Engine Stalling Issues.... 98 GTS with a ROE....

[eabrillon1978]

Hello all,

I recently finished rebuilding my motor with a Roe Supercharger to it. The car has not been run in 5 years. It has a vec 2 that has been upgraded to a Vec 3. Started up like a champ, was a little rough at first but when it warmed up idled great and everything looked good.

When cold, it idles pretty rough and almost seems like it's going to die. After a minute or so and it's warmed up it idles great and steady. Tap on the gas, it returns to idle no problem. Well, I finally took it out on the weekend for a test drive to break it in a little. Took it easy on the car and drove it around with no issues, started pushing on the gas a little more and fine. When I finally came up to a light the car died on me. Cranked it and started up just fine and idled normal but seems a little low. I drove it around a little more and it seems to keep doing the same thing, sometimes it'll die and sometimes it'll be fine.

Next day, started it again, still rough at first but then goes to a perfect idle. Took it out again, does the same thing when you come to a light after driving it a minute or two. Wants to die, but barely running. It died on me a couple of time, but starts right up just fine with a kinda low idle it seems.


Checked my vacuum an at idle it's steadily at 10

So far, no check engine light.


What do you think could be the issue?

Here's what I'm running

I am running an aftermarket air intake sytem and my IAC valve does not go into the air box. I just put a little K&N filter right on the tip of it.

53lbs injectors

70mm Accufab throttlebodies

As far as plugs I'm running Bosch FR8DC's and they are gapped at 29.

91 Octane

I have a 8lbs pulley on the roe with David Weaver pulley on the crank.

Running stock heads that have been ported by Greg Good and have 2.02/1.60 valves.

T&D's with a custom solid roller cam that have been gapped cold at .006 on both intake and exhaust.


I have not done any tuning as of yet, just programmed it with the stock card that came with. I'm wondering if it has to do with the IAC or throttle bodies, they appear to open up at the same time.


Any help or advice will be appreciated....

Eugene Brillon


.

 

[SingleMalt]

Well, it does seem to be IAC-related. Let's see:
1) When I reset my PCM the car does have a tendency to die on decel for the first 2-3 stops, but the maps fix themselves after a few minutes and I'm good. If you're driving for 5-10 minutes and it's still happening, that can't be right.
2) Maybe the filter you have on the IAC is too restrictive? Seems unlikely, but may be worth a try.
3) If not those items, try to think of heat expansion stuff that may be causing some difference like maybe in the throttle bodies...
4) Have the injectors been tested?

Hope you get that figured out -- sounds very annoying!

 

[Greg Good Cylinder Heads]

Just for grins.........disconnect the IAC and see if it drives better.

The vacuum sounds low. IIRC that cam has pretty short seat timing and should have almost as much vacuum as a 708.

Something you can do to pick up a little vacuum is open the lash up .002".

Do you have a sound clip?

 

[mjorgensen Woodhouse]

The stock card may not be able to deal with the other mods, there is a fair amount of tuning for the VEC to get it right in my experience anyway. Is there any black smoke during any of this on startup after warm of when running, could be excessively rich in some load/rpm/temp ranges.

 

[eabrillon1978]

Thanks for all of the input. I'll try disconnecting the IAC today and see if that helps. Does anyone know if the IAC is tied into the A/C system as far as telling the computer where to idle? I have not run the A/C as of yet because my system is not charged at all or maybe I'm drifting out to left field.

I'll try a different gauge on it today to see what the vacuum is at. I checked it briefly after I just started it. When I pressed on the gas a little, it went to around 20-25or so. Maybe my idle is just too low i'm thinking.

As far as smoke, haven't seen any smoke, just spits out alot of condensation at first. Makes a mess on the driveway. I'll pull a plug or two out today and see how they look.

 

[speedracervr4]

I"m plan on putting GG heads and cam on my Roe car, so I emailed Sean and asked him his thoughts of if the VEC is good enough to tune the car. " The VEC is good at up to doing two things at once (blower and injectors, cam and injectors, etc), but not three (blower, injectors and cam)" was his reply. He suggested I change my VEC in for an SCT or AEM. Not saying that's your issue, but I figured I would throw that out there. Good luck and post up if you figure it out.

 

[VIPER BAZ UK]

SCT over AEM all day!!!!!!!!!!

 

[eabrillon1978]

Took a look at the car and decided to try a couple things. I went into the VEC program and set all the fuel injector pulse offsets to zero as recommended in the VEC Instructions, but what I'm not sure of is how you determine the correct offsets???

The earlier post about the filter on the IAC valve that I installed had me curious as to if it was too restrictive. I pulled it off, loaded the program to the VEC and started the engine. Holy Smokes!!! Sounded like a ***** ape with no slow hesitation... idle sat just under 1000... I let it idle for about 5 seconds then shut the car off. I then put the little filter I had back on the IAC. It did the struggled to start and was very choppy. Took the filter back off and started up like a champ again.

I thought this was a K&N look-a-like, but it's not. I have a little K&N breather on my other car took it off and the blew into both to see the difference. The K&N is pretty much non restrictive. The little filter I have is slightly restrictive and the hole before the filter is only about a 1/4 inch. I'm thinking this has to be problem. Not sure if it's in combination with the vec impulse offsets that I changed as well. Still curious how you determine what is right. I'm guessing by looking at the plugs, but that would be alot of removing and installing.

I'm going to go to Yearwood and get a larger K&N breather that'll fit on the end of the tube because my other K&N is just a hair too small to fit on the tube.

I'll let you know if it works or if I still have the same issue. I've attached pics of the filter I was using.

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[eabrillon1978]

Just posting that I fixed the idling problem.

The culprit was the cheapo breather I was using. I purchased a 3/4 inch inlet K&N breather installed it in the same location. Idles great and starts up great. The inlet of the other breather was only 1/4 inch, so must have been starving for air when the throttlebodies close and just cause the car to shut off.

Maybe this will help someone out in the future with the same issue.