Starting issues

[shmiet]

So I swapped a 5.3l into a 98gmc, and i cant get it to cold start. If i squirt fuel into the intake, until the engine warms up, it runs fine- i can shut it off and start it up again no problem. But if i let it sit till its at room temp it wont run. It also wont run, even if the engine is warm, if my iat is hooked up. I have the maf removed for sd tune. I wasnt pushing boost yet(have the tubing disconnected before the tb- has the iat and bov on it). Any ideas as to what could cause this issue?
it has 60lb/hr injectors, tu1 cam, 2bar map, aeromotive 340 stealth- if you need more just as.

[lukesmith01]

I was having the sort of the same issue with mine. I was told I have to do an IAC relearn. When the PCM is swapped or stuff (IAC) gets unplugged the PCM looses track of where the valve is and is consistantly trying to compensate and "learn" how to idle again. These are the two things my PCM and harness guy told me to do.

PCM Hard Reset: (Gets rid of all the bad stuff I was trying to teach it.)
Unhook Battery for 15 seconds or more.
Reconnect Battery.
Put key in on position.
Push pedal to the floor (WOT) 5 times.
Key off.



IAC Relearn: With IAC Plugged in...
Key On 5 seconds.
Key Off 5 seconds.
Key On 5 seconds.
Key Off 5 seconds.
Start.

Good luck!

[shmiet]

Well i can get it to idle, but only when my engine is warmed up. It sucks really hard before it dies when i try to start it cold. As soon as i connect my iat(intake air temperature sensor) when the engine is running it kills the engine. I will try what you have suggested today or tomoroow though, thanks man

[blacstar]

check fuel system. do the spark plugs get wet on cold start?

[shmiet]

Ill check that too, although i think when it starts sucking really hard its cuz its not getting enough fuel- I squirt some fuel in the intake and it keeps it going. All injectors pulse, constant 62psi fuel pressure- (drops to 40 when off -slowly goes down to zero after 6hrs or so). Can parameters in the tune be altered to squirt more fuel, when engine is below a certain temp?

[shmiet]

I think it has something to do with the tune. I got hp tuners today and it looks like the iat works fine(shows 26 degrees Celsius, which was the ambient temperature), so Ive concluded its just not enough fuel. Smells a bit rich when i do get it running-I assume more fuel due to the default -39 degrees celsius when iat is disconnected. I'm booked for the dyno next friday so heres hoping my tuner has a solution for it. Right now it has a tune for a 6L procharged mustang ls swap, which he said it already shoots more fuel than he typically tunes for. Ill prolly get a WB02 next week just so I get a better idea of what the afr looks like. Thanks guys for your help, I really appreciate it. I will post a build thread within the next month, i have alot of pictures so hopefully it will be helpful to someone.

[pl4yboy]

Ill check that too, although i think when it starts sucking really hard its cuz its not getting enough fuel- I squirt some fuel in the intake and it keeps it going. All injectors pulse, constant 62psi fuel pressure- (drops to 40 when off -slowly goes down to zero after 6hrs or so). Can parameters in the tune be altered to squirt more fuel, when engine is below a certain temp?

The majority of fuel tables reference egts.

[lost06]

I had a similar problem. I had a bad ground and the O2's were bad.

[shmiet]

It was a tuning issue. Fixed it. Blew up the motor on the dyno. Bought a 5.7l LM7 from Thompson engine and itll be here this week

[BIG BLOCK 555]

^

what happend ? tune problem or something els ?