Fuel system issues (probably)

97 tacoma 3.4l V6 230,000 miles

What's going on: sudden and momentary engine stall. Out of nowhere it'll just lose power for a split second. Started earlier this week and would stall every 30 miles or so. Now it's happening a lot more. Tackometer won't sit still, it's gently surging then dying back down to whether the engine is hot or not. Seems like it's wanting to sit at 750 for the most part but sometimes it'll be at 1000. Also occasional weak idles around 500 rpm's.

About a year ago the stalling issue started. I replaced the fuel filter with a shitty duralast one, it leaked everywhere so I put the old one back on and the issue stopped like it never even happened. Seemed like a clogged fuel filter (later replaced with an OEM filter). Then about three months ago the stalling started up again followed by a bad misfire. A shop replaced the fuel injectors and all was well for a few months. Now the stalling is back and worse along with the engine seeking for the right fuel trim (I think that's what the surging RPM is about). Is this a bad fuel pump? With the truck running, I could here a high pitched ringing from the tank when I got underneath the truck (not loud, you'd never hear it just standing there) like if you have tinnitus, it sounds like that. Idk if that's happening all the time with these fuel pumps though.

Let me know your thoughts.

 

I’m just throwing ideas out, but could it be an electrical/spark issue? The way it goes away and comes back makes me think it’s a ground issue somewhere

Though symptoms lean more toward a fuel issue, and I don’t think there should be any ringing from the fuel pump but I’ve never laid under the tank while it’s running

 

Thanks for the reply. Electrical has crossed my mind. Unfortunately I really don't know anything about that stuff. I plan on taking it to a good shop this week.

 

I really don’t think it’ll be this simple based on ur symptoms, but it would only take 30 seconds to double check that these two grounds are clean and tight. My lower ground is disconnected in the picture, but it connects to the bolt in the circle.

Could also trace the ground from the negative battery terminal, it should have a larger gauge wire ground though I’ve never disconnected it before so I’m not sure exactly where it goes.

I’ve never taken a look at the fuel pump, but you could also see if there’s a ground wire directly off the tank somewhere to the frame.

Probably isn’t it honestly but at least it’s something easy to double check before paying someone to dive into more complicated causes. Bed has to be pulled off to get to the fuel pump as far as I know so it might get pricey

 

Grounds are all good. But while I was at work today my battery light came on. Battery is less than a year old, could the stutter and high idle be caused by a failing alternator? I've noticed my headlights surging recently too. I'm going to pull that and get it tested tomorrow

 

I had the same thing just happen to me. Engine temporarily lost power. i pulled over and sat for a minute in grief (never had a mechanical problem with my 2003 2.7L thinking the worst). But after a few minutes I tried to start it and it powered up like normal. Really curious what you find out about yours.

 

Cam or crank sensor could do this

 

explain Trey

 

If the ECU doesn't receive timing pulses, it won't know when to inject fuel or fire the spark plugs, so you'll get hesitation until it recovers

 

I think you may be right. I did a quick search and pulled up this about a 3rd gen:

Scared! I have a 2008 V6 PreRunner with 199k miles. I do all my routine maintenance including oil changes like clockwork. Never had the slightest of problems with this truck, it’s been a dream. Yesterday I was just driving down the road (residential area was only going 35 Mph) and the truck shut off and oil light came on. It honestly felt like I ran out of gas. Happened really quickly with nothing alerting me that something was about to happen. Out of the blue. It was Just a quick shake and sputter, oil light came on and engine cut off and that was it. Attempted to restart several times and nothing.​

The only thing I can add is that I recently had check engine light come on. I use a small local Toyota-only mechanic but he’s always booked out for a month or more. So I stopped by one of the National auto part stores and let them pull the code for me which was P0345 (camshaft position sensor A circuit-bank 2). I am handy with general/routine maintenance but all of this is above my skill set. I don’t even know where to begin diagnosing what’s happened here.​

https://www.tacomaworld.com/threads...iving-oil-light-came-on.823386/#post-29531910

But I didnt get a CEL or I would have checked as I have an onboard code reader.
​

 

3rd gens have their own problems, but this will be a universal EFI symptom

 

I figured that its the fuel filter.

 

I mean, change the cheap/easy things first for sure

 

Hapax1
I have been down the ‘fuel pump trail’ many times
Until one of my race buddies (engineer) said FP is linear. Huh? I said.
He explained that pump works or pump doesn’t work

no codes huh?
That would at least point to a direction

Fuel Pressure Regulator??

 

Ok so I tested the alternator and it was toast so I put a new one in. This drastically improved the issue but didn't completely resolve it. Its stuttering a lot less and the high idle is gone, but now it tends to have a low idle, like 600, and when it's at 750 it's still gently surging. I tested the battery and it's fine

 

Interesting…..
If the condition changed
Might be on to something

let ECM re-learn with drive cycles?

Plz keep everyone updated!

 

Air intake boot was leaking. The end

 

WOW
Good job