05 4.7 hard starting

Need some advice. 05 Tundra DC 4.7 108k, well maintained. Owned for over 8 years. New battery in May.

Few weeks ago it was hot (100+) and truck sat for couple days, on startup it didn't start after 10 seconds or so of cranking. Tried again and it fired. Never done this before and figured it was vapor locked. Did it again a couple days later.

Put in 1.5 cans of seafoam.

Driving back from a backpacking trip (3hr) it ran fine, get to town and leaving a stop light it hesitates and dies. Starts right up. Hesitates couple more times but doesn't die.

Cleaned throttle body on truck. Throws CEL P0102 and P0113. Both MAF related. Not surprised with the spray cleaning. Cleared codes.

Cleaned MAF. Cleaned Throttle body off of truck thoroughly. Still occasional hard start.

Took truck to dealer for prescheduled transmission flush (100k sealed trans service). While I'm there I have them do the intake/fuel system cleaning. Not sure exactly what all they do, but I know they hook up injector cleaner to the rail and pump it in.

It still has extended crank times periodically, maybe up to 5-7 seconds. Seems to be worse when truck is warm and then sat for a couple hours. Seems to be worse when its warmer out, but its summer so can't say for sure ambient temp makes a difference.

Checked all spark plugs (replaced at 100k) for fouling for a possible injector issue. They all look clean with correct gap.

Have had a few long drives including towing my boat and in hot weather. Couple tanks of gas. Haven't had any more hesitation/stalls, truck runs great (as always) just the ongoing occasional hard start issue. No further CEL have come up.

Hoping someone has resolved a similar issue. I've gone a few days without any issues, then it will be back. So not sure whats going on, any advice would be appreciated! I am often in back woods areas alone and can't have reliability doubts on my truck. Hunting season is approaching so need this resolved. Thanks!

 

Do you know if they replaced the fuel filter?

 

Just a shot in the dark...Maybe a problem related to the fuel pump. If the gas in the line is letting fuel go back into the tank, it will take some cranking to get it back up to the engine. Good luck!

 

fuel filter was my first guess too, so I climbed under truck looking for one and couldn't find it. turns out 05-06 is a strainer internal to the pump. So no it has never been replaced.

 

fuel pump is high on my suspected culprit list. From tireless searching it doesn't seem that these trucks have too many fuel pump issues though. Also seems like fuel pumps either work or they don't, but not sure how accurate that statement is. Dropping the tank to replace a pump is not something I look forward to doing, especially if I'm not 100% confident that is the problem. Luckily the tank sits between the rear axle and a front crossmember, so shouldn't be too difficult to drop if it comes to that.

If enough people jump on board thinking that could be it then I'd commit. So thank you for the feedback. I'm just really stumped with the intermittent nature of the problem.

 

I had a similar issue with a long crank or no start at times. I cleaned the MAF, throttle body and intake tube and haven't had a problem since. Here is my thread for reference: https://www.tundras.com/threads/occasional-crank-no-start.57039/

 

New battery in May! Did we meter test it anyways?

 

It may not be a "typical Tundra" problem, but I'd certainly look at every possible solution before I drop the tank, too.

 

Brand new from Toyota. It turns over really strong so I'm fairly certain its not a battery problem. Had that battery for a couple months before this problem started. But no I have not tested it and suppose I should look a little closer.

 

Check grounds.

Maybe check/clean up your grounds at the battery and the one behind the engine at the pass side firewall. There are also 2 ECU grounds back there. One one each side of the block just below the Valve Covers.

 

I read your post in my initial searches and took from it that your ground cable was the bigger issue, haha. I removed and cleaned the TB meticulously and cleaned the MAF twice with appropriate cleaner. I have not cleaned the intake tube, but did blow dust out with a leaf blower (removed from truck of course). Thank you for your input.

 

I did unhook battery cables for a time for a "reset" of sorts after the initial TB and MAF cleaning, at that time I cleaned both Battery posts. I have not but should go through and clean up all the ground connections. I will do that tonight. Thanks.

 

This is a cheap (free) and easy start before throwing money at it. The grounds behind the engine block are difficult to access, but doable. I use electrical conductive grease on all my stuff. Not required, but nice if you have.

 

You mentioned you already cleaned your TB and MAF - I'm a potato, didn't read your whole thread, sorry.

Any chance for a vacuum leak somewhere?

