1997 Q45 P0400, P0171 - Lower Intake Gaskets

[fontana dan]

Hello all,

I'm planning on doing a full plenum job on this car including lower intake gaskets, knock sensors, fuel pressure regulator. Can anyone give me some insight on parts I should gather for this job besides the obvious? I'm really convinced theres something down there leaking vacuum. However I am faced with this hellacious vacuum schematic on Amayama


Is there any easy way to Ohm the injectors on the VH41? As a replacement can anyone vouch for the Beck/Arnley 1580861 on rockauto?

Since purchasing this car 2 years ago I've been dealing with symptoms of a vacuum leak but I've been unable to chase it out. I've also recently started noticing some PING around 1600-2100 RPM. There is also a lack of throttle response in this range - the pedal just feels dead. The car will set P0171 and P0400 once in a blue moon.

[fontana dan]

Right now this is my parts list:
Intake Gaskets upper/lower: BECK/ARNLEY 0376161
Knock sensor: HITACHI KNS0001 (I will need 2 of these, correct?)
Fuel pressure regulator: BECK/ARNLEY 1580912
-What is the function of this fuel pressure regulator? What happens when it goes bad? Will it cause an extended crank on a hot restart?

[VStar650CL]

The FPR reduces fuel pressure when high vacuum is present (idle and low power demand) and increases it when vacuum drops (open throttle, high power demand). It can cause hard starts (especially warm) if the internal diaphragm leaks, because then it dumps unmetered fuel through the vacuum port back into the plenum.

[fontana dan]

Thanks VStar. My car is displaying that symptom of hard warm restarts.
Would the FPR be a likely source of unmetered air as well? Because I'm almost definitely having a significant amount of that. Will I damage something if I pinch off the vacuum line to the FPR while the engine is idling?

[VStar650CL]

No, unmetered air is the opposite. It's possible for an FPR to leak air without leaking fuel if the housing is damaged or corroded, but that's very uncommon. Typically the diaphragm gives up and they leak fuel into the vacuum port. That's easy to check, idle the car for a little while and then pull the hose off the port. If gasoline dribbles out, the FPR is blown. It is possible to get "hidden" vacuum leaks from plain dashpots like power valve actuators because they leak air and not fuel if the diaphragm gives up. Your P0171 can happen from things besides vacuum leaks, notably a bad front O2, an exhaust leak near the front O2, or fuel with too much alcohol.

[Ryantzer]

I'm not totally familiar with the VH41, but on my '90 VH45 the connectors for the injector harness are above the right valve cover towards the rear - you can do a resistance test on every injector from that point by probing the proper terminals, which you'd need to look up in your FSM. Unless your injectors test bad, I would just send them out to any of the reputable injector blueprinting services to have them professionally cleaned and flow tested. Places like RC Engineering, AUS Injection, and others will provide before & after printouts showing the spray patterns and flow rates of each injector.

I would just pick up a roll(s) of vacuum hose in the correct metric size(s) to replace all the vacuum lines you'll come across.

[Ludeaem]

Oh this is a fun job. Did it about 5 years ago. Label label label. I took some pictures and had the FSM to reference (pic above) but someitmes you look at it and your eyes cross. I think there is a youtube video someone did as well. Anyways good luck and yes, you'll need 2 knock sensors. you may want to replace the rubber coolant hose in the valley as well. I have the warm start issue as well but just circumvent it by letting the pump prime for a few seconds before starting. Im just not wanting to take it apart yet.

Vstar, good to know about pulling the vacuum line and checking for fuel. I will do this soon. Appreciate the tips

[3Q Jay]

Dan- Here's my parts list from the last time I did a VH41 (back in 2014!)

SENSORS, KNOCK (2) NISS#22060-30P00
HARNESS, ENG SUB INF#24079-6P020
GASKET OUTLET (2) INF#11062-6P001
HOSE, W/P CONNEC INF#14055-6P000
GASKET, MANIFLD (2) INF#14035-6P001
HOSE, NISSAN BULK #A6440-N7686
CLAMPS, FUEL (3) NISS # 2xxxx-53A00
HOSE INF#92400-6P100
HOSE, WATER/HEAT INF#92402-6P100
HOSE INF#92410-6P100
HOSE, HEATER INF#92413-6P100
HOSE, WATER INF#14056-6P011
HOSE, WATER INF#14056-6P012
HOSE, WATER INF#14056-6P015
HOSE, WATER INF#14056-6P110
HOSE, RAD INF#21501-6P000
HOSE, WATER- INF#14055-6P000
GSKT, ROCKER INF#13270-6P000
GSKT, ROCKER INF#13270-6P010
PLUGS (8) INF#22401-1P115
HOSE, NISSAN BULK #B2318-N3301
GSKT, EGR TUBE INF#14722-6P100
GSKT, EGR C/V INF#14719-W7001
GSKT, THROT CH INF#16175-6P001

note this list does not include the soft rubber upper to lower plenum gasket as I re-used one that had only been in service about 15k miles.
that p/n is:
GASKET, INTAKE- INF#14032-6P010

[fontana dan]

Thanks to all for the responses of advice. Gathering up parts now, 8 coils, 2 knock sensors, and FPR on the way.
Jay, that is quite a parts list!! Gathering all that up today would cost a pretty penny. Most of those hoses are discontinued and would have to be sourced from Amayama. Trying to figure out how to get the best bang for my buck. Will definitely get a couple rolls of vacuum hose, but do I really need all those individual molded lines??
On the topic of testing fuel injectors, the service manual says to Ohm them at each individual injector. Looking at the wiring diagram for bank 1 looks like it could be done through F101 which is at the front side of the valve cover for that bank.

