4th Gen 4Runner V8 Hesitating / Losing Power During Acceleration & on Cruise at 65mph +

Hello...long time user, first time poster, so joined the forum as I use it a ton.

Searched scores of threads related to this topic, but couldn't find one that seemed to detail specifically my issue. Most were all around the issue, but didn't seem to quite nail mine. Hence, my post here. Apologize for the detail up front, but hope it paints a better picture for diagnosis from folks way smarter than this me. Here goes:

Two years ago (2018), while driving at 70MPH on cruise control on I-29 for several hours, my 4Runner (2008 Limited 4WD, 4.7L, @ 135k miles) began hesitating, like it was losing power ever so briefly. Best way to describe it is like having the gas pedal pressed firmly holding at high speed, then letting go of the gas completely, then punching the gas pedal again. It was like it was cutting out (not getting fuel); lurching. Felt a lot like a vehicle running out of gas, where it cuts out, then begins again. It did this very intermittently, but by the time I got home, it was happening every time I accelerated from a stop light or went up a hill. No CEL light ever came on. I did self diagnosis and repair (I'll explain at the bottom), with no luck.

Took it to a buddy who had a $10k diagnostic tool (he's the head mech at a local shop). He ran the diagnostics and said he was almost certain it was the fuel pump (or filter). So, I took it to the local mechs here in Omaha (ToyoTechs) who specialize in Toyota/Lexus. They diagnosed the same thing. Since it's out of my desire to do, I had them lower the tank and replace the pump/filter. It seemed to work for about a year.

One year later (2019), same highway (first and only highway trip since previous year and previous issue), same trip, almost exact same mile marker, while the 4Runner was on cruise for 3hrs straight at 70MPH, it started again. Got it home, but the lurching and hesitating under load, power, or uphill kept getting worse as each day passed. Took it to ToyoTechs again, they said it was likely a bad fuel pump again and that it may have gotten clogged from bad fuel that may have corroded the ascending unit. They believed the ascending unit might be the problem ruining the fuel pumps -- that it was corroding and destroying the fuel pump. They replaced the entire ascending unit and fuel pump and filter (Denso Toyota Part), and stated the fuel tank was spotless, no corrosion. It worked for about a year.

Last week (2020), wife drove to Chicago on I-80 (first and only highway trip since previous year and previous issue). After several hours driving 70mph +, she called me and told me it was happening again, except this time, the CEL, VSC and Trac Control lights came on. Got it home, and the same exact issue is occurring...bogging out, hesitating, lurching, cutting out, especially while accelerating or going uphill or under load (e.g., pulling trailer).

I ran the codes (then cleared them) and they were P0171 "System Too Lean Bank 1" and P0174 "System Too Lean Bank 2". Before I take it back to the mechanic, I was hoping someone here could offer some suggestions as to the problem. I have a really hard time believing that I have THREE straight failed fuel pumps in THREE years (considering the quality of Toyota's...and my luck with them over 20+yrs). Suburbia driving = not a single issue. The second I take it on a long highway trip, this issue seems to flair up. Just three times on the highway in three years and the exact same three issue has occurred (and I'm to believe its THREE fuel pumps?).

I have driven only Toyota's (1997 Camry, 2008 4Runner, 2012 Highlander) for over 23 years (my 1997 Toyota Camry 2.2 I've had for 22 years now...runs like a top) and I've never had prolonged issues with any of them until this issue with the 4Runner. It is fairly mint still and was mainly kept in California where I was stationed. Clean inside and out and I do all regularly scheduled maintenance religiously, and then some.

There are just too many "potential problems" to chase down based on all the threads I've seen for something related to this issue. Potential problems I've seen:
- Torque Converter
- Ignition Coil
- Fuel Filter/Pump
- PCV
- TB
- MAF
- Spark Plugs
- Transmission Flush
- Fuel Injection Cleaning
- Cylinder Coils
- Dirty Throttle Body
- A/C Compressor Dragging
- EVAP Purge Valve stuck
- Crimped / Flattened Fuel Line
- Throttle Position Sensor issue
- O2 Sensors

Bottom line, there are too many scenarios for me to chase without knowing the real likelihood (or a better guess) of my current problem. All I know is that this thing runs like a top every day of the week, until I take it out on the Highway for hours at a time. That's when it starts hesitating/bogging/lurching/dying out, and then continues, even around town, until it seems I replace the fuel pump.

I'm not saying it isn't the fuel pump, but my instincts are telling me that perhaps the problem is something else that could be causing the fuel pump to fail/clog. I can't keep dumping a grand every year to replace a fuel pump at this rate, so hoping someone here can help a knuckle-dragging jarhead out. Thanks in advance!

