***FIXED***



I have a '99 4Runner that's been giving me some problems for the past month or so.

1999 4Runner Limited 6cyl 5vz w/ 4WD
270k miles and trying not to limp it to the 300k mile club. Lol

Codes:
P0171 random - doesn't come on reliably when issue presents itself, but on 85% of the time (system too lean bank 1)
P0110 once - only saw this one once (intake air temp sensor)

I believe it to be a fuel related issue whether it's the computer not sending the right signal or something wrong with the fuel injection system.

Symptoms:

Car cranks, battery and starter are strong. Either it will start normally, struggle to start, or not turn over at all.

Pumping the gas pedal really doesn't help unless it starts to turn over.

Car runs like it has no problems at speed, starting and idling are the issue.

Starting fluid sprayed directly into the airbox while cranking worked initially, now it's barely effective at keeping engine running after attempting to start.



What I've done to try and "fix" it:

MAF cleaned
MAF replaced
Throttle body cleaned
Hoses checked for leaks - sprayed starting fluid around engine compartment while running
Fuel filter replaced
Fuel pump tested - removed fuel filter and a ton shot out the open tube while cranking, way more than expected
Front O² sensor replaced
Fuel treatment added to tank x2
Seafoam added to tank
Disconnected battery
Disconnected ecm fuses
Disconnected ecm wiring harness from ecm
Swapped EFI Relay/new fuse
Air filter replaced

---> Fuel Pump replaced

Applicable work done within last 10k miles:
Most recent - timing belt/water pump and had hoses done in last 3k miles
Oil/filter change every 5k miles
Spark plugs, wires, and coil packs
Air filter


Here are some numbers while the car is idling (800rpm) and at 3000rpm:
(Maybe these will help, they don't mean much to me. Lol)


Timing +16° to 24°............+30°
Intake temp 113° F....................117° F
MAP 29 kPa...................30 kPa
MAF 0.7 lb/min..............2.8 lb/min
O² sensor 0.08-.725..............same
Fuel flow 0.5 gal/hr...............1.9 gal/hr
BST VAC -10.7 psi.................-10.2 psi
Fuel trims ST +17.2 to 19.5%.......3.1 to 10.9%
Fuel trims LT +39.8%..................same



Really don't want to replace the engine control module..


Other than that, I'm stumped

Here's a fun pic of the nasty fuel filter that is probably 270k miles old after cutting it open. Helped with the lurching upon quick throttle reduction at speed.



The unhappy 4Runner I want to be reliable again



Any advice is welcome and thanks in advance!

Here's some short videos of it not wanting to start...





The faint popping is the engine backfiring out the airbox..


I tried swapping the EFI relay and fuse today, no change.

Didn't get to test the fuel pump pressure like I planned.

Going to take it to the dealer to
Diagnose the problem Monday or Tuesday..
Hoping it just needs a new fuel pump.

Took it to Toyota today and had a coupon for $49.99 check engine light diagnostic.

Fuel pump has gone bad.

They want $795 to put a new one in.
Going to attempt it myself.


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Did that actually fix it? Seems odd it would not supply enough fuel at speed but not at idle.

I've been on vacation the past 2 weeks and haven't gotten around to it. That combined with needing a jack, extra set of hands, time, and a faulty fuel gauge are holding me back. Lol

I plan to do it next week though.

After coming back from vacation, I went to start it and the battery was dead...
Jumped it and drove around a little bit and it read 12.23v last night and this morning 12.0v.

Don't know what could have drained it. Must not have shut a door all the way or something.

It started like it has been after jumping it yesterday.


I hope it is the fuel pump. With the car running and access door open, you can hear the pump sputtering with the drops in rpm at idle.

Well, today I decided to attempt to remove the tank. I managed to get the skid plate off before it started raining... perks of working on the truck w/ street parking.

Planning on resuming the project tomorrow.

Now, for the interesting part!

I determined I was running on fumes last I drove it today so it's perfect for taking out the tank. (Have to guess because the fuel gauge doesn't work)
With this in mind, I decided I wasn't going to drive it (figured I'd run out) and leave it till I can work on it tomorrow.

Next thing I know, I get a call from the landlord's wife asking if I can drive him his keys because he locked himself out of his car at the Lowes nearby. Lol
I couldn't say no, so I went to bring him his keys.
I really didn't want to drive as tank wasn't strapped in all the way, and was essentially out of gas.

Walked next door to the neighbor's and got a can of gas from him and put a little in and took it with me.

Half way there I saw something I've never seen in the 8 years I've had the 4Runner!

Low fuel light!



Lol wasn't sure what I was looking at. Historically, empty is the half full line up until recently where it has been empty at about 3/5.

Side note: the tank holds 18.7 gal. Ran out of gas and rolled into the pumps a few months ago and filled all the way to the cap just to see. The pump clicked off around 16.5 and I squeezed the rest out. Lol

Anyways, going over a bridge is when the light came on after the faulty gauge dropped to the peg. I think what cause it was the tank dropping about 3" in the front from the bump while driving.

Hopefully that fixed it! Lol

Got the new pump installed!

Pretty excited it all went well.
Did it all myself with only hand tools and no jacks or anything. First time removing the tank. Just me and a towel to lay on parked next to the curb.

Took about 3 hours to remove everything and put it all back together. Saved me $700 to do it myself instead of having the dealer to do it.

She turned right over when I went to start it the first time and the CEL hasn't come back on yet after a few short drives. Praying that fixed it!
It feels better and smoother acceleration, I think.

Here's the tank outside the car




Few rust fragments here and there in the otherwise excellent looking tank.







Gas gauge is back to acting weird however... lol

Soo, 150 miles after the fuel pump replacement the CEL hasn't come back and starts every time!

Happy to report that I think it's fixed! The old trusty 4Runner is back to being reliable again.


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Great! Glad to hear it, thanks for sharing! I'm currently working on diagnosing my own mystery problem, which I will be posting about soon hopefully, I'm new to the forums and can't make a post until I reply to a few others apparently.

It's been 5k miles and safe to say the symptoms are gone! Except the fuel gauge is still unreliable. Too lazy and cheap to fix that. Lol