Tacoma 4.0L hard to start when warm

I posted this thread in the technical chat, but apparently that forum doesn't get much traffic. So here is the link

https://www.tacomaworld.com/threads/2015-v6-hard-to-start-when-warm.500076/#post-15599452

Basically the issue is, when my truck has warmed up from driving, and I let it sit for around an hour, it is hard to start. It will turn over fine, but won't start for about 5 seconds. Cold starting is fine, and if I start it after only shutting it off for a short period it does fine.

So far I have:

Installed new plugs, old ones looked good, but we're definitely worn down.

Installed new air filter

Had battery tested, and it was good

Cleaned MAF

Cleaned pcv, will replace it, but Napa didn't have in stock so had to order.

 

Lots of potential problem here.
Cam/ crank position sensors
Fuel pump
Fuel pump relay
And more

 

I would put a fuel pressure gauge on and see what's going on.

http://www.customtacos.com/tech.old.../06toyrm/06toypdf/06rmsrc/rm2006ta/009000.pdf

 

I am not intimately familiar with these beasts, however I have seen bad ECT and/or IAT sensors cause this on other engines--if either is defective the ECU does not know that the engine is "cold" and does not enrichen the start-up AFR. As others have suggested low fuel pressure, dirty injectors and fuel filter are also suspect candidates. Do not discount the CPS either they can get temperature dependently wonky...

 

FWIW the IAT is with the mass air sensor not separate.
The Ect "should" throw a check engine light. It's near fire wall and hard to spot.
Let us know what you find

 

Thanks for all the responses. I'm not throwing any codes, so I believe the ect is good, but I might just go ahead and replace it.

I'm going to try to do a fuel pressure test sometime in the next week, and I'll update everyone on what comes from that

Also, I'm going to try to resistance test the CPS sensors

 

I'm going through the EXACT same thing as you and it's driving me crazy. I haven't had the truck not start yet, but it's just really weird since I haven't thrown any codes/check engine light/etc. PLEASE post back if you figure this out!

How many miles are on your truck by the way? I'm at 30k.

 

I haven't had mine not start either. Just takes a while sometimes. But cranks right up when it's cold.

My truck has 70k. I bought it about a month ago.

 

Funny. I have the same issue except it long starts when it has sat for a day or so. Not when warm. I should have time to change crank sensor next week.
I'll let you know when mine stops the weirdness

 

Please do. Do you have new sensors? Where did you get them and how much did they run you?

 

Yes I have everything I got it from rock auto using Denso OEM stuff. Changing the water pump so I'll just do the crank position sensor then.
I've change the fuel pump,the fuel pressure regulator, the injectors, and the cam position sensor. I just change the fuel pump relay I'll let you know if that does anything.

 

Damn, sounds like you covered all your bases

 

I would've done a little more diagnostics before throwing all those parts at it, but more power to you!!! Hopefully you have nailed it.

 

Well 185k I figured parts were warranted anyhow.
Also not sure exactly how to diagnose this mystery problem.
Fuel pressure was good thought pump was flaky or leaky injector. What diagnostics would you recommend cuz I need the help

 

I would've started with duplicating the condition. Put a fuel pressure gauge to it and start with the key off then have a buddy turn the key on. I've seen fuel pressure regulators give a long crank symptom. If you got good fuel pressure as soon as you hit the key the pump and regulator are fine, if it's taking a long time to build chances are the regulator is fucked. If everything is all good. It's time to bust out the scanner and start checking crank sensor voltage.

 

I actually did not think about throwing a scanner and watching live data. Good idea. I'll see if mine does that. Parts weren't too pricey. I figure I've saved compared to a shop attempting fixing this.

 

I did this with a buddy's scanner and everything looked fine as far as the computer was concerned.

 

Can anybody explain alittle better what you need to put a temporary fuel pressure gauge on? The parts in the link earlier didn't pull up anything on Google, and there isn't alot of info out there on adding the port.

BTW, tacomaholic, I really enjoy your YouTube channel. I've been watching alot of your videos lately. Good work

 

Thanks man! Much appreciated! I just crossed 1,000 subscribers.