05 4.7 hard starting

Installed new regulator (for a second time). pressure goes up to 44psi (little higher then the previous tests that were 40-42), at shut off it now holds. it drops to about 42. after 5 mins it was at 30psi.
after 1 hour it was down to about 12. The FSM only does a 5 min test (21+ psi), so not sure if it should hold for hours or days? I'll do a test tonight and leave gauge on overnight and check in the morning.

So once again, I install a new regulator and it fixes the no pressure problem. Perhaps the Toyota one I bought did in fact fail. Or maybe the pump caused it to fail? I'll keep my eye on this new one for a few days and see what happens.

ordered my set of dirty deeds 12 hole injectors. excited to get those installed!

 

was still having problems, so installed new fuel pump couple weeks ago. Had a long drive and then experienced a few hard starts and a couple stalls/engine die while leaving a parking lot. So fuel pump didn't fix the problem, as I was afraid of. Waste of $300...

Installed the Dirty Deeds 12 hole injectors. Haven't driven much, but does feel like it drives smoother. But have still had some hard starts so that didn't fix it either. I wasn't expecting it too, but figured it was a worthwhile improvement regardless.

So I've done fuel pump resistor, fuel pressure regulator, fuel pump and injectors. I think I can rule out a fuel issue.

So now what? not getting any check engine lights outside of when I cleaned the Throttle body. Must be a sensor, first guess would be the MAF (which i've cleaned a few times).

Any advice before I throw more money at it? Hard start can be 2 or 3 tries before it fires, and a few times now after a long drive it will die while at idle/low speeds. So not something I can just ignore.

 

inspect the purge valve on the intake above the oil fill cap. Stuck open or a vacuum leak in that line will cause similar symptoms. do you have a way to look at your fuel trims?

 

I don’t know how/why I over looked this but has anyone mentioned cam/crank sensors? Different model but they are notorious among many brands for causing starting issues.

 

You can check and clean up all of your battery/engine grounds. Sand the paint down to bare metal. Clean the contacts. Grease things and snug them down.

There is a big ground behind the engine on the pass side to firewall and one next to battery. Two smaller ones behind engine for ECU. Cheap and easy fix if this is the case.

 

I'll check purge valve. Hopefully FSM has something about checking that. I was starting to lean towards EVAP, PCV, VSV and such emission items as possible causes.

I have a code reader, but think you need an obd/smartphone app for checking fuel trim, correct? it runs great all the time besides the occasional hard start and a couple stalls after a long drive. Besides the new injectors this truck is all stock engine wise and I plan to keep it that way.

I've thought cam/crank sensor since day one but without a code that seems less likely to me. The hard start makes me think those, but not the warm engine issue where it dies at low speed. That seems more like a fuel issue (now ruled out) or an emission problem. But anythings possible. Don't feel like tearing into change those without a stronger case for it, especially since I just did the full Timing belt job 10k ago... I'll do some more research on these. Also need to see if I can check my MAF sensor as the other sensor on my suspect list.

new(er) battery and all connectors and grounds are clean.

 

I would think if sensors were to blame there would be an engine light or code associated with it. That being said, the original code was for MAF. May be worth replacing that. 05 is an air pump system engine correct? No idea how those behave when they're going out. You only need fuel, spark and air. You've chased the fuel component from one end to the other. You said the plugs were good, how about the coil packs? I've heard tell of the tubes going to the plugs cracking and shorting to the block instead of sparking. Heat would effect the expansion or contraction of that plastic and could have some effect on when it happens. Worth a look if it hasn't been checked. With no CEL lights on, I'm less inclined to believe it's a sensor. Best of luck, the solution will present itself, stick with it.

 

P0102 and P0113 are circuit codes. This suggests wiring issues/ or failed maf failed iat? Is Iat integrated into the maf? or is that measured elsewhere? If they are both housed into one harness those are strong clues. Your symptoms suggest unmetered air entering somewhere. So I wouldn't buy anymore parts until you resolve whether your maf is reading correctly, and no air is entering somewhere else. And as PHM has expressed a bad ground will do nutty things to sensor behavior.

 

agreed, I've mostly ignored sensors due to having faith in the CEL.

I cleaned the MAF a couple times, I did get a check engine light after cleaning the TB (while on the truck) for the first time. I didn't strongly consider it though because it only occurred from the TB cleaning (might have got a little carried away with the spray cleaner). since then no MAF codes. But I am leaning towards replacing that sensor anyways. If nothing else it is the easiest one to do.

All the coil packs look good. No obvious signs that one or more of those are to blame.

edit* yes my truck has the notorious air pump. but from research that gives a very specific code and limp mode condition. I've researched the hewitt-tech bypass which i intend to do someday. but don't think it's related to my current problem.

 

the IAT is part of the MAF. I chose to ignore sensors as the symptons and fuel pressure tests kept me focused on the fuel system. apparently incorrectly so. I will start checking/testing what sensors I am able to.

the intake is all stock, i've had it off to clean it out and inspect. no obvious signs of damages or possible leaks. truck runs great besides the hard starting and couple dies after long drives (over last 3 months).

I have a strong suspicion it is the MAF. Mostly due to the few times it has stalled/died.

I've checked/cleaned battery connections and grounds. My truck is in really good shape, and engine bay is about as clean as they come. I'm confident this is not a electrical problem. It doesn't occur very often, and when it does occur seems to be under similar circumstances.

