Strange Engine behavior

[peepsalot]

First a little background information:
I have recently removed VTCS and ported my intake manifold. While I was at it, I put on my Outlaw Engineering thermal spacers for IM and TB. I also did the coolant bypass mod for the TB. First time I tried to put it all back together, I had a major vaccum leak from my gaskets, which caused my engine to hardly run at all. I fixed it by using some gasket sealant, and the car is running ok now...for the most part.

Here is my problem:
When the car is started, before it has warmed up, if I gently ease in the gas pedal, or tap it very lightly, the rpms dip way down and the engine almost stalls, but eventually it revs up if I keep giving it more gas.

I thought maybe I still have a vacuum leak, but I have not been able to verify this. Anyone have some ideas of how I can pinpoint the source of this problem?

I was thinking it was linked to VTCS somehow, since I only notice the problem during warmup(shrug). It seems there are a few people that have done these mod, and yet I am the only one having this problem. I guess I have screwed something up on my car, I just can't figure out what it is.

[peepsalot]

bump

[azian6er]

what is your idle at?

it almost seems as if it is too rich and bucking when you give it that gas when it is cold. The vcts helps tumble the air durring cold start so the fuel mixture is optimal. When you start the car cold it is oober rich already, and without the vcts im guessing it is running even richer because those plates arent there to help create the same mixture.

I am running a map sensor with my haltech so i dont think i will have the same issues as you because all my fuel needs are predetermined in a map i programmed.

I hope i dont have the same isssues as you.

-Bryan

[Spooled]

^^^ What he said.

Engines need extra fuel and rucher than normal conditions on cold startup. the VCTS is what keeps the engine from falling over itself with all that extra fuel. If you have some sort of fuel control, pull a little when the coolant temp is low.

[peepsalot]

idle is 750. The idle seems just fine, not rough or anything, but when I just give it enough gas that would normally allow me to engage the clutch, it almost stalls instead. Doh, I guess engine management would solve the problem, but I don't have the money for that right now. And what if it didn't? (boom02)

I'm now guessing that my problems are a result of a the combination of all these modifications: no vtcs to tumble rich air, smoother runners (probably too smooth) not creating any turbulence, and differently placed injectors(from spacers) creating different spray pattern. Maybe I will just put everything back to normal, no spacers, and back to the original manifold. I'd hate to do that, as that would mean I am admitting that I wasted much time and money doing this crap.

viVid had this problem, and he claims it just went away, I wonder if my ecu will eventually learn to cope with the problem or something.

edit: BTW, I seem to be getting really horrible gas milage, but I'll have to go through a couple tanks before I'm certain.

[BlkZoomZoom]

I would say something is wrong. I have had none of those problems. Also I have done this for other people and none of them have experienced this either.

I have gotten better gas mileage since this has been done.

[peepsalot]

Well, I'm still stumped.

Other possible sources of the problem
1) EGR system?
2) I still have a vacuum leak somewhere?
3) ???

Any other ideas, or methods to test the source of the problem?

[peepsalot]

My vacuum at idle is a steady 20 in. hg, does that sound about right?

[peepsalot]

Dammit, I am almost about to take this to a mechanic, but I have a feeling they won't find a problem, and I'll end up paying hella cash for nothing.

[jonlong]

Hey...same problem now on my P5. Has anyone else with a P5 and P5 ecu done this mod and had the same problem?

[peepsalot]

bump

[jeffmsp]

joeP fuel pressure reducer + stock boost until you get it figured out? Get this new product from DSM? I dont know if just a FCD would lean you out enough to make a diff.

[peepsalot]

Yeah, that AFC from DSM looks sooo nice. But I think there is something going on here besides wacky a/f ratios. Plus I wanna get a wideband before fooling with that thing.

Another thing I noticed, which is really starting to bother me, is that I think my car smells a little like burnt plastic or rubber or something when I park it. And it ain't from the tires.
(boom07)
Ack I'm going insane!

[FSDET]

did u feel any gains from all ur mods ??

[peepsalot]

I can't tell, my car just feels fucked up to me now.

[peepsalot]

Bump for any thoughts on what I should do.
I noticed my idle is now kinda screwed up even after warmup. I push in the clutch, and the rpm drops and almost dies all the time. It usually dips down way low, then pops up, then settles eventually, but even sometime, it just settles at some crazy low rpm, and my car just shakes and grumbles.

[thewrench]

Just a couple of shots in the dark, maybe the egr isn't seated right due to the spacers, or maybe the plug you used for the VTCS shaft is leaking. Could be that it leaks when cold, but after the mani heats up it's sealed, or at least sealed better. (dunno)

[jonlong]

Ok, posted another thread about it, but no one responded, so i'll mention it here...
I also removed the VTCS and ported/polished. I had a problem w/ my idle after I did it, but then I took it all apart again and put it back together, this time paying more attention to sources of a vacuum leak. I did not remove the actuator arm for the VTCS system so I didn't have to plug anything. My car runs beautifully now. It idles at a steady 750. It revs fine regardless of whether or not the engine has warmed up, so removing the VTCS has NO negative effect on the car. I do feel a much stronger pull in the high rpm range, like past 4k.