Car runs great until throttle is given, then nothing!

[carcrazyguy]

Just as the title says. My dad has a 94 Q45 which starts up just fine and runs great if you are driving at light throttle. However, when the throttle is pressed, it absolutely acts like the fuel is not there at all...it will not go. You can back off of the throttle, and it will accelerate as normal but if you stay in it, it will basically accelerate as if the car has 75hp. Nothing has shown up on the screen either.Anyway, when this is going on, there are no weird noises, no bucking or anything...it just acts as if the car has no power although the engine sounds like it is opening up as it did before this problem started. Hopefully this is something that some of you guys can help diagnose. There is no Infiniti specialist within 100 miles of here - and there is no way I would take it to Billy Joe Jim Bob so he can "throw parts at it". However, if I cannot figure out this out soon, I think he will!!!

[maxnix]

Probably ought to post this in Infiniti Online Mechanic.

Why don't your start by reading the fuel pump and FPCU threads? Without a maintenance history nor any quantitative data, is it is difficult for us to isolate a cause over the internet. Check your MAF connection also by wiggling it with the car running at varying rpm.

Please look around and start with the Articles. You have found the best source of archived information for the G50 on the internet.
Modified by maxnix at 4:16 PM 8/24/2006

[carcrazyguy]

I have read several threads and will continue to do so. I just hoped someone had the exact same issue w. their Q and could be right on this one - I have had such luck in the past w. my cars!So far I have cleaned the MAF as I saw in one post. This did not seem to make any difference at all. After cleaning it it looked the same too - there was no visual difference, but then again, it looked nearly new somehow.The car doesn't really have a service history so to speak...has 190K (all highway) and probably nothing done other than regular stuff (fluid, belts, filters, etc) since it was purchased at 100K where it was bought from an Infiniti dealer - and they claimed to have done everything to make it current at that point.Either way, the car is super clean could pass for a 5 year old car, easy. But then again, this car has been driven all highway for about 6 years by a 63 year old and was a Doc's car before that (since new) and has always been a TN car. BTW, the fuel pump sounds quite audible, but he says it has always been that way. However, in my opinion, it is much louder than what you would think a $50K car would be. Is that normal for these cars? I have yet to own anything where it is this noticeable, even my Z cars.On a totally different note, upon browsing lots o' posts here, I keep seeing people quoting their Q45 as 4300 lbs. I remember reading many articles on these over the years and it was nothing like that. I looked one up and the published weight for one w. everything was 4015, and test weight (actual scale weight w. test equipment on board) was 4160. I have seen them listed in the high 3K's before too. Either way, that is ALOT, but I am used to forum people underquoting weight, if anything. BTW, I own a 3200lb Z32 which gets lots of flack about being too heavy too. Anyway, dad has been relying on local repair (hack joints) to keep his car serviced for years, and now I am in the picture - I will try to steer this in the right direction and use this forum to learn everything I can and keep his car out of those places that basically only have experience working on diposable stuff (Neons, Grand Ams. etc). Hope you guys can help save a Q from this fate!

[Q451990]

If the fuel pump is noisy I would absolutely replace it. The noise you hear is normal for a worn out pump! I think your acceleration issue could be a faulty pump, or it's controller if the pump fried it.

Heath

[Skibane]

When was the last time the fuel filter was changed?

[maxnix]

1.) So far I have cleaned the MAF as I saw in one post. This did not seem to make any difference at all. After cleaning it it looked the same too - there was no visual difference, but then again, it looked nearly new somehow.

2.) The car doesn't really have a service history so to speak...has 190K (all highway) and probably nothing done other than regular stuff (fluid, belts, filters, etc) since it was purchased at 100K where it was bought from an Infiniti dealer - and they claimed to have done everything to make it current at that point.

3.) BTW, the fuel pump sounds quite audible, but he says it has always been that way. However, in my opinion, it is much louder than what you would think a $50K car would be. Is that normal for these cars? I have yet to own anything where it is this noticeable, even my Z cars.

4.) On a totally different note, upon browsing lots o' posts here, I keep seeing people quoting their Q45 as 4300 lbs. I remember reading many articles on these over the years and it was nothing like that. I looked one up and the published weight for one w. everything was 4015, and test weight (actual scale weight w. test equipment on board) was 4160. I have seen them listed in the high 3K's before too. Either way, that is ALOT, but I am used to forum people underquoting weight, if anything. BTW, I own a 3200lb Z32 which gets lots of flack about being too heavy too.

