Still stumped on this after about 2 weeks of fiddling and researching. My Q started acting funny 2 weeks ago, the idle started to stumble noticable, idle speed also dropped to around 500 at idle under load. Gave it some time to pass as it stumbled from time to time as most Q's will do. Few days later, problem still persists and developed a loss of power in the low end. I eventually had to resort to bumping up the idle speed to keep it from getting worse. Ive gone though what I can see as logical steps with no luck. I believe that I may have a failing fuel pump or some kind of issue with the ignition like a bad coil or spark plugs maybe? Previous owner replaced the pump with a known good pump from a G35, also new fuel filter which I can verify. Car is running and starting fine but ive still got idle issues and what seems like a dead spot when accelerating. no power until I reach about 1800 rpm.Heres what Ive tried so far:

Pump is silent, no buzzing.
ran seafoam through gas tank and through the vaccum lines
*ran lucas injector clean through gas tank(had luck with this once before), ran this twice
checked battery charge
checked fuel control unit(I have a 93 base model)- found that it had already been upgraded to the second revision, found no burnt areas
Jumped the pins on the control unit and ran full power to the pump just to see and it had no effect.
removed and cleaned
Removed and cleaned IACV- wasnt overly dirty anyway.
Cleaned throttle body- already cleaned it a few months ago so not very dirty
Unplugged tps sensors to try base idle reset - may not have done this right, I only know how to do for 240sx

*after the second lucas treatment I did get some power back but may have just been a coincidence. still has the dead spot.

You ran through a good bit of diagnosing.

Have you done any checks to your ignition system? Coils may be slowly going out, or it may be time for new plugs & wires. At the least, replacing them wouldn't be a bad idea.
How are your O2 sensors? They could be sending something faulty to the ecu.

frapjap wrote:You ran through a good bit of diagnosing.

Have you done any checks to your ignition system? Coils may be slowly going out, or it may be time for new plugs & wires. At the least, replacing them wouldn't be a bad idea.
How are your O2 sensors? They could be sending something faulty to the ecu.

Have yet to dig into the coils, I wanted to get some experiences from others or some other ideas first. Most of what I have read says the the coils have a pretty long lifespan so dont look at them until youve gone through everything else. Same was said about the plugs but ill probably do them anyway. I had an I30/maxima last year and I had coil issues with that so I do have some experience. This is similar but I still want to be sure. That car needed a full set brand new which cost me $600 from the dealer as only OEM was compatible. I expect the same for the Q if it comes down to the coils but im afraid of the cost and if I can actually get them. My local junkyards have some availible so id start there probably. Id then need to find out if the coils are compatible for all G50 90-96 since the cars at the junky are all different years.

I'm not sure about the idle issue but have you ohm tested the knock sensors? They could be the cause of the lack of power/acceleration issues. The bundle of connectors shown in the picture is on the passenger side of the plenum.

UPDATE: FALSE ALARM !

Went in tonight ad decided to grab a set of plugs and dive in to the tune up. Low and behold I discovered a few things. First off, the coils seemed to all have been replaced at some point. They looked newer and didnt have nissan logos on them. Im cool with this so now I know ill be good with those for a while. Second, I also saw that somone had repaired a couple pieces of the coilpack harness. Was actually well done and should last. Finally, I took out the coil in cylinder 1 only to find a small pool of oil in it which was clearly the source of all my issues. I checked all the other cylinders on the drivers side, all good. So now I decide to take the diagnosis a step further. Instead of doing the full service I decided to clean the cylinder out and swap in a spare plug rather than a new one. I happened to have a spare plug from my S14 which was identical to what was in my Q. My goal was to see if I had a small leak that just pooled up over time or if it were something major. Fired up good and sounded much healthier. Then I throw in some lucas oil treatment to see if it would have an effect as I remembered kinda cheaping out the last oil change I did.lol. Seems to be working so far but im gonna take it to work tomorrow and see how that goes. Looks like the thin oil may not be maintaining the seal. The leaky cylinder also had what looked like a brand new coil on it so this may have happened to the previous owner in the past and fouled the coil. Most likely my band aid fix will have to be addressed later with a full valve cover gasket job but for the moment im good.

Glad to hear it, and thanks for posting your resolution!

You'll likely have to do the full valve cover gasket job in a little while, but you've at least got the knowledge and time on your side now.

frapjap wrote:Glad to hear it, and thanks for posting your resolution!

You'll likely have to do the full valve cover gasket job in a little while, but you've at least got the knowledge and time on your side now.

YES! Just when you think you know it all, something new happens. I do have one more question though. Im looking into neccisary parts for the valve cover gasket that I will hopefully takle in a couple weeks. Most what I read shows that our cars use RTV for this instead of a regular gasket. However, I have searched and found some regular gasket kits that say they are compatible. So far ive seen them on rock auto and ebay, the local autoparts places list the kit with RTV. Anyone shed any light on this for clarification?

