Member Credit: sdot82

This write-up is for a 2000-01 VI manifold swap on to 95-99 Maxima. There are many ways to do this swap so first I will number the ways I know how to do this and then go into detail on how to do it. There are a couple of different Upper manifolds you can get Fed spec. or Cali Spec the difference is one may not have the swirl valve control (don’t need it anyway). I believe (don’t quote me on this) that the 00 Fed Spec do not have the swirl valve control and all 01 (Fed and Cali) do not have the hole for the EGR guide tube. You may want to ask the People from the Junkyard this because you want to know this if you are going to keep the EGR or not.

(note when I say 00 that means both 2000-2001 unless I specifically say otherwise for that part)

1. 00 Upper and Lower (Fed spec), 00 Fuel rail & injectors or 01 QX4 fuel rail & injectors (they are the same because I am using the QX4 fuel rail and inj.), 00 Throttle Body w/ 00 IACV, 00 EGR guide tube. (no adaptors needed for this)
2. 00 Upper and Lower (Fed or Cali), 00 Fuel R&Inj. Or 01 QX4 Fuel R&Inj, 00 TB w/ 00 IACV, and running no EGR. (Make a plate to cover the hole in the manifold)
3. 00 Upper and Lower, 00 Fuel R&Inj or 01 QX4 Fuel R&Inj, 00 TB w 4th gen IACV (need a adaptor plate made for the 4th gen IACV), and 00 EGR guide tube or no EGR (need to make a plate to cover the hole)
4. 00 Upper and Lower, 00 Fuel R&Inj or 01 QX4 Fuel R&Inj, Pathfinder TB (need a adaptor plate made) 4th gen IACV (need a adaptor plate made), and 00 EGR guide tube or no EGR (need to make a plate to cover the hole).
5. 00 Upper and Lower, 00 Fuel R&Inj or 01 QX4 Fuel R&Inj, 4th gen TB (need a adaptor plate made) 4th gen IACV (need a adaptor plate made), and 00 EGR guide tube or no EGR (need to make a plate to cover the hole).
6. 00 Upper and 4th gen Lower, 4th gen Fuel R&Inj, 00 TB w/ 00 IACV, and 00 EGR guide Tube or no EGR (need to make a plate to cover the hole).
7. 00 Upper and 4th gen lower, 4th gen Fuel R&Inj, 4th gen TB, 4th gen IACV, 00 EGR guide tube or no EGR.
8. 00 Upper and 4th gen lower, 4th gen Fuel R&Inj, Pathfinder TB, 4th gen IACV, 00 EGR guide tube or no EGR (need to make a plate to cover the hole).

I think those are all the different ways that u can do the swap parts wise. In addition to those parts listed above you need to get:

• a lot of new hoses (different sizes), some fittings and tees.
• hose clamps
• new gaskets for the 00 lower, the upper should not need new gaskets since they are rubber (unless they are torn)
• Bolts for the upper manifold (8 of them) unless it came with it, should be able to reuse the lower manifold’s bolts.
• New bolts for the VIAS back cover (metal cover) and the vacuum switch (just a suggestion because you might have to take it off later and the OEM screws strip easy).
• Bolts for the 00 TB, if you are going with the 4th gen or Pathy TB you will have to find out from the person you get the adapter plates from what bolts are needed.
• Adapter Plates for 4th gen TB, 4th gen IACV, or Pathy TB
• Cover Plates for EGR or 00 IACV (explain later)
• JB weld the liquid type and JB weld Stick
• New different PCV w/hoses

Tools:

• Dremel or grinder
• socket set (deep as well as regular) you will mainly use 14mm, 12mm, 11mm, 10mm so get those in deep socket.
• Flathead, and Phillips head screwdrivers

Prep. work, before you start installing you want to do a couple of things:

• If you are using the 5th gen lower and it has the swirl valve, remove everything so it’s just like the 4th gen (See PIC 4 below). Once it’s removed use some the JB Weld Stick to cover the holes so there will be no leaks. I just plugged the two outside holes (see pic the holes are highlighted in red.)

