TOPIC: 1997 Nissan Sentra XE 1.6 Ltr

Just finished grooving a 1997 Nissan Sentra XE.
1.6 Ltr. Engine
4 Clyinder
Automatic

It was easy to get at the throttle body & PCV hose.
The hard part was dealing with the Idle Air porting.
see pics.






After all the hard work and many hours of waiting for the JB-Quick weld to dry, it was put back on and
the ECU Conditioning process began. At first it didn't want to start up unless I gave it some gas, so I adjusted the set screw to allow the throttle plate to remain ever so slightly open, the car now starts on its own without having to press on the gas pedal. This was an interesting challenge as I had to find a 'sweet spot' were the car would idle high enough to stay running, yet not to the point were the car wanted to drive itself forward too much.

So once the idle was fixed, I re-conditioned the ECU again and proceeded with the drive cycles.

Also the PCV hose from the manifold was capped. I installed a new PCV hose from the valve cover and tee'd it into the Breather hose, which both lead into the Air Hose prior to the Throttle body.

The customer was quite amazed with the immediate horse power response! Will be interesting to see how the fuel economy goes.

Hey JV good job! A power increase is always good.

Just curious did that Idle Air setup just dump incoming air thru that big opening that you dammed off? Does the remaining passage behind the dam still feed into the intake manifold, or did it only dump thru the area now dammed off?

Does the idle RPM start high at cold start then reduce down or is it always now fixed RPM? IAC controls idle RPM for different situations like cold ambient temp starts (like choke/fast idle on a carb) or when A/C is turned on.

Just pointin'out the IAC function gig! Elimination of IAC air totally(if that's what is goin' on here) can cause driveability issues potentially.

Luke Wickenhauser (I think it is) up in Saskatchewan has documented how he takes IAC function for cold temps into account when reducing IAC air flow. Others have also spoken of this.

Good that ya re-directed the PCV.

Does the tailpipe smell cleaner?

Anyhow thanks for the pics, Got me to thinking of how I might have done the IAC on this pup!

Keep Grooving!

Tracy G

I see what you're saying and have been thinking about that lately. From what I recall, the 'Idle RPM' remained constant.

The customer reported that he had some trouble starting up the car one morning. I made a simple fix by adjusting the 'Throttle Plate Screw' to allow some air in but, I have a feeling that's not the best solution. (Maybe someone can explain any potential issues in doing so?)

However, my first attempt was by adjusting the 'Idle Air Screw' but, that didn't seem to do anything at all! Now looking back on it, it's probably because I blocked off the idle air flow to the manifold, as you mentioned (Thanks).

I'm now considering re-routing the 'Idle Air' towards the plate's axle, kind-of like how you did with the Jeep Cherokee.



Sound like a good idea?

Perhaps I replied too quickly? I just found a service bulletin video that Ron made on same car! He did a 1999, I did a 1997. Perhaps the Throttle Body is the same?


Apparently I'm ok after all by merely adjusting the 'Throttle Screw'.

Ron, if you could show me or explain how you dealt with this Throttle Body I'd be highly interested!

Hi JV! I think adjusting the throttle stop screw is a quick fix to allow it to idle. but, if that's the only way the engine can get air to idle, well ask yourself why the factory put the IAC there to begin with.

IAC allows varying amount of incoming air for engine idle under different conditions. Cold start, a/c on, etc. A fixed amount of idle air can't handle all possible conditions. Notice how big that Idle air bypass port is--when IAC opens up fully it will flow a ton of air!

BTW the smaller hole to left of main IAC port in TB base--what's that for, I cant tell from the pics. A separate hole implies a different function to me.

Looking at the last pic w/ red lines you added--I think I might do something similar, yet different. I notice the faint gasket line visible at outer edge of TB. Looks like factory TB gasket just barely covers those 4 trapezoidal recesses in TB base. I can imagine a narrow trench cut from outer edge of the filler material you added, but heading into the lower trapezoid cavity on each side. Then another such trench from each cavity, towards an exit into the throttle bore as close to the axle as practical. In other words just take your red lines and connect them thru those 2 lower cavities. Kinda like a canal using a lake for a connection, see?

Thing to be aware of going this way is the base gasket MUST seal the trench's AND those cavities. Any sealing failure at TB base is a vacuum leak. The trace of a gasket line visible to me looks like gasket just barely meets or covers those cavities. So I would make my own TB gasket from bulk gasket material sold in rolls. I'd look for something thats got some thickness to it, so it can compress and still seal. This is what I did on that Jeep TB I first did last year. Alternatively, might carefully fill in outer area of those 2 cavities w/JB flush to TB base, so that a stock replacement gasket has more surface to seal there.

There is too little width of cast aluminum in areas you drew those red lines in to try to trench as you drew it.

Those trenches likely dont need to be big--I bet as wide/deep as 1/8" drill bit tip could be enough. I would stay as centered in all directions plotting those trenches as can be. Allows room to slightly enlarge 'em if needed.

I'd draw lines on you pic for ya, but I'm still a computer Shputz, ah dunno how!

That's my 3 cents, JV!

Tracy G

I think I understand you perfectly well and if so, I agree with all you're saying.
See Pic.



The picture below is my understanding of the function of the Idle Air system.



The picture below shows the mating surfaces of the Manifold.



So my question now is, do you have a good source for getting rolls of gasket material?
I've never ventured in that direction yet and know nothing of it.

