q45 Stalling/Dying

[black g50]

[Turbon8er]

so dude dipped out?? COOL!!

now i'm gonna jack his thread like a crackhead

SOoooo on July 4th (last week) my fuel pump went on the fritz. (i think it's the FP). It was great.. i missed not only fireworks n cookouts, but a first date with an incredible young lady because my old ricebox s*** itself. Awesome sauce.

So i managed to limp it to my shop 12 miles away, cutting off and bucking like a bronco the whole time. I went in the trunk and listened, it did kinda sound like a swarm of bees, but not crazy loud. I remembered what Goody said about the FPCU and tried messing with it some, but didn't quite understand what pin to ground since the connector wasn't pinned on the jumper's location (in his pic). I thought about grounding the FPCU port's corresponding pin, but didn't have a computer handy to look up the diagram, and reallllly didn't feel like cooking my unit on chance.

While i had the FPCU disconnected, no jumper, i started the car (forgetting it was unplugged) and it ran fine for a min, until i realized i left the FPCU disconnected and i shut it off. Plugged it back and started the car again, it ran just the same. At this point the car had sat a couple hours. So i let it run for 15 min.. nothing out of the norm. I kept it running for literally an hour in the parking lot thinking maybe that circuit needed to get hot, revving it to simulate gear changing w rpm's, let it idle, kept it at the cruising rpm that it was previously stalling at (~1.5k).. no stumble. It drove me nuts. i could Not reproduce the problem!

I have a parts Q45 and was gonna rob the fuel pump out of it, but couldn't find the only key i have, which was probably a good thing since it's only a few thousand less miles than mine (@ 177k). After wrestling with myself, dumping over toolboxes and stomping around like a pissed off 4 yr old, i went home and decided to just order a new Fuel Pump. Found one BNIB OEM Bosch on ebay for $123.xx shipped to my door from Mrfuelpump in Miami, Fl. Bam. Done. Ordered Friday, got here Monday. word.

I did some searching on here, but i've got tons of other stuff to do besides dig through piles of unrelated posts. Would someone be kind enough to just tell me if i really have to remove every connection off the fuel tank for enough wiggle room to get the pump out?? I HATE dealing with gasoline.. it just permeates everything forever, and i dont think pulling it out through the rear deck lid pocket is worth a drop of gas having the chance to reach my interior. And removing all that rear section isnt much fun anyways.

I took a pic of the whole tank area to indicate all the components and verify before the removal process, but i cant upload them at the moment. So you could just tell me, since i have it pretty well memorized at this point. I'll post some pics of the swap after if wanted.

Thanks guys!!

[black g50]

Unbolt the 3 connections on top. Pull pump out turning towards you,carefull of the float arm while removing from trunk.20 min job,start to finish.

[Turbon8er]

^thanks btw.

So i did the backseat, rear interior removal. I think it might be necessary to remove the black plastic middle tray to get the room to pull out the pump, but i didn't try with it still in, only out, which definitely made it easier. After installing the new fuel pump, the car was doing the same thing, it was late and i went home for the night. I returned the next day. I was originally mistaken on which module the FPCU was, and realized this while reconnecting the FP harness once i replaced the pump. None of the pins looked to be scorched, and taking the FPCU apart showed no signs of a cold-solder, burnt circuits or any loose connections. I didn't have my multi-meter with me at the time (note: never let your step-brother borrow important tools), so i couldn't check continuity.

Next day.
I remove/inspect/re-assembled the FPCU, put it back in the car, and all the problems were gone. It ran fine. It ran better than before in fact. Took it around the block, fine. So i drove it all day sunday (maybe 100 miles in total) stop and go, romp-n-stomp take offs, long distance highway cruise in the heat of the day. It was fine. Then coming back from a friends house at 3am on the highway, nice cool weather, it starts hiccuping. I throw it in neutral (while cruising) and rev it, revs up fine. Back in D(rive) it bucks. Hitting bumps didn't seem to make a difference, so i dont think something is loose. It feels like it loses all fuel momentarily. No lights dim, nothing seems to be wrong electrically (outside of something controlling fuel or ignition) i did get a CEL flash, but it was late and i didn't check it.

I know an injector has to be going out, but it shouldn't act like it is just on that.

i hate to be THAT Guy, but does anybody have any ideas? i just got bombarded with a ton of life changing s*** this weekend, so i'm not up to par on my typical 'car-mindedness' at the moment. I just need this thing running, because i have 5 cars to sell and all my tools to move in the next 30 days.
Thanks again fellas.

[db_autotek]

With the engine running (but cool) , get close to the plenum and check those several small vacuum lines in and around the throttle body, especially those running under the plenum. Feel and listen for any leaks or cracks in the hoses.

I spent a couple frustrating weeks doing all manner of wrenching... Only to eventually find the 1cm cut in a vacuum hose by the plenum.

[Turbon8er]

thanks db. I'm gonna check that again after work. I did listen closely to the plenum area for any vacuum leak noises, without hearing anything prominent, but didn't inspect any further. That's definitely a good idea though.

Did you encounter the car stalling or cutting out with the leak you found?

