Random no start

[extreme3807]

Ok, I need to pick someone's brain who is smarter than I am. Every morning my truck will start fine, but if I drive somewhere and shut it down, it will not start back up. On the other hand, if I leave it shut off for a few hours it will start right up, I just can't shut it off and start it right back up. Now this is where it gets weird. If it doesn't start, I can plug my Livewire in, take the truck to stock, reload my IDP tunes and it starts everytime.

No weird codes are being thrown, hooked up a AE to it and everything looked fine. Just need some opinions on what to look for.

 

[Dzchey21]

i take it your batteries are in the bed or something right?

 

[extreme3807]

Single battery on the drivers side

 

[Dzchey21]

is the security light flashing on the dash or anything?

 

[Dzchey21]

I'm going to have about a million questions
usually if you get a no start its something with the security or something, that being said the most common thing to do is use the fender plug that goes right to the starter and jump it to the battery, but since your battery isnt there that complicates things a little but it might be worth a shot.

You have a 4r correct? Is the ecm a manual ecm? What im wondering if something isnt working correctly with either the Park or neutral safety and or a clutch switch? These are all just initial thoughts i have.

 

[extreme3807]

You are correct on the ECM. Now when I initially got the truck, it would start fine everytime. This has only started happening recently. I was also thinking it might have something to do with the ECM or sending signals for park/neutral etc..

At this point I don't even know where to begin. I already tried jump starting it, that didn't work either

 

[Dzchey21]

Well i think what i would need to know is what they do about the truck needing a clutch switch to start, so they may have just jumped pins to make that work or maybe that's part of your PRND321 switches i honestly don't know.


I agree that its weird that it just started doing it and nothing really apparent has changed. And sitting for awhile and working doesn't make sense either. If it was a egt sensor in the exhaust or something you should log a code and have a high idle.


have you tried to clear codes while it wont start? Even though you cant read a code doesnt mean that something might not be there. I dk im kinda grabbing straws here

 

[extreme3807]

Everytime it starts, it will idle up to 1500rpms, as soon as I touch the brake pedal it goes down to 700. When this happens I clear my codes and the idle returns to normal.

While the engine is running it doesn't throw any abnormal codes, and what really confuses me is how reflashing the truck allows it to start everytime

 

[extreme3807]

Originally I had thought a bad ground or a bent pin in my PCM. But I'm not sure how either of those would be fixed by reflashing the truck

 

[Dzchey21]

reflashing almost sounds like an egt sensor problem.

If the truck is idling up maybe you should try to monitor the downstream egt sensors and see if they look like they are reading correctly (not sure what you monitor with)

there are only a few things that will cause high idle
egt sensors
low Ambient air temperature
low coolant temperature
low battery voltage

maybe you have a battery cable issue?

 

[extreme3807]

I'll check my egt sensors tomorrow. I have a Livewire and a CTS I use. Awhile back I thought it was a battery issue too. KOEO I'm reading 12.2 volts and it will jump up to 14.1 shortly after it starts

 

[extreme3807]

I can see the egt sensor causing the high idle, but would it cause the random no starts? I mean if I leave the truck sit about 4 hours it will start again. Just can't shut it off and start it right back up

 

[Dzchey21]

unplugged egt sensors can cause a no start for sure. It may be a deal where the sensor gets hot and causes a reading the computer doesn't like and then after it cools off it will work, i dk.

Check all 4 egt sensors... let me know what you find ill stew on it some more

 

[extreme3807]

Went to start the truck and no joy again

Trucks been sitting an hour now
Primary 140
Second 82
Third keeps jumping from 78-83
Fourth keeps jumping from 68-73

The 3-4 are the only ones that are moving. This is all KOEO from my Livewire

 

[Dzchey21]

thats all about normal i think.

 

[Dzchey21]

stupid question, have you tried to press the brake and try to start it?

 

[extreme3807]

Yup, that never worked. Only thing I have found to work is reprogramming the truck. I have to add that I have to take the truck back to stock, if I go from one pre loaded tune to another it won't start

 

[Dzchey21]

Thats odd...

 

[extreme3807]

Totally lost lol

 

[extreme3807]

Wouldn't start again this morning. Unhooked the battery for 10 min and it started, didn't even go into a high idle for the first time.

Out of curiosity, If a individual egt sensor is bad, what should it be reading on the Livewire so you know it's a bad sensor?