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Old 12-01-2012, 07:15 PM   #1
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Default 5000 RPM's at start!?

I vent a boosted 99 motor a little over a month ago (https://www.miataturbo.net/engine-pe...der-1-a-68618/) and now I have a new motor and other goodies all ready to go. I have a MS2 PNP from Stratified Auto. I adjusted for the larger injectors and calibrated everything. I believe everything is connected correctly. EGR delete. Innovative Mtx-l.

When I went to start it for the first time, it fired after about 3 attempts.
The problem is that the motor revs up to 5k right away without any input to the throttle. It's like I am flooring it before I turn the key. I turn it off asap. It's not the TB cable. I disconnected it and checked the plate. All is well.

I saw a little bit of smoke coming from around the intake manifold closer to the firewall a couple of times. One of my friends said he thought he saw a spark coming from the area around the #4 injector. We switched places and I didnt see anything.

I dont think it's a vacuum leak because all of the holes are accounted for.
Please help.

Thanks. Sorry if I left out any vital info out.


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Old 12-01-2012, 07:18 PM   #2
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There are three ways for air to get into the engine:

1: Past the throttle plate.

2: Through the idle valve

3: Through the gaping vacuum leak.

If the throttle is closed, then it's #2 or #3. I don't think the IAC valve can flow enough air to achieve 5,000 RPM, even with no load.

So that leaves the vacuum leak. Brake booster hose? Manifold? EGR valve? Not a whole lot of places to look, really.
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Old 12-01-2012, 07:23 PM   #3
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In fact the IAC hose is sorta kinked so if anything there is a lack of air flow.


I checked everything that I think there is to check as far as vacuum. Ill keep looking and make sure everything is sealed. Is there anyway I can screw up the vacuum hoses around the manifold that will cause this?

Also, I didnt put any sealant or anything on the EGR delete plates but used the metal gasket where the solenoid was. Could that be a potential problem?

Thanks
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Old 12-01-2012, 07:37 PM   #4
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To get to 5,000 RPM, we are looking for LARGE leaks. Bigger than one of the small vacuum hoses or a tiny little gap around the EGR blockoff.
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Old 12-01-2012, 07:41 PM   #5
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Can you do a datalog 2-3 seconds before start through maybe 10 seconds of operation & upload it? That may give more insight to what's going on. Upload your tune too if you can.
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Old 12-01-2012, 07:43 PM   #6
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Right which theoretically will be easy to find.

I will be able to do that tomorrow but I am afraid to let it run for that long.
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Old 12-01-2012, 09:07 PM   #7
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How's your timing?
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Old 12-01-2012, 09:09 PM   #8
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I haven't had a chance to check. I put the cas sensor with the plug dead center.
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Old 12-02-2012, 08:56 AM   #9
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I remember seeing 4500-4800 rpm while fiddling (trying to follow the setup guides) with the IAC on my stock 99 engine, so the 99 IAC can flow quite a bit.
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Old 12-02-2012, 09:47 AM   #10
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Thats freakin scary as hell to me especially on a newly rebuilt motor that has never ran before.
Did it go down on its own after a while or did you do something to lower it?
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Old 12-02-2012, 10:23 AM   #11
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Quote:
Originally Posted by Kinavo View Post
Thats freakin scary as hell to me especially on a newly rebuilt motor that has never ran before.
Did it go down on its own after a while or did you do something to lower it?
This was when trying to figure out the closed loop idle control, during the test cases.
If you want to rule out the IAC control, just disconnect it and control idle with the Idle adjustment and the right foot.
I don't know if the IAC can be stuck open.
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Old 12-02-2012, 10:25 AM   #12
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Ahh ok. Thanks.

I do have a spare TB with IAC which I can swap with and see what happens too.

EDIT: Back story: The reason I have a spare TB is because while setting up the MS before the first start with the last motor, the IAC started buzzing very loud. It didnt do it all the time and it stopped when I unplugged it. I thought is was bad so I got another one. This one does the same now whenever I am click Burn/change a setting in TunerStudio. It doesn't buzz when I am trying to start the car.

