Tacoma 4.0L hard to start when warm

Yes, swapped plugs, put all new ngk all around. Also replace pcv, and tried a temporary new coolant temp sensor. Also swapped relays around inside the box to see if any of them were bad.

Fpr next? Or crankshaft position sensor?

 

Go with the cheaper of the two, as of right now and rule out fuel system malfunctions and replace the FPR. If the issue is still occurring it would be wise to replace both VVT/ CMP sensors. There should be one per bank unless Toyota has some sort of way of integrating both can/vvt signals into one sensor.

I really can't see the PCM being at fault here but failures have been reported on them in the past and in automotive, anything is possible. Try what I suggested in that order of elimination, if that fails, you may have a deeper underlying cause which would require professional shop style tools and equipment to further inspect.

 

So far to date I've changed
fuel pump
fuel pressure regulator
All injectors
cam position sensor
Crank position sensor
fuel pump relay
Long start remains.

I'm thinking vvt next I think there's two also thinking temp sensor but I have no money because long travel.

 

As far as I know, VVT sensors are the cam sensors also. Without taking an in depth look at the way our trucks are designed using a system like AllData which I have access to, I would be more inclined to believe that VVT and CMP sensors are one in the same.

 

Hmm. Could be I haven't gone there yet. Good point/question.

 

If these items are replaced by you and you are still experiencing a long start condition, there could be an underlying issue in the computer itself. I hope not.

 

Yeah same problem. It's just annoying really. It always starts, I've been on massive road tripsand all, It's just not normal so I've been after it. Started at about 183k miles.

 

Any clue how tight the fuel pump housing needs to be screwed on the tank? It said in the instructions to Mark a line and tighten it back til it lines up, but it's either too loose, or I am going to have to really crank on it to make another turn to line up. Any thoughts?

 

Also, after a fuel pump swap, would the ECU need to do a relearn? I'm hoping maybe the long starts might go away in a day or two as the system relearns.

 

You know at 183K the issues are so vast that it could be anything really. Right now we are taking shots in the dark as all the parts have a good amount of miles on them.

The large fuel tank o ring handles sealing, get it to the point where it is tight and if you cannot turn it anymore with a mallet and a large flat blade screwdriver just call it good.

I tightened mine using the mallet and flat blade screwdriver method. As long as the o ring is seated properly the tightness of it is negligible as long as you get it good and tight.

In my experience it would be wise to do a battery terminal disconnect and touch the two wires together for 10 seconds to drain all computer capacitors. Reconnect to battery and run to allow the computer to relearn proper values. Sometimes that tends to resolve odd running conditions or start up glitches after the particular part causing said odd running or start up condition has been replaced and is now functioning properly.

 

Yeah with my mileage I've been okay with shotguning parts into it as they are all probably due for a change anyhow. But the problem remains... (sad face)

 

Rather than continuing to throw parts at it, I would start here. When you had the FP gauge connected, did you check for pressure while cranking? It sounds like there may be a delay in the fuel pump signal.
http://4runnerclub.com/i/4r_files/f...7toyrm/07toypdf/07rmsour/4runnerr/0050028.pdf

Here's a link to a 2005-2006 FSM. I wouldn't think much has changed in circuit opening and fuel pump energizing circuits. Unfortunately the online version doesn't work, so you'll have to download the zip file. Engine control system pages start with 005.
http://web.archive.org/web/20080731033603/http://www.ncttora.com/fsm/

Good luck.

 

I checked pressure while cranking, and I believe it was within spec. I don't trust the fuel pressure tests, since I had to use multiple adapters. I will resistance test my relays according to the flow chart you linked. I had been looking for that, but couldn't ever find it.

 

So I dropped the tank again today, pulled the fuel pump assembly cap, cleaned and lubed the o-ring, and it went back on perfect. No leaks... Thank goodness.

Now onto the real problem, still having long starts. I reset the computer, and checked all the relays according to the link posted. Everything seemed to be within spec.

As I was working on the tank I thought of another possible cause. What if I have a leaking injector, and it is flooding the motor on startup? If I don't leave it off very long, not much leaks into the cylinder, and it cranks fine. If I let it sit for a long time the fuel evaporates and it cranks fine. But when it sits for 30 minutes to a few hours the fuel floods it out giving me the long start. Does this line of thinking make sense?

So as a rudimentary rest of this theory, I pulled the relay and release fuel pressure right after I got home. I waited for an hour or so, reinstalled the relay, and tried to crank it. It cranked up pretty good. So without having fuel pressure, the injectors couldn't leak right?

I'm going to try this test a few more times and see if it keeps cranking fine. Also, I ordered the urd fuel tap, so I will be able to conduct pressure tests more accurately once it comes in and I can install it.

 

Have you clean the air flow sensor? that was a solution to my 1st gen .

 

Yes, that was one of the first things I did. Mine was pretty dirty, but it seemed to clean up fine with a can of MAF cleaner

 

That not only isolates the issue at the injectors but it also isolates the issue to the FPR as well. I have heard of issues with the FPR before on the 2nd gens, though somewhat rare it does happen. Injectors are super rare, as the ones which come supplied in the truck do not have a history of failure rate for leakage. Now, me personally I would pop on a new regulator before I condemn the injectors. If and when that times that you do need injectors if the FPR is ruled out I have a set of OE N/A fuel injectors off my 12 with about 50K on them if you do end up needing them. As I am supercharged so I no longer have any need for them. As I said though, rule out the simpler suspect in the FPR before you go removing the intake manifold to replace injectors.

 

Thanks for the offer, and I'm not going to do anything until I get an accurate fuel pressure reading. I plan on installing the urd fitting Saturday and trying to do the pressure test then. I'll check running pressure, and then check to see how much leak down I get. If I have any significant leak down I will isolate the injectors. To isolate the injectors I will crank the truck, get the pressure up to appropriate levels, shut it off, and then quickly clamp off the supply and return line. That would leave the only point for fuel pressure dropping to be a leak in the rail, or the injectors.

I was really just wondering if my line of thinking that I could be flooded after a certain amount of time made sense.

 

When it comes to cars ANYTHING is possible.

That is a valid test method for isolating fuel pressure leakage at the injectors and FPR. Just make sure you don't damage the lines when clamping them down. They could potentially break/ tear when doing so.

 

Yeah, I got some duck nose vice grips and I'll put rubber tubing on them and clamp down. Hopefully I'm not buying new fuel lines.