  

• Also, you want to either fix or just prevent the VIAS from breaking by using the regular liquid JB Weld. If you want to you can replace the bolts that hold the VIAS solenoid and the metal plate on the there side in place (see pic). I had to because one of the screws stripped on me so I went to Home Depot & bought a kit that removes stripped bolts or screws.
• Fuel rail depending if you went with the 2000 Maxima fuel rail you will have to buy something like that (see pic 1 & 2 ), and if you used The 01 QX4 fuel rail you can do what I did (see pic 3). I took off the piece you see in the pic and used a grinder to cut off the extra metal tube and bent it into place so it would reach the fuel line hose. It did not line up exactly with the hole so I just screwed in one side of the fitting and have no problems with it. I made it just like the 4th gen fuel set up wise (like the place of the FPR).

  

  

  

• First go to the fuse box located on the dash of you car and remove the fuel pump fuse. Then you want to start your car and let it run until it dies, do this process until you can’t start you car at all. This will remove most of the fuel out of your fuel rail and injectors.
• Next up remove your intake (note: I would label all of you hose either by marking it with something or with numbered stickers, and right it down in a note book what it means).
• On the Throttle body disconnect the plugs from the TBS and the cables. Now get a towel or a container so you can catch the antifreeze when you remove the hoses on the bottom of the Throttle body. Once you have everything disconnected from the TB remove the (12mm) bolts in the throttle body.
• Start disconnecting all three coil packs, IACV plugs, and other wires to clear up space when removing the upper manifold.
• After you have the TB off start removing all hoses and components that are on the upper intake manifold and labeling them. When you have everything off the upper manifold, begin removing the bolts in the front of the upper manifold (note: there are 2 bolts on the back of the upper manifold that you will have to remove). Remove the ERG guide as well.
• For those that are using 4th gen fuel rail and 4th gen lower manifold skip to preparing the engine for the upper manifold. If you using the 5th gen parts read on
• Once the upper manifold is remove began removing the fuel rail, I remove the fuel hoses first (I placed a towel around the hose from the fuel filter to the fuel rail so gas would not spill onto the engine). Then remove the bolts for both the fuel rail and lower manifold.
• Once you have removed the lower 4th gen manifold you can now place the 5th gen lower manifold and bolt it up.
• Then you can put then new fuel rail on the lower (if you are using a 2001 QX4 one or to of the holes will not line up, like mines, but it will still be good). The next thing you don’t have to do I just did: you’ll need the rubber washers that came of your old fuel injectors to place them around each of your new injectors. I did this because there was a gap from the lower manifold to the fuel injectors. After you bolt the fuel rail down it’s time to cut the old 4th gen fuel injector connectors off and solder them (or connect them anyway you want to) to the 5th gen connectors. Most people don’t like cutting wires but it’s not hard. Also, you need to grind the fuel rail (I bolted them down onto the lower manifold because it was the easiest location for me.) Now get some of the new hoses that you should have purchased and connect them from the fuel filter to fuel rail and fuel rail to fuel filter.

Preparing the engine for the upper manifold

Now that the lower manifold and fuel rail are on, cover up the holes in the lower manifold so nothing can get inside. Remove the PCV out of your valve cover because it will not let the upper manifold sit properly on the lower manifold (later I will tell you what I did for this).

For the next part, you will need your grinder or Dremel. You will need to grind down the coil pack mounting bosses BUT ONLY THE FRONT MOUNTING BOSSES#3 AND #5( SEE PIC ABOVE). #3 and #5 are the ones to the right of you if you are standing in front of the car looking at the engine. Grind down as much as you need to just keep putting the upper manifold on to check for clearance. Once you are done clean up the mess you made grinding down the bosses.

Next up is the PCV, you should have bought a new PCV valve one that would allow you to connect to some hoses. The hose’s outside diameter should be ½ inch for it to fit in the valve case hole tight and cut it to be about 6-8 inches long. You might have to lubricate the hose for it to slide in (at least that’s what my girl keeps telling me j/k lol).

Note this is only for people that are keeping the EGR and 5th gen IACV.

