Car Starts Up & Dies, BUT Throttle Input = Stays Alive. Why?

[cj428mach]

You re way to rich.

Coming up with a maf transfer for your setup is just a guess when starting out. Im running the same intake and relied on Malcolm for a maf transfer since he had the same setup and i purchased the crusher intake from him.

Im sure Kevin will get it, have you discussed it with him?

 

[MackDombles]

have you checked your IAC?

 

[GM2Ford]

You re way to rich.

Coming up with a maf transfer for your setup is just a guess when starting out. Im running the same intake and relied on Malcolm for a maf transfer since he had the same setup and i purchased the crusher intake from him.

Im sure Kevin will get it, have you discussed it with him?

What do you mean “MAF transfer?”

have you checked your IAC?

Yes, I even bought a new one just to make sure I wasn’t going crazy.

 

[cj428mach]

A maf transfer is a air flow "chart" that tells the ecm how much air is flowing through the maf housing based off a voltage the maf sensor sends back to the ecm. If you change the housing size but keep the same maf sensor then the maf transfer gets all screwed up.

Thr gt500 maf transfer no longer works in the crusher because the crusher maf housing is larger than the gt500 maf housing. Some math can be used to figure the difference in air flow to adjust for the difference in housing size. The problem is the gt500 housing isn't round so it makes figuring the airflow difference between it and the crusher housing more difficult.

 

[ViperRed91GT]

Have you set the minimum air rate? If adding throttle keeps it running, that’s probably at least part of your issue. Logging your IAC duty cycle would be another indicator if it’s high, I like to get mine to the 30-40% range.

Unplug IAC, start car. In your case, your probably going to need to turn the TB set screw in a bit to even get it to start and idle. Once you get it running, slowly back off the set screw until it starts to want to die, then turn it in slightly. Plug in IAC.

 

[GM2Ford]

A maf transfer is a air flow "chart" that tells the ecm how much air is flowing through the maf housing based off a voltage the maf sensor sends back to the ecm. If you change the housing size but keep the same maf sensor then the maf transfer gets all screwed up.

Thr gt500 maf transfer no longer works in the crusher because the crusher maf housing is larger than the gt500 maf housing. Some math can be used to figure the difference in air flow to adjust for the difference in housing size. The problem is the gt500 housing isn't round so it makes figuring the airflow difference between it and the crusher housing more difficult.

Ah I see. Good info. I didn’t realize this.

Have you set the minimum air rate? If adding throttle keeps it running, that’s probably at least part of your issue. Logging your IAC duty cycle would be another indicator if it’s high, I like to get mine to the 30-40% range.

Unplug IAC, start car. In your case, your probably going to need to turn the TB set screw in a bit to even get it to start and idle. Once you get it running, slowly back off the set screw until it starts to want to die, then turn it in slightly. Plug in IAC.

I could log the IAC too as well. I’m currently not logging that. I’ll have to look into setting the min aid rate. I never even heard of that.

I do have 2 DTC’s that came up.

P0602
P0453

 

[hotcobra03]

P0602 - Control Module Programming Error This Diagnostic Trouble Code (DTC) indicates programming error within Vehicle ID block (VID). VID data corrupted by the scan tool during VID reprogramming
Using the scan tool, reprogram the VID block. If PCM does not allow reprogramming of the VID block, reflashing PCM will be required.

P0453 - FTP Sensor Circuit High Voltage Detected The PCM monitors the EVAP control system FTP sensor input signal to the PCM. The test fails when the signal average jumps above a minimum allowable calibrated parameter. FTP circuit open
VREF shorted to VPWR
Damaged PCM
FTP circuit shorted to VREF or VPWR
SIG RTN circuit open
Damaged FTP sensor
FTP V PID reading greater than 4.50 volts with key ON and engine OFF or during any engine operating mode indicates a hard fault.

 

[SecondhandSnake]

It sounds like you're in the exact same situation as I am.

A couple thoughts-

On fuel pressure, your regulator is manifold pressure referenced, right? So your fuel pressure is going to be FP = 39psi base pressure + manifold pressure. Since you're in vacuum, you can treat it as a "negative" pressure and you'd be subtracting. 22inHg is pretty close to 10psi, so I don't think it's fuel pressure.

Your mention of the new throttle blade set off a big flag for me, because I fought this like crazy on mine. You may need to remap the ISC transfer function, at the very least dial in neutral ISC air function and set the throttle body bypass air. Without those correct it's going to idle like garbage, but do ok when you manually control air with the throttle blade. If they still have it mapped to a 2V tune based off the processor code (like mine was) it will be waaaaaaaaay off.

