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MY1PATH

TBI Component Listing & Loctaions

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This is a component listing of the vg30i and z24i TBI system. Both engines use the same components shown except the z24i air boxes are smaller. All pictures were taken from my 1989 vg30i and spare parts collection.

This is more of a reference page than a straight read and will not be all the information you need On each particular part put it will be enough to get most people going in the right direction and will make for great reference the next time someone says is there a way to adjust the thingamajig and where is it?

OUTSIDE THE AIR BOX

AIRBOXoutside.jpg

Air box & Air box Lid-

Houses the air filter, Crank case filter and Hot air pickup control module. It can whistle, rattle and let unwanted debris past the filter if not secured all the way; 5 latches around the edge should be springy and fir and the 2 wing nuts should be finger tightened 2-3 rotations further once they touch the lid. Over tightening will strip these very easily.

 

Idle Up Solenoids-

Under the driver's right side of the air box are 2 solenoids that open a passage around the throttle body to increase idle speed when the A/C compressor turns on or when there is an increase in electrical load. I believe the right one in the picture is for the compressor and the left is for electrical. If your Idle drops when under electrical or A/C usage chances are the Idle up adjuster needs to be turned. Check wires and plugs too before announcing them as broken. If you pull them out they should have a rubber tip, round is good cone shaped is worn and if there is metal showing on the tip it needs replaced.

 

Idle Up Adjuster-

This slotted screw head controls how much air is allowed to bypass the throttle body. Counter clockwise increases idle-up (It may tak a full rotation to make a noticeable ajustmet). It should be set so that there is about 50-100 rpm increase when the compressor turns on or electrical load increases (blower motor, rear defroster etc...)

(Another picture of the Idle up solenoids and adjuster can be seen in a following section about the actual throttle body.)

 

A B Valve-

Short for Anti-Backfire Valve this valve Reduces backfiring during deceleration.

 

Crank Case Breather Hose-

Allows un-regulated Ventilation of the crankcase so that heat, oil gasses and (if) any combustion gasses enter the crank case has a way out. This can reduce stress on the oil and prevent valve cover gasket failure. It vents into the intake and directly into the manifold thru a PCV valve (regulated) for emissions purposes and to keep cleaner air circulating thru the crank-case. Older vehicles just had a vent and maybe an external screen or filter over it.

 

Hot Air Vacuum Motor-

Opens the hot air pickup door in the intake to allow air from around the exhaust manifold pickup (also called stove pipe) into the intake and then closes it as the air box heats up. It can become jammed; restricting your intake and keeping hot air flow at all times or fail so that it never opens, a bad vacuum line can do this too. Check your Vacuum Control too if you suspect problems.

 

Hot Air Pickup Hose-

This is an insulated high temp hose that delivers hot air form around the exhaust manifold. When old it can become brittle and tear letting cooler air in or the insulation can collapse and restrict the flow of hot air.

 

Idle Screw-

Head points divers right, Adjusts engine idle speed; clockwise is faster. 750-800 rpm is typical the typical setting but anywhere from 700-900 is also acceptable. (Measurement is with a warmed up engine & all accessories turned off)

 

Fast Idle Screw-

Head points skyward and is often mistaken for the normal Idle Screw. When the engine is cold the Fast Idle Cam increases the idle for faster warm-up. This screw sets the fast idle speed which should be between 1,000-1,200 rpm set depending on how cold your climate is.

 

INSIDE THE AIR BOX

AIRBOXinside.jpg

 

Hot Air Pickup Control-

This little vacuum control device shuts off when it heats up. If your hot air door is still open after full warm up on a warm day (stick your hand thru the intake you can feel it) then it is either stuck or needs readjusting. It comes form the factory with a hard loc-tite like seal around the screw and the tab next to it (be careful, it's sensitive). Counter clockwise makes the vacuum shut off @ lower temps, try your adjustments in 1/4 turn increments if you feel you must tamper with it. Staying open too much restricts intake air-flow and robs power from "hot-engine hot-air-mixture" and too little makes warm-ups longer and may make richer smelling exhaust from "cold-engine cold-air-mixture" The goal is (hot as in operating temp);

"Hot-engine Cold-air-mix"

&

"Cold-engine Hot-air-mix"

 

Crank Case Ventilation Filter-

This catches the oil and particles that come out of the vent so that it doesn't gum up your throttle body or air filter.