Hi JV your graphics on last pics are exactly what I would do.

For gasket material, most any auto parts store will have something. Will be a small roll of flat material maybe a foot wide. Look for something between fingernail/thumbnail thickness, that is not too stiff, so when ya pinch it you feel a fingernail makes a slight impression. Ask to see/ feel a replacement base gasket for a holley or Edelbrock 4 barrel carb. Those are usually a grey fiber composite material w/ a lot of give to material.

The bulk roll stuff is usually thinner and stiffer than 4 bbl new base gaskets. You want something that can conform to the small surface irregularities in a TB base. and with filling in those areas w/ JB you need to seal against those too.

I'd slightly over-fill those pockets, let dry, then run the TB base flat back and forth over a wood block w/ some fine grit say 180 or finer sandpaper on it to get whole base area flat.

A replacement stock TB gasket might work as well, it just depends on what you wind up with.

I just looked at your pics again-Ok so does the IAC valve actively control air flow thru the left smaller port only, right port only or?? That is another critical question. I would go no further until I had the answer about exactly how/where IAC controls air thr this TB. sometimes Nissan does some odd stuff...I;m wondering if Nissan has the IAC control air thru large port at right and left port is just open, does IAC control air thru BOTH there ports in staged fashion, or what? Solonoid valve for R.H. cant compute that. If you could show pics of the IAC on this one then remove IAC valve and show interior passages that will clear this question up.

Tracy G



This job is easy and you will understand IAC re-routing so much better!

Tracy G

Ok, I went ahead and did the rerouting of the idle air and now the idle air control screw functions as it's supposed to once again. All seems fine in that department now.

One more thing I'd like to add is, there was an engine light on (it has been on since before the groove). The local parts store found 2 pending codes, one which I assume has always been there, the 'evaporative emissions' and the other one(I assume from the 'Groove') was a 'Throttle position sensor' error. (I do not recall the actual code numbers at this time.)

From my recollection, the 'throttle position sensor' error is a common side effect of the groove and isn't anything to worry about cause it'll likely correct itself in time, right?

The 'Evap Emissions' error has me wondering... A problem that needs resolved perhaps?

Good job, JV!

As you didn't have the codes before cutting The Groove, it's likely the light was on for the EVAP, caused by a vac leak somewhere. Check your lines to the system (pumping will not help) and clean your gas cap and the seat for the seal. Clear the codes (ECU Conditioning will do that) and drive it.

WHEN the light comes on, check it. Do not wait. Frequently, when one code presents and the ECU adapts to it, other codes can appear leading to false indicators for your diagnostics. The FIRST cause must be addressed. In this case, it could be either a serious vacuum leak somewhere from the MAF (start your search there) and the valves OR it could be two causes.

This is where the shops make the lion's share of their profits, making repairs based solely on the codes presented rather than using their brains to figure this stuff out. They don't understand the systems and trust computers to do the work for them. (Sharing this type of information with your customers can empower them GREATLY!)

The TPS error code is common for newbies, and is usually caused by hitting the accelerator too early in the conditioning process. Some vehicles need to idle for a couple of minutes first, and as I don't know them all and the time invested is slight, I recommend to all to let it idle at its own until coming to temp, restarting as directed and only hitting the accelerator after it has been started a few times.

This usually takes care of the TPS occurring. Of course, it may be a flaw in the wiring if it was present before The Groove.

This is a case in point for clearing not just the codes themselves prior to doing The Groove but the CAUSE of the codes. (anybody else see income opportunity here for the service?)

Remember, the computer is DUMB. It only knows what it can sense, and cannot reason. This is where you will earn your salt as a Gadgetman.

Great Post!

Thanks for the info. and complements Ron!

Speaking of the gas cap, I just remembered that there is a leak in the gas tube (somewhere just below the gas cap) That's likely the cause of the Evap. Emissions error?

This vehicle as I understand, does not have a MAF, only a IAT sensor (shaped like a fat plastic needle) that plugs into the air intake tube. (which now that I think about it, I faintly recall having left that detached accidentally during the first start up)

It's clear to me that the ECU should be reconditioned as you mentioned and the codes re-checked.

I attempted to check the codes via my Scan Gauge2 but, it could not read anything other than the battery voltage. The auto stores were closed at the time so I couldn't get a proper scan.

Anyways, here's a custom gasket I made to further help seal up any potential leaks.

You are absolutely CORRECT, amigo! That is what's causing the EVAP code. You MUST fix this, although it will have only a minor effect on The Groove. Still, a little can go a LONG way...

As to the gasket you made, just drill a small hole into the gasket to allow some air in. I recommend starting with 1/8" if you have access to the vehicle, 3/16" if it's a customer's vehicle. That allows for fewer "BeeBacks".

So, your marching orders are 1) Fix the EVAP leak. 2) Allow air through the IAC. 3) Clear the ECU (and all attendant codes in the process). 4) Make CERTAIN all items are reconnected before starting the engine.

That ought to do it!

Ron

No need to drill a hole Ron as I already rerouted the Idle Air passages around the bore into either side of the throttle plate's axle areas (See previous pics.)

All the idle air will be handled in between the gasket and the throttle body.

Now thinking about what you said, I suppose your method would've been much faster/easier (If using aluminum for the gasket, so it wouldn't break apart into the manifold)