5.) Anyway, dad has been relying on local repair (hack joints) to keep his car serviced for years, and now I am in the picture - I will try to steer this in the right direction and use this forum to learn everything I can and keep his car out of those places that basically only have experience working on diposable stuff (Neons, Grand Ams. etc). Hope you guys can help save a Q from this fate!

1.) If it looked clean and didn't have any film, it probably was clean. Failure to use OEM filters changed annually is the primary cause of failure. I won't even talk about CAI "mods."

2.) I assure you it does have an Infiniti dealer performed service history. Submit the VIN to the friendly service writer you have cultivated or register as the owner with Infiniti Customer Service. Then there are your receipts. Dealer maintenance is only sufficient to get it beyond intial warranty period after which failures are your expense.

3.) BINGO! We have a winner! Dont' fry your FPCU by continuing to drive it. See Tangaloras excellent post on fuel pump R&R.

4.) 4300 reflects all fluids, at least 11gals. of gas and driver plus various sundries.

5.) You can save it, we can't. My old man was the same way and nearly destroyed our 2800CS with incompetent garage mechanics.
Modified by maxnix at 8:40 AM 8/18/2006

[elwesso]

I agree on the pump... Try that first at least for maintenance..... It may not be the actual problem, but you want to do it anyway.....

[Q45tech]

Based on 10+ years in repairing 90-96Q we change many more fuel pumps and FPCU than any other component..........not counting the normal maintenance items: filters, spark plugs, lubricants, idler pullies and belts.

Then comes Alternators, water pumps, compressors..........MAF failures are rare unlike their connectors............even rarer are primary TPS and IAC.

Generally most things just need cleaning.

[carcrazyguy]

When was the last time the fuel filter was changed?

I forgot - I also changed that too for him. That didn't make a difference either however.

Quote »Based on 10+ years in repairing 90-96Q we change many more fuel pumps and FPCU than any other component..........not counting the normal maintenance items: filters, spark plugs, lubricants, idler pullies and belts.Then comes Alternators, water pumps, compressors..........MAF failures are rare unlike their connectors............even rarer are primary TPS and IAC. [/quote]I guess I will center on the fuel pump and FPCU for now then. So far at nearly 200K nothing has ever went wrong with the car, so I guess it might be time. His last car, an 89 Maxima SE (that he bought new) never had a single problem either, and had 280K when he sold it...so I guess he is lucky with cars (until now).

[Q451990]

So far at nearly 200K nothing has ever went wrong with the car, so I guess it might be time. His last car, an 89 Maxima SE (that he bought new) never had a single problem either, and had 280K when he sold it...so I guess he is lucky with cars (until now).

If by some chance this is the OEM fuel pump, or even the second, I would say he's incredibly lucky. These typically make it to about 80K!

Heath

[CrimsonQ]

My car had the same issues. Fixed by replacing the MAF wiring/connector.

[carcrazyguy]

My car had the same issues. Fixed by replacing the MAF wiring/connector.

Are you speaking of the little 3 prong connector? In other words, precisely what did you replace? Was it visually bad?

Quote »If by some chance this is the OEM fuel pump, or even the second, I would say he's incredibly lucky. These typically make it to about 80K![/quote]Obviously I am new to these cars, but hearing this really suprises me, particularly since these are Nissans. I have had many cars and never replaced a FP, MAF, etc. - most of them over 150K, often more. I have had (3) Z32's which might have the same or similar pump, and never had an issue either - actually never had any issue with my Z's other than the AIV - which goes out about every 50K and is an $80 fix. For that matter, I have an 88 MR2 with 210K and still has everything original, even the original muffler (but the tips have mostly flaked off). I am learning ALOT on this forum...I've learned that Q45's are still $40K-$50K cars, even when they cost $2500, for example. Kinda like the old expression, "there is nothing more expensive than a cheap Porsche"?

[maxnix]

I've learned that Q45's are still $40K-$50K cars, even when they cost $2500, for example.

As far as the Infiniti parts managers and technicians are concerned, it is a $50K car. There are is no further discount over the used price you paid for all the deferred maintenance. This is true of all cars.

[Q45tech]

It is worse than THAT because of inflation a $50,000 1994 Q is now a $75,000 vehicle and 5% of that a year is $3,750 per year in parts and labor.