I buy 90% of my parts on Rockauto than the parts stores for reasons like you just mentioned. RTV might be a possible solution, but I'd rather have a full around gasket and I bet when you take it apart, there is a full gasket there. Of course, it never hurts to add RTV, but if there is a full perimeter gasket available, I'd go that route.

Look in between the space of the valve cover and the top of the head and if you can, poke a small flat blade screw driver in there and see if it feels like rubber. Apparently if your car was built after February of 93 then it may have rubber valve cover gaskets.

mattd1979 wrote:Look in between the space of the valve cover and the top of the head and if you can, poke a small flat blade screw driver in there and see if it feels like rubber. Apparently if your car was built after February of 93 then it may have rubber valve cover gaskets.

Thx all. I was actually able to verify with my mechanic that I do have a rubber gasket, lucky me. However the saga with this continues when I got the quote to do the job. Got a good decent deal ($400) but my finances got a tight unexpectedly so I took the car back and its sitting in my driveway. Its probably a bad idea but im considering trying one more fix so that I can drive the car in the meantime. Im moving this coming weekend and I could use it since its wayy bigger than my 240 obviously. Anyway, Ive been backtracking the last several months to see if I could come up with some ideas. Not too long before all these issues I did a basic oil change which was the first id done since owning this particular Q. Found out in the process that it hadnt been changed in about 8-10 months of regular driving, eww. Car was running fine prior to the change by the way, merely trying to start a process of regular matinence. Searched around, and wasnt quite sure what oil to run so I changed it with some real cheap basic quaker state 10w-30 and the best filter I could source from wally world (fram premium high mileage). My logic was that fresh oil was better than what I had. My thinking here is that the cheap oil could be a possible source for the leak or could be speeding it up? Had a similar problem in my 240 and it cured it quickly. Its also been very hot here in Jacksonville over the last few weeks which doesnt help. Im thinking of changing oil again tomorrow but im gonna run 10w-40 mobil one full synthetic and possibly a bottle of lucas stop leak for insurance. Also run some seafoam prior to changing it to clean out some of the mess.

I know this sounds crazy but I do believe something good could come of it? what do u guys think?

Forgot to mention I also changed plugs last week too so that can be checked off the list.

Call me crazy but my next oil change I will run Mobil 1 15W-50. I have been running 0W-40 and once I ran 0W-20 (never again engine sounded horrible on cold mornings).

Lucas Stop leak is a waste of time as it could do nothing or plug something else up that shouldn't be!

Seafoam is useless enough to not do much or any damage if used correctly.

the inside of the plenum could be black. the rear differential fluid may need changing. the spark plugs and oil you use. belts may play a role too. and do you have anything heavy in your trunk?

Infinitiguy19 wrote:Call me crazy but my next oil change I will run Mobil 1 15W-50. I have been running 0W-40 and once I ran 0W-20 (never again engine sounded horrible on cold mornings).

Call me even crazier, cuz my next oil change will continue to be Mobil 1 0W-20. My Q is super quiet on the 0W-20 in comparison to the noisy 10W-30 I was using before that. Especially on cold mornings, the difference is night and day. Car warms up much quicker on the 0W-20 too. Which brand did you use btw?

Wow, all this different info confirms how hard it was for me to figure this out.lol. Anyway what I ended up doing was a full oil change to mobil 10w-40 high mileage (not mobil 1 but the one just under), also added blue devil oil sealant. Did some good reading on the blue devil and it has a good track record. I know people feel negatively about this additives but its not like the molyases type stuff like lucas or berdahl, also cost $20 a bottle as opposed to $5 to $10 like the others. Its like water basically but has some kind of sealing agent that is activated with the hot oil. Instructions say you must run the car for 2 hours continuiosly upon adding it to the crankcase for the best results. Followed this to a T, and let the car sit for several hours. Power seems to be coming back, motor is super quiet now almost to the point where it sounds like is not even running. Still need to eventually clean the plugs that are most likely fouled a little. I think im going to stick with the 10w-40 for a while, and may even add more blue devil as the 1 bottle treats 4-6 quarts of oil and ours is 6 and 3/4. The heat here has been crazy, soo bad that im starting to have electrical issues! My dash was so hot the other day my trip was completely blank, and my power locks act up depending on how hot it is.lol

Took her for a joyride last night after sitting for 2 days. Runs like nothing ever happened. will be like new once I can clean my plugs. Also need tires bad!! Negative camber chewing through to the belt.lol

Sounds like you need upper links!

Infinitiguy19 wrote:Sounds like you need upper links!

definately could be! been running some super used tires, and found out a while back that my tension rods were toast so I think the damage was already done. Ive since replaced the rods with a set of mint S13 ones for the moment. Just need to get some good tires. Drove it yesterday around the neighborhood, I could hear the belt crunching up against the street!LOL. Also scooped up a clean, all original Z32 this weekend so ive been a little distracted to say the least.

Don't drive too long like that otherwise it may bend the third link too.

ill be replacing the tires this weekend. The S13 rods are the same as the G50, only difference I saw was that the bushing was slightly smaller and might be a bit stiffer.

