Car dies when let off gas or randomly then won't start back up?

[jesseusmc73]

I've been dealing with this motor for little while finally got it running and finally got the car drive able after fighting a map sensor. I bought the email tune and I'm gonna talk to the tuner tomorrow morning, but i just wanted some more opinions and just to gain some knowledge I guess.

The will randomly die after you let off the throttle and it idles for a sec. It'll go as low as 350 rpm at a stop sign. If its idling in the garage the lowest it'll go is 600. Both of which are concerning. I'd have to give it gas to keep it from dieing on me.

I don't think its related, but if it dies it won't start back up. I'll get a click and that's it. I have wrapped headers, heat wrap on the starter as well as a heat shield and heat wrap on the cable so I don't think its heat soak. After it sits for a few minutes it'll cough and almost sound like its spraying fuel out of the intake(i don't know how to explain it but it sounds moist), but it'll crank and cough and wont start back up until a few more tries. I do have cam pos code so I'm hoping thats it, but ive had multiple cam sensors in it and I've had some sort of cam sensor code for as long as I've had this motor.

Attached is the tune and two idle logs aswell as a running log where it died. The file name will tell you.

Specs-
99 5.3 LM7
Stock PCM
LS3 MAF/
BTR Stage 2 turbo cam-- 226/231 .605"/.598" 113+4
BTR .660 lift springs
LS7 Lifters
LS9 headgaskets
Fitech intake/ Fitech 3bar map


Thank you for your time!
-Jesse

[5FDP]

You have the completely wrong MAP sensor settings for a LS3 MAP sensor.

Try 128.20 for the linear and -0.30 for the offset. With those settings, see if your key on engine off KPA reading is correct for your sea level. So around 100kpa at sea level and less if the live higher up.


The settings you have right now are for some 3 bar MAP sensor.

[jesseusmc73]

You have the completely wrong MAP sensor settings for a LS3 MAP sensor.

Try 128.20 for the linear and -0.30 for the offset. With those settings, see if your key on engine off KPA reading is correct for your sea level. So around 100kpa at sea level and less if the live higher up.


The settings you have right now are for some 3 bar MAP sensor.

My fault i thought the ls3 map was a 3bar, but it has a fitech intake that came with a 3 bar map sensor and thats the one i am using

[5FDP]

Do you have the linear and offset information for that sensor from FI-Tech?

When it stalled it went to 105kpa, that isn't right. The 1 bar channel is maxed out at 105kpa, so the value is even higher than 105kpa.


The log shows it's extremely lean as well, which isn't helping anything. Once the MAP data is corrected, then you can tackle this lean issue.

What injectors are installed and what fuel pressure are you running?? Is the flow rate data setup for the correct fuel pressure??

A wideband will be needed as well, no way to tune this without one.

[jesseusmc73]

Do you have the linear and offset information for that sensor from FI-Tech?

When it stalled it went to 105kpa, that isn't right. The 1 bar channel is maxed out at 105kpa, so the value is even higher than 105kpa.


The log shows it's extremely lean as well, which isn't helping anything. Once the MAP data is corrected, then you can tackle this lean issue.

What injectors are installed and what fuel pressure are you running?? Is the flow rate data setup for the correct fuel pressure??

A wideband will be needed as well, no way to tune this without one.

I do not have the info from FiTech I tried calling them but they weren't any help. I think I'm just going to swap my map sensor off my ls1 intake and get the linear and offsets for that.
Any ideas on fixing the lean issue? I wouldn't even know where to start.

Also I'm running stock LS1 ev1 injectors, A walbro 450l pump with a stock corvette regulator. Its a returnless fuel system with the end of the fuel rail capped off.

Appreciate the help

[mybadrat]

curious, did you ever figure this out?