 

Injector Cap-

The injector cap covers the injectors and holds the Injector Retaining Ring down. It has a Vent on each side and no these vents are not just to cool the injectors. They are to allow air to the Mass Air Flow Sensor. Unlike other vehicles where the MAF is directly in the air-stream the Nissan TBI has separate channels that run beside the throttle body.

 

Injectors-

Nissan TBI injectors pulses just the drivers right injector @ idle when cruising or as fuel demands increase both injectors will begin alternating pulses.

Don't tamper with these, if they fail they cost allot to replace new or remanufactured. Problems can include leaky, clogged, incorrect resistance and a whole slew of other diagnostics that should be found on another thread(s). You can remove bad ones by pulling firmly on the wires. Remove good ones only by taking the throttle body halves apart and using a hollow point punch or socket to press them out w/o damaging the injector nozzle.

Edited by MY1PATH
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Throttle Body

Ok here's where people get confused there's over a dozen components in such a tight space. This time I'm going to show all the pictures first and then do the list. There will be repeat labels on some components to try and help keep on going orientation of the parts location.

(To save space on the page I made 'em all clickable thumbnails. So ya, just click to enlarge and try not to get overwhelmed.)

 

 

Mixture Heater-

The mixture heater heats the air fuel mixture before it enters the intake manifold. A Few people have gutted the core (not removed) for less flow restriction at the cost of having a rough idle on cold days.

 

Flange-

Though this is really part of the mixture heater it is essential that this stays in place even if the heater core is gutted. This flange creates a very narrow gap for the PCV and EGR tubes on the intake manifold, this gap forces carbon buildup and gunk to build up in their tubes rather than inside your heads and block or worse yet from accumulating a piece big enough to score your cylinders.

 

Coolant Lines (throttle body)-

These simply allow coolant to travel a short distance thru one side of the throttle body heating it up. Some people have bypassed this for cooler Throttle body temps doing so may affect warm-up on cold days.

 

Fast Idle Control Device (FICD)-

This device actuates a fast idle cam based on coolant temperature flowing thru it. The temperature at which the fast idle cam eases off can be set by the FICD Adjuster. The fast idle cam pushes on the fast idle lever and how much this lever adjusts the idle is controlled by the Fast Idle Screw.

 

Fast Idle Screw-

Head points skyward and is often mistaken for the normal Idle Screw. When the engine is cold the “fast Idle Cam†increases the idle for faster warm-up. This screw sets the fast idle speed which should be between 1,000-1,200 rpm set depending on how cold your climate is.

 

FICD Coolant Lines-

I have not heard of this being bypassed and can't see why one would but hypothetically if it were; the FICD would have to be either removed, or a screw stuck between the 2 holes that meet up in the cam (not pictured) when the device is warm.

 

Throttle Position Sensor (TPS)-

Tells the ECU what angle the throttle butterfly is tilted acceleration/deceleration air/fuel mapping.

Fuel Pressure Regulator-

This regulator is supposed keeps the fuel pressure @ 36 psi for both vg30i and z24i. It does not function properly with aftermarket fuel pumps that are more powerful than stock. The Vacuum line shown is very specific because it allows the regulator to open and close proportionally to the throttle body vacuum (variable but always present) so the pressure can keep up with the demand as the injectors stay open longer.

Mass Air Flow Sensor (MAF)-

The thin wires are heated above ambient temperature inside the throttle body As air moves over the wires voltage must be increased to maintain wire temperature. The ECU reads this voltage and interprets it as the mass air flow. Dirt can act as an insulator and give false readings. This can be solved by gently whipping the wires with an alcohol soaked q-tip

 

Dash Pot-

This seemingly pointless plunger actually prevents rpm's from diving to fast (to a stall) when the throttle is let off. If your rpm's drop dangerously low when you ‘suddenly' let off the gas then try turning the adjuster clockwise. The adjuster is not seen very easily but it is on the throttle opposite the idle screw, turning the throttle (w/engine off) should reveal it enough to get a small screw driver on it.