Businesses budget 3-5% per year for maintenance of assets.

[Jesda]

When I had this problem, the FPCU was dying.

[carcrazyguy]

When I had this problem, the FPCU was dying.

I guess I will need to figure out if his car needs that or the pump itself.Unless there is a quick technique that someone wants to offer, I will research on this forum.

Just out of curiousity, why is the Q so prone to have problems in these areas and the MAF too? Yesterday dad and I were discussing it and he also is in denial and I could not give an explanation.

[maxnix]

1.) I guess I will need to figure out if his car needs that or the pump itself. Unless there is a quick technique that someone wants to offer, I will research on this forum.

2.) Just out of curiousity, why is the Q so prone to have problems in these areas and the MAF too? Yesterday dad and I were discussing it and he also is in denial and I could not give an explanation.

1.) Read Tangalora's excellent post in this forum.

2.) MAF failures usually are connector failures, usually caused by changing the oil filter form the top. MAF failures are caused by poor air filter maintenance or after market units.

You Dad is a drive'em into the ground type owner. All vehicles benefit from maintenance.
Modified by maxnix at 1:55 PM 8/23/2006

[carcrazyguy]

MAF failures usually are connector failures, usually caused by changing the oil filter form the top. MAF failures are caused by poor air filter maintenance or after market units. You Dad is a drive'em into the ground type owner. All vehicles benefit form maintenance.

Yes, he is more less like that. He has gotten away with it however for a long time...longer than many of us have been alive.Anyway, I am still stumped on the frequent failure of the pump and control unit in Q's. As mentioned I am a Z guy, and I would bet they have the same pump and nearly identical control unit. Also, they do seem to have nearly the same MAF (but the Z even has 2 of them). So why would a Q have all of these issues when I have never heard of a Z32 needing either - and people typically drive the crap out of them?

On the car...I have the seats out, and I guess I will physically inspect the FPCU (when I find it). Even if it is bad and is causing the problem, I will go ahead and urge him to get a new pump too - since it is relatively loud. He says it has always been like that since he bought it 6 years ago (over 100K miles ago) so my newest theory is that the pump has been slowly on its way out since then and is finally going kaputt, or worse, has messed up the FPCU. Either way, I will post as soon as I get this figured out!

So far this forum has been a big help. Maybe I should check out the Z sections here too. I have always used the more popular 300ZX forums, but you seem to get more "rice talk" on there and people looking to argue rather than be helpful.

[Jesda]

Just out of curiousity, why is the Q so prone to have problems in these areas and the MAF too?

Exposure to heat. It really needs a shield like MBs have around their batteries.

Also, the oil from K&N filters destroy them, and infrequent air filter changes cause large dust particles to hit the element at high velocities.

[peety]

driving down frwy and car hesitates then falls dead. Q45 1994

[peety]

the MAF sensorneeds to be cleaned? i am a first time Q owner. and at 148,000 miles i cant figure out why the car does this at about 60-70mph. i let off the gas and coast off into a lot. i waited a while then it cranked right up then i drove home at slow 20-30 mph. and a couple of time it did the same thing but never stalled. it wouldnt let me get over 30mph and sometimes over 20. but made it home w/o stalling. and the engine light comes on but goes right off atrer a little bit. no enough time to put on diag. this has stumped me for a little while now.

[maxnix]

no enough time to put on diag. this has stumped me for a little while now.

You will probably be stumped until you read more here, update us on your maintenance history, and probably get a power balance test performed by a senior tech.

Ignoring maintenance will render these cars (and most others) very expensive to repair quickly when parts need to be replaced or multiple labor repetitions are involved.

[carcrazyguy]

Update:

I did the jumper technique on the FPCU (will make some pics in a little while). The car ran fine! So I guess the car has a bad FPCU.

So now I am thinking maybe I will talk Dad into - getting a good used FPCU, a new fuel pump, filter (strainer?), and gasket. Just for good measure, I will also have him get a new MAF connector...seems like it is only $12 or something.

Seems like I remember someone that sells good used FPCU's on another similar thread I read the other day but cannot re-find...is that any of you guys? Also I noticed several people mentioning buying their OEM parts from a certain person that is on this forum, but I never could find a phone number or contact info. Does anyone know that off hand?

