Try to understand aged Q45

[gordonq45]

Hi,

I have 90 Q45 with 130k on it.Major history:. Did 60k maintenance.. Replaced the fuel line recommended by Infiniti dealer.. Rebuild transmission several month ago.

Check Engine light:

1. Four month ago, I noticed the check engine was on sometimes. I checked, the engine oil was low and I filled up. Then the light went off. 2. After changed the oil by myself, the engine light back to on again and I realized the oil was overfilled. I dripped the oil to required level and still got the light on sometimes. If I drive the car, the car is very hard to run with viberation and shaking at abound 50mph, sometimes stops on the road and hard to restart. I can see the idle goes lower close to zero before the car stop.3. I left the car in garage for a month during I out of the town. After I got back and start it again, it just fine. So far it has no problem for two weeks.I still think there is a problem, but I don't know what and where.Any idea why?

Idle speed:

After the car gets cold start, the idle is above 700 that is ok. If I drive for a while, the car gets warm up and idle back to just about 500 when I am waiting for a signle or the car is in idle.

MPG,

What is the reasonable MPG for this aged Q45?

Any suggestion?

Thanks all

Gordon

[PalmerWMD]

Hi Gordon, and welcome to our little club!:jazz:I will move this to Infinti Online Mechanic for you, were our Gurus live.

We'll figure it out.

Fred...

[maxnix]

Hummmmmmm. Do you hear that from behind the rear seat with just the key switched on, but the engine not started? If so , do a search on fuel pump and learn how to replace it before it fries your FPCU.

No mention of new timing chain guides? Are you the original owner?

Welcome to a great resource. Do spend a few minutes each night reading the previous posts.

[elwesso]

MPG is sole dependent on the condition of the intake tract, sensors, and driving habits......

I have bad knock sensors, a dirty plenum, good O2 sensors (per-se of the OBD test, flickered about 10 time in 10 seconds).... Anyway, I get about 13-15 mpg, usually its around 12.9..... My experiment of using higher quality gas hasnt gotten me better gas mileage...

For the check engine light, you need to check the OBD codes.... Do a search, I posted a good writeup on how to do that (super easy).......

Idle speed: Im guessing something is wrong with your IAC (dirty) and its not changing the idle...... Sounds like you are in for a plenum job!!!! If your anywhere near Indy, ill be glad to come and help!! Hopefully you didnt try messing with the adjustment on the FIC (fast Idle cam, on the throttle body), because that will reek havoc to you, as it did me (dont worry, I got it put back in its original place)......

[Jesda]

Im enjoying better gas mileage here in St Louis than I had in Spokane. Getting 16mpg vs. 14mpg. Idles smoother too. Fuel thing?

[elwesso]

16mpg.....?? What kind of driving do you do?? City/mixed/highway??

[Q45tech]

" good O2 sensors (per-se of the OBD test, flickered about 10 time in 10 seconds).."

I wouldn't consider these good switching times [cross counts] but adequate.............it is possible to see 2-2.5 per second.

really just have to see the inector opening time at cruise and block learn corrections with a Consult.

And depress the accelerator less.Exceeding 70 mph gets you out of the economy mode.

[gordonq45]

MPG issue:

Thanks everyone. Basically is in City of Bay area, CA, sometimes freeway. My car now is below 10mpg.

elwesso wrote: "For the check engine light, you need to check the OBD codes.... Do a search, I posted a good writeup on how to do that (super easy)......."

Is there a quick to your posting? Or I can search for it.

I'm 2nd owner and get the car with 40k long time ago.

[elwesso]

You can search for it, or you can read below because Im gonna post it again (im really bored)

First off, the ECU is located in the kick panel on the passenger side..... If you open the passenger door, and look at the door speaker its in that carpeted panel right there......

Anyway, you take a nut off at the very back (near firewall), unscrew it all the way.... Then you gotta pry this panel out (it comes out, but dont stick anything too far in there, cuz the ECU is in there......)..... Then there are 2 screws, one on the top and one on the back, near the big harness connector...... I have found it necessary to remove the panel underneath the glovebox to get to that top screw...... undo those, and then you ***CAREFULLY*** undo the harness connector to the ECU..... make sure it comes out evenly, because if you bend a pin you get to buy a new ECU!!!

Anyway, you undo the 2 screws and the harness connector out, you take out the ECU..... Then you need to reconnect the ECU harness conector, make sure its in all the way and very secure..... There is a plastic screw on the front ECU and... Then all you gotta do is turn on the ignition to ON, and turn the screw (dont force it, it turns easy and when it wants to stop, dont go farther) fully clockwise, wait 2 seconds, then fully counter clockwise.......