Cruise Control Cam-

Acts independently of the throttle cam via the cruise catch lever to prevent a dragging or resistance feeling in the gas pedal

 

Idle Up Solenoids-

Under the driver's right side of the air box are 2 solenoids that open a passage around the throttle body to increase idle speed when the A/C compressor turns on or when there is an increase in electrical load. I believe the right one in the picture is for the compressor and the left is for electrical. If your Idle drops when under electrical or A/C usage chances are the Idle up adjuster needs to be turned. Check wires and plugs too before announcing them as broken. If you pull them out they should have a rubber tip, round is good cone shaped is worn and if there is metal showing on the tip it needs replaced.

Idle Up Adjuster-

This slotted screw head controls how much air is allowed to bypass the throttle body. Counter clockwise increases idle-up(It may tak a full rotation to make a noticeable ajustmet). It should be set so that there is about 50-100 rpm increase when the compressor turns on or electrical load increases (blower motor, rear defroster etc...)

Edited by MY1PATH
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INFO NOTE. I mislabeled and Item; the FICD is actually the "thermo module" Its function is still to raise the idle for warmup and it is still controlled by coolant flow. FICD is another name used to describe the ilde up ajuster and idle up solenoids.

 

Madcat- I know you were talking about doing a tbi writeup. If you have something to add feel free to do so.

Mods- feel free to sticky or move this as you see fit, I just put it in where I thought is was best for now.

everyone else- I hope this helps if you need it.

Edited by MY1PATH

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Awesome thread dude, this MUST be stickied. I was planning to just take some large pics then add some text but this is much better. I have to acquire a scanner. I can try to scan in all the pages for the TBI adjustments.

 

The only nag I have is the text. Some of the text is blurred, and the red makes it blend in with the picture quite a bit. Maybe different colors? Other than that, the photos are good.

 

Im gonna do some experimenting on the TBI for the hell of it. Ive gutted the heater core, plan to replace the A/C solenoid with a bolt, and not use the coolant lines going through the TBI.

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Are the pics permanent, meaning are they linked to an account that you may "clean out" in the future? IF so, please re-host them in a place that they will be safe!

 

The only nag I have is the text. Some of the text is blurred, and the red makes it blend in with the picture quite a bit. Maybe different colors? Other than that, the photos are good.

 

 

Agreed, placing the text in a solid colored box would work out the best.

 

 

 

 

*cleaned out bump and request posts and pinned* thumbsup.gif

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Are the pics permanent, meaning are they linked to an account that you may "clean out" in the future? IF so, please re-host them in a place that they will be safe!

 

The only nag I have is the text. Some of the text is blurred, and the red makes it blend in with the picture quite a bit. Maybe different colors? Other than that, the photos are good.

 

 

Agreed, placing the text in a solid colored box would work out the best.

 

 

 

 

*cleaned out bump and request posts and pinned* thumbsup.gif

The uploads are safe in my photobucket. I do not have the originals or my PhotoShop CS2 anymore so we're stuck with the hard red for the time being.

thanks RedPath88

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I am about to name my first born after you.....Being a poor fella(disabled), I am my own mechanic, and trying to make sense of the throttlebody has been a bit intimidating.....Now I have warm fuzzy feelings, and in the morning going to start testing, tweeking, fixing my beloved PF.

 

thanks

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Like the information you provided here. But I have a Question that someone here might know. My kid bought a 1988 XE 4x4 and the engine (V6 3.0) was messed with to the point that the kid he got it form removed almost all vacuum lines from the manifold and TBI. Missing also was the air cleaner,canister and even the A.I.V system wasn't in the truck. So we hit the wrecking yards around here only to find a piece here and a piece there.

 

I got everything he needed, hooked the stuff back up, but no reference where some of the vacuum hoses go.

 

When getting the parts like I said it was a hit and miss and nothing was complete to look at. Does anyone have any good pictures (like the TBI pictures) they could share and post.

 

We even found the fuel pressure regulator hose connected to the manifold vacuum, and the TBI we got from a guy has it just like what is shown in the picture connect to a port on the TBI.

 

 

Thanks in advance for your help on this.