And of course you'll have to dial in the MAF as part of the tuning process to sort it out as well, but usually off the shelf MAFs and intakes are pretty close.

Are you using SCT software? If so I can send you a screenfile to log with and maybe take a look at it.

 

[GM2Ford]

It sounds like you're in the exact same situation as I am.

A couple thoughts-

On fuel pressure, your regulator is manifold pressure referenced, right? So your fuel pressure is going to be FP = 39psi base pressure + manifold pressure. Since you're in vacuum, you can treat it as a "negative" pressure and you'd be subtracting. 22inHg is pretty close to 10psi, so I don't think it's fuel pressure.

Your mention of the new throttle blade set off a big flag for me, because I fought this like crazy on mine. You may need to remap the ISC transfer function, at the very least dial in neutral ISC air function and set the throttle body bypass air. Without those correct it's going to idle like garbage, but do ok when you manually control air with the throttle blade. If they still have it mapped to a 2V tune based off the processor code (like mine was) it will be waaaaaaaaay off.

And of course you'll have to dial in the MAF as part of the tuning process to sort it out as well, but usually off the shelf MAFs and intakes are pretty close.

Are you using SCT software? If so I can send you a screenfile to log with and maybe take a look at it.

That is come good info!

I am using SCT software.

So we’ve go to it a point now were when it’s cold, it’ll start up and idle perfectly. But if I shut the car off after it was warmed up, it will not start. Sometimes it’ll start for one revolution, then die instantly, after enough tries of that, it’ll just crank endlessly.

Cliffs

1. Making progress. Lol.
2. Starts up and idles when cold.
3. If I shut it off after it has reached operating temp. It does not start up when warm.

So because of this... I’m investigating the cam shaft & crank shaft position sensor right now. I haven’t tried any warm start ups yet.

 

[cj428mach]

So what have the changes been? the tune?

You probably need more fuel when warm, my dead head setup requires more cranking lambda than normal at warm conditions. I assume you've tried playing with the accelerator pedal while cranking when warm? That can tell you if you have too much fuel.

 

[Soap]

On fuel pressure, your regulator is manifold pressure referenced, right? So your fuel pressure is going to be FP = 39psi base pressure + manifold pressure. Since you're in vacuum, you can treat it as a "negative" pressure and you'd be subtracting. 22inHg is pretty close to 10psi, so I don't think it's fuel pressure.

Hmmm

--Joe

 

[CRidge]

Following...I have the exact same setup as you and have the same crappy cold startup problems, will start then die or if you”catch” it and give it some gas it’s constantly surging like crazy for 30 seconds then I can let off the throttle slowly to get it to idle.
A new issue that just started is it will idle fine after warm up, but if you rev it up over 2500rpm it will come down like it’s going to idle but then keep falling and just die.
‍‍‍

 

[cj428mach]

Following...I have the exact same setup as you and have the same crappy cold startup problems, will start then die or if you”catch” it and give it some gas it’s constantly surging like crazy for 30 seconds then I can let off the throttle slowly to get it to idle.
A new issue that just started is it will idle fine after warm up, but if you rev it up over 2500rpm it will come down like it’s going to idle but then keep falling and just die.
‍‍‍

Your tune sucks. Contact Malcolmv8

 

[Jiffy]

Unplug IAC, start car. In your case, your probably going to need to turn the TB set screw in a bit to even get it to start and idle. Once you get it running, slowly back off the set screw until it starts to want to die, then turn it in slightly. Plug in IAC.

So - this is very interesting for me - I have a cold-start issue. I start the car from cold and it runs really well hot or cold, but when cold it won't idle. If you keep it running on the throttle for 15-30 seconds, it idles and runs well thereafter but idles a little high when warm (950rpm). Car is a 2003 Cobra with 2.3L Whipple, SBTB, SCT2600, 60lb injectors and BaP with the original returnless setup.

Is the process described above the 'standard process' for setting the "Minimum Air Rate" using the IAC?

 

[mobywoods]

Did anyone find out what the problem was goin through the same thing. Thanks

 

[MG0h3]

Did anyone find out what the problem was goin through the same thing. Thanks

His was likely in the tune and the car was heavily modified.

I'd start your own thread to save confusion.

But if you have an otherwise stock car or didn't change anything and a stalling issue cropped up, first place to take a quick look is the IAC.

 

[SVTdreamin04]

Did anyone find out what the problem was goin through the same thing. Thanks

O.P. had a couple of issues. The regulator he was using on his deadhead return setup was causing too much fuel pressure and the other part was the tune.


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