Your upper links are whats going to help bring the camber back more to the upright position. My front tires were getting eat up on the inside edge and this was after I replaced the upper links. I ended up shimming the upper link brackets out using the formula that Q45tech used to get it has close to -.7 as possible. The tension rods will just help mainly with the wheel caster which will effect how well the wheels will return to center.

Matt

Yea Ill have to take another look at it to be sure. I had the car laser aligned at a buddys shop earlier this year and he didnt mention anything. I did take another quick look at the tires the other day though and the one with the damage is on the same side as the bad tension rod.

Soo... the saga continues

Got the bad tire replaced last friday. Everything was silky smooth again that weekend. Drove the car all around town smiling. I got in it on sunday just to move it out my buddys way so he could back out my driveway and BOOM, Misfire. So far im about halfway through my diagnosis. I pulled all the coils and plugs yesterday, inspected all the wires. Everything looks good. All the plug wells and coil boots are bone dry (thx to blue devil stop leak), plugs are clean. I ran the car and started pulling them one by one but so far ive only been able to test the coils on the passenger side as they are easier to access when pulling connections to the coils. All seem to function properly. Also ran some seafoam through the motor and crankcase, injector cleaner in the gas tank also. Doesnt seem to make a difference but whatever. I need to go back in and swap them so that I can test the rest of the coils but I havent gotten to it yet. This misfire is kind of odd though because it has thrown no check engine light? In the past my other infiniti I30 CEL stayed on until I replaced every single failed coil. This G50 already has 2-3 replacement coils already, very strange. I think i'd like to try another MAF as well just to rule that out, I know sometimes a bad MAF can feel very similar to a coil misfire performance wise. Right now its missing at idle, and has an obvious loss of power all around. Exhaust sounds like an old clunker. Soo depressed right now. And my Z32 has a cracked windshield now also:(

I have never seen coil packs on a 1990-1996 Q45 fail. What kind of fuel injector cleaner did you use?

Blue devil stop leak may cause you some issues down the road. I would fix the leak no matter what it is rather than potentially clogging up something else.

What is the idle RPM's? I would be more inclined towards injectors. Did you check them?

Infinitiguy19 wrote:I have never seen coil packs on a 1990-1996 Q45 fail. What kind of fuel injector cleaner did you use?

Blue devil stop leak may cause you some issues down the road. I would fix the leak no matter what it is rather than potentially clogging up something else.

What is the idle RPM's? I would be more inclined towards injectors. Did you check them?

I was gonna wait until I got home tonight but I think I may have jumped the gun on this. Got some advice from somone on another forum to just kepp trying to clean the injectors out. Like you he said the coils rarely fail also. Funny tho because my car surely has at least 3 replacement coilpacks. Anyway, I decided to use somethind different. Read up a little here at work, decided to try a bottle of techron which I have never tried before. 1 bottle, and $20 worth of gas, motor started responding within 10-15 mins of driving(my tank was close to E btw). I really want to close this thread but the Q wont let me!lol

this is still really strange because Ive treated the fuel system kinda like this twice already and it keeps coming back. buddy on the other forum said I may just have some crap in the tank but how long would it really take to clear it out? I run this car down to E a lot due to my long commute to work, and ive got a newish fuel pump and a new filter.

changing valve cover gaskets on this car, like anything Q45, requires time and persistence. on the driver side, you have all the pcv tubes, as well as a little antifreeze bypass hose that you have to remove to get to the back corner of the valve cover that has a 3/8' diameter hose. gasket cement, grey nissan spec, is only used in the back where you have the half circle cut out. use a hand held mirror to make sure its seated properly before you tighten. change the plugs while you are in there as its a pia. the good news is iridium plugs are a lot cheaper than they use to be. i got 4 for $28 delivered on ebay. on the driver side, you have your share of issues as well, getting to the back connectors is the main pia. i tossed that black plastic cover for the valve cover gasket so you can see the coils. take your time and if you dont finish in one day, no biggie. i did one side at a time. you dont want to have to take it back apart!!!

frapjap wrote:You ran through a good bit of diagnosing.

Have you done any checks to your ignition system? Coils may be slowly going out, or it may be time for new plugs & wires. At the least, replacing them wouldn't be a bad idea.
How are your O2 sensors? They could be sending something faulty to the ecu.

No plug wires in 1997-2001 Q45. Has coil on plug ignition.

marcyprojects wrote:

frapjap wrote:Glad to hear it, and thanks for posting your resolution!

You'll likely have to do the full valve cover gasket job in a little while, but you've at least got the knowledge and time on your side now.

YES! Just when you think you know it all, something new happens. I do have one more question though. Im looking into neccisary parts for the valve cover gasket that I will hopefully takle in a couple weeks. Most what I read shows that our cars use RTV for this instead of a regular gasket. However, I have searched and found some regular gasket kits that say they are compatible. So far ive seen them on rock auto and ebay, the local autoparts places list the kit with RTV. Anyone shed any light on this for clarification?

You only use the Nissan Grey Spec RTV on the half moon part of the gasket (in the back). otherwise no rtv is used.