94Q at 90k miles

[94Q Atlanta driver]

Greetings, Fellow Infiniti Drivers.I’m an infrequent poster (only second time) but regular NICO reader who appreciates all the good advice and knowledge transmitted in this forum. I’d appreciate any advice that y’all can offer about my rapidly approaching 90k mile service.

Without further ado, then, here’s the major service history of my 94Q (standard suspension with TCS) that has 89,000 miles on it (I got it third hand with 71,000 miles on it).

--at 87,856 miles, T3/Smyrna diagnosed the fuel pump is making noise and probably needs to be replaced (original fuel pump still in place); also then, I met Dennis (Q45tech), who very kindly performed a diagnosic and found a failure detected of the knock sensor. When Dennis did a new test, however, no current failure was discovered. (I forget the name of this sensor--it's under the plenum, I think...)

--at 81,958 miles, T3/Smyrna removed, cleaned, an resealed the valve covers; replaced a leaking oil pressure switch; replaced the trans mount; and installed a rear sway bar.

--at 73,585 miles, T3/Decatur replaced front and rear rotors and front and rear brake pads; replaced both tension rods and both upper links; and replaced right side rack boot.

--at 67,404 miles, Troncalli replaced the water pump.

--at 57,018, Troncalli replaced the air cleaner filter and fuel filter; flushed and replaced engine coolant; replaced all dive belts; replaced spark plugs; replaced leaking power steering hose.

--at 43,789, Troncalli replaced front pads and machined rotors; transmission flushed.

--at 42,985, Troncalli replaced rear brake pades and machined rear rotors.

--No major service between 42,985 and 24,926 (where the service records I have begin).

So, having read widely on the Infiniti online mechanic forum, I can see that there are quite a lot of major service functions that have gone undone or have been done less frequently than many of the folks who post here do them.

I’m intending to go to T3/Decatur this week or next for the 90k service, and would very much appreciate your input on how I should prioritize the services.

It seems that I should go ahead and have the fuel pump replaced; what about the fuel filter and cleaning dirt out of the fuel tank?

What about a transmission flush (I’ve printed the “Q45 transmision” article, which I assume is the procedure T3 follows.

What kind of attention should I give the radiator and cooling system?

What about new spark plugs?

And below are some other service procedures I’ve gleaned from the site. How do they fit into the prioritization?--put new GL-5 into the rear diff (prefer MOBIL1 GL-5)--flush braking system--exchange power-steering system use MOBIL1 syn ATF (yes ATF).

And finally, I don’t want to come across as a heretic, but are there any advantages to going to Troncalli over T3? (I understand that it’s ideal to ask for David the service writer and Bobby the tech.) The only reason I can conceive of for Troncalli having an advantage is that they might have a fuller range of diagnostic tools (due to automaker policy of withholding from independent shops the diagnostic codes necessary to evaluate newer engines).

I’d like to keep the car another 60k to 70k miles, but I’m somewhat reluctant to spend thousands bringing it up to peak operating order. I’m especially reluctant since I understand that the Q engine, being a sophisticated, heavily computerized, largely sealed object, defies an accurate forecast of its longevity. Put another way, I’m under the impression that a Q owner could do everything right and still have the engine crap out one day. But then, I’m not a terribly knowledgeable car person, so please feel free to correct my observations here and anywhere else in this post.

Thanks very much for any input y’all can offer. And thanks for all the good posts that have made for useful reading for me.

Glenn

[PalmerWMD]

Glenn,

Welcome !!!:jazz:

Yes, replace fuel pump before it burns out the (much more expensive) controller.Yes new fuel filter, about the gas tank it'll be hard to find a place thats clean it as getting rid of the gas can be a challenge for the shop.

transmission flush, MOBIL 1 ATFBrake flush, ValvolineSYnPower DOT3/4Cooling system flush ( refill with distilled water+ Nissan Green)New rear diff fluid(MOBIL1 GL5

New spark plugs will give you better milage+ performance.

