Cold start issue: 2.7L Stumbling/Stalling UPDATE: Fixed

Something's definitely a little odd, hard to figure out much more without being at the vehicle.

 

https://datazap.me/u/goldentaco03/log-1617998488?log=0&data=16-17-20
These seem muchhhh better...a little lean at one point and a little rich at one point though

 

I'm not sure why it's showing two banks because it only has one but bank 1 fuel trims look pretty normal (should be +/- 10% Total Trim (Long Term+Short Term)).
Based on symptoms I'm thinking you have a fuel pressure bleedoff problem.
You would need a fuel pressure gauge tapped in when the problem occurs to confirm (fuel pressure should not drop below 21 psi for at least 5 min after engine is turned off) but that's the classic symptoms.
When the fuel pressure is allowed to bleed off there will be no fuel in the rail when you go to start the engine and it takes time for the fuel pump to build pressure, when the engine is hot the problem will be worse because without pressure the fuel will boil in the rail and force everything back to the tank leaving nothing but vapor in the lines so the pump has to prime everything back up.
If you determine that is your problem you will have to pinch off fuel lines to determine if it's the regulator, injector leaking, or faulty check valve or seal in the fuel pump.

 

I'm also starting to think fuel now...I went to fill up this weekend and it wouldn't start after I filled up my tank. There is some sort of pressure loss/gain going on when the engine is hot and I try to restart it.

 

Interesting; purge valve?

 

Charcoal canister replaced 4 years ago
Fuel pump assembly replaced with Bosch less than a year ago
Strainer replaced with denso less than year ago
All vac lines replaced with silicone lines about a year ago

Entirely possible that one of the vacuum valves in the engine bay is malfunctioning. That’s easy to test, although they generally throw a code. Or something along the lines of the fuel pressure regulator. My evap test still hasn’t completed since I reset computer....it’s been over a week with lots of cold nights sitting.

 

I hesitate to bring up something so simple, but you haven't mentioned it in your lists of parts replaced.
Have you ever replaced the fuel filter?
My 2003 2.4 was getting very weak off-idle; I had to slip the clutch to back out of the garage. I replaced the (original) fuel filter, and now I have to be careful leaving a stop or I chirp a tire.

 

I have not, I’ve thought about it but it’s such a pain to replace on these 4 cyls. It is on my to do list eventually

 

Shoutout Spokane lol

 

Hey man, I’m having the same exact issue on warm days or after driving to the store. I drive a 96 2.7L 4 cylinder manual. I’m not sure what’s the deal. I’m just now starting to try to figure it out, mind you I have 280,000 miles on it. Let me know what you figure out!

 

You out in Spokompton too?

 

Grew up there, now I live in a small town by mt hood. I recently bought my taco from someone in Spokane though!

 

I'll keep this thread updated...seems to be a pretty common hot start issue for these trucks. Not really a huge issue though cause the truck still starts and runs fine. Just takes a little coercion

 

it only happens when I drive a lot or on a hot day. But the yota never seems to leave me stranded. Always starts up on the second or third crank. But recently it’s happening more often with the warm weather coming in, so let’s get it fixed before summer! Lol

 

Maybe our Throttle body’s could use a cleaning

 

On the old 4 bangers, I had one for a long time, the intake air temp sensor is a separate item in the airbox and it goes bad, might be worth checking to see if its registering correctly, if not it will cause long hot starts from over fueling

 

I was reading some other threads on it last night, I think they were v6s. But there was a long list of possible fixes and some things worked for some people and didn't work for others. It's gonna be a tricky one. My TB was cleaned about 30k miles ago.

 

It wouldn't hurt to do it again, but I doubt that's your issue

 

Okay so this is only happening when its hot and sunny out...today sunny and 70 deg. I got a log of todays episode. If it's warm enough I'll have trouble with hot starts and cold starts. If I pump the gas it starts up. I'm starting to think its a fuel issue...leaky/stuck injector, FPR, bad pump check valve. I'll be adding injector cleaner to my gas tank this week and I'll also pull the vac hoses from the FPR and see if any fuel is leaking into them indicating that regulator is going bad.

I unplugged the MAF after it stumbled and stalled today and it still had trouble starting so that is ruled out. Still need to test the IACV

 

OKay this is the weirdest log file yet. Issues cold starting and hot starting yesterday. Drove 10 minutes to the creek, went fishing for about 30 minutes hopped in turned on my datalogger and tried to start it again. Turned over and stumbled and ran for a second at very low rpm then died. Tried starting again and it just kept cranking until I gave it a good bit of gas. The log file seems to be indicating that RPM reached about 200 RPM for 2 seconds and then reads 0 the rest of the time. The log file is 46 seconds long so the second (successfull) attempt starting should've been captured along with about 10 seconds of idling. Is this an indication of anything or just a bad log file? Bad crank position sensor?

Note: I tried to load it into DataZAP but I was having issues and the short term fuel trim was not displaying