[db_autotek]

Oh yes, exactly the kinds of symptoms you had described. Although it was fairly constant, not intermittent.

[Turbon8er]

so i tugged and wiggled every line i could get to and found the vacuum line coming off the very front solenoid (maybe swirl control or something secondary) under the driver side front plastic to be split, But with the line taken off on engine side, it runs fine. i felt the suction with my finger to make sure it wasnt clogged. i stuck a new line on it and drove it.

The Problem came back same as before. Once it is warmed up and cruising it intermitently acts up, CEL comes on, and it progressively gets worse. It knocked off while i pulled into a gas station, then when i started it back, it was seemingly fine. A few miles down the road same thing, progressively worsening. If i goose it constantly it doesnt do it nearly at all, and the injector-type of vibration is now evident at a lower speed. It was coming in only at 70mph rpms, now its also noticeable (to me) at 50mph rpms. Im gonna check the resistance in the morning, but there's just no way one or even two bad injectors would make it die like it is..... or at least i dont think so.

thanks for the help though, at least i feel like something got fixed... even if it did nothing for my big problem. lol

[Brew Q]

Gotta be fuel cutting out... and since you replaced the pump, I bet it's the FPCU. I don't think 1 or 2 injectors would cause the bucking you describe. Do you have access to a bone yard where you can pull another FPCU to test out? That or check ebay for one shipped to your door.

We need Craig to chime in here...

I don't have the time / experience on Q's, but that's my 2 cents.

[Turbon8er]

that's what im leaning towards. I actually have a '94 Q that i bought as a parts car (the motor n transmission I swapped into mine), and was going to pull the FPCU out of it, but i cant find the frackin key!! It's driving me crazy. I suppose i'll drill the lock cylinder out.. which i was trying to avoid. But that car has almost as many miles (167k) and it went from Michigan to Texas to Pennsylvania... so i'm kinda leary about it's FPCU condition. My FPCU looked fine, no scorching or visually evident cold solder on the board.

It's so intermittent that i feel crazy... like it's fine, cruisin'- chillin, then it goes full-retard. I literally even had a lady in a Prius flip me off today because of it. I guess there's a first time for everything.

[goody90q45]

Is the check engine light on?
Listening from the trunk is the fuel pump buzzing like a swarm of bees?

You haven't mentioned the CEL being on and haven't responded to Wes' suggestion about the fuel pump being the culprit so I'll take a wild guess and suggest that the fuel pump controller (FPCU) has a bad solder joint that doesn't act act up until the circuit gets hot. The FPCU is mounted under the rear deck on the passenger side above the fuel tank. You can get to it easily through the trunk. Try unplugging the connector and run a jumper from the pin shown in the pic to ground. (When you unplug the connector is there any scorching on the FPCU pins?) If the engine runs without stalling the FPCU is bad. If it doesn't start you could have a bad fuel pump. The FPCU can be repaired by opening it up and resoldering the connections in the ground circuit. Let us know what you find.

......I remembered what Goody said about the FPCU and tried messing with it some, but didn't quite understand what pin to ground since the connector wasn't pinned on the jumper's location (in his pic). I thought about grounding the FPCU port's corresponding pin, but didn't have a computer handy to look up the diagram, and really didn't feel like cooking my unit on chance......

I reread the thread and realized that you didn't understand how to bypass the FPCU. The picture I posted only shows the pin on the FPCU connector that you need to run a jumper from. You need to build a jumper cable (a wire with an alligator clip on both ends) and connect one end to the connector pin shown in the pic and the other end to a grounding point. The frame between the fuel tank and the trunk works well since it's unpainted. You'll be leaving the connector unplugged from the FPCU as you drive the car for a couple of days and see if the bucking/stalling comes back. The fuel pump will be running on high speed only but all the excess fuel being fed to the injector rail is pressure regulated and goes back to the fuel tank. Let us know if this solves the problem and we can go over the solder repair to the FPCU.

[mattd1979]

I just posted a shorter version a split second after what was just mentioned above but deleted it because it was unnecessary at this point. Anyway, what he said. LOL

[Turbon8er]

ok... thanks guys!!! i actually have a jumper laying in the trunk now from where i was going to do that. lol. The reason i didn't do it, which doesn't make sense if you're looking at the ACTUAL FPCU connector, is that the pin on the plug i was looking at did NOT have a wire in that location. Hence the "i dont wanna risk it". Turns out i was an idiot and looking at the wrong module (on driver side). Once i looked at your picture again, i realized it was toward the passenger side and shared the same harness as the pump, which made more sense.

I then removed the correct module, FPCU, and visually inspected the board and connections. It looked ok. I didn't notice any burnt areas or scorching, but i know a cold solder or bad connection is not always visible. In fact, i wiggled the connector before i drove it today and it was goofy for a few minutes immediately. and intermittently afterward.

I'm gonna try it once more after work tonight. thanks again!

do you have a link for the FPCU repair? you can post it here, since i'm sure i'll be pulling that thing back out and heating up the soldering iron in a couple hours...

[goody90q45]

.......do you have a link for the FPCU repair? you can post it here, since i'm sure i'll be pulling that thing back out and heating up the soldering iron in a couple hours...