Member Credit: maxiiiboy (Vol.4, Spring 2017)

Summary

The 5^th Generation Maxima is a very reliable car – if you know how to maintain it. The problem is that the car suffers from a few design defects that can make it expensive to maintain. For example, a worn-out engine mount may damage the Engine Control Unit (ECU) resulting in a major inconvenience and a dealer repair bill of $2,000-$4,000. Other actuators may fail with similar effect, sometimes repeatedly.

This note describes these problems and the remedies for eliminating them. The remedies are inexpensive and easy to do. If you own a 5-Gen Maxima, I strongly suggest that you do the following as soon as you can:

• Implement “Coolant Bypass”, or replace your Idle Air Control Valve (IACV), or both.
• If your car has an Automatic Transmission, then disconnect your two electronic engine mounts, both front, and rear.
• Replace fuse #58 (15A, labeled ENG CONT1) in “Fusible Link and Fuse Box” by the battery with a 7.5A fuse.

Do the above even if your car experiences no problems at this time. If your car already experiences problems such as P0505 or damaged ECU, then read this document before attempting any repairs.

The above instructions may not make much sense unless you understand what the problem is. The next section describes the problem, and the subsequent one explains the remedies in more detail. If you own a 5.5-Gen Maxima, keep reading but you can dismiss the IACV issue – your car does not have an IACV to worry about.

Problem Description

The fundamental problem is that in the 5-Gen Maxima the Engine Control Unit (ECU) is not properly shielded from the failures of some components it controls. For example, we know that the ECU can be damaged by a) Failed/shorted IACV, and b) Failed/shorted Electronic Engine Mount. There are also some reasons to suspect that failure or misadjustment of the TPS (Throttle Position Sensor) may have a similar impact; I am still investigating.

How the IACV Fails

Most often, the IACV fails after the engine coolant¹ shorts the wiring in its stepper motor. There is an O-ring gasket that should prevent the coolant from getting into the IACV, but after 10-15 years, it tends to fail. I suspect that there are other reasons why the IACV fails. For example, the thermo-valve inside the IACV may get stuck, or there is an intake leak; the IACV then tries to correct and eventually fails. The bottom line is that IACV failures (code P0505) are reasonably common and that they have disastrous consequences.

1 Engine coolant circulates through the Throttle Body and IACV to eliminate potential starting problems in cold weather. However, this seems unnecessary as the TB/IACV is nicely hidden between the two engine banks. There are multiple posts on maxima.org that confirm that there are no starting problems with coolant bypass, even in Minnesota winters.

Figure 1 illustrates how the damage occurs. With a healthy IACV, the resistance of each IACV half-coil is 22 Ohms. Together with other factors this limits the maximum current through each half-coil to 0.5-1.5 Amp, and to a maximum of about 3-3.5 Amps through each of the two ECU ports and the STA509A transistor behind each port.

When the coolant eats up the insulation, the coil shorts, and the resulting current – up to the 15A limit imposed by fuse #58 – will flow through the IACV and “fry” the ECU. The 15A fuse should blow out, but usually the STA509 driver transistor in the ECU burns first, sometimes taking adjacent components with it. Appendix A shows how a damaged ECU looks like.

The horror story does not end here. Typically, the result is that both the IACV and the ECU are damaged. If the owner replaces just one of the two parts (say, just the ECU), he will find out that his new ECU is immediately damaged by the IACV he hasn’t replaced yet!! Even Nissan dealers are known to have made this mistake! The bottom line is: Make sure both parts are OK before replacing either!

Failure of the Electronic Engine Mount

5-Gen Maximas equipped with an Automatic Transmission have two Electronic Engine Mounts (Rear by the firewall, and Front by the radiator). Figure 2 shows the wiring schematic for these two mounts. Again, failure of either mount can damage the ECU in the same manner that the failure of an IACV can.

Each electronic mount has two states – Firm and Soft. Normally, the ECU puts the mount into the soft state at low RPMs (below 1000 RPM) and into the Firm state when the engine runs above 1,000 RPM. Disconnecting the mount eliminates the danger of ECU damage. It has no effect on the car (no codes or SES light) apart from occasional vibrations; more on that in the “remedies” section.

