2002 3.4L Rough start after car is at warmed up.

As the title says, I have an 02 v6 tundra with the 5vz-fe I bought recently. Truck runs and drives great. Idles at around 750 rpm when warm. After the truck is up to temp and is shut off, if you try to start it soon after it cranks a few times and starts extremely rough. The last time this happened it started after cranking within a few seconds and stalled. Second attempt it was rough but started up. Once the truck cools down it cranks up smoothly again and it's not throwing any codes. I've done a bit of research but it seems like there's a host of problems that could cause this. Crankshaft sensors, bad ecu, failing fuel injectors, ect.. I'm wondering if anyone who knows the 5vz can help me narrow it down a little. Thanks!

 

I have a 5VZ-FE 2002 Tundra as well. Been trouble free mostly for all of its 350k Miles. How many miles does yours have?

I would clean the MAF with MAF cleaner first. Not Brake cleaner, Not WD40, Not Windex. MAF cleaner.

Do you know the last time the spark plugs were changed? They need to be a double prong spark plug like shown below.


I replaced the old ones shown above on the left with these.

https://www.rockauto.com/en/moreinfo.php?pk=33251&jsn=723

 

The truck has 150k. I have not checked the spark plugs but I did find some old spark plugs in the box with the receipt in the center console with a receipt from a little over a year ago. The used spark plugs they put back into those boxes did not look as bad as the ones in the picture. Also I did clean the maf sensor and throttle body with the correct cleaners.

 

150K aint shit for one of these trucks/engines. What is the part number on the spark plug boxes you found?

Hmm... how do the vacuum lines look?

 

That's why I bought it! haha. I threw away the spark plugs and packaging when cleaning out the truck.. If I weren't so new at working on vehicles I would have picked up on that. Definitely needs new vacuum lines. I just replaced the valve cover gaskets and spark plug seals myself a few days ago. After pulling the hoses off of the intake plenum, I saw quite a few cracked lines at the connecting end. I threw some worm clamps on them in the meantime. I just really hope it's nothing that too serious.. such as gas in the oil.

 

Where was the receipt from, and what's the model#?

The once-hot-runs-rough sounds strangely like something electrical. Like, resistors (fuel pump resistor) and sensors that use resistors (heat) tend to get fouled up when hot, more so they're on the fritz. But again, finding suspects for this is like shooting fish in a barrel.

 

I'm not knowledgeable enough to perform diagnostics at that level... yet! Also the truck runs great at temp.. rmps don't move at all when idling. Only issue is that extremely rough start. First noticed it after fueling up. I'd like to resolve it before damaging something because it doesn't feel healthy.

 

Explain "extremely rough start". Like, rough how, and rough when?

I read it and thought you were saying it was initially running rough (like idling funny) when started warm. I don't think it's the case after your last msg.

 

When cranking from a cold start, it's smooth and starts right up. After the engine is up to temp, if you shut if off and then start it soon after while engine is still hot, it's very rough. Rough as in the truck shakes and struggles to start.. Flywheel is spinning but getting those cylinders to fire seems pretty rough.

 

I replaced almost all of my vacuum lines with silicone from here. -> https://www.siliconeintakes.com/silicone-boost_vacuum-hose/

They have several colors to choose from. @bmf4069 also replaced some of his, and he ordered from the same website.



I used a "Dress up kit," and it was more than enough hosage to get the job done. I went with blue...




Word of caution! If you replace the vacuum hose going to the brake booster you'll need a check valve. Which they also sell... I believe mine was an 8MM hose.

 

Also I should mention after the truck is running all is well.. Even after the hot start.

 

I might as well go ahead and replace mine as well. Do you know where to find a diagram of the vacuum lines?

 

I didn't use a diagram. I just pulled one hose off at a time, and cut to length.

 

When you start to run low on the silicone hoses, hold up the hose to the tube before you take it off the truck to make sure you've got enough length to reach. Don't want to be down just because of one little piddly hose.

 

I'm not that big of an amateur haha

 

Noted.

 

@JimenEazy. Did you ever figure out this issue? I have the same problem.

 

CHECK THE TIMING BELT / VERIFY TIMING!

I had a 5vz for a while. When the water pump failed the coolant crusties eventually grew large enough to fall into the timing belt on startup and jump three teeth! Truck drove okayish to the gas station about 10 miles away. It would not restart after fueling. Eventually it cooled down enough to start and run like ass back to the shop where I found the carnage.

The silver lining is that the 5vz is a non interference engine.

 

From the 5VZ FSM in trouble shooting section (page 196) for Hot hard starts there are 2 things to inspect and test.