The connector pin that you are jumpering from is the ground circuit so match it up to the same pin on the FPCU and examine the circuit internally. On the few sensors I've repaired there's usually been a brown residue around the solder joint so just melt it with a solder gun and add a bit more solder if necessary. Start where the ground pin enters the FPCU and work your way down the circuit board resoldering the solder joints on the ground circuit, even if they don't look like they've melted. I'm a hack at soldering but have been able to do the first 3 or 4 solder joints on the circuit easily and have repaired a couple of FPCU's this way.

There have been a couple of members over the years post pics of their repairs so you should be able to find these using the SEARCH function.

[Turbon8er]

I'm uploading two videos i took last night after doing the FPCU test. I'm not sure that the FPCU has anything to do with it. And the only code i pulled from the ECU (led flash) was 46, Secondary TPS. I watched it flash plenty of times to be sure. I pulled the code after the following.

After i jumped the connector pin to ground (on the unpainted metal brace) and started the car, the fuel pump wound up and was quite obviously running at it's maximum output. Ok. Then i brought up the RPMs slowly, then quickly, let them fall slowly and quickly. Everything seemed to respond as it should, i cut the car off. A few minutes later i restarted with this result:

[youtube]http://www.youtube.com/watch?v=-C2VoDUM9bU[/youtube]

Puzzled, i gave it a minute, then restarted it. It ran normal, no CEL thrown.

[youtube]http://www.youtube.com/watch?v=aF0JZeoutoU[/youtube]

wtf. I wouldn't think a secondary TPS would make it act full-out stupid like this. Any ideas?

i guess i never mentioned that my TCS and Slip lights have been on since i put this motor set in. Hence the piece of paper over the lights. I didnt care b/c the TCS was just a pain in theass to begin with. I'm much better at counter-steering the loss of traction, than i am at dealing with the reaction of this things TCS.

edit: i'm wondering now if i accidentally cleared the code out before i read it. I did go through the sequence of retrieving a couple times before i realized it would repeat the flashes. And clearing the code is pretty much turning the diagnostic knob back to it's original position. fml

[Brew Q]

seems obvious, but have you already checked the MAF?

when I was much younger and dumber, I cut wires to a MAF on my maxima at the time... before I fixed my stupidity and wired it back up correctly, the car ran almost identical to the top video - like it was running on half the cylinders.

[OwnerCS]

seems obvious, but have you already checked the MAF?

when I was much younger and dumber, I cut wires to a MAF on my maxima at the time... before I fixed my stupidity and wired it back up correctly, the car ran almost identical to the top video - like it was running on half the cylinders.

Very good point Bret!

[black g50]

Been a few months ,my hiccup hasn't returned.Have you checked your I.a.c.? Mine was turned pretty far out.Maybe sucking too much air? Last time a consult was used,I was lean on both banks even after replacing pump,maf.o2's came yesterday gonna have em put in.Had 4 bad injectors one time,this doesn't seem like the problem.

[Turbon8er]

While i'm not completely ruling out the MAF, i'm seriously wondering if it could be the Secondary Throttle body, since it is basically a big butterfly valve that closes (air intake) to kill motor power, thereby eliminating wheel spin. I want to completely rid my car of it's uselessness anyways. I suppose for the moment i'll just remove the butterfly and it wont have the chance to operate, even if it tries to.

If it were the MAF, then i'd think the idle would be erratic, or at least consistent, but it isn't. It would actually level out at idle if i didn't touch the accelerator.

just realized i didn't push "submit"... 5 hours ago. lol. ugh.

[Turbon8er]

Used two different multi-meters last night and the main injector harness is showing 52 ohms on 7 injectors and 61 ohms on #1. Went straight to injectors, showed 11.6 ohms and then 25 ohms on #1. I'm guessing the under plenum harness is toast? Also one knock sensor read .524 and no reading for the other, maybe it's bad or disconnected? The last owner(engine) said he just did the knock sensors and all injectors, i even have his receipts, but i guess it's time to pull the plenum and re-do some stuff.

(edit: for reference, i went through the receipts and found 8 injectors, 2 knock sensors, 8 NGK laser platinum plugs done 5/2010 @ ~130k; 173k on motor now)

I'm not sure if the sum of all these things could lead to the car acting like it is... but it's gotta be fixed anyways, so i guess we'll see.

Can someone tell me the difference (what it means) on injector markings?? I looked on Rockauto and they specify injector with black mark or white mark, and they have different part numbers to each. I need to order one, and get this thing going asap.

What is the best OE injector brand to go with?

[OwnerCS]

A few guys (me included) have used BWD black dots. The color code usually means a spray pattern consistency (or tolerance) level. I think BWD black dots may be the most expensive.

I think Deatschwerks in OKC remarkets BWD injectors. If you get a full set try to get all with the same color coding for a uniform spray pattern.

[pilot_456]

@black g50
Sorry man! I haven't been on nico for a while. And I gave up on the Q45. I pulled the engine and am now going to keep it as a parts engine for my vh45 swap into my s13.



I strongly believe the wiring was f*** though. After I pulled the harness I found that it had been moved before and there were places where it looked like the PO had messed with it.