My tundra cranks for a while when hot

And if you haven’t picked up on what some are laying down, the parts matter. Toyota electrical systems are a bit finicky with aftermarket parts. Some of these sensors operate in a narrow range of voltage reporting. The OEM tolerance operates within this range, the aftermarket ones are all over the place and will result in erratic operation. If the fuel pump, maf, or O2 sensors were not OEM, then you may have swapped in another problem.

 

@George6436 we still haven't heard what engine you've got either, the V6 or V8? I've been running on the assumption it's V8, and a couple hints above kinda confirm it, but we should probably ask you.

If you're telling me it was popping a P0174 before the fuel pump replacement, that's interesting and therefore I'm not necessarily going to tell you I think it's the fuel pump, but failure to provide adequate pressure across both rails ould result in a lean condition on the passenger side, because it's the final rail to get fuel. But if you aren't sure the check engine light prior was in fact a P0174 code, then I'm almost always going to blame an aftermarket fuel pump in this case. More on that later.

The smell thing is interesting also. I'd be curious to hear more about that. Is it inside the cab, outside the truck, above or under? Is it stronger in the engine bay, or at the exhaust end of the truck? If the smell was your cats being clogged, which smells sulfur-y, like a grille cleaner brick rubbed across a flat top grill, I'd expect other codes. But rodents are notorious for nesting up in our trucks and chewing on wires and plastics, chewing apart filters which can lead to mildew, paper touching hot stuff, etc. Or you may be smelling exhaust from running rich (smells like gas) or lean which can smell a bit eggy also, but almost like dusty eggs to me.

From a logical perspective, there's a few more obvious things I think it could be, but without being there in person and being able to test things, I can't say for sure. Of those things:

1. Bad upstream O2 sensor on the passenger side, the sensor between manifold and catalytic converter. This could be malfunctioning, and reporting bad info (i.e. "the engine is running too lean") back to the ECU. Running lean can also cause slow starts. Sometimes inspecting the spark plugs nearest the block, if they're light orangey-tan on the normally-white parts, can conrifm you're actually running lean. As much as dumbasses will try to convince you O2 sensors are some big brother gov't EPA conspiracy, the upstream sensors are pretty critical b/c they provide combustion data to your ECU which helps the engine run optimally without burning up your spark plugs and creating other wear and tear. IF YOU REPLACE your O2 sensors, I cannot stress three things enough, and those are (A) replace both the upstream and downstream on the impacted bank at the same time, (B) only use Denso brand parts from a reputable source (i.e. not scAmazon, not fleaBay) and (C) never cut/splice your O2 wires to install a sensor, you're going to create more problems later! and (D) look up your correct "exact fit" (not universal) part number at www.densoautoparts.com - if you need help to get the correct part numbers LMK. You can absolutely do this work yourself, it's not hard as long as you aren't in the rust belt.
2. Fuel pump is failing to push fuel adequately. If your mech used an aftermarket fuel pump, one of the store-brand shit "lifetime warranty" pumps, they're lifetime for a reason - they're poorly remanufactured, built in sweat shops for cents on the dollar, only designed to last 2-5 years, but sometimes fail early due to bad QC. They're often not tested for basic functionality, because that would cost money. So on this forum alone, we've seen people have pumps DOA straight out of the box, and seen pumps fail within weeks.
3. Fuel pressure regulator/damper has failed on the impacted rail. But IIRC, the V8/4.7L (2UZ-FE) on these trucks only has a single pressure regulator and single damper, so I doubt that's it.
4. Fuel filter is jammed and reducing fuel pressure to the rail. We've seen it on here before with '00-'04 trucks ('05-06 don't have fuel filters), but so far, it's been super rare, and only with aftermarket fuel filters, where someone replaced the filter. It seems the OEM filters aren't very aggressive with filtering, which leads to less clogging. You can absolutely replace the fuel filter yourself, but it's a bit of a knuckle buster, you'll get a face full of gas in the process, and you should stick with an OEM filter unless you want to potentially be here again in a couple years.
5. There are various other things that could lead to lean condition related to air/vacuum. Like (A) intake manifold gasket is blown on the impacted side, and allowing extra air in, which would foul the air/fuel ratio with more air, which would lead to lean running, or you've got a vacuum hose cracked/loose/off somewhere, or (C) a bad gasket somewhere along the intake/exhaust chain between the intake manifold and the upstream O2 sensor. There are symptoms of an intake manifold gasket leak would be hissing noises, and I'd expect to see misfire codes.
6. Incorrect or fouled spark plugs on the entire side of the engine with problems; if you've been running rich or lean for a while, you can foul the spark plugs on that side, which will just exacerbate the problem. I don't think it's bad plugs or bad coil packs, only because the chances of it being all four on a single bank, with no evidence on the other bank is like your chance of hitting the lottery this week.
7. Rodents/shorts/gremlins. Rodents have chewed something up, or a line is shorting or rubbed out somewhere, which is causing problems with fuel delivery.