The Remedies

The ideal remedy would protect the ECU by using onboard fuses on all its critical inputs and outputs. However, I rejected this approach because of its risks: adding components to the ECU board and cutting traces or modifying wiring is just too dangerous for the average Maxima owner. For the same reason, I also rejected any solution that would cut/modify the Engine Room Harness.

This left me with the remedies described below. All of them have been successfully tested by the author.

Remedies for IACV Failures

There are three remedies that will reduce the probability of an IACV failure:

1. Preventative IACV Replacement. It seems that most IACV’s fail at around 100-120k miles. To replace your IACV, you have to remove the Throttle Body and unscrew the four Phillips screws holding the IACV. This is not a pleasant task, as the screws tend to be frozen. Once the job is done, a new IACV (use OEM part only) should be good for another 100K miles or more.
2. Coolant Bypass. Coolant Bypass (see figure 3) eliminates the possibility that your engine coolant will eat on your IACV wiring. On a 2000 Maxima, the bypass requires no additional parts – neither hoses nor clamps – apart from a good set of hose pliers. The job can be done in about 5 minutes (excluding the access/re-assembly time), with the Throttle Body in place. When you do the bypass, remember to blow out any residual coolant so that the IACV is as dry as possible. Also note that in a departure from figure 3, you can completely remove the IACV “half-hose” leaving the two coolant orifices on the IACV open.

   

3. ENG CONT1 Fuse Replacement. Replacing fuse #58 (15A, labeled ENG CONT1 in the Fusible Box next to the battery) with a 7.5A fuse provides an improvement over the OEM setup. Be aware that the 7.5A fuse does not guarantee protection: The STA509A transistor can be damaged by any current exceeding 3A (see footnote²), but the fuse needs to be larger than 3A because there are multiple devices on it³. However, going with the smaller 7.5A fuse increases the probability that the fuse will blow before the STA509 transistor will, and it decreases the probability of large-scale damage – such as burned traces – to the ECU board itself! The fuse costs a few cents (http://www.delcity.net/catalogdetails?item=77075) and can be swapped in/out in 30 seconds.Important Note: If/when the 7.5A fuse blows, you need to treat it as a signal that your IACV has failed. You should check the IACV, and if indeed shorted, replace it.

To summarize, there is no reason not to do #3. The same applies to #2. So, the question is: After you are done with (#3 + #2), should you do #1? I have done it eventually when my IACV experienced other problems (needed cleaning).

Isolating Engine Mount Failures

Only AT Maximas have Electronic Engine Mounts. For these cars, the following remedies exist:

1. Disconnect Electronic Mounts. Disconnecting the Electronic Mounts is the quickest solution. The connectors are brown, each with 3 conductors, and both are located close to the AT dipstick. Depending on whether the mount is disconnected in Firm or Soft state, you may experience the following side-effects:
   A: Mount in Firm State: Some/minor vibration when the engine idles.
   B: Mount in Soft State: Minor in-line vibration between 1,800 and 2,400 RPM, when the engine pulls, only under some conditions, depending on how you step on the gas. I suggest you do not worry about the Firm/Soft state too much: once disconnected, the electronic pump within the mount will stop firming up the mount, and the mount is bound to become (semi)Soft no matter how you disconnect it.
2. Replace with Manual Mounts. Using the mounts from MT Maxima is possible. It is also relatively easy as the MT mount is a direct fit. This is the preferred solution when the original mount is physically worn out. The side-effects are the same as in (1a) above.
3. Add a Fuse to the Mount. It is physically possible to add a fuse to your Electronic Mount. The logical place is at connector terminal #3 where the battery power comes in (see figure 2). However, this would be best done when the mount is being replaced. Otherwise, #4 below may be a better choice.
4. Non-ECU Control of Electronic Mounts. Yet another solution is to keep your Electronic Mounts, but take the ECU out of the loop. One would have to implement a semi-intelligent control that is both fuse-protected and decoupled from the ECU (or any other expensive part). I am tinkering with this solution.