[Ryantzer]

Yes, testing the injectors at the common injector connector is far easier than removing the plenum to test them.

[fontana dan]

Thanks, I will have to test the injectors before I take it apart. Especially since I have another more concerning issue cropping up with this VH41.
In the past few months the car has started lightly pinging/knocking around 1500-2000rpm at light throttle, usually when going up a hill. It will do it in 2nd or 3rd or 4th gear but only in that RPM range. Doesn't seem to make a difference whether it has 89 or 91 in the tank.
Any ideas on what it would be? No engine codes stored currently. Clogged injector? Knock sensor? Bad coil pack?
Took this video. Its knocking at around 6-7s but you can barely hear it. Then I drop it into first gear then punch it and there's no knock at all.

[fontana dan]

Ok so I finally got around to doing this. No one told me that the entire fuel rail would be seized together with phillips head screws and non-serviceable spring clamps on tiny little fuel lines. Couldn't even get the wire harness connector off of a single injector. I put it back together after only replacing knock sensors and lower intake gaskets because I don't have a week to tinker with all of that s***.
The factory injectors (28 years old, 223k miles) all tested between 12.5 and 13ish ohms and click away happily. Car runs like a top. Always has for me.
Didn't replace a single rubber hose either. Most of them are still pliable and are not cracked. I don't know why the car acts like theres a huge vacuum leak down there. Set a P0171 today. Steady at +25% short term fuel trim bank 1 and 2 at idle.
Is it time to finally just throw 2 new o2 sensors at it?

[Ludeaem]

I had a p0171 after doing the gaskets and found it was because of the vacuum lines being routed incorrectly. At least one or two were. It took some trial and error and also the help of a smoke machine to see where leaks were. Good luck

[fontana dan]

That's an interesting idea ludeaem. Was it the larger hoses related to PCV or the smaller pin-sized ones?
The long and short term fuel trims have behaved the same through all repairs since I bought this car. I just can't chase it out. The condition doesn't seem to affect drivability whatsoever. The car responds excellently and idles smoother than a lot of brand new vehicles. It has never stalled a single time in 30k miles.

[Ryantzer]

No one told me that the entire fuel rail would be seized together with phillips head screws and non-serviceable spring clamps on tiny little fuel lines.

Your Q45 has no Phillips head screws on it anywhere, they are all JIS screws which are slightly but significantly different from Phillips. The Phillips screwhead design is intended to "cam out" the screwdriver when reaching a certain torque - the reason they are commonplace today is because Henry Ford adopted the design to reduce stripped fasteners on his assembly line. Get yourself a set of JIS screwdrivers and you'll be amazed at how much better they work - you'll get more torque for both removing and tightening, and you will be far less likely to strip out the screw heads when the screws are stuck or seized.

You've got a lot of experience working on Q45s, so if this is something you already knew and just used "phillips" as a common use term, feel free to ignore my comment.

[fontana dan]

No one told me that the entire fuel rail would be seized together with phillips head screws and non-serviceable spring clamps on tiny little fuel lines.

Your Q45 has no Phillips head screws on it anywhere, they are all JIS screws which are slightly but significantly different from Phillips. The Phillips screwhead design is intended to "cam out" the screwdriver when reaching a certain torque - the reason they are commonplace today is because Henry Ford adopted the design to reduce stripped fasteners on his assembly line. Get yourself a set of JIS screwdrivers and you'll be amazed at how much better they work - you'll get more torque for both removing and tightening, and you will be far less likely to strip out the screw heads when the screws are stuck or seized.

You've got a lot of experience working on Q45s, so if this is something you already knew and just used "phillips" as a common use term, feel free to ignore my comment.

Haha, this is not something that I knew after working on this car for years. However this is the first time I've ran into problems with JIS fasteners on the car.
I was actually able to get the metal cap off of an injector, and the damn thing was still stuck in the fuel pipe. What are the tricks, besides using the correct screwdriver? Heat? Oil?
I appreciate the insight.

[Ryantzer]

If you’re replacing a dead injector you don’t need to be gentle with the old one when getting it out. They do tend to get stuck but should come out with some moderately forceful persuasion. I don’t remember exactly what tools I used, I think it might have been vice grips on the injector with the fuel rail in a bench vise.

[Ludeaem]

That's an interesting idea ludeaem. Was it the larger hoses related to PCV or the smaller pin-sized ones?
The long and short term fuel trims have behaved the same through all repairs since I bought this car. I just can't chase it out. The condition doesn't seem to affect drivability whatsoever. The car responds excellently and idles smoother than a lot of brand new vehicles. It has never stalled a single time in 30k miles.

It was the smaller lines. I just had to triple check vs the FSM diagram that is in the first post. Good luck. Also, one of my fuel trims are slightly off (want to say short term) and its just not worth chasing down as you put it, it runs well for a almost 25 year old car.

[Q451990]

Your Q45 has no Phillips head screws on it anywhere, they are all JIS screws which are slightly but significantly different from Phillips.

Well, I learned something today! Any particular brand of JIS drivers you like?

[Ryantzer]

Any particular brand of JIS drivers you like?

I picked up this set on Amazon and have had no issues with it. https://www.amazon.com/Screwdriver-JISP ... 30&sr=8-23

In retrospect I probably should have stepped up to a higher quality brand and a kit with a few more screwdrivers in it, but what I've got works well for now.

[fontana dan]

I'm still getting these codes, but now with a LOT of ping, detonation in my engine and I cannot for the life of me figure out what the f*** is going on. The EGR valve is not lifting. Smoke test yields no results. New plugs, coils, intake gaskets.
Fuel pressure test? f*** this car honestly. If it wasn't so god damn reliable I"d have an excuse to get rid of it.