'92 Q45, appx 215K miles: A little history.... I replaced fuel pump Aug 2004 as a preventative measure (getting noisy). Everything was fine but occasional flat spots and sluggishness (like once a week). I had injector cleaning, intake cleaning, and fuel filter replaced at dealer in early May 2005 (was hoping it would help, but actually got a little worse). Also used a bunch of Isoheet, but didn't help.

The last 2 months car was more sluggish and would surge slightly at 3-4K RPMs in 2nd gear (like climbing a hill) and was also sluggish from a start (even with 1st gear start '93 TCU).

So I went to T-3 last week and Bryon checked everything and said low fuel pressure was bad pump (one year old pump). So he replaced the pump and then checked the fpcu (control unit) and said it has a few "hot spots", so he suggested replacing that too. Car was much smoother and more energetic with new pump & fpcu. Picked on car on Thursday and all was fine (also new front shocks, rotors/pads all around, and replaced fuel hoses which were leaking again after 18 months).

Friday on the interstate the engine shut off abrubtly once but then started back immediately. Did the same thing once on Saturday on interstate. I took a short trip on sidestreets tonight and engine shut off twice while idling at a stoplight (had to crank to restart). The shut off seemed a bit abrupt to be bad gas or water in the tank.

I drive the car for about 45 minutes tonight on interstate and a few fun roads and has the shutoff problem at highways speeds at least 6 times and it stalled twice at a stoplight. I was hoping driving hard would help, but guess not.

I'm thinking maybe the new fpcu is bad? Since it happens so fast it seems more electrical than mechanical. I think I'll drive it for a few more days and see what happens.

Is there any break-in period for a new fuel pump or fuel filter?

No break-in period. My new pump gave new life to Layla.

Sounds like electrical. Any CEL (check engine light)?

When my MAF was making a poor connection, it would die on the interstate, and I would have to put in in neutral, and re-start it. But it would bring on the CEL, ususally.

I am sure Byron can get to the bottom of it.

No CEL. Byron checked MAF, O2 sensors, injectors, power balance, etc. last week and said all were fine. With 15 miles of mixed driving so far today it's been fine. I think I'll try to burn through this tank of gas and then do 2 bottles of isoheet in 1/2 a tank, see if that helps.

Wondering if it might be a charging problem? Battery is less than 2 years old and I never have problems starting, so I think alternator is charging OK.

Was your replacement FPCU used or new?

Heath

FPCU is new, but one that T-3 had in stock, so not sure if it was sitting around a while. Is the part the same for 90-93? Or does it work for 94-96 too?

I checked connecters today and they look OK. Car stalled twice last night, and only one slight hiccup so far today.

Now I'm thinking it may be battery or alternor issue. I got a "low battery charge" the last time it stalled tonight, and has been harder to start today for the first time. Ugh.

greg_atlanta wrote:FPCU is new, but one that T-3 had in stock, so not sure if it was sitting around a while. Is the part the same for 90-93? Or does it work for 94-96 too?

no. and yes.

there was a revision at some point. the early fpcu p/n -60u00 i think, had a single capacitor near the 'vulnerable' power transistor. the later one [didn't record the p/n, but i noted it was different] has dual parallel capacitors of higher rating. pure speculation on my part, but perhaps the engineers realised that fpcu's were getting smoked [albeit from an external issue--i.e. the pump going bad] and 'beefed up' the later versions.

i've used both p/n's in my car with no issues.

The positive battery terminal was not 100% tight, I got about a full turn on the screw last night (not loose by any means). Figured my problem was solved..... but still acting weird. Guess I'll visit T-3 tomorrow.

Sounds to me like you need to take it back to T-3 and ask what gives? If you got charged 3 hrs labor for the fuel pump, which takes 30 minutes to change, I hope they removed and cleaned the gas tank to get rid of the grime as well. Certain T-3 folks swear that is how it should be done and for 3 hours labor for a 30 minute job, I hope that's what they did.

That's some serious problem having your car shut off on the Hwy after being worked on at T-3.

red

Nope cleaning the fuel tank is extra..[2-3 hours plus disposal of gasoline]...........still waiting to see someone change a pump and fpcu [the correct way] in 30 minutes [or even 2 hours] without bending the fuel level sender arm and changing calibration.

Time: In the bay door, out the door including time spent diagnosing [attaching fuel pressure gauge and test drive [at least 15 minutes to take or test route] plus service writer time and bill paying time............nothing is free unless you do it yourself.