To interprit the codes, you have long blinks and short blinks..... The long blinks are the first digit, and the short blinks are the second.......

So, for instance code 34 (knock sensor) would look like this

---- ---- ---- -- -- -- --

[PalmerWMD]

Gordong,

under 10mpg is too low.possible reasons (assuming your plugs +ox sensor are good)

-bad MAF ( highly likely)-running too hot or too cool-dirty TB ( may contribute a bit)

Fred..

[elwesso]

Bad knock sensors also!!!!!

[DAEDALUS]

Dirty injectors also a possible cause.

[gordonq45]

The plugs was replaced at 60k maintainance. I have a friend who work for big 3 told me that the this find of plugs is good for a life ( i.e. no need for a replace. Is it right? so I can not assume the plugs are OK.

I haven't put cleanner for a long time(3 years?). But I strat to add fuel injector cleaner (Chevron's fuel injector cleaner from Costco) few weeks ago. Is it a right cleaner to use? Or there is better one for Q45.

I can check the ox sensor by OBD, and thans elwesso for the procedure.

Can I check the knock sensor condition by OBD code?

One question. Is there a Online Q45 menual available? It is easier for a search by key words. I have the manual come with car. Thanks for your sugesstion.

[gordonq45]

Hi Fred, In a post, you mentioned: Example: In some cars,improperly done oil filter changes, can cause MAFconnector problems, which can result in a wholeplethora of serious symptoms. Could you give a detail pls? What is the MAFconnector and where it located? Thanks, Gorodn

[elwesso]

The OBD codes will tell you a malfuntion of about every major sensor onboard....

There is no online manual, but you can download one from http://www.infiniti-techinfo.com for $20..... Cheaper than the $120 for the real FSM..... Or you can email me and ill hook you up with something (I have a 90Q45 service manual for sale!!!!!) Your car should have come with a service manual, check the spare tire area of the trunk!!!!

Your plugs are past due..... Unless you replaced them at 60k AND 120k.... In the latter case, you are fine........

Techron is decent stuff, probably the best OTC stuff available.... BG44k is the best, but I have mixed results with it!!!

The MAF= Mass airflow sensor...... It detects the amount of air coming into the intake tract by changing voltages over a heated wire (summarized version)

Anyway, its the thing right downstream of the airbox..... Youll see a little black box on top of it, and a little connector hooking onto it......

What oil changes do is they unhook the airbox (too lazy to go from the bottom), and thereby having to unhook the MAF, and its not designed to be hooked/unhooked a lot........

[Jeff Williams]

Gordon, I just saw this post. I have been out of town for a few days.

1. Us an entire can of Brake cleaner on the MAF (Take it out first).2. Pull the plugs, and check each one, for lean or rich mixture. (Only use the NGK's - NO exceptions)3. Use at least one can of Throttlebody cleaner on your intake. Use a toothbrush, and a whole roll of towels, to clean it out. (It will be hard to start afterwards).4. Use some additive to the gas (BG44 is the best).5. Check the oms of each fuel injector.

My check engine light has comes on, and the car idled rough, ran rich (black smoke), and got horrible fuel economy. This has been traced to a dirty MAF, caused by my K&N Filter charging oil. The rest is recommended for smoother idle, and better fuel economy.

Good luck!

[gordonq45]

Thanks everyone. I got to work on my car soon because last night I saw the check engine light on and car stopped after I slow down for parking. I restart it by pressing the gas paddle.This time I will check the ECU to read the code. This job may take me a while. I'll back when I need more help.

Thanks again.

Gordon

[gordonq45]

I checked the ECU code and it is very interesting:

take the ECU out ( thanks for elwesso's instruction).

First time check:1. Turn the key to ON position.2. turn the model screw clockwise and wait for 2-3 sec.3. Turn the screw back.

Result:The led shows code as 11. This suppose to be the model I result and I can not find code's meaning from book.

3. Turn the screw clockwise again and wait for 2-3 sec.4. Turn the screw back and read the result:

Result:The led shows code as 55. This should be the Model II result.

Then I try to repeat my test by turn off/on ignition and back to step 1.

Result: code 55 and steady on.

So the result is nothing to tell me the problem.

My car's problem is hard to diagnostic because it is not steady, i.e. the check engine light sometimes on, sometimes not.

ANY SUGGESTION?

I check the car anyway. I find out that the MAF cover is not tight enogh, one corner is up on, so I tight it again.

Thanks,

Gordon

[gordonq45]

I may need to change the plugs as you mentioned. I still can remenber that I tried once long time ago and failed to take one or two plug(s) from the engine, that is/are the plugs at inside of left end of the engine if I face the engine. Do I need the special tool or I have take some other parts out to reach those plugs?