[CrimsonQ]

Update:

I did the jumper technique on the FPCU (will make some pics in a little while). The car ran fine! So I guess the car has a bad FPCU.

So now I am thinking maybe I will talk Dad into - getting a good used FPCU, a new fuel pump, filter (strainer?), and gasket. Just for good measure, I will also have him get a new MAF connector...seems like it is only $12 or something.

Seems like I remember someone that sells good used FPCU's on another similar thread I read the other day but cannot re-find...is that any of you guys? Also I noticed several people mentioning buying their OEM parts from a certain person that is on this forum, but I never could find a phone number or contact info. Does anyone know that off hand?

CALL JOE FOR ALL YOUR PARTS NEEDS, 1 888 216 5328 http://www.infinitipartsusa.com

There are several FP and FP control units for sale in the classifieds.

Most MAF's dont fail themselves, its the connecting piece. I figured that out the hard way by buying 3 of the damn things.

[carcrazyguy]

Thanks to everyone so far with all of the help. Hopefully I can also help. When I searched initially, I never found any actual pics although there were a few writeups that helped somewhat. Anyway, here is a super simple how to "bypass" the FPCU for test purposes that worked for me.

First make a jumper wire. A foot of wire 20 ga or better will be fine - put .110 male tabs on each end.



Now, remove the "wall" in the trunk that borders on the back of the seat.You will now see the fuel tank clearly.



Next, look above the tank slightly to the right directly under the package shelf structure. You will see the FPCU. It looks like a stereo amplifier and has a white connector with 8 pins.



Now, unplug the 8 pin connector and while you are at it, unplug the passenger side Bose speaker / amp connector (at the bottom of the speaker).



Keep in mind this means with the harness release tabs facing up.Plug your jumper wire into the bottom left female connector of the FPCU harness and the other end into the top left female connector of the Bose harness (which is a decent ground btw).



This is what worked for me. Car ran like mud before, and ran perfect once I did the test. Now I know for a fact my FPCU is bad! Hope this info helps someone.

[mcastro]

Great writeup! This is the kind of stuff that makes this community so valuable. This should be reposted under

"G50 FPCU Bypass Instructions (w/pics)",

so that it doesn't become one of the many buried treasures the SEARCH tool can't find when someone needs it.

Thanks for the post! Even the simplest of procedures can be made clearer with this kind of stuff.

[maxnix]

I did the jumper technique on the FPCU (will make some pics in a little while). The car ran fine! So I guess the car has a bad FPCU.

Well, not necessarily, unless you measured the fuel pressure, which should be >43 psi. Don't forget the new O ring.

A crude test is if it runs well at WOT until redline.

Try the pump first, and nice write-up!

[squeefoo]

Take the FPCU apart before you get another one.Look at the point where the pins connect to the board, and look if the solder is melted between the board and the pin(s).Then look at the 2 (or 4 ?) silver flat looking things on the sides and see if those are burned.

If the solder is melted try that first, then you might be able to save it and $$$$.When the flat silver-colored things are burned it's junk.

[carcrazyguy]

Take the FPCU apart before you get another one.Look at the point where the pins connect to the board, and look if the solder is melted between the board and the pin(s).Then look at the 2 (or 4 ?) silver flat looking things on the sides and see if those are burned. If the solder is melted try that first, then you might be able to save it and $$$$.When the flat silver-colored things are burned it's junk.

I took the FPCU apart already and it looked perfect at every joint, nothing burnt, no smell, etc - I could not have imagined it in better visual condition. Aftert doing some thinking, I relized that by bypassing the FPCU in my test, I was also bypassing the TPS and the MAF more less too, right?So yesterday I tested the TPS and it was within spec. I removed the MAF cap and it smelt a funky inside that area, so the problem now could be the MAF...but the connectors and the actual air flow area look perfect.Unless someone has any more ideas, all I know to do at this point is buy a good MAF and FPCU and see which is the issue, but I guess I will try to start with the MAF to potentially aviod buying an unnecessary FPCU.Too bad there isn't someone locally that had a good running Q to "borrow" a MAF / FPCU from just long enough to see what the deal is.

[maxnix]

Aftert doing some thinking, I relized that by bypassing the FPCU in my test, I was also bypassing the TPS and the MAF more less too, right?

No, you only by passed the FPCU control from the ECU.

You can check output votage of the MAF, if you have a very accurate DVM.

I would check fuel pump pressure first.