Old Q are a constant challenge as all the old wiring, connectors, system are worn out [way beyond any Japanese engineers concept of usable life].

Even the electronics gets tired as capacitors have a maximal life based on temperature cycles.

Q45tech wrote:still waiting to see someone change a pump and fpcu [the correct way] in 30 minutes [or even 2 hours] without bending the fuel level sender arm and changing calibration.

Nope, I didn't bend the sender arm when I did my fuel pump. With care and a little patients, you can get it in without bending the arm. It helps doing it with two people. I lowered the FP from the back seat while my buddy guided it in from the trunk. My FP works fine now and the fuel gauge reads correct.

When you use 2 people you have to pay for 2 people.........back to the alleged 30 minutes for changing a pump and the fuel pump contoller and all the diagnose/testing time to determine IF a new pump is necessary!

Many times 2 people are not twice as fast as a single tech unless they practice together a lot to optimize the movements.

I'll be happy to push the stop watch button to time the operation.

In my 93, I got the fuel pump in and out of the car in about an hour.

As I understand it the new problem [greg_atlantashutting off] is now a bad MAF [intermittent inside].........when it rains it pours. More testing and a swap out will tell [prove] the story.

MAF tend to commit suicide in Summer. Especially on newer models why Nissan recently made it a screw in assembly into housing........however the ecu must be recalibrated every time you change the MAF element NOW....requires a Consult 2 to recalibrate........OBD2 scanner won't do it another reason the dealers get a lock up on many repairs

Reminds me to add a MAF to my "carried spares" along with FPCU, ecu, tcu until the weather turns cooler.

When it rains it pours.... yep, that's it.

Byron checked the car around Noon and consult was giving MAF code (it was OK last week... oh well). He said the stalling and stumbling I've had is perfectly explained by an MAF going bad. He said the idle was a little low so he turned it up a bit, but said I may also need a new IAC (idle adjust) since the idle screw was maxxed out.

Battery checked out OK. The positive terminal was a little dirty/greasy, so I cleaned that last night and used a new screw/bolt so it'll stay tight.

I cleaned the MAF screen with intake cleaner when I got home (just wiped the outside of the screen) and it was a little dirty, but not too bad. Can the MAF element be cleaned too, or is that risky? I'll probably replace it soon, but I'm curious to see if it gets better in cooler weather.

Looks like MAF is an easy DIY... but will the idle need to be adjusted again after I replace it? Does anyone know the appx cost of an IAC? Can't find it on Scottsdale site.

At least these cars are predicitable! I had MAF quick fix with ground wire done in 2000 shortly after I bought the car. 215K on one MAF ain't bad.

It took me about 35 minutes when I did mine. No bent sending arm with just me doing it. I did not change the FPCU however, just the Fuel pump.

I have a spare TCU, ECU, FPCU, Assorted hoses, two fuel injectors, suspension springs and some other things, but no MAF. A MAF would most definitely be a great thing to add to my spare list as well.

red

redmanfx wrote:I have a spare TCU, ECU, FPCU,....

As a note, the manual does not call these units, but modules.

Thus TCM, ECM and FPCM are the correct acronyms.

I knew ever time I let my Q get near a members car ---troubles wear off.

Now my MAF is going crazy in heat -- as Greg says 15 years is a long time.

" PAY ME and ......................"I'll love you long time".......American" Japanese Bosch

Sorry!



My car drove like a dream yesterday, but kept stalling again today after sitting out in the sun for two hours. I'm going to clean the MAF and connector one more time see if it helps.

hey man....i have a '93 q45a and i recently had the exact same issue and i believe i have your answer. luckily for me the fuel ecu harness made it somewhat obvious to anyone with a little electonics experience. what happened to me was the harness burnt up on the lower left pin (white wire) which according to the schematic is the ground. what i did was to disconnect the wire from the harness , put on a ring connector , and just grounded it to the tank. this is how many/most other manufacturers will ground out their systems. this happened almost 3 months ago (mine too was an intermittent fault) and ever since i did that.....perfect!! i think this will solve your problem. at the very least mention it to whomever you let work on your car. hope to hear you're up and running again soon!

jesus:

I had the same quick fix done 4 years ago, now the whole MAF unit is bad.

New one is on the way ($360 + $30 shipping)....

Car is driveable now when started cold, but too much running around and it acts weird again.