 

Drew

 

Vancouver, WA

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This is a component listing of the vg30i and z24i TBI system. Both engines use the same components shown except the z24i air boxes are smaller. All pictures were taken from my 1989 vg30i and spare parts collection.

 

 

 

_______

james

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I am currently dealing with the problem of not having the #2 injector firing or squirting after having both of them rebuilt by GB Manufacturing in Long Beach, CA. The injector tech told me all rebuilt or remanufactured injectors are bench tested for spray pattern and OEM volume.

 

The tech that diagnosed this repair was trying to determine why my VG30 was going into 'fail safe' mode and limiting the RPM's to 2800-3000 PRM's before the truck started 'bucking' and jolting until the rpm's dropped below 3000 RPM. (CODE 51) from the ECU.

 

He says he has a signal to the injector from the ECU, but the injector wont fire.

 

Has anyone else encountered this? Could the TPS cause the problem. Also what is the correct procedure for clearing the fault codes from the ECU?

 

I'm just throwing possibilities out there to see if anyone else has encountered this. Been working on it for 2 weeks and growing frustrated, as the problem started all of a sudden. Otherwise the truck runs and warms up normally until 3000 RPM is reached and 'Fail Safe' kicks in!

 

Thanks for any help or suggestions.

 

 

 

Sent from my SPH-L710 using Tapatalk

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I am currently dealing with the problem of not having the #2 injector firing or squirting after having both of them rebuilt by GB Manufacturing in Long Beach, CA. The injector tech told me all rebuilt or remanufactured injectors are bench tested for spray pattern and OEM volume.

 

The tech that diagnosed this repair was trying to determine why my VG30 was going into 'fail safe' mode and limiting the RPM's to 2800-3000 PRM's before the truck started 'bucking' and jolting until the rpm's dropped below 3000 RPM. (CODE 51) from the ECU.

 

He says he has a signal to the injector from the ECU, but the injector wont fire.

 

Has anyone else encountered this? Could the TPS cause the problem. Also what is the correct procedure for clearing the fault codes from the ECU?

 

I'm just throwing possibilities out there to see if anyone else has encountered this. Been working on it for 2 weeks and growing frustrated, as the problem started all of a sudden. Otherwise the truck runs and warms up normally until 3000 RPM is reached and 'Fail Safe' kicks in!

 

Thanks for any help or suggestions.

 

 

 

Sent from my SPH-L710 using Tapatalk

 

I'm having a similar problem, if you find anything out please share!!

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Been a long time since I worked on TBI...
Does swapping around injectors still net the same problem?
I think #2 is only used under load; as in real life driving conditions. (Idle and free-revving in the garage do not introduce any load)

I've had bad injectors both NEW and REMAN so don't rule that out.
Check your engine harnesses, especially where the bundle runs between the battery and radiator.
CAREFULLY Clean your MAF
Cyl Head Temp Sensor working right? (the one behind the timing cover)
Does Unplugging the O2 sensor do anything?
Just go through each part and check it out.

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Both injectors and the ECU has been tested, replaced. The engine still cuts out both under load and just running while parked. What happens when the I2 sensor fails? Will the OBD in the ECU still show a code 51. Any other ideas? This defies logic ! Thanks and I look forward to your reply.

Krmiller07

 

Sent from my SPH-L710 using Tapatalk

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Does anybody have a color to letter diagram for the MAF or even just a picture of the connector without the insulation any help would be appriciated

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Does anyone have any more information on this issue?

 

I am also seeing this issue (aka "Fail Safe Mode" aka "Limp Mode") with my daughter's 1989 Patfinder with VG30i engine. I've built a tool to remove the injectors and am considering having them refurbished by RockAuto for $60. I believe RockAuto sends the injectors to GB in Long Beach for the work. Has anyone done this and gotten good or bad results they could share?

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Custom tool made to pop injectors out of throttle body

2016-02-13%2009.57.43.jpg

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Is that a Centerpunch? Looks like a good idea. But I've never had to pull mine.

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Anyone resolve their issue with code 51 and fail safe? Any help would be appreciated.

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Posted (edited)

10 years later the red letters are still blurry

Edited by Storm_Trooper
Edit

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And yet they're still readable... :rolleyes:

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