Hot start issue

[03venomdsg]

So my 03 has a hot start issue. Any day I go out cold fire it up starts perfectly fine idles great around 14 afr. Can drive it for hours I've went on long trips. The minute I shut it off and go to restart I have to blip the throttle to get it to idle or it will bounce from 300-1000 rpm and shudder for a few seconds till everything "stabilizes" onto the second issue is that the afr will be between 15-16 on a hot start and until 5ish minutes of driving it will go back to 14. When the afr is 15-16 it runs like shit exhaust pops and misses at idle. When driving low rpms in this condition the afr continues to increase with more throttle and car misses. If I let it sit a few hours or overnight back to running great again. No stalling issues. Car is 2.3 whipple deka 60s twin gt pumps with dual fpdm, stock maf with Mafia dyno tune with x4. Voltage to the pumps is normal after the fpdm fuel pressure is unchanged maf counts normal, ltft and stft normal as well. Wot afr is always around 11.3-11.8 This has been driving me insane any help or suggestions appreciated.

 

[Skitzerman]

I had similar issues years ago. I got rid of the MAFia and got an SCT BA-2600 MAF and a tune. It was like night and day. You may have other contributing issues, just something to consider.

 

[03venomdsg]

I had similar issues years ago. I got rid of the MAFia and got an SCT BA-2600 MAF and a tune. It was like night and day. You may have other contributing issues, just something to consider.

Yeah I was considering that being an issue I tried another unit still same issue although intermittently better. Was trying to make it another year before going standalone.

 

[03cobra#2]

Has it always done this, or is this something new that has started?

Sent from my Pixel 2 XL using Tapatalk

 

[03venomdsg]

Has it always done this, or is this something new that has started?

Sent from my Pixel 2 XL using Tapatalk

It's been going on for about a year, and I feel like I've been through just about everything trying to track it down. I live up north so it only gets driven part of the year

 

[01yellercobra]

What is the voltage like when dealing with the hot starts and the engine running like crap?

 

[03venomdsg]

What is the voltage like when dealing with the hot starts and the engine running like crap?

I have an autometer volt gauge and lowest I see is around 13.7, stays right at 14 more often than not. I do have an interceptor gauge as well and that's usually about .5 lower than the autometer not sure if thats significant or not.

 

[DSG2003Mach1]

I have an autometer volt gauge and lowest I see is around 13.7, stays right at 14 more often than not. I do have an interceptor gauge as well and that's usually about .5 lower than the autometer not sure if thats significant or not.

the discrepancy between battery and OBD2 voltage reading is normal

 

[01yellercobra]

I have an autometer volt gauge and lowest I see is around 13.7, stays right at 14 more often than not. I do have an interceptor gauge as well and that's usually about .5 lower than the autometer not sure if thats significant or not.

That throws out my theory. I had an alternator that would drop voltage when it was hot. The fuel pumps would go to 100% duty cycle according to my Aeroforce and the car would run funky until it cooled off and the voltage came back.

 

[ERod123]

I had a similar issue as well and tried just about everything. My solution was correcting my vacuum lines. If you have a OBD scanner, check for logged and pending codes. Check your STFTs and LTFTs.

See my thread here: https://www.svtperformance.com/threads/p0300-p0316-after-car-is-warm.1192554/

Reference the attached file and compare it with your vacuum lines.

 

[03venomdsg]

I had a similar issue as well and tried just about everything. My solution was correcting my vacuum lines. If you have a OBD scanner, check for logged and pending codes. Check your STFTs and LTFTs.

See my thread here: https://www.svtperformance.com/threads/p0300-p0316-after-car-is-warm.1192554/

Reference the attached file and compare it with your vacuum lines.

Thanks for the reply but I have the egr deleted and the port on the bottom of the blower capped

 

[ERod123]

You may have a vacuum leak or your injectors are stuck closed when your car is warm. Have you checked any of these things?

Seems like with the EGR delete and things being capped, something could have become loose.

Is the end of your Vacuum reservoir capped, or is it connected to your intake pipe?

 

[03venomdsg]

So weird theory, but is it possible that my injectors are actually stuck open on a warm start since adding some throttle/air helps the issue, also noticed that on my fuel gauge on a Cold start pressure is built instantly and on a warm start it took .5 to 1 second to see that normal cranking pressure build. Pumps prime normally and the priming sound does not sound weak on a hot or cold start, nor is the voltage bad on either. I thought of disconnecting the line before the rail and hitting the key on a warm start with a hose attached to it going to a can or bucket to see if it's priming normally on a warm start.

 

[03venomdsg]

Upon more research, I'm running stock rails and lines and have heard of the regulator going bad and the diaphragm sticking when hot, now to try and find one.

 

[ERod123]

If you have a fuel pressure guage, when warm, how long does it take for the fuel pressure to drop?

You can use a mechanic stethoscope to hear your injectors clicking.

What did it for me is capping off my vacuum reservoir. Compare this picture to your setup. If it's the same, you should try capping it.

 

[01yellercobra]

You don't have a regulator since you're still returnless. It sounds like a tune issue to me.

FYI, if you get a decent MAF now you can still use it with a stand alone. Depending on which one you go with at least.

 

[03venomdsg]

If you have a fuel pressure guage, when warm, how long does it take for the fuel pressure to drop?

You can use a mechanic stethoscope to hear your injectors clicking.

What did it for me is capping off my vacuum reservoir. Compare this picture to your setup. If it's the same, you should try capping it.

That line is capped. And it's more that it

You don't have a regulator since you're still returnless. It sounds like a tune issue to me.

FYI, if you get a decent MAF now you can still use it with a stand alone. Depending on which one you go with at least.

Wasn't sure if that small round metal piece attached to the fuel line on the passenger side was a regulator or not thanks though.

 

[ERod123]

I believe the fuel is regulated by the Fuel Rail pressure sensor on driver side fuel rail. And that round metal piece on the fuel supply line is just a damper I believe.

If you have a good tuner, you can also datalog the car to see what it's doing. Are both STFT and LTFT's for both banks close to 1.0?

 

[03venomdsg]

I believe the fuel is regulated by the Fuel Rail pressure sensor on driver side fuel rail. And that round metal piece on the fuel supply line is just a damper I believe.

If you have a good tuner, you can also datalog the car to see what it's doing. Are both STFT and LTFT's for both banks close to 1.0?

Both 1.0 flat or very close to it

 

[ERod123]

Interesting. Im assuming your intercooler pump is working so your IATs are fine.. I would clean out your IAC valve. Run some fuel system cleaner through your tank. Then I would look at your factory O2 sensors if those haven't been replaced.

That's my opinion, could be wrong. Was this issue present when you had it tuned? Or did it develope after getting it tuned?