Starter contacts possibly worn out?

 

I visually checked all the vacuum hoses. But could check a little closer.

It always turns over strong, just delayed in firing. So don't think it's a starter issue. My truck has "auto start" I think it's called. So one flick of key and it turns over until it fires. Always use to be instant start up, now it's sometimes several seconds. Not normal.

 

Excellent thread, SP--peeps often miss grounding issues causing electrical problems.

 

You could try bypassing the fuel pump resistor for a couple weeks to see if the issue continues.

If that solves it, it could be as simple as the resistor not passing enough voltage when it's heat soaked.

 

this sounds interesting... Could you elaborate? are there specs in the FSM for checking the resistor?

 

Yes.

 

Thank you, I'll check this.

 

went to remove the fuel pump resistor after a 15 minute drive so I can check it tomorrow morning, it was really hot. could only touch it for a couple seconds hot. I know a resistor generates heat, hence its mounted in a heat sink, but seems like it was hotter then it should be. Anyone care to feel theirs after a short drive and report back how it feels? I will check the resistance on mine tomorrow morning when it has cooled down. but early results aren't promising, not sure my multimeter is designed to measure resistance that low, as my readings are not repeatable and move around a bit...

 

checked the resistor with my cheap-ish multimeter and it fluctuated between .6 and .9 ohm. randomly fluctuated and never settled, but seemed to be more in the .8-.9 range. Borrowed a $1000 Fluke meter from a co-worker and the readings on that also bounced between .7 to .9 but was more consistent around .8. This was measured with resistor off of the vehicle in air conditioned building more then 12 hours since last installed on truck. Its supposed to be .7 so I think I'll bite and purchase a new one of these. But with summer wrapping up and this seeming to be more of a hot weather problem, time will tell if its really the solution.

would still like to hear some feedback if anyone else's resistor (located on passenger side fender well near the air box on my 05) gets very hot after a short drive. guess I'll find out for sure when I get the new one installed.

 

Just checked for you.

I let the truck idle in the driveway for about 10 minutes. The resister is definately way too hot to touch. My IR thermometer said 175 degrees F.

 

Thanks, appreciate it. I'm surprised they get that hot but honestly never checked before now so I guess it's normal. My resistance readings were still outside of normal range, so will give it a shot.

 

I was going to ask you how much the resister cost. Then thought, I have Google, I can find that out in about 5 seconds.

First hit that came up was this: https://www.tundras.com/threads/fuel-pump-resistor.54240/

He bypassed his. Might be worth trying for diagnostic purposes. I'm not sure the reason for a resistor. All the fuel injected vehicles I've owned have a fuel pressure regulator on the fuel rail, and the pump runs 100% all the time. The fuel pressure regulator dumps off excess pressure and re-route's fuel back to the tank.

 

Mine read .8 solid in the 90° heat of mid day when I checked it a few months ago. Figured it was good to go since the ambient heat was giving to slight Ohm Boost.

I wasn’t having any problems, but was just checking it for grins since I was submersed in the FSM Reading.

I’m wondering if the multimeter rounds up to .8 if the reading is .75 or .76?

My Ohm didn’t bounce around.

 

I wire brushed all the Aluminum Oxide off the Resistor and made it look shiny. That Oxide can hold heat. Sprayed some Fluid Film on it. I also cleaned up the contact point on the frame to resistor mating and put some conductive electric grease there.

 

yeah I saw that thread, thanks. the hard part with mine is most of the time the truck starts just fine. maybe over last few weeks 1 in 20 starts is a hard start (extended crank). so bypassing wouldn't necessarily tell me much, especially since I don't think we'll have any more of the hot weather that seemed to aggravate it more. Don't want to leave it bypassed for an extended period either, although I'm sure it's safe I'm the type that likes to think it's there for a good reason.

I ordered one from a local dealer and will pick it up in next couple days. I'll check the resistance on it compared side by side to my current one, that might tell me something right away. If it tests the exact same as mine then I will return it. I will report back with my findings.

 

thanks for the feedback. Mine was definitely bouncing around, saw it briefly up to 1.0 a time or two. .8 to .9 was the more common reading on both multimeters I used, and that is at 70 deg or so inside temp. Will compare readings with the new one I ordered. That should give me a solid answer on the condition of my current one. I will check the readings a few more times on my current one in next day or two under different conditions.

 

None of this probably matters, but I did it anyway.