1) Starter circuit and 2) Fuel pump circuit. This will entail testing for connectivity and specific voltages on the ECMs connector and for open circuits for 1). Page 321.

2) will need connectivity tests between ECM connector and starter relay (pg 327).

 

Clicking on his username, doesn't look very positive he'll respond. We get a lot of fly-by-night folks who don't even bother to say whether we helped fix their problem or not. All that does is make people not want to help.

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On your problem, I'm guessing you have the 3.4L V6 or you wouldn't have replied to this thread. If that's not true, and you have the V8, it'd be super helpful if you gave us any details about your truck, year, engine, cab type, if 2WD/4WD etc. If you have one of those shitty K&N air intakes or use an oiled filter, this would also be really important info, because buildup inside the throttle body from oiled filters happens! And on that note, how's it look inside the throttle body? Shiny and smooth, or do you have a lot of gunk where the throttle plate meets the body?

Another important piece of info: Are you throwing any codes? Like, is the check engine light on? If it is, and you don't have a reader, most chain auto parts stores will scan codes for free and give you a printout.

I guess one thing to realize is "What things heat typically affects". Generally speaking, in electronics, heat will affect anything with a resistor in it. Resistors are used all over the place, but thinking about components related to the engine, some big ones: MAF, ECT, Fuel pump resistor, etc.

Have you tried testing the MAF to confirm operation? (Note: Ambient outside temp will affect resistance)

Have you tried testing the engine coolant temp (ECT) sensor resistance? (If you tell us the year of your truck and engine I can tell you the process)

Have you tried bypassing the fuel resistor, or testing it? (Again, year and engine, I can tell you the process)

I'm picking off a couple of items that would be impacted by heat above, we know the engine will run rough if the ECT is faulty/unplugged per others on here's experience. It may be something stupid, like your ECT is failing, when it gets hot, it starts reading 'off' and the engine is behaving poorly. But there are a couple of other potential things...

Gas pump ... it's entirely possible the pump is fine when it's cold, but when it gets hot after pumping for a while, it may degrade operation. I would expect it to be consisitently bad though...

O2 sensors ... I'd love to see the output, if the upstream is being stupid or failing, you can expect poor fuel/air mixture and poor running.

 

Yes thanks so much. I have a 02 Tundra 3.4 V6. I changed out the valve cover gasket and spark plugs. Didn’t look into the other things mentioned like timing belt.

 

We had first gen Tacoma that did same thing and spark plug change fixed it. However during research way back then I came across a TSB about bad engine ground that was an issue. TSB must be rescinded as I can't find it anymore. However, this one is in there now and is close to your issue.

 

Well, not we know the year, I can give you this, which you should download. It's your key to debugging your truck.

But @Tunrod touched on what I was poking at above, and why I wanted to see inside your throttle body, and to know if you have an oiled air filter, or you're using a "hot air" intake.

 

Any CEL codes?
I would try MAF cleaner and replacing MAF Sensor first before getting crazy on this because it's just so simple to clean/replace MAF.
I had the same exact symptoms on my '08 Yaris just a month ago and a new MAF sensor ended up solving it.
I know it's a different car, but MAF problems give these types of issues.
Cleaning the MAF sensor solved it for a week, then the problem came back. Replacing MAF solved it for good.

Just as you said, super clean cold startup. But then 10min drive to Walmart + shopping, then warm start the car and it sounded like it was about to keel over. Halfway home, it would run good again.

Edit: I forget the codes I was getting but can look it up if you want

 

No no codes yet. Worried that cleaning the MAF will bring a code. Heard they are sensitive

 

They are sensitive, which is why you want to clean them. Debris and gunk loads up on the sensor inside, and that coating causes them to read wonky. Inside is just a couple of electronics as seen here and here. Those electronics get covered with crap, the cleaner sprays it off. No magic involved.

The process is not difficult, just make sure you use "MAF cleaner" specifically. Piotr from Toyota Maintenance Channel covers it here. I'd just tell you: It will get cold after dumping half a can into it. Give it a solid 20-30 mins to come up to ambient temp before reinstall and startup.

https://www.youtube.com/watch?v=DDgbiHe__j4​

 

^What shifty said.
Replacing it outright shouldn't be more than $100 and 2 mins of time worst case.
Your symptoms match up v well with a bad or clogged MAF - system is having trouble figuring out how much air is coming into the engine, which makes it start running too lean/rich. Especially so at idle or slow speeds when less air is running past the little filament.

 

I had the same problem. I cleaned the MAF sensor and it was noticeably better although it still stumbles a little on a hot start occasionally!