changed to retard and/or the knock fuel map was accessed?

[bigal8627]

im thinking a low octane gas plus bad knock sensors may be the culprit.it is shifting and running fine today not like 2 days agoand the idle is smooth

[bigal8627]

i want to verify the fuel problem by adding 5 gallons of 89 octane and see what happens if i can duplicate the problem if i feel it start to get wores or happen again then i will go to 87 octane just to be sure if it is happenning more frequent after the 87 octane then i will fill it with ultra 94 octane and see if it goes away. if it does then i will just do the knock sensors and replace all the good stuff you guys talk about when you remove the plenum.Remeber we do it right the first time so we dont have to do it again....what do you guys think

[maxnix]

That is a poorly designed experiment! Anyone who reads the owner's manual knows the car requires 91 octane.

Think about sharing your recent maintenance history of the intake, engine, and fuel system.

Think about a couple of bottles of ISO-HEET and maybe some BG44K assuming your fuel pressure is correct and the fuel filter is new within the last year.
Modified by maxnix at 9:22 PM 5/8/2007

[bigal8627]

why do you feel its a poor experiment? i just purchased the vehicle. and i have no way of constantly duplicating the problem and now its not happening. the problem went away gradually after i added the new gas from the begining when i picked it upremeber i picked it up happened every 10 sec. until i reached the gas station as a matter of fact it shut off pulling into the gas station. after i filled up it kept getting less of an issue untill yesterday it didnt do it at all .how else does a problem go away gradually. i need to make sure that was it. either way i want to do the knock sensors but if i do them now we will never know if it had an effect on the vehicle. because its not happenening.

. only way to duplicate it is to add lower octane fuel its not a long term fill im only putting a few gallons if it starts to act up then i will add full super 93 or 94 octane and see if it goes away. after the new fuel blends in with the old lower octane .seems like a pretty controlled test to me . and if it does work out corrctly then we have a new form of knowledge and questions to ask othe nico members before we try to throw parts at it.

[bigal8627]

maybe my knock sensor issue is intermmittent and the factor of low octane fuel which will cause pinging mixed with the time the knock sensor wake up and hear pinging is when they decide to retard the engine and that is the sputtering hesitation i get. thats what it feels like a hard jerk back or complete lack of power instantaneously not bogging or gradual loss of power. i see my rpms drop and jump 750 in a matter of a split sec up and down

[96Qowner]

... Or you could check out the MAF.

At least email bigdog - click on his name and you'll get an email address.

This is EXACTLY how a bad MAF behaves in a G50 Q45.

[maxnix]

why do you feel its a poor experiment?

That is a poorly designed experiment! Anyone who reads the owner's manual knows the car requires 91 octane.

What's not to understand? If it is so good, why don't you start with diesel or kerosene? Because they are the wrong fuels? So is gasoline below 91 octane. Beleive me, the members here don't need an experiment to know which fuels to burn. Extensive posts on the subject in the archives.

Why do you keep avoiding posting the maintenance history?

[bullittandy]

What's not to understand? If it is so good, why don't you start with diesel or kerosene? Because they are the wrong fuels? So is gasoline below 91 octane. Beleive me, the members here don't need an experiment to know which fuels to burn. Extensive posts on the subject in the archives.

Why do you keep avoiding posting the maintenance history?

You're absolutely wrong. It was a very good experiment, because he had a problem, changed one variable, noticed an improvement and is considering going back to the orginal condition. Its called an ABA design.

Is it the problem? Maybe, maybe not.

Also, lower octane fuels do not damage the engine, the engine adjusts for the lower octane. You're such a Cassandra.

[maxnix]

Also, lower octane fuels do not damage the engine, the engine adjusts for the lower octane.

Not really, not long term. The point is, we know that sub 91 octane fuel is not the correct fuel for any VH engine. Well, all but maybe one of us.

[bigal8627]

thanks bullittandy i want to duplicate the problem again and i want to start isolating variables.like ive read in previos post some problem are a combination of things gone wrong what if i have a bad maf connection. with bad knock sensors and fuel. im new to inifitis thats why i turn to you guys. ask me about a saab or mereceds or a chevy and ill tell you everything you want to know. but these cars were built with very advanced technology... maybe too advanced thats why there are so many driveabilty problems.but as far as a maintenace history is concerned i have non i just got the vehicle.

[bullittandy]

The most common failures are MAF and MAF connectors, fuel injectors and pumps and knock sensors.

Check the MAF sensor connector by wiggling and if you have a known good MAF put it in. Knock sensors are a good investment as are O2 sensors.

If you've got experience you'll absolutely figure it out with this board's help.

Excuse Maxnix, he likes to insult new members

[bigal8627]

Hello everybody just wanted to give some people who have similar problems like mine some good news. I Did get the problem resolved thanks to nico i would have never guessed it but the connections from a visible examination under a magnifying glass didnt turn up any cracked solder but i removed the old air flow sensor solder connections from inside the sensor and resoldered the three connctions at the elbow . cleaned the air flow sensor with carb cleaner and had instant results ! I ruled the a/f sensore when i heard it start to act funny then i tapped on with a screwdriver and the car shut off. now that i have fixed this problem i noticed the same issue with my maxma same thing but i had an extra maf sensor for it so i just changed it.

Bottom line when the car starts to act up like. Intermittent no start,dies after start up , bucking violently, not idling correctly, surging under acceleration- clearing up at higher rpm... try this quick fix first it will save you a few hundered bucks. took 20 min and an inch of solder and a can of carb cleaner.hope to hear some good news back.I completely doubted the maf before i started to work on nissans now that own 3 and all 3 had the same problem diff symptoms its the first thing i go after REMEMBER THAT

[bigal8627]

OH yeh there is a link floating around on this site for the procedure i did if you have any questions just ask