Troncalli vs T3:

T3 anyday.I am one of those ( many) club members that drive 100's of miles to have my car srviced at T3 ( at least for bigger jobs).

Living in ATlanta and not going to T3 would be unthinkable for me.They have everything they need to properly maintain your 94Q45.

If properly maintaienmd your engine will last for a very long time.Now 90-93 have that guide issue which if <not> addressed can cause the engine to "crap" out at any time, but not in 94's.

Your car can last a very long time if properly taken care of ( oil changes)

At T3 you can afford to keep your Q well maintainmd and continue to have a great car for <so> much less than a new cars payments for often a lesser car.

Fred...

[elwesso]

I dont think you have the right idea..... The Q engine is very easily accessible, not very sophisticated, and not really very computerized...... This is in comparison of vehicles of similar year/class......

Id go ahead and replace the pump for good measure.......

I think that T3 has adequate tools for diagnosing a 1st gen Q....... Other than a consult, there really isnt a whole lot more you need.....

I think the best thing to do for the cooling system is just to flush and fill every year or so...... And then do a full flush when its time for the Tstat to be replaced.......

You should probably do the diff..... Any GL5 will work, but I prefer valvoline synpower..... Its easy to find, and pretty inexpensive....... Also, id DIY it..... Its really easy, and only takes about 15 mins......

You are also due for new plugs...... Check out my website, and see if you will be able handle it..... It was my inaugrial job on the Q, and its a very good one to start out with..... Straightforeward, but will give you a good idea on what to expect for later repairs.......

Your service record is MUCH better than most, and Id say that you have a very good Q....... Just be sure to keep going on the same path, and you'll be fine....... Id say your car would hit the 250k without much difficulty......

[maxnix]

No 60K service? Then plugs are overdue. Yes on the three fluids.

If I were in Atlanta with your car, I would take Dennis to lunch and map a strategy to return it to as new condition.

I am betting T-3 (Decatur?) sees more G50 Q45 than Troncalli.

[Q45tech]

I'll go head to head with any dealer in the US on diagnostic equipment [and personal diagnostic skills on 90-96Q] other than a Hunter 9700 which we don't have!

I personally have $67,000 worth of electronic test equipment adapted to automotive service [which I use in my real business]igital Oscilloscopes, Frequency counters, Spectrum Analysers, Dc current probes to see the ampere waveforms, Dozens of Manometers sensitive enough to measure the air resistance of different brands of air filters - resolution 0.1" of WC., vibration meters and accelerometers, Fast Fourier Transform Analysers to see the frequency distribution of vehicle vibrations. Digital pressure gauges to 5,000 psi with 1 psi resolution.

Things dealerships couldn't conceive in their wildest dreams--research lab stuff.

I have ecu simulators, sensor simulators, function generators to simulate any component.

But I'm sure the factory research labs have me beat, at least their equipment is probably newer and smaller.

David is no longer at Troncalli but Bobby still is if you insist ask that only he do the work.

[greg_atlanta]

Troncalli is OK for routine stuff, but their prices will be a higher for major work.

Sounds like you have enough stuff for a day or two of work. I'd recommend leaving the car at T3 Smyrna since the techs there have a lot more Q45 experience. Last time I was there they were not too busy.

Everything you've mentioned is normal for a 9 year old car despite the below average mileage.

Good idea to go ahead and replace all hoses too (overlaps with knock sensor replacement, if needed).

[94Q Atlanta driver]

Thanks for the input. I hope I didn't give the impression that I don't like T3 or was knocking them. I've gone there for all major work since getting the car, plus oil changes and other minor things, and have been very satisfied. Being that I'm not an expert or even a knowledgeable enthusiast, however, it seemed like a good idea to ask about Troncalli vs. T3. It would appear that in terms of cost, capabilities, and competence--the areas any consumer would be interested in before laying out over a grand in auto work--there's nothing Troncalli has to offer that exceeds what T3 brings to the table.

