Stalling and poor running when cold started
 

Working on a 13 FRS had a hydro locked motor, replaced with a forged internal engine has king bearings, Manley rods and Pistons 12.5.1 compression. And perrin lightweight crank pulley. When starting first thing it starts the high revs then sputters and dies. Restart starts right up stays running but misfires and coughs and sputters the whole time it does the cold start process. After that runs perfect drives fine no codes other than p1603 and p1604. I'm not sure what else to check. Ive changed the di ecm on the side of the motor no change, tried new MAF new upstream O2 sensor, different throttle body, smoked the intake system found no leaks. Fresh 93 fuel put in. It's driving me crazy because it runs so good after the cold start. Also if it's warm or hot like you stopped at a store and went in for an hr and restarted the car starts up no problem and runs fine. Has to sit for at least 4hrs or so till the coolant temp gets back down to 80 degrees or less for it to act up. :mad0259:

Both codes are related. Sadly EVERYTHING involved with running the engine can trigger 1604 on startup. I’d focus more on what may be causing the 1604, The engine speed is less than 500 rpm with the starter signal on for a certain amount of time (Depending on the engine coolant temperature and atmospheric pressure).
After the engine starts (engine speed is 500 rpm or more), the engine speed drops to 300 rpm or less immediately.
1603 is just engine stall history due to the 1604 code. So what you are basically dealing with is hard start/stalling while cold. It’s really not easy for us to tell you what’s going on based on your description as there could be a million different things involved. I would start with talking with your tuner and letting them know you have a hard cold start condition triggering these codes. They may just need to tweak some parameters. The joys of dealing with a modified car.

I asked Bubba and he says the automatic choke is sticking.

Oh, wait one, I just realized that he is hung over from drinking a case of beer last night.

Sorry to have bothered you. - :bonk:

Going to need to log it to see what is going on. Sensor or tune related?

There are very specific tables that relate to engine cold start and are based on the ECT (engine coolant temperature). This could be so many different things, we need a datalog, but I'd love to start by asking- what kind of tune ( if any) is on this car?

As far as I know it's a stock tune, I've change pretty much every sensor I could think of and nothing changes the problem, decided to get it tuned so I could have datalogs and I've sent the first datalog off to the tuner using Zach at CSG. Hopefully just some small changes to the tune and it'll be good to go, ECU wasn't unlocked for a data log until Friday but I will let you know what happens and or what it was.

I check the auto choke...appears to be missing usually has a ignition hot wire on it right? I'll look a little more maybe this car uses the cable style one :iono: jk jk thanks for the funny though lol

Sounds like a mixture problem to me! If your fuel pumps are fine and there are no vacuum leaks its *probably* a tune-related problem.

Update, still fighting this issue also tuner says that everything looks fine and doesn't think it's a tuning issue. I have replaced the high pressure fuel pump because when compared to the BRZ I own it holds pressure in the high pressure rail after I shut it off from a start. The FRS that has this issue would not hold pressure it would immediately start dropping. The new/used pump holds pressure after shut down, I've got 56psi on both port and DI lines running and sitting and they hold pressure for more than 15 min and don't drop. High pressure on start up is about 1800psi @ 1500rpm the when it idles down it's stays around 580psi @ 650rpm. I will say the new/used HPFP does seemed to have helped, at first I thought it was good didn't stall first time I started it but rpm did drop down to 600-700 then it caught itself and stayed running. But more I have driven it with this pump seems the worse the cold starts have gotten maybe another bad pump? I'm not sure because this one doesn't seem to have any flaws I can see in testing? Anything else I could try? Was hoping to figure this out quicker but man what a pain.

:lol:

They all say that.