I just had stage II heads, cam (224/224 .581 lift cam ground on a 113 lobe seperation), PPC LT Headers, 4:10 gears and MTI computer tuning installed on my car. I also have a y-pipe with RT metallic cats on back order so I'm currently using an Off Road "Y" for the time being. The PCM tuning was based on a car with cats.
Here's the problem. Cold starts are fine untill I back down my driveway then the car has a problem keeping idle. Not sure why it does that but that's no big deal. The real problem is when I try to re-start the car after it has warmed up. It simply won't stay running unless I keep my foot on the gas for the first 5 minutes or so. I drive it anyway and it seems to learn the idle as I am driving because it begins to drive/idle... more normal. The second I cut it off and try to re-start it though it starts all over again.
Last weekend we ported the throttle body per MTI's advice to allow more air to get in. This worked fine as we drilled and tested until we thought it was going to be ok (It appeared to be working). Well, I drove away from the shop, stopped off at a store (About 30 min later), got back in the car and it acted as if we had done nothing to it. And, it's still acting the same way if not worse. We have not drilled the largest hole yet 7/32" in the throttle body but I'm wondering if that's really the problem.
Sorry so long but I tried to list the information as accurately as possible. If you've experienced this please let me know what you did to correct the problem.
Thanks

<small>[ April 03, 2003, 08:29 PM: Message edited by: SS3933 ]</small>

 

First off why didn't you change your injectors? You're problem might be coming from the tune itself. If the car isnt tuned perfectly or the timing is off it wont stay running. I had the same prob with my car after the cam install. Usually with the LS1 people always have a problem with either start up or idle. In other words you can say that the cam might be trying to find it's balance which causes the idle to jump high and low. You might want to take it back and see if the tuning needs to be adjusted.

 

I've found out wht the problem is but why would the the injectors make a difference

 

So what was the problem? I have the exact same problem, <img border="0" alt="[worship]" title="" src="graemlins/gr_hail.gif" /> I would LOVE to know. Thanks

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by 1LastZ:
<strong> So what was the problem? I have the exact same problem, <img border="0" alt="[worship]" title="" src="graemlins/gr_hail.gif" /> I would LOVE to know. Thanks </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">My car is a 2001 and below is part of the explanation I was given.
</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">The main problem is the year of the car. For 2001 the EPA told the car manufactures they could not inject fuel into a motor unless the starter is cranking. Before when you turned the key to ignition position fuel would be shot into the intake. Now that this is not happening, the cars with bigger cams are having trouble during startup until the computer can catch it. There is a few things MTI is doing to try and fix this. First is drilling the throttle blade like we did. But MTI normally starts at 7/32 and goes bigger then that. We haven't yet gone to 7/32. SO yes the blade needs drilled more. Now this may not totally fix the idle though. He said if this doesn't work there is a few things he can do in your computer to help the idle. He says its been a case to case deal on getting idle right. Sounds like we may get the idle back to normal but we may also have a slight startup idle surge. I don't think the car should be dieing on you once it has been started. That sounds like the throttle blade needing to be bigger. I was not aware of any idle issues after computer tuning was done. So this sorta caught me by surprise with the 2001 models. Did Jayson mention any of this to you when you talked to him about computer tuning? I have a few other ideas of stuff to try, but I wanted to wait to see how the car did with the larger drilled hole. I had a weird idea, but its worth a try if you don't mind. Try tapping the motor with the key once before starting it. Then start it. This may inject a little extra fuel for startup. I done think this is a cure, just something that was worth a try. </font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I'm getting ready to go drill the Tb out a little more but it's raining pretty hard here today so I don't I'll get much testing done. Just have to wait and see.

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif"> coolant bypass mod </font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Install University???

 

Here's a good thread about a guy with a C1 cam that had your same problem and you can see how nogo helped him solve it:

https://ls1tech.com/ubb/ultimatebb.p...=003892#000016

 

I noticed in your original post that the engine seems to start up and run fine when cold, it's the hot restarts that are the problem. I know I've seen this problem addressed a couple of times over in the computer tuning forum section. If I remeber correctly, the solution was to use LS1edit to copy values from the cold running section into the hot running section.

I've also heard of the "backing up" problem before also. My theory is that the PCM retards the ignition timing when you are in reverse, causing the cammed engine to die. You should be able to fix that problem with LS1edit also.

As far as drilling out the TB blade, you should be using Autotap or EFILive to monitor the IAC position, and stop drilling when this reading is down into the 30s, otherwise you could drill it out too much. You want the IAC to still be able to do its job by keeping it in the middle of it's range.

<small>[ April 05, 2003, 12:09 PM: Message edited by: Cal ]</small>

 

Thanks Cal, I'll relay this info to my installer. As far as drilling, I'll drill, drive it for a few days and try again if it's still not right. MTI said they're working on this on a case by case and they said if the drilling didn't work they've got some things they can do ot the pcm to help.

 

I had a lot of hot start problems with my car after stage 2 heads and cam on an a4. What really helped out hot starts was doing the coolant bypass mod on the the throttle body. After I did that the car didn't stall anymore. Still had a lope for five seconds before the computer took over, but was manageable for me. Playing with the air injection system will also allow you to stabilize the idle. Reverse usually dies because the rpm drop a lot, and even more so than in drive. I had my idle set to 950 rpm, and did pretty well not stalling.

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by strokedls1:
<strong> I had a lot of hot start problems with my car after stage 2 heads and cam on an a4. What really helped out hot starts was doing the coolant bypass mod on the the throttle body. After I did that the car didn't stall anymore. Still had a lope for five seconds before the computer took over, but was manageable for me. Playing with the air injection system will also allow you to stabilize the idle. Reverse usually dies because the rpm drop a lot, and even more so than in drive. I had my idle set to 950 rpm, and did pretty well not stalling. </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">What year is your car?