Does it occur with the hood open? Could a vacuum hose be collapsing or perhaps has become leaky under heat? (in which case it's not the right kind of hose, but it could be hard to spot) I would check the MAP sensor hose to the FCON. If that reads inaccurately, you'd be stuck for sure.

 

nope, Vac is fine right at the point where it is stumbling(that is due to the drop in rpms). Also that wouldn't explain the backfiring

 

Vac level may be fine, but is the FCON reading that vac level? If the hose collapses or leaks it will read 0 psi and shoot in a bunch more fuel than it needs to and WILL backfire.

 

no the vac level was fine on my navigator also (which gets the readings from the fcon)

 

d@mn it - back to using Cipher, log everything!!!

If you want to test the charging system, hook it up to another car that is idling with jumper cables. If the problem persists, then it's likely not the charging system. If it's heat related it may take longer to appear with the hood up though...

 

ah! this must be that great PF customer service we have all heard about

 

Typically I would say this is tune related, since you say all the sensors are fine, and the fluctuating at idle begins only after the engine is hot.

But, these settings don't just change on their own, so if the car was running fine when you first received it, within the same scenarios, then there is something else going on.

The only other thing could be that the AF compensation was left on, and is making to many changes depending on what % it was limited to, that is the only way the tune would change from when you received the car to now.

Also if you are having problems with your wideband, and its giving false readings to the VPro, that could also be the problem. I would ask JT if the a/f feedback was left on or off.

Hopefully you figure this out soon, I wouldn't worry its probably something really simple, just annoying to diagnose.

-George

 

agreed! Thanks for the help George

JT said that the a/f feedback was NOT left on. He said he only uses this feature when using the knock amp(i am using the innovate w/b)

 

Well, if I think of anything else I will post it up. Let us know what you find to be the cause of this problem.

Good luck,

-George

 

After you have started your car once and let it run through the 20 minute process until it dies... How long until you can start your car up again? What happens when you turn the motor over with the starter after it stalls/dies? Does the engine still turn over on the battery? Does it try to start?

When you start your car up the second time, does it go through the exact same 20 minute process that it did the first time? Is anything different the second time you start it up?

Does it go through the same start-up and then die process when you start it up in the middle of the day and at night. Wondering about temperature differences...

Still might be worthwhile to take a video of the engine when it dies... Maybe start the video after it's been running for 15 minutes or so...

 

Once it dies after the 15mins i can start it up and it immediately stumbles and dies. It will keep doing this unless i let the car cool down substantially.

 

I strongly feel that this issue is tuning related. Especially since you only had your car back for a day.

Im sorry but I think your going to have to drive back up to PF.

Hopefully I'm wrong

-George

 

Well the car was run on the dyno for days and driven around orlando by JT prior to me picking it up.

Also on a 10 hr drive home w/ various driving conditions i would think these conditions would have brought about a tunning related issue. The night this happened i had been driving the car all around town for hours that same day w/o a hiccup. It just seems that something would have shown up before hand.

 

Like I said, I hope you can figure the problem out with out having to drive back, I still think the A/F comp. might have been left on by accident.

 

Me too George. Hopefully for my sake, you are wrong

 

Just for ***** and giggles I would change out the crank position sensor. I have seen strange things happen with these cars and it turned out to be the sensor. I have seen this happen and the car does not throw a code. The part cost about $60 bucks, it's cheaper than a battery, altenator, shipping and or driving your car back to your tuner. The worst that can happen is you have an extra sensor. It really isn't that hard to damge this part and not even know it.

 

It sounds like it is wiring or ECU related to me. I've been reading and thinking about this issue since the first day you posted....
What can change from just a change in operating temperature? Air density inside the engine....and how the ECU reacts to that. Of course, while at PF the car was on the dyno, getting hot, and I'm sure Jeremy drove it for at least 15 minutes in town after testing. So that leads me to wiring. Expansion under warmer conditions can foul connections. I had a heat issue with a B15 chassis Sentra and it ended up being poor wiring connections that would fail when hot. Strange as hell, but from all of the other ideas not working.....
Good luck

 

+1

That is the first thing I would check as soon as you can get access into the F-CON. The A/F compensation seemed to create some issues for me as well when we had it left permanently on. Roger then changed it to re-set everytime the car started, and that helped. Finally, when he got a chance to do a road tune with me, he turned it off.

 

I have verified w/ Jeremy that the A/F compensation is not on. He didn't use it since i don't have a Knock Amp.

 

I would contact Garret at HKS and find out if there are any HKS dealers in your area with the F-CON Pro Writer software. If so, maybe they can take a peak to see if there is anything going on in the F-CON. If there aren't any HKS dealers in your area, I would sell the F-CON and get a Haltech. Don't get me wrong, I like my F-CON, but I only need to drive 1/2 hour to get it looked at... If I didn't have an HKS dealer nearby, it probably would not have been my first choice because only HKS dealers can get into it.