 

appreciate everyone's help on this! I'm a capable mechanic but input from others who have possibly experienced it before is very valuable. I'm trying to thoroughly document this process to hopefully help someone get to the solution easier (and cheaper, dang fuel pump...).

I plan on keeping this truck for a long time, or at least will stay in the family so replacing some of the components without it being the problem is not a big deal. I'll call it preventative maintenance and that can help me sleep a little better.

 

the maf circuit codes require large voltage malfunction. So if you are in a incorrect voltage but not extreme it will not set a code it will just over/under report airflow. when running at 20-40 g/sec a 3g/sec error is small percentage and it will run fine but wrong. At start up or idle , it will cut fuel to match 3g/sec but you might be sending 6, that would be 29:1 af ratio = hard start or stall at idle. get out the multimeter and test test test.

 

you got a spike on the iat and a voltage loss in the maf, but only when you removed the intake tube (which wiggles the connections). The sensor could be bad. but, inspect that connector, pins and wiring because that is a fishy combo.

 

I'll search the FSM after work on MAF testing.

I've had the MAF sensor and entire intake tube off/on several times with no change in behavior. I like to say anything is possible, but I don't think this is a loose connection.

Although I've said previously it is a random problem, it is consistent in when the random problem happens. the only times it has died was after a long drive (2+ hour). The hard starting is also more prone to happen in certain conditions. At first it all seemed random, but the longer it has gone on the more I have learned when to expect it. Such as it never hard starts when I leave for work in the morning, but it occasionally hard starts when leaving my kids soccer practice (sitting for 1 hour after a 20 min drive). That consistency leads me to believe its not any sort of electrical gremlin... But who knows, anything is possible.

thanks for the feedback.

 

This is the part that would lead me to test the vsv purge valve. That one is even easier to test than the maf.

 

when you mention VSV purge valve, you are referring to the EVAP valve correct? I don't see any mention of a purge valve in the FSM.

 

VSV purge valve from charcoal can to throttle body should be closed at start up. And all those lines need to be airtight.

I don't know the exact phrasing, because my fsm calls it different things in different pages. But, yes it is for evap, not sais. The fsm over complicates the diag. But its definitely in there. When I search vsv, my ipad crashes because there are so many results.


basic function test-
https://www.youtube.com/watch?v=PDVcuJZn3YM&t=118s

 

Throttle Body Cleaner, per FSM, is not to be sprayed on the butter fly. It will travel down the pivot and into the sensor carrying dirt and solvents.

Per the CEL in general, my o2 Sensors were way out of spec (zero resistance! ) and didn’t set off the CEL. Yes it works/lights at starting truck, but not for the bad sensor.

 

Changed MAF sensor. no fix.

Changed Crank position sensor. Started truck, it idled really erratic. So unhooked battery for 20 min. Re-hooked up battery and started and it ran fine. I let it warm up/idle for 10 min or so. Did not drive it anywhere. Feeling pretty good that this was the problem all along and called it a night.

This morning I go to leave for work, it starts hard and is idling really erratic again. this time check engine light is flashing. Code is P0300 random misfire. So took the camry to work instead, have the day to think it over and scratch my head for a bit. New crank sensor obviously made a change, but why is truck running bad now? Any ideas appreciated.

 

Alternator still the original? Might be electrical problem. Not enough generation to maintain the Mojo. Just a guess.

 

yesterday got home from work. checked the codes again, p0300 random misfire and a misfire on each cylinder. unhooked battery for 30 min.

started truck up again. erratic idle but not misfiring as bad, no codes. let it warm up at idle. Then drove around neighborhood for 20 minutes or so. everything seemed fine, idled well. Restarted several times and running normal.

This morning start the truck up. again erratic idle, misfires and check engine light comes on. check codes, random misfire, misfire on every cylinder and P0335 crank position sensor code. This is a brand new toyota oem sensor I just installed. tried to start again and didn't want to start.

so now I have battery unhooked. Will remove the sensor and check connectors and such. Running out of ideas...

 

was removing the LH timing cover to inspect/test the cam position sensor. this required taking off top radiator hose and unhooking several sensors, in the process saw that the crank position sensor cable was touching the accessory belt and had been half way cut through... YIKES. sure that explains the odd behavior last 2 days.

Not sure if this has been my problem all along, or if it happened when I first removed the crank sensor, re-installed, then replaced few days later. Although I didn't have to move the harness much, good chance it was moved enough to to interfere with the drive belt.

So all the codes and rough idling should be corrected. We'll see if it corrects the original problem. now I have to go clean up that mess in a blizzard while my truck is stuck in the driveway...

 

Well I was somewhat close! Lol.

I would beat that has been your issue all along. All the symptoms point to crank sensor issues. If the sensor isn't reading the crank position correctly, it will effect drivability issues like you mentioned. Keep us posted and let us know how it works out. Good luck!

 

I would like to think it was something as simple as the bad wire, but then it also makes me feel stupid for having done so much other crap. But never really crossed my wind that a wire would be damaged.

From the beginning I thought cam/crank sensor but had faith that a code would be thrown if it were in fact one of those. So between no CEL and the weird no pressure at shut down thing my attention was fixed on fuel system. The occasional stall when warm just complicated diagnosing further.

I've got it all put back together, it's running just fine now. Time will tell if the original issue is fixed or not. I really hope so!

 

Nice job tracking it down. Thanks for posting back with the results.

 

UPDATE: been driving quite a bit last 2 weeks, short trips, longer trips, cold starts (winter), hot starts... no issues. RESOLVED.

 

Thanks for reporting back, this may help someone in the future.