What I've done:
- I Replaced the MAF (2018)
- I Replaced all four O2 sensors (2018)
- Mechanics replaced Fuel Filter and Fuel Pump twice (2018 and 2019) with ascending unit (2019)
- I Replaced the Air Filter (2019)
- I Checked for Vacuum Leaks (I'm no pro...just sprayed brake cleaner in key spots I learned from youtube)
- I changed Spark Plugs and Wires at 94k miles (2016)
- Resecured Air Intake -- it was pretty loose (2020)

 

I had an issue with my 2005 4Runner that sounds very similar to yours. I also have the Limited 4WD, 4.7L. The shop diagnosed it as a bad ignition coil and replaced it. It has run like a champ ever since. Good luck!

 

^^^ This... Sounds like definitely a faulty ignition coil.

Cheers,

Sean

 

Thanks, ATX4Runner and Brownersd. Perfect timing for your replies. Scheduled to take the 4Runner back in tomorrow to discuss with the owners/mechs on what the problem is and how to proceed.

I just went out, and with the engine off, I tested all eight engine coils (via my Klein Multimeter) and all registered positive readings -- meaning, numbers registered above zero when the circuit is completed (.34 ohms, to be exact). When I turned the engine on, it sounded/ran smooth as it normally does. So, I then unplugged and re-plugged all eight individually, and noted that the engine performance changed (RPMs lowered and it ran rougher) when each was unplugged and then the engine went back to normal RPMs and operation when each was re-plugged.

Unless I'm doing it wrong or there is another technique to verify faulty engine coils, I think all eight engine coils are functioning properly (could they intermittently be faulty, and "shorting" out when under load or high fuel demand -- meaning they could test good one moment, but bad another??).

I appreciate the suggestions, as I was able to at least eliminate another option and am one step closer to figuring the problem out. Thank you, again!

Semper Fi...Justin

 

Closing the loop on this...for now. The diagnosed problem is, again, a failing Fuel Pump.

Went back to mechanic and they found the same “goop” accumulating on the Fuel Pump. I saw it on the previous two that were replaced.

After long discussions, on what could be causing, their best guess (along with calling other Toyota experts in Kansas City) was fuel contamination. I have only used one gas station in town (the busiest one...so thought it had high turnover) the last 4 years, filling up with 91 non-ethanol every time.

That same morning I went in to pick mine up, a Toyota FJ came into his shop with exact same symptoms. His pressure for Fuel Pump was at 1%. After replacing it, he noticed the same gunk buildup around the filter net and on the metal parts of the pump. He had only seen this a few times in his career (excluding my three) — and he is a master mechanic with over 25 yrs experience leading Toyota/Lexus dealer shops (he is independent now).

After discussing with the FJ owner trying to find any similarities with his and mine, the FJ owner states he exclusively uses 91 non-ethanol at the same station I go to. Both vehicles have the same Fuel Pump design with a plastic ascending unit. Another seasoned mechanic noted that not all gas is the same, and a particular local chain was noted to have more acidic gas a few years ago. It’s “possible” the gas I had been getting — which is from a station (Hy-vee) that does not have a Tier One Fuel Rating — may be to blame (or bad stuff in the tank that the 91 non-ethanol is stored in) and may react corrosively to this style of fuel pump on larger engine block Toytota’s (he seen it in others over the years in this area — all bigger blocks).

That said, he replaced my pump at no cost, and I have switched fuel stations to one that has a Top Tier Fuel Rating. Time will tell. Hope this may help someone else who has similar symptoms.

 

I have this exact same problem, right down to the Hy-Vee gasoline! My only pending codes were P0230, which is the fuel pump primary circuit. If your fuel pump has been replaced more than once, it might be a faulty pin connector. Please keep us informed if you have problems with your fix.

 

So I've been trouble shooting my issue. I ended up replacing my fuel pump relay. So far no issues.

 

Ok, my problem wasn't solved by a new fuel relay. I had several stalls between 60-70 mph today within the first 10 miles.

Attempted solutions:
1. 2 tanks of Seafoam
2. New fuel relay
3. Removed fuel cap to rule at vapor lock

I will rerun the scanner tool to see if the P0230 code came back.

 

You should also reboot the fuel rail: replace the fuel pressure regulator and the injectors. If you've been getting bad gas, it's probably traveled up stream and could be screwing things up in there.
ALSO: are they replacing the entire fuel management module in the tank? Or are they just snapping a new pump in the old module and dropping it back in?

The module is quite a bit more money, but it has the filters and the sending unit for the fuel gauge and new frame for everything. I would recommend doing that instead of just replacing the pump within the module, would be worth asking the shop exactly what they're doing... And as far as bad gas, they've done this how many times and didn't dump the tank and vacuum it out?!

 

What was the final verdict? Contaminated Fuel?
TIA

 

I have a 2005 4runner with 150,000 miles.

I'll bet your P0171 "System Too Lean Bank 1" and P0174 "System Too Lean Bank 2" are the issue. Ask a Toyota mechanic what to do.

I have never replaced any of the items on your list, and never had a check engine light code in 15 years - except at startup.