Removed VTCS: Big Problem

F

Flagship

Member
:
2003 P5
I just put my intake manifold back on the car, VTCS removed, and reset the ECU. Now when I start it, I have about a 900rpm idle that intermittently dips down to almost dead, then the computer compensates and I'm back up 900 again. A bit of a rough idle also. What's going on and has anyone experienced this?

Thanks in Advance,
Frank
 
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the stock ecu is turned to require the VTCS system durring cold start. therefore, without the VTCS sytem, your cold start will not idle correctly. to really benefit from the VTCS removal, you will need an MP3 ecu.
 
it seems to me that a lot of MP5'ers on the forum are doing this, but I haven't heard of this happening. Could it be something else?
 
njaremka said:
the stock ecu is turned to require the VTCS system durring cold start. therefore, without the VTCS sytem, your cold start will not idle correctly. to really benefit from the VTCS removal, you will need an MP3 ecu.
Click to expand...

I'm running the MSP ecu (expects vtcs) and it cold starts just fine? Yeah, it doesn't warm up as quickly in the middle of winter, but I knew that going into it.

If the idle keeps wanting to drop, I can almost guarantee there's a vacuum line missing somewhere.. definitely sounds like a leak.
 
yeah, just noticed it... on the manifold, there's a metal nipple that accepts a rubber tube on the third-from-the-left port. I can't find a loose tube anywhere. Someone else on the forum said it connects to the fuel rail. Any idea where?
 
Kansei said:
I'm running the MSP ecu (expects vtcs) and it cold starts just fine? Yeah, it doesn't warm up as quickly in the middle of winter, but I knew that going into it.

If the idle keeps wanting to drop, I can almost guarantee there's a vacuum line missing somewhere.. definitely sounds like a leak.
Click to expand...

"MSP" or MP3"?
 
I removed the VTCS, ported/polished intake mainfold, have stock P5 ecu & have no idle problems whatsoever nor any warmup issues so I would suggest looking for leak somewhere or track down whatever isn't hooked back up. I'm assuming you had the battery disconnected while doing all this so the ecu should be ready to go.
 
Flagship said:
yeah, just noticed it... on the manifold, there's a metal nipple that accepts a rubber tube on the third-from-the-left port. I can't find a loose tube anywhere. Someone else on the forum said it connects to the fuel rail. Any idea where?
Click to expand...
I think the one on the fuel rail goes somewhere else. Are you talking about the one that goes from the manifold to the cruise control? Check out this pic & see if this is the one you are talking about..............http://www.msprotege.com/members/i12drivemyMP5/Attachments/P5engine_03.jpg
 
Custom tuned cold air intake. The chamber volume is such that peak HP gain occurs at 5250rpm, the point at which torque grows exponentially and is 1:1 with HP. Also, taking a page out of Ferrari's book, the chamber length is such that reflected sound waves reach the vacuum chamber perfectly in phase at 5250rpm, pushing even more air into the chamber. I'll take a pic sometime.
 
i12drivemyMP5: thanks a ton. I think that's the deal. Goingout to the garage right now. I'll keep you updated.
 
I've been thinking abt doing this (esp since I've got the MP3 ECU and it's just taking up space). Maybe when the miata's a little more sorted this'll be the project for the P5 :D Scribbing to see the fix :)
 
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njaremka said:
"MSP" or MP3"?
Click to expand...

MSP.. hence why I clarified with the "expects VTCS" part. As long as you keep the solenoid plugged in (you can have 0 vacuum lines attached to it like I do) you get no CEL :)
 
Got it all fixed up. Turns out that it was a vacuum leak. My dumb ass forgot to hook up the criuse control tube. ANYONE WHO IS READING THIS THREAD... don't be afraid of doing this mod. Just be sure not to get too excited while hooking up your manifold. You'll start getting sloppy and forget to hook up a hose like I did. Otherwise, the mod is working out great. Thanks to all of you who helped me out. Lifesavers.

-Frank
 
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