My Q45 has stalling problems

[danby]

Hi I am a new member and live in Queensland Australia. I know nothing whatsoever about cars.My 1993 Q45 has 385000 kilometers(purchased with 185000km. 8 years ago) and is having stalling problems when coming to traffic lights and on the freeway it starts to shudder madly.I have always had it serviced at a Nissan garage(very expensive).The transmission has been refurbished 3 years ago and the car has been servised every 10000 km.Two years ago the fuel pump was humming so I replaced it with a new one. The car always starts and ticks over smoothly but every now and then have the above mentioned problems.Reading through your forums some have mentioned that the FPCU should be replaced the same time as the fuel pump.This I have not done.Any help would be gratefully appreciated.

[Jesda]

Is it bucking and jerking at cruising speeds? It sounds like a mass air flow sensor going bad.

Post this question here for better answers:
q45-forum-cima-forum.html

[danby]

Thanks for your response Jesda. It jerks and bucks sometimes when you start driving and the engine is cold.( If i drive into the city I travel at 60km.p.h. for about 3 miles and it is ok.Then I speed up to 100 km.p.h. on the freeway and it starts to buck and jerk and engine stops.After stopping for a few minutes I restart and drive slowly for 10 miles and then increase speed ,she is ok)

[goody90q45]

Is it bucking and jerking at cruising speeds? It sounds like a mass air flow sensor going bad.

Jesda knows his Q's (and P's) and you could very well have a bad MAF but here's a couple of things to look at first.

At idle are the rpm's bouncing up and down between 1500rpm and 0rpm? If so it could also be a dirty and/or loose MAF connector. Pull the MAF connector and if it has any corrosion present clean the connector and MAF pins and lube lightly with dielectric grease. Tighten the 3 pins in the connector to look like the middle pin in the pic. If they all look like the pin on the left the connector is loose and tightening, cleaning and lubing will help.



When the engine is acting up does it lack power and take longer than normal to get up to speed? If so you could have a FPCU with an intermittent problem, usually a melted solder joint in the ground circuit. To see if it's the FPCU causing the problem it can be bypassed which will run the fuel pump on high speed only. Reach in from the trunk and unplug the connector from the FPCU. It's mounted under the rear deck on the right side and can be seen in the background in the pic. Run a jumper from the connector pin with the clip in it to ground. The unpainted support in front of the fuel tank makes a good ground. Take her out for a spin and if the problem goes away the FPCU is bad and will need repair (DIY) or replacement (>US$700).



Has the fuel pump started to buzz again? A dying FPCU can kill a new fuel pump which is why they're normally serviced/replaced at the same time.

Let us know what you find. Welcome to NICO.


Can a mod/admin move this thread to the Q45 forum?

[danby]

Thanks Mike. At idle the rpms sometimes do bounce up and down as you explained. When the engine is acting up it lacks power and takes longer to get up to speed especially going up an incline. As i mentioned I am not a DIY type but also dont want to take it back to the garage as they could not resolve it the last time it went in for service.Only about 100 Q45 cars were sold in Australia in the early 90's and there are only a few mechanics with experience, mine included. Parts are also at a premium here in AUS. Where is the best place to purchase a MAF sensor and FPCU and I will attempt to install. Hopefully this will resolve my problems.I will also check to see if the fuel pump is humming. Many thanks

[goody90q45]

Our Infiniti Parts forum is a good place to buy used and your Nissan dealership may be able to help with parts if you buy new.

Both tests I explained are easy so don't throw $$ at parts until you've done the diagnosis. Do you know anyone with a little bit of mechanical aptitude that could help? A caveman could clean and tighten the connector pins for you.

We have a few aussies in the Q45 forum, all with active suspensions. You may find a member/owner closer than you think.

[danby]

Thanks Mike. Yes I do have someone who can help but he is difficult to tie down. I should be able to check out the MAF sensor connector myself and possibly the FPCU. I have given the car to my son to use so will do the check tests you reccomend when i see him.Of course I would like to save $$$ but if I have to purchase parts it would be a lot cheaper from the US then here.They wanted something like US$900 for the fuel pump plus installation charges.I bought a new one from the States for around US$300 and my friend and I fitted it.

[danby]

Mike, I forgot to mention that soon after we fitted the fuel pump 18 months ago, I was loading something in the trunk while the engine was running and I heard a shorting/ crackling sound coming from near the FPCU. I thought it was shorting the speaker which is located near the FPCU.Since that day I have never turned on the radio.Perhaps it shorted out or melted something on the FPCU which is causing my problems.However I will do the checks you reccommended.Cheers Danny

[Jesda]

Those Bose amplifiers are known to make crackling sounds after a decade of service. It is likely unrelated.

[Ozzie]

Can a mod/admin move this thread to the Q45 forum?

You got it Mike
Hey danby, welcome to the Q45 section of Nicoclub.
There are lots of guys here who can help you out.
I have had parts shipped out here (Australia) for me on quite a few occasions by these guys.
Their knowledge is good, and their kung-fu is strong.
Use the search function to find solutions for any problems you come across.
(It has saved my butt plenty of times!)

[danby]

I have checked to see if the fuel pump I installed about 18 months ago was humming.Unfortunately it is humming.So does this mean I have to replace the Fuel Pump again but this time repair or purchase a new FPCU as well. By doing this will it also solve the rpm's bouncing up and down at idle or is this unrelated to the Fuel Pump and FPCU.When I get the opportunity I will do the check on the MAF as you suggested , Mike.

[maxnix]

Not if it is a soft mum inaudible for the most part at idle inside.

Check your FPCU board first for burned out resistors.

[qship96]

If the fuel pump is just barely audible while sitting in car at idle with radio/hvac fan off, it does not need replacing {my brand new oem 2nd pump was audible under these conditions and lasted over 150,000 miles. My recently installed 3rd pump {Bosch} is dead quiet.