2 Each of the two IACV half-coils is powered by a single STA509A transistor within the ECU. Each transistor can withstand a maximum current of 3A in steady-state mode and 6A in pulse mode. The desired protection would insert two fuses – one into the lead/connector port #2, and one into port #5 of the IACV (see figure 1). It would allow for proper fuse sizing, somewhere in the 3A-6A range for each fuse.

3 Powered off this fuse are multiple subsystems: IACV, EGRC1, MAFS, TP/SW, and others.

Repairing vs. Replacing Your ECU

ECU failures are annoying and expensive. When the ECU can’t be repaired, the only solution is to purchase a “new”⁴ ECU and then tow the car to the dealer to have the keys reprogrammed. In some places, you may be able to find a locksmith that can do this task but it is not clear this is always possible. The key point is: because of the hassles associated with key reprogramming, you always want to repair your ECU rather than replacing it.

4 “New” means “appropriate ECU of the same type, in working order

The following outfits provide ECU repair and are considered reputable:

• AvPro ECM in Fort Meyers, FL (http://www.avproecm.com/nissan.htm). These guys will not only repair ECU, but also they will also improve it by adding fusing protection. All this for $250, with 2-3 day return and a lifetime warranty. I have talked to them, and they know what they are doing (Update 7/19/2016: It appears these guys are no longer in business).
• Module Repair (http://www.shop.modulerepairpro.com/Engine-Computer-ECM-Nissan-Maxima-htm) will repair your ECU for $199.- and ship it back within two days. They advertise the same service on eBay for $99, so make your choice. They are rated 4.5 stars on Yelp.
• Automotive Scientific (aka ASI) http://www.autoecu.com/electronic-control-unit-ecu/nissan/maxima-infinity/repair-service-nissan-maxima-engine-powertrain-control-module-3-0/
  This is a larger outfit that will repair your ECU (and many other electronic components) for $149.
• Foreign Auto Computer Repair, Big Sandy, TX. (http://www.foreignecurepair.com/Nissan.htm).  ECU repair for $250.

Reputation questioned:  Circuit Board Medics.

Acknowledgments

Directly or indirectly, many members of maxima.org (and Nakis in particular) contributed to this note. I have learned a lot from other MAXIMA.ORG members. This note is an attempt to re-pay some of my debt.

Appendix A – How a Damaged ECU Looks Like

The above pictures are just examples. Not all damaged ECUs look like this. Sometimes, a burning smell is the only indication.

Appendix B – Notes re. Improved Fusing

Existing fusing:

Fuse #58 covers, via ECM relay pins (#6, #7), the following: MAIN, MAFS, POS, EGRC1, EGVC/V, AAC/C, TP/SW, IGN/SG (acronyms from the FSM). From the circuit diagram, this is only:

• IACV, EGR/C1, IGN/SG (Coils) – and nothing else; still, this is too much for a single fuse, so we must insert the fuse at F52 (the IACV connector)

Fuse #59 covers, via ECM Relay pins (#3, #5) the following: MAIN, MAFS, POS, EGRC1, EGVC/V, AAV/V, TP/SW, IGN/SG, EMNT, TPS, NONDTC, NATS. From the circuit diagram:

• ECM pins 110+112, CPS-POS, MAF, TPS, EMNT,

Solution requirements:

• Should be switched by ECU/other relays
• Avoid cutting the harness!

Possible implementations:

2. Insert two fuses at IACV connector (F52). Insert them serially into IACV pins/leads #2 and #5. After splicing, bring the four “fusing” wires to some convenient place where the fuses would be placed. Use 3A fuses.
3. New Power Circuit for IACV. Bring two new power lines to the IACV (use fuse adapters to create them). Fuse them either after, or before, the ECU Relay. The latter case will only work if the ECIU relay has two spare pin(s).

STA509A Datasheet:

http://www.datasheets360.com/part/detail/sta509a/-2407484356475109966/

Maximum current is 3A, max V is 47V

Member Credit: dustey

The Issue

• Purchased new OEM coil and installed on cylinder 6
• Switched out the new coil from cylinder 6 with a coil from a known good cylinder
• Replaced all 6 spark plugs
• Switching spark plugs between cylinder 6 and known good cylinder
• Switched fuel injectors from cylinder 6 with a known good cylinder
• Tugged and pulled on the wiring harness from the front bank of cylinders all the way back to the firewall by the passenger side strut tower
• Sprayed starting fluid all around intake plenum, no change in idle
• Flashed ECU to an updated version

I have done all of the above, and none have made any difference in the misfiring. Always on cylinder 6.