[Q451990]

Let me weigh in here too... I drove to T3 from Columbia to have my "Q2" worked on (guides, transmission flush, rocker cover reseal) - because I think they're the best in the country. They defintately have the diagnostic tools needed, and they probably have more experience on the older Q's than anywhere else you could go...

I suspect you'll be better off at the S. Cobb location vs. the other one - at least I think that's what Dennis said once.

As far as the life of your engine - it should be fairly bulletproof to 200K with proper maintenence. Just make sure it doesn't overheat and keep up with the oil changes and other stuff and you'll be fine...

Heath

[Q45tech]

I live about 15 minutes from the South Cobb Store so that is the one I've chosen to concentrate on, spending my free time there.It is the location where we have a proper street road course [curves, straights, hills, dips, bumps, railroad tracks PLUS a bridge where you can accelerate safely without fear of a car pulling out in front of you at 80 mph! 300 feet to an Interstate on ramp!------and can do zero to 60-80 mph measurements safely...............the other location [Dekalb County] is just too congested for safe testing above 35-40 mph. Pretty much the Cobb/Smyrna police are use to us doing serious testing and use our lot to hide sometimes and we have been their since 1995 without a ticket or stop for vigorous driving.

I have hundreds of diagnostic charts on Q covering the same stretch of roads, so it takes me a minute to feel a problem.

I always redrive the same stretches every week in my Q with the Consult recording to hone my sensitivity.

[Q45tech]

Had a 94Q [140k] member from Huntsville drop by on a business trip to ATL this week. The usual - bad knock sensors [harness?].I used my sensor simulator box to double his acceleration.......proof of concept and solution! Unfortunately his dealer had not found the problem in his last 3 visits [?].......Shame shame seems nobody put a Consult on the car? They talked about valves, MAF, and ecu and IAC everything under the sun except what the real problem was?

Then he drove my Q over the same course.

[szh]

Then he drove my Q over the same course.

And his reaction to that?

Z

[Q45tech]

I'm sure he'll post, I assume it was positive considering the half power he was use to with faulty KS.

[Bayarea Q]

I was under the impression that you would see a code in the display box when the KS's were bad?

[Q45tech]

Only the Consult shows a code on 90-95Q [ecu flash codes but no MIL/CEL light], but the drivability is so VERY bad [lost acceleration/heistation on mild acceleration, drop in mpg, etc, etc] that a sensitive Q perfectionist should be able to tell from a conversation or putting his magic hands on the hood. Even the average owner notices something is wrong IF he had the car when it was right!

It is so common we think of Knock sensors or MAF as the first thing...........and just use Consult as proof.

We have replaced multi hundreds or sensors and harnesses, a month doesn't go by when another one [or 2-3] doesn't comes in.

[maxnix]

We have replaced multi hundreds or sensors and harnesses, a month doesn't go by when another one [or 2-3] doesn't comes in.

Correct me if I am wrong, but aren't you still using original KS at 265K+? Isn't overheating/high temperature operation the real killer, and not time?__________________Brian1995 Q45 & Q45t & 2000 Q45

Discover the power of the button!

[Bayarea Q]

Is there any other condition besides overheating, that can damage the knock sensors?

Q45 Tech, you say very noticable loss of acceleration on mild acceleration....would I notice a difference @ WOT?

[reggiegsd]

What resistance does the ECU see when it looks at a healthy knock sensor?

[DAEDALUS]

550k-ohms nominal. But having a good reading isn't enough. It can still throw a code. Best to just get down there and check at the ECU.

[elwesso]

IF its throwing a code their as good as useless.....

[szh]

I'm sure he'll post, I assume it was positive considering the half power he was use to with faulty KS.

Oh, I would definitely assume the same! I was merely wondering if he had a wide grin on his face at the end of his drive of a properly functioning Q! I will certainly never forget the drive test I had on my first Q (a 1991 Q45 that I ended up buying that evening)

Z

[maxnix]

I'm sure he'll post, I assume it was positive considering the half power he was use to with faulty KS.