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Old 12-02-2012, 11:09 AM   #13
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The egr hole is big enough to rev to 5k, I'd check your block of plate, make sure it's sealing properly.
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Old 12-02-2012, 02:58 PM   #14
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I changed the TB. I sealed the EGR plates. I triple checked every vacuum hose/plug and removed the kink from the hose going into the IAC.
Same thing happens.

Here is my current tune.

Also a log with IAC unplugged and the last one is with the IAC plugged at start. They are very short since I am afraid to leave it running at those rpm's.

Thanks guys.
Attached Files
File Type: msq 1996_97 Miata PNP ND64 MSII_Extra_3.1.0 Base Map for stock igniter_230cc_20120625.msq (83.6 KB, 90 views)
File Type: msl Start Up.msl (43.4 KB, 101 views)
File Type: msl Start Up IAC.msl (21.7 KB, 135 views)

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Old 12-02-2012, 05:06 PM   #15
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Air is getting into the system somewhere.

If you still suspect the IAC valve, pull the hose and block it off. Simple test.

Did that fix it? If not, it's somewhere else.

Maybe the two halves of the intake manifold aren't sealed. Maybe it's the throttle body. Maybe something got between the intake manifold and the head. Maybe the brake booster hose (or some other vacuum hose) is the culprit. Maybe the PCV valve is completely open.

This is going to be some basic gumshoe work.
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Old 12-02-2012, 05:45 PM   #16
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Did you use the correct IM gasket to the head?

I started up my brand new motor (with 96 head) with a 99 gasket on it and it was a MAJOR leak. motor sat at 4k. . . epic fail.

I feel your pain, its tough to find the leak because you dont want a brand new motor sitting at 4-5k while you feel around for a leak.
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Old 12-02-2012, 06:02 PM   #17
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I will have to do the IAC vavle test with both of them. I know the TB is okay. Its closed and the spring works fine and plate looks good.

I checked the brake booster line. It's okay.

The 6 bolts for the top half of the IM are torque and with the metal gasket in between. Anyone use gasket sealer there?

How do I test the PCV valve?

I forgot to mention that I am using the Hondata IM gasket. I torqued all of the nuts to spec. The engine was out when I did all of this so I had a good view of all the surfaces and whatnot and all looked well. Is there any way to test this without taking the entire IM off and the engine off or briefly on?

Is there any way to slow the engine down using the MS despite the additional air getting in?
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Old 12-03-2012, 04:28 PM   #18
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If you have a "leak down tester" try the following:
- with the engine switched off...
- Turn over the crank until one cylinder is at bottom dead centre and the intake valves are just about to close (I.e. At the end of the intake stroke)
- insert the leak down tester into that sparkplug hole and pressurise the line to 20 psi or so (you should not need much, 100 psi for example may start damaging unrelated stuff like the PCV)
- listen carefully, you should be able to hear air escaping out the same place it's leaking in when running...
Good luck...
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Old 12-03-2012, 04:55 PM   #19
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There are two holes in the back of the intake manifold(94-97 for certain) from EGR. Make sure the correct one is covered.

I've heard of air getting past the seal on the throttle shaft pivot points. If you've clean the plate you can clean the seal off the outside edge too. That will cause problems too, not to that high of a rev but it could add up.
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Old 12-04-2012, 01:34 AM   #20
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Re-check the torque on the intake manifold bolts, IMO. I haven't heard of anyone using gasket sealer there and the FSM does not indicate it should be used.

And triple-check all of the little vent fittings. There's on low on the side of my throttle body that I've missed before.

Also, double check that the TB itself is torqued down properly.

You have a leak somewhere, it has to be either a fitting with no hose attached, a leaking hose, or something's not torqued down properly and it's leaking around the gasket. 5k rpm is quite a bit of air. Check everything methodically and you'll find it.
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