This looks like a pretty busy sub but I thought I’d see if i can get some suggestions. I have a 2003 Toyota Tacoma Pre-runner with the 5VZ-FE V6 engine. I’ve been having this issue for awhile now, had it at a couple different mechanics and the dealer who all have not given me much to go on.
Symptoms only appear when the engine is hot and has been running/driven for about 5+ miles. On a cold start, everything is fine. Starts right up and stays running at idle.
Then if I drive it for a bit and then shut the engine off, it has a lot of trouble starting while it is still hot. Sometimes it will start, and then stall a few seconds later or after I put it in drive and try to get moving. Also, normally on the highway, if I try to accelerate too quickly it will lose power around 55mph or so and i have to let off the accelerator and ease into it again to get up to speed. It has also gotten to the point where if will sputter on me if I am at a stoplight or in traffic and have been driving for awhile, I have to feather the gas a little to keep it running.
Codes are showing P0300 Random/multiple cylinder misfire, P0302 and P0304 misfires, and P0171 System Too Lean Bank 1
This all seems to point to a vacuum leak, I changed out the air intake boot that was cracking on the ends and it seemed to help a little, but not fully. I changed another couple of vacuum hoses but otherwise haven’t found any myself that look like they could be the issue. I have had the fuel pump changed because one of the mechanics indicated the pressure was low and that should fix it, but it didn’t. I have also had the brake booster replaced, and am wondering if that could be a cause also? I’ve changed the spark plugs/coils, MAF sensor, and I think that’s all I can remember off hand.
The thing that throws me the most (I’m handy but don’t know that much about engines) is that it only happens when hot. After awhile of researching I have concluded it’s likely a fuel injection issue, bad brake booster, or the fuel pressure regulator. Otherwise I’m pretty stumped with my limited knowledge. Any advice at this point would be appreciated.
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This could be an injector issue, or something like a crank sensor glitching when it gets hot. But considering how many parts have already been thrown at it, I hate to speculate. Sorry you’ve had no luck with shops so far, but you really need someone who can properly interpret the engine data and/or utilize an oscilloscope to capture the glitch.
I have a 2003 Toyota tundra with the 5VZ-FE engine. Never had an issue of this kind, but I’ve done some research into these engines and I can provide some advice. Yes, your issue does indeed seem to be isolated to fuel pressure regulator and/or fuel injectors. Should you need to replace them, your intake manifold needs to be removed. I will recommend what else you want to address since you’re there, but let me expand more into your fuel injector replacement procedure. Please keep in mind you’re dealing with gasoline and make sure you have a clean environment free of sparks and well ventilated.
- If you have money to spend, definitely go OEM, but midwest performance has a set of reman denso injectors for a fraction of what they cost anywhere else (thank you, timmy the tool man). Google midwest performance 5VZ-FE denso injector set. These do not come with the seals, so keep that mind. You can buy these seals anywhere, but Rock Auto is your firend here.
- For your fuel pressure regulator, yotashop is your go-to. Also you may find good parts on Rock Auto. I highly recommend you change the crush washer too (its a banjo bolt set-up scenario).
- While your intake is out, inspect it for cracks. Check all the vacuum hoses. Since you’re there, replaced them all. They’re 20 years old and once removed, they may never seal the same.
- Check your upper and lower intake plenum. Inspect of cracks and other issues. They’re aluminum so if something is amiss, it is hard not to notice.
Now, since you’re there portion and assuming these have never been done before:
- While your intake manifold is out, the v-valley of the engine will be exposed. These engines have a heater bypass tube that runs from the front of the engine, to your heater core. Over time, the sealant used to seat this tube to the engine will become brittle and cause coolant to spill into the v-valley of the engine. Highly recommended you pull the tube out, and reapply Toyota black RTV gasket maker to ensure this leak never occurs.
- Replaced your intake manifold gaskets with a high quality gasket set. I used a good set of Rock Auto when I did mine.
- Knock sensors and knock sensor wiring. Let me put it this way: if you have everything apart and put everything together without replacing these sensors, you will HAVE to take everything apart just to replace these sensors when they go bad. And they will go bad. If you opt in to not replace the sensors, at least replace the knock sensor wiring. Google it and you will see yourself.
Thats it. I hope you have this issue resolved. Should you need anything else, feel free to DM me.