I, fortunately, know a tech at the local Nissan dealership who also tested the wiring harness and intake plenum with similar results. He also flashed my ECU. He is now saying it’s the ECU because none of the other things have fixed it. His cost on the ECU is $650!

I called David from SpeedometerRepairGuy.com and explained what I needed and he said the ECU rebuild he does for Maxima’s wouldn’t fix my misfiring (only fixes damage from a bad IACV), also stating he had never heard of this problem before. Again, I have no problem with my idle.

Not sure what to try next. A friend of mine suggested the fuel filter, but the Nissan tech was adamant that it couldn’t be the fuel filter, also citing its a “lifetime” part. Thought about just changing it, since it’s so cheap anyway.

Any other ideas of things I should try before getting a new (or used) ECU? I have already purchased one used ECU through car-parts.com and it was bad, so I am 1) trying to avoid the hassle of trying to find a good used ECU and 2) trying to avoid spending $650+ on a new ECU from Nissan. After all, at this point, I don’t know it’s a bad ECU, it’s by deduction that I/we think its the ECU.

I replaced the ECU with a reman unit from the dealership and had them install and reconfigure everything. (I did this as I pulled my then current ECU out and it was clear that water had gotten into the unit and there was corrosion on the board plus my buddy the Nissan tech is usually spot on.) Didn’t misfire for a day, but its back with vengeance now.

Since the posts above, I replaced the spark plugs again with OEMs (had Auotlites before), and today I switched coils between the bad 6th cylinder and a good cylinder (2), and it still continues to misfire and throw a P0306.

I just don’t understand why it would not misfire for 2 straight weeks when I replaced the fuel filter/strainer and then come back. Could it have something to do with fuel pressure? I mean, replacing the fuel filter/strainer does mess with the fuel pressure since you have to disconnect the lines and pull the fuse? I may be wrong, I am no mechanic…

What’s next? Switch out the injector again? I am second-guessing everything I have done now…

The Fix

To follow up on this thread, I checked the compression (dry) and it was 125 across the board. Low, but not inconsistent which is good. Despite the Nissan tech’s advice to not replace the fuel filter (strainer) since it’s a “lifetime” part, I did anyway because it was a $13 part, easy to do, and $13 isn’t a lot to take a chance on in case it does work. I did both the compression test and fuel filter last Thursday (8/19/10) and it hasn’t misfired since. Unbelievable.

It started doing it on Friday 9/3/10. It went 2 weeks without misfiring, and started back again. The frequency seems to be less, however, it is throwing the P0306 code again (same cylinder as before). Since the problem started however long ago, it hasn’t gone that long without misfiring. It leads me to believe that its fuel-related somehow.

A friend suggested that it may be caused by a dirty fuel tank… reasoning that it ran fine for 2 weeks with a brand new fuel filter until it reached the dirty stuff in the tank. It did start misfiring just after I had filled up at the gas station (waiting in line for the car wash at the same station, actually). I just find it hard to believe that a dirty tank could do that and cause the exact same cylinder to misfire, but stranger things have happened.

Well, I got it figured out. There is something loose or a bad connection with the actual connector on the wiring harness which connects to the coil pack. Me and a friend of mine just starting wiggling all of the wires we could find after determining that it had to be something electrical related. By moving the connector itself a hair this or that way, I could cause it to misfire and then stop. We rigged it up to hold its place where it’s not misfiring:

So far so good. It has misfired maybe once or twice in the last week but it was literally just ones or twice and then it would be fine.My mechanic buddy at the Nissan dealership is going to replace it when he can find a spare. I know what you are thinking… Shouldn’t I have noticed this a really long time ago? Well, in hindsight, yes of course. But, it was one of those things that I took for granted and looked past. I never considered it could be something like that…