Anyway, if it were me, and I just bought your truck, and I was chasing down this issue, the first thing I'd do would be:

• Get a can of ether. Spray it into the throttle body before starting the truck. If it fires up immediately, your problem is probably fuel delivery related.
• Inspect the O2 wiring on bank 2, i.e. the passenger's side exhaust bank. Make sure the O2 sensor harnesses have never been cut. I'd start the engine and get a kleenex/tissue and hold the end against every exhaust joint to check for leaks, or if you're a smoker, you could hold a cigarette around each exhaust joint to check for leaks. If the truck has more than 100-150k miles, I'd replace the upstream and downstream sensors with legitimate Denso brand exact-fit sensors on the side throwing the lean code, since I'd be super suspicious of the upstream sensor specifically. I'd remove the negative battery cable during the replacement work, and make sure it's off for at least 10 minutes to let the ECU reset and enter re-learn cycle after.
• I'd take a minute to clean the MAF, specifically with CRC brand MAF cleaner. I'd do this when the engine is cold. Once I was done, I'd pop off the negative battery cable, then leave the MAF out to return to ambient temperature (it'll be cold af after spraying). There are videos online showing how to clean MAF, and CRC MAF cleaner is $10 or less at every chain auto parts store. I don't think the MAF is the issue, but if your throttle body was dirty as hell as you say, the MAF will have just as much shit built up on it. Both MAF and TB get dirty fast if you're using oiled filters and/or aftermarket air intakes like what K&N offer (which are basically shit in a box, sound and look cool, but don't actually do much other than adding a tiny torque bump in these trucks at the cost of dirtying up your engine, reducing long-term performance/longevity).
• I'd really be interested in checking the fuel pressure at the rails, I don't think I could resist, but I'd probably do the above steps before then, and see where I landed.

 

Cylinder 6 misfire would be P0306

 

Couple of things I've done with my truck and what I've noticed in the last year. Might help your endeavors might not, but hell why not check right? I also have noticed that when I key on power and let the fuel pump prime (5 beeps or when it stops beeping with the door open I can't remember) it starts a little quicker for cold starts. I wouldn't say that my truck cranks for a long time, but normal than what I'm accustomed to with toyota trucks.

I also have done the following:

• Denso starter (no start condition; bad diagnoses - was bad ground terminal)
• Cleaned MAF
• Cleaned throttle body
• Replaced battery terminals - Issue was corrosion at the ground wire connection, not the connection directly to the battery.
• Battery - was replaced by prior owner with the cheapest duralast they sell. I did notice that it had pretty low cold cranking amps.

You've got a CEL so I'd start there, but wouldn't even overlook all the simple things. Old trucks play old tricks.

 

My bet is leaky injector(s)

The truck starts perfectly during cold starts.

The truck long cranks when the engine is heat soaked. The reason is the fuel system is under pressure when truck is off and hot. The leaky injector is letting in raw fuel. This is flooding the engine. The engine has to long crank to clear out the raw gas before it will start.

The reason this doesn't happen on cold starts is the gas has evaporated overnight.

I believe you have 2 issues. A bad injector and a bad 02 sensor.

The 02 sensor code may go away if you find and fix the injector(s).

 

The engine is a v8 and it’s tough cause I don’t have cash to throw around so I’m trying to make sure I get the right solution I’m going to look at the steps you offered to see which ones I can do quickly. Already cleaned MAF and throttle body. The smell isn’t gas and i smell it inside of the truck when it cranks long.

 

I got a Walmart battery to.

 

I hear what you're saying, I'd expect a leaky injector to fire off a rich code, though. Although it would explain the loss of pressure to the passenger fuel rail.

 

Cheap test?

When engine is warm and should show the condition, get starter fluid/ether. Pop off the intake hose at the throttle body. Lift up the throttle plate and shoot some ether into the intake. Put the intake tube back on the TB.

Now go start the engine. If it fires off right away, you have a fuel delivery issue. It's either something like what @koditten is saying, or similar. But it'll likely tell you if this is fuel delivery or something else.

 

https://youtu.be/AzG388iE5w4?si=P3YqCIl3LBO-WHEE

 

Ha! They show the same cause I said and @koditten said

And my biggest susect, upstream is high on the list. That guy does a great job of breaking it down.

​

 

Okay I'm going to look into all of this then I'll come back to see what was the solution. it's just like you said it can be many things. I might just have to get it looked at by the mechanic at least to see his diagnosis seems like most of the solutions are easy.

 

Occam’s razor is usually the way

 

Just got word and my upstream was Bosch and downstream is walker brand

 

The mismatch isn’t good. Like a said, sensitive voltage ranges here. Best bet is swap both for OEM. I’ve had good luck with Bosch, but OEM is always the right answer here

 

These trucks are usually pretty sensitive on electronincs. O2 sensors especially. And they don't like when people cut the O2 sensor wiring to install non-OEM parts.

