nickleahy23

iTrader: (1)

This is on my Lq4 swapped Tahoe. Stock Motor, LTs, BB tune, Intake, Efans. Hasnt been changed or messed with in 3 years mod wise, only regular maint.

This problem came around a month ago or so when it got really cold and it hasn't gone away. It DOESN'T happen every time which confuses me.

I start the truck and it instantly starts (not like a bad FPR, also doesn't make a difference if I prime it or not). It will idle down and die. I have to give it throttle most of the time to keep it running. Once im driving, its fine and it runs great, no miss, rough running etc. Pulls as hard to 6k as it always has.

Most of the time (when its doing this) it will idle down so low(2-300 rpm) when i'm coming up to a stop sign or turning that it dies and I have to quick get it in Neutral and start it up with some pedal. I cant find or hear any vacuum leaks, and because it happens randomly I sort of ruled that out

I almost think I can smell a faint smell of raw gas (Long tubes and ORY) which makes me wonder if its running too rich sometimes and it kills it?

2 days ago I seafoamed it, changed oil, changed plugs (NGK Tr-55), fuel filter, air filter etc and it didnt change a thing.

Like I said, this doesnt happen every time. I can drive it and its fine, shut it off, start it 10 min later and it wont idle.

Im going to hook up the autocal tonight and log some data. Ill try sending it to Justin if he has time to look at it. Just a real pain in the *** when i have to 2 foot it all the time to be able to drive through town.

Going to check fuel pressure as well.
Might try swapping TBs with my other truck, could be an IAC?


Cliffs-

Truck sometimes idles so low it dies on start and when coming to a stop. Sometimes it runs perfectly fine, no pattern to when its good or bad.
Did a tune up and problem still persists

Not sure where to check next, any help would be awesome.

nickleahy23

iTrader: (1)

Well **** it was the FPR. Swapped it with the other truck and it went away.

nickleahy23

iTrader: (1)

Well never mind that..the pos did the same thing this afternoon..started and ran fine probably 20 times last night and this morning..I don't get it

greasemykey

iTrader: (5)

does it only do it in gear? i think maybe your TC is not unlocking and stalling the engine.

nickleahy23

iTrader: (1)

no sir, its normally on start up. It will start and sputter and die, start then idle at 2-300 rpm , or start and run normal without a hitch. Last night I must have started it 20 times, drove it around for 25 miles and it never missed a beat, started it this morning (-11F) and it started instantly and idled normal. Started it for lunch 4 hours later and it died and I had to 2 foot it at every stop sign heading home or else it would idle down so low it would die.

Fuel pump was a new Delco pump about 3 years ago. I guess ill go rent a fuel pressure gauge and try that along with some datalogging.

greasemykey

iTrader: (5)

idle air control sensor or TPS sensor may be bad. do you have access to a scanner with live data?

i didnt read that part you had a way to data log.

nickleahy23

iTrader: (1)

Thats my next guess. I was thinking I could just swap sensors with my other truck as I know those are new, but ill check it out on the laptop this afternoon and see if I can tell anything from that.

nickleahy23

iTrader: (1)

I have no idea. Looking at the logs, everything seems damn near the same from a bad, rough idle to a perfect smooth idle. I did have one log where the IAC went 29-10239 but the other bad idle log the IAC was about the same as the good idle. cold, hot it doesnt matter. Once it runs good, it wont run bad until after a restart. Same with running bad, if its running bad, it wont idle good until after a restart.

greasemykey

iTrader: (5)

unplug your iac and see if you can cause the same symtoms. what about your map sensor? how is it reading? check it koeo and engine running

greasemykey

iTrader: (5)

also what about your O2 sensors. i see you have a tune. one other thing that caused the same issues on my truck was my intake came loose from the TB and it would idle like **** and stall out