So he is a NICO member from AL with a 1994 Q45? Hmmmm......__________________Brian1995 Q45 & Q45t & 2000 Q45

Discover the power of the button!

[Chally]

Bayarea Q YES! It gave me a good second to 60mph.

The Knock Sensors make the ignition retard when there's a problem, & full power is down under WOT.

[Q45tech]

Almost every customer with bad KS swears the car was never overheated............maybe before they got it or they didn't notice.Something causes the plastic housing to crack..........they don't crack on the shelf.

I have seen coolant temps rise above 230F with marginal Q idling for 15 minutes in 90F ambient/AC on. The KS position might get to 260F............still 100F below the crack temperature.

Maybe 7-10 years of exposure does them in?????????

Make sure your WOT ignition advance is at least 26 degrees at 6,000 rpm. {Consult]............bad KS= 20-22 degrees.

[elwesso]

Curses....... One more thing I gotta buy for the Q.......

[bamaQ45]

I haven't had a chance to check this forum in while... so apologies for the late reply. I am the 94Q owner from Huntsville with the knock sensor diagnosis. On my October business trip to Atlanta, I couldn't pass on an opportunity to visit Dennis at T3. First, let me share the obvious with the members on this board, I want to personally thank Dennis, who so generously spent his time with me and my humble '94Q. After more than three years of asking my dealer tech what's wrong with the power in my car, Dennis dianosed and verified the knock sensor in just over 60 seconds. T3 clearly won my respect and future business. I just have to give more thought to my garage visits now that my garge is more than 200 miles away. To answer the questions, I could absolutely feel the difference in my car and the power in Dennis' car. It reminded me of the power that made me buy my car in the first place. You guys remember the feeling.... you didn't know you even missed that kind of power until you drove the Q for the first time.

So, following my lesson from Dennis and upon my return to Huntsville I wanted to understand what is going on with the knock sensor. I used the manual method of checking the codes to confirm the knock sensor code using the blinking lights on the ECU. Then I reset the ECU and promptly received the no trouble blinking lights. I drove around town for a week, with the ecu tilted down in the passenger floorboard, checking codes with the beginning and end of each drive. About a week later the knock sensor code showed up again... reset the ECU and the knock sensor has gone off only more time since. I can tell now without even checking the ECU when car is driving much, much better... power on acceleration, and when the knock sensor code has defaulted the timing.

So here is the question. Do knock sensors fail completely?... or is it possible that KS operate intermittently? Replacing sensors and harness my be required, but I don't want to spend that kind of money only to find the very same code failures again. Recently, including today, the car is running awesome again.

Whatever I do, Dennis and T3 get my business. My thanks to Q45tech! Nice Q too Dennis!

[Q451990]

Maybe 7-10 years of exposure does them in

I'm beginning to like this theory...

Heath

[Q451990]

So here is the question. Do knock sensors fail completely?... or is it possible that KS operate intermittently? Replacing sensors and harness my be required, but I don't want to spend that kind of money only to find the very same code failures again. Recently, including today, the car is running awesome again.

They will have intermittant problems... mostly due to corrosion in the harness, but I'm sure the sensor can be intermittant too. With plenum labor costing what it does, I'd go ahead and replace the sensors with harness if they even look questionable. Have all of the coolant and PCV hoses under there replaced at the same time. After the work, you should then have a lot of trouble-free miles ahead of you.

Heath

[elwesso]

Do you know what kind of gas mileage improvement I should expect??? Like 3-5mpg sound reasonable???

[Chally]

I too tried to avoid the cost of replacing the sensors for ages. I have a machine, like the Consult, which I can re-set the codes very simply & it always came up with the knock sensor.I finally replaced both, repaired the wiring harness & got instant power, the likes I never had before.Just DO IT!

NB Economy didn't improve very much, maybe 1 mpg, but maybe that's just how I drive...

[Q45denver]

I assume the problem is the harnesses are getting wet and the contacts are corroding. Is there some way to seal the connectors or to elevate them so they are not exposed to moisture?