Just finished up a set of 50mm TWM ITB's on my LSVTEC.

Had everything ready to go, went to fire her up, and upon firing, the engine speed increased to 3500 RPM, then to 3700 RPM.

I shut it down a couple seconds later, thinking it was a vacuum leak.

I have a buddy of mine grab the brake cleaner, and I fire her up again. I have him spray all parts where there could be a leak, and nothing happens.

I shut it down again.

Next, I had said buddy and and another come over to hold their hands over the velocity stacks, to see if the engine would still pull air from a leak, and stay running.

They get into position, and I fire it up once more. This time, a split second after firing, the engine stumbles and stalls.

Here is my question...

Upon looking at the datalogging on Neptune, the TPS signal is showing 95% when the throttle is not depressed, and 1% when fully open.

Also, the wideband reads a steady 10.5:1 right now, when running at 3700 RPM idle.

Any help and suggestions to get this thing running would surely be greatly appreciated.

Thank you,
- Derek

 

Well, i have the same TWM's as you, i haven't finished my install yet, but if you would, could you post pics of how you have your fuel returnline setup and everything of that nature??

As for your problem, its sounds like the idle screw needs to be adjusted..along with a possible vac leak but i'm not sure..sounds like the idle screw on the left side needs to be adjusted.

try taking some fuel out, it should lower the idle..

 

The fuel return line is simply a stock-like rubber hose.

My TWM's were used, so they came with a fitting to allow a regular fuel return line to be used. It's a nipple-type fitting.

Also, I don't think it's a vacuum leak, seeing as the car dies when we cover up the stacks.

The throttle plates seem to be closed, and the plate-stop isn't even touching, it's so far back off.

- Derek

 

Back off the idle screw and try it again. Its located at the end of the linkage and looks like an allen stud with an 8mm nut to lock it in place. It is very sensitive to adjustment.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by soulpwr &raquo;</TD></TR><TR><TD CLASS="quote">Back off the idle screw and try it again. Its located at the end of the linkage and looks like an allen stud with an 8mm nut to lock it in place. It is very sensitive to adjustment. </TD></TR></TABLE>

 

You might want to wire up the TPS correctly also.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DonF &raquo;</TD></TR><TR><TD CLASS="quote">You might want to wire up the TPS correctly also. </TD></TR></TABLE>

As in not backward.

 

Make sure the tps is wired properly of course.
Make sure the throttle plates are syncronized.
Also if your covering up the the trumpets and the engine stalls, it could still be very probable the plates are partially open at idle. I ran into this problem myself. In my situation it turned out that the two springs on the bottom werent strong enough to shut the plates fully every time. I added a third spring and it fixed all the problems.
Also when you proceed with the tuning keep in mind it often helps to use the tps scaler feature to regulate your readings. (if neptune has it)
good luck
-roma

 

Check proper TPS voltage
Sync the throttle plates (any motorcycle shop can do this)

Are you using an external vacuum log for the MAP sensor?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DonF &raquo;</TD></TR><TR><TD CLASS="quote">You might want to wire up the TPS correctly also. </TD></TR></TABLE>

def sounds like the tps is your problem area, is it possible that the tps could be fliped 180degrees to correct the problem???? just thinking out loud here

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mx621 &raquo;</TD></TR><TR><TD CLASS="quote">def sounds like the tps is your problem area, is it possible that the tps could be fliped 180degrees to correct the problem???? just thinking out loud here</TD></TR></TABLE>

Not with the TWM style.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DonF &raquo;</TD></TR><TR><TD CLASS="quote">You might want to wire up the TPS correctly also. </TD></TR></TABLE>

Indeed.

Fixed up TPS wiring right before I left last night.

If that doesn't fix it, then I'll be unbolting them and taking them to the bike shop.

And yes, I am running an external MAP sensor off the vacuum log. It's a firewall-mounted unit.

- Derek

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by D-Rob &raquo;</TD></TR><TR><TD CLASS="quote">

If that doesn't fix it, then I'll be unbolting them and taking them to the bike shop.

- Derek</TD></TR></TABLE>

They will have one hell of a time adjusting them when they are not on the car. Not as simple as throwing it together and getting lucky this time.

 

Upon further inspection, I believe there to be a vacuum leak at the injectors.

The o-rings that came with my RC 370's are about half the size of the other set of stick ones I have laying around the shop.

Upon insertion of the smaller RC o-rings into the manifold, I noticed it to be EXTREMELY difficult to apply enough pressure to bolt down the fuel rail.

So, I took the taller stock ones, put them on the injectors, and bam, the things drop right in, but it is obvious they do not seal 100%.

Let's see what we can do about this...

- Derek

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by D-Rob &raquo;</TD></TR><TR><TD CLASS="quote">Upon further inspection, I believe there to be a vacuum leak at the injectors.</TD></TR></TABLE>

I can almost garuntee you thats not it. Its either the idle adj. screw is way out of whack,theres a vacuum leak somewhere else, or the butteryflys arent synced properly and one is way out. Hook up a vacuum gauge to each individual runner and see if they pull equ. vacuum. It will be tough to see because its not like a manifold, the needle will be bouncing like crazy, but it will give you an idea.

 

The injectors are noticeably loose, though. You don't think they're leaking?

I completely removed the idle screw, and it's now idling at 2700 RPM.

 

Try spraying some brake cleaner on them like you suggested.

If its enough to raise the idle over 1000 rpm you should hear the hissing if its a vacuum leak unless your car is loud as *****.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by D-Rob &raquo;</TD></TR><TR><TD CLASS="quote">The injectors are noticeably loose, though. You don't think they're leaking?

I completely removed the idle screw, and it's now idling at 2700 RPM.</TD></TR></TABLE>

No, mine are the same way. Your problem lies elsewhere.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Combustion Contraption &raquo;</TD></TR><TR><TD CLASS="quote">

No, mine are the same way. Your problem lies elsewhere.</TD></TR></TABLE>

Just for ***** and giggles, I took the stop-screw the whole way out, and proceeded to pull the linkage closed.

I finally got the TPS to read 1% instead of 3%, and next thing you know, BAM!

Perfect smooth 1500 RPM idle.

I think I need a third return spring.

 

What kind of gasket are you using?

 

Manifold gasket?

Password: JDM that's been reused twice.

- Derek

 

still should be able to get those things to idle lower...

 

Of course. This was just a cold start-up idle.

I'd like to retain that.

I found a third return spring, so it should be going on tomorrow, and will be going for a street tune.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by D-Rob &raquo;</TD></TR><TR><TD CLASS="quote">Just for ***** and giggles, I took the stop-screw the whole way out, and proceeded to pull the linkage closed.

I finally got the TPS to read 1% instead of 3%, and next thing you know, BAM!

Perfect smooth 1500 RPM idle.

I think I need a third return spring. </TD></TR></TABLE>

Sounds like youre on the right track.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by D-Rob &raquo;</TD></TR><TR><TD CLASS="quote">I think I need a third return spring. </TD></TR></TABLE>

I thought as many throttle return springs as you can fit were common practice for TWM 2000's.