Q is not idleing :(

[SunnyTk]

soo like the titles says, my q is not idleing... it has spark, and fuel. timing should be ok. I thought it was the fuel pump, soo i got a new one. but same problem as before. its cranking, catching, but not holding a idle.

checked the maf sensor, cleaned it the connector... nothing.

Im not sure where too look anymore. it might be a vacuum line.... just not sure where to get a diagram

any help would be appreciated

[S13xCrazy]

when was the last time you id a standard tune up? Fuel filter/spark plugs/air filter?

[BCC93QT]

Starts right up after it stalls everytime? a bad MAF is hard to diagnose unless you get another working one in there. Fuel pump control..... Try to undo and reconnect some vacuum lines.... tighten hose clips and clamps.....

[RustyBucket]

Have someone else start the car up and try to keep it alive while you watch the tailpipe. Check for the smell of unburned gas coming through the tailpipe (it may smell kind of like paint thinner).. any visible emissions? When my MAF needed cleaning, my Q would sometimes have trouble idling and you could smell unburned gas out the tailpipe. It also gave trouble starting as well, though. A bad MAF could do the same thing.

Also, does it only do this when cold? Does it idle fine by itself when warm? If it idles fine when warm, I'd suggest looking at the IACV.

[Lokim]

Try unplugging the MAF and starting it. The computer will sub a value and the car should run if the MAF is the problem. Are you getting any codes?

[SunnyTk]

Did a full tune up 4 months ago when I bought the car, didn't need too, but I always do.

its unable to fully start. it will instantly catch very roughly, go to to about 3-400rpm, and instantly die. doesn't matter if I mess around with the throttle or not.

I thought the problem was the fuel pump. the fuel pump was very loud, and initially when my car didn't start, I thought this was my problem. Before I replaced the fuel pump, the car wouldn't catch at all.

This problem only started when it became -1 Celsius outside (im in Canada lol)

Speaking of the MAF... I just discovered an unplugged harness that breaks out of the main harness around where the MAF harness goes into the main harness, underneath the rubber accordion intake pipe. I have no idea where this grey 3 pin/wire connector goes... it seems important cause the gauge of the wires and its grey....

Thanks for your help soo far... ill try unplugging the MAF in a couple hours before I head into work

[goody90q45]

It sounds like you may still have a fuel problem. Are you hearing the fuel pump prime for 5 seconds when the key is turned to the ON position without starting the engine? Since you mentioned a noisy fuel pump that you replaced it may have damaged the fuel pump controller (FPCU) in the process. A simple test would be to bypass the FPCU which in turn runs the fuel pump on its highest speed.

From the trunk, unplug the connector from the FPCU which is located under the rear deck, passenger side, seen in the background in the pic. See any evidence of charring on the connector pins or FPCU? Run a jumper wire from the connector pin shown in the pic to ground. The unpainted frame in front of the fuel tank works good if you're using a clip. If the engine starts and runs well the FPCU needs resoldering or replacement.

Weather permitting......If bypassing the FPCU doesn't pinpoint the problem then measure fuel pressure by teeing into the fuel line past the filter. A simpler test would be to unplug the hose, run it into a can, have a helper crank the engine and see if a good amount of fuel comes out. Be careful.

.....Speaking of the MAF... I just discovered an unplugged harness that breaks out of the main harness around where the MAF harness goes into the main harness, underneath the rubber accordion intake pipe. I have no idea where this grey 3 pin/wire connector goes... it seems important cause the gauge of the wires and its grey....

Is it a small, flat connector, 1" x 1/4" in the area of the power transistor mounted on the spark plug cover? We all have it. If it's larger like the TPS or MAF connector then you've probably found your problem.

[OwnerCS]

I see MIke posted the note I was thinking about a couple minutes before mine -- so disregard..

If I understand correctly, the car hasn't returned to running mode since the fuel pump started making noise and it was then replaced. Replacing the fuel pump helped a little, but it still didn't return to running mode?

I read stories about the Fuel Pump Control Unit (FPCU) burning out when the fuel pump operates in a noisy mode for an extended period of time. FWIW the fuel pump should be replaced as soon as it starts making noise. Some people replace the fuel pump at 100,000 mile intervals as a preventative maintenance item.

Do you have a copy of the Field Service Manual (FSM) downloaded to your computer?

I understand there is a way to wire around the FPCU to determine whether it is causing the problem. Though I don't have that instruction at my fingertips it should be easily found using the Search capability.

Do you have any "self pull" part salvage yards in your area where you can find a Q45 with a used FPCU? I recently purchased a used FPCU to keep on hand as a spare for $25 from a self pull salvage yard.

[SunnyTk]

No it wasnt the TPS or MAF sensor plug, I plugged the unplugged connector into its loose counter part harness and it didnt make a difference, I bypassed the fuel pump computer during my initial test to find out it was my fuel pump. Ill try bypassing it again now with a working fuel pump....

I also tried starting the car with the disconected MAF... no difference.

There are literaly no Q's at any yards in this part of canada

[RustyBucket]

Can you post up a pic of this connector and the area it is in? If your Q is a Canadian market Q like mine, I could do a quick comparison and take a photo of the same area on mine.

I seem to recall something about most Canadian Q45s coming equipped with TCS... Maybe the connector is related to that.

I hear ya about the lack of Qs in boneyards up here. I'm pretty sure that since I bought my G50 I've only seen about 3 others, 4 if you count the one my wife spotted in Hamilton that I missed. Come to think of it, I've only seen 2 Y33s and 2 F50s as well. I spoke to a parts counter guy back in April who told me he worked for Infiniti when the G50 was new and he told me that the Q45s on the lot got flat spots on the tires because they sold so poorly. The $72,100 price tag probably didn't help matters any.

[SunnyTk]

Ill post a picture Wednesday when im not working during the day...

NEWS: Soo I bypassed the Fuel Pump Computer, and the car ran and idled perfectly!!!! but it was running super rich... not sure if 100% was caused by the whole bypassing procedure or cause of that mystery harness i connected lol

ALSO for got to mention... The fuel pump i used to replace the OEM q45 fuel pump, was an aftermarket fuel pump. Walbro 255LPH fuel pump fit for the 300zx. it fit perfectly, just have to re-wire the fuel pump to the oem fuel pump wires. (which is really simple. a red and black wire...)

[goody90q45]

You don't want to run too long with the FPCU bypassed or the consensus is you'll be replacing the fuel pump in a short while. The pressure regulator at the end of the fuel rail should keep the psi in range so I don't think the FPCU bypass is causing the rich condition you're describing. It wouldn't be a bad idea to check fuel pressure just to make sure.

If you're good at soldering the FPCU is repairable. Chances are the ground circuit (the one the bypass clip attached to on the connector) has a melted solder joint. Do a search, lots of threads are available on the repair.

[SunnyTk]

yeah im driving the car. I just bypassed the fuel pump computer too see if thats the problemits running way to rich.

my brother is good with all that electrical stuff, im going to give it to him tomorrow to see if he can get it fixed.