Thanks,

Gordon

[Jeff Williams]

Gordon, have you tried to remove and clean the MAF?

To answer your questions about the plugs, no, you do not need any special tools, just 2 hours, and allen wrench to remove the plastic covers, a screw driver to remove the coil packs, and a plug wrench to remove the plugs.

Make sure you have plenty of light, time, and bandaids. Do not rush the job, and be sure to blow out the plug holes with compressed air, before removing the plugs completely, to eliminate dropping any trash into the cylinders.

Do NOT use any plug, except the NGK's (You can get them off of eBay, fairly cheap). And make sure you use the Anti-sieze compound on the threads, (You can get this at any Auto Zone) to prevent ruining your heads, the next time you remove the plugs.

Cleaning the MAF and throttle butterfly, will probably fix your check engine light, and stop the poor idle. This will take all of 30 minutes.

Good luck!

[gordonq45]

Hi Jeff,

1. I did not cleanup the MAF, should I do it? If it is, I will do it. I can see some dirt in it.2. Is it safe to buy plug on ebay? Does the plug on ebay meet the spec?

Thanks,

Gordon

[elwesso]

Ebay plugs..... Do a search on ebay for part number (put it in, and search titles and descriptions) PFR5B-11... They WILL be NGK laser platinums, and the perfect match.!

Clean up the MAF with a can of brake cleaner! you wont always see dirt on it, but its probably got fuzzies on it and its messing up the reading..... Whenever I do it, it always results in a glass calm idle....... it will also most likely clear up your MAF problems also.... If not, then its the connector......

[gordonq45]

Thanks for the plug info and part #. I'll search on ebay.

Thanks and have a good night.

Gordon

[gordonq45]

Did someone mentioned there is online NISSAN store I can find the plug for Q45?

I look at the ebay, ther plug is NGK IRIDIUM IX. I'm not sure it is right type.

Thanks

[elwesso]

Joe at http://www.infinitipartsusa.com will get them for you at like $6/plug.....

His number is at the bottom.... Ask for Joe, and say your a NICO member... He'll take good care of you!

[gordonq45]

Thanks lot.

I'll call Joe tomorrow for the plugs. I also will cleanup the MAF.

Gordon

[Jeff Williams]

Thanks lot.

I'll call Joe tomorrow for the plugs. I also will cleanup the MAF.

Gordon

Gordon, sounds like you are on the right track.

Also, while you have the plastic plenum off, use a can of Throttlebody Cleaner (Fuel Injector Cleaner) NOT Carbureator cleaner (It is not good for the Plenum coating) to clean the butterfly Valve and Intake. Use a screwdriver to prop the throttle wide open, and a toothbrush to clean all the carbon off the valve, and as far in the plenum you can. Use a cloth towel, or a bunch of paper towels to catch the pooling cleaner, as it flows out the TB.

Let us know the results.

[gordonq45]

Hi,I believe I made mistake last time to watch the ECU code. I did it again today because the check engine was on again. this time I did in this way.

Test 1 (Mode 1)1. warm up the engine.2. run engine at 2k rps for 2 sec.3. stop engine.4. turn the key to on position (do not start)5. start engine.The result shows that led is off and check engine light is off.

Test 2:1. keep the engine as warm up condition.2. turn the key to on position.3. turn mode selector clockwise4. wait more than 2 sec.5. turn mode selector counterclockwise. This way set the test as mode II. 6. start engine and watch the result.

Question regarding the reading.

1. the code displays only once. IS IT RIGHT? If I can not catch it, I have do it again. For example, if it displays as 12, it only displays it once and then nothing shows. 2. code interpreter. To keep the result, I video recorded the display of ECU.

My car show Mode I is ok.

Mode II display is interesting:one long on ( more then 2 sec.)one long on ( about 1 sec)three shots ( less then 1 sec)as:

-------- ---- -- -- -- 1 1 1 1 1

So how can I read it? as 23 or 13.

I guess the first long on may be the left over from ( please some one with experience help this !!!!)?? and there is no code 23 in the list.If it is 13, it is the engine temp sensor problem.

My symptom is:The check engine light on and car shakes at about 50mph (my feeling is the some cylinder misfire or lost fire) and sometime stop. Can the engine temp sensor failure cause this symptom? My car once lost lot of water and temp went to very high.

ps. I order the plugs from joe for $8.25/pc and will get it tomorrow.

Thanks,

Gordon

[gordonq45]

Spark plugs.

As I mentioned the check engine on in last mail and ECU CODE. Should/Can I replace the plugs before I pin point out the problem.

gordon

[PalmerWMD]

Gordon,

Do the plugs first.

Fred..