Bosch is a great brand and everything. Don't get me wrong. But I'd be suspicious also if the mechanic cut the O2 sensor wiring to install. And I've seen too many cases where bad codes were thrown from non-Denso (i.e. non-Toyota) O2 were used.

But mixing and matching sensor brands is also bad idea too.

 

I'd only add this also - you're at the mercy of hoping the mechanic is doing what's right for you, and you're basically paying him to put food on his plate. It's almost like renting a house versus buying, you're throwing money away.

You'd be better served doing this smaller stuff on your own, like O2 sensor replacement, spark plug replacement, and basic troubleshooting. I highly doubt your mechanic knows anything any of us use, unless he's a veteran Toyota-specific certified mech or something. We've found problems other mechs have missed on this forum a number of times.

Having $100-200 in basic tools and not being afraid to use them will save you thousands of dollars. Especially if you have a group of people who can help guide you on what to do, which is something your mechanic will never do. Mechanic is out to make money by billing hours. He'll throw parts at problems all day long, it's what pays his bills.

 

Yeah I have all the tools I need but I might go ahead and install fuel injectors since it seems like the cheapest option and might be probable cause not Sure if it is a job for a rookie though. then ill probably buy o2 sensor if that doesn't work. but the cold start is good then when its hot it barely starts. so it seems like that might be it. But if that doesn't work ill get some o2 sensors.

 

Can I use carb cleaner, throttle body cleaner, or MAF cleaner, to do that test in the throttle body? what is ether?

 

Put the parts cannon down. I personally would put fuel injectors way down my list for your symptoms. An entire lean bank with no other codes screams O2 sensors. But driving around for 3 years with the CEL illuminated also tells me there are likely many distracting variables here

 

Ah, you had two codes. P0306 also.

That's an easy one, but taking the right action maybe a bit more complicated because a misfire on a bank with a lean condition could be related - you could be misfiring because of the lean condition (too much air in cylinder at combustion), OR the misfire could be because your spark plug is fouled/burnt up from running lean too long. But your coil pack may just be old and may need replacement. OEM (DENSO brand) typically last a good 10-15 years or more. Part stores brands are usually lasting 2-5 but they don't spark as hot, so can cause other issues.

BUT it's something you can both easiy troubleshoot and diagnose at home, and repair if the coil pack is the problem.

Your cylinders are laid out like this, where all the passenger side cylinders are even numbers. The computer is bitching that cylinder 6 is misfiring. At the top of each cylinder is a coil pack, it's a black flat square thing on top of a big long tube with one bolt holding it in. In case like this, we would typically get out our trusty 10mm socket (IIRC, maybe be 14, I forget), remove the bolt and put it somewhere safe, then unclip the harness, and swap the coil on 6 with the coil on cylinder 4. Then clear the codes. If the codes come back, we would check again. If the code changes to P0304, indicating the cylidner 4 coil pack is bad, you know you need to replace that coil pack with a new DENSO brand coil. But I would also pull the spark plug on cylinder 6 while I had the coil pack out to take a picture, inspect, and see if it's burnt up/fouled. We've had people who bought auto parts on here get counterfeit plugs from scAmazon and fleaBay, you just never know these days. If the P0306 comes back after swapping coils, it's probably the spark plug, the connector on that coil not being snug, or cracked manifold gasket on that cylinder (which could also trigger a P0174!) causing it.

​

 

Okay well about two days ago I was checking my engine and I would un screw the coil/lift it and see if it made that clicking noise, turns out that the ignition 6 was not making it so I replaced it already. but I didn't replace the spark plug

 

Do the other ones make popping noises when you do that?

Store bought coils tend to fire colder. We had a guy on here who tested them and it was crazy how much hotter the OEM/Denso ones fired.

But if you're gonna check that spark plug, do yourself a favor. The back two plugs (6 & 8) almost always look the worst, those are what you want to look at. Do this.

• Mark your coils for 4, 6 & 8 with their respective numbers so you know which was where, then pull all three coils.
• Get a piece of cardboard, and draw the numbers 4, 6 & 8 on it.
• Remove the spark plug from each cylinder and lay it on the cardboard in front of the number cylinder it came out of, take a pic so we can see.
• Reinstall plug from #6 in cylinder 8.
• Reinstall the other two plugs in any cylinder you want.
• Reinstall coil pack #4 on cylinder 6.
• Reinstall the other two coil packs in any cylinder you want.

Why are we doing this?

By moving the spark plug from cylinder 6 onto cylinder 8, if you start throwing a code P0308, that's a misfire on 8, you know that #6 spark plug was BAD.
By moving the coil pack from cylinder 6 onto cylinder 4, if you start throwing a code P0304, that's a misfire on 4, you know the "new" coil pack you installed on cylinder 6 was BAD.
If the code stays P0306, because the spark plug and coil pack on this cylinder are now stolen from other working cylinders, you know the problem is not the coil or spark plug.

Easy at-home diagnostics like this can save you a shitload of money, and help you avoid breaking out the "parts cannon" to shoot random parts at things, which gets expensive fast.