98 Tacoma 3.4L power loss surging idle with codes

Got my first running issue today after 1100 trouble free ownership miles. 5sp 4x4. Truck was running great and plenty of power, passed CA smog with new Cat 1000 miles ago. 325k miles. I drove it 11 miles on the freeway and went into a store for 15 minutes, came out and it started but quickly died and didn't respond well with throttle after restarting. Seemed okay but low on power so I drove a few blocks and then CEL came on and I pulled over. Barely idling. Towed home and pulled codes - PO125, PO171, PO130, PO133. A friend suggested the K&N cold air kit (the only mod), may have caused the MAF to get dirty. Cleaned MAF and truck restarts but revs high, and then, almost dies, then revs high and then dies trying to idle. I've tried a known good spare MAF and the same result. Codes are for an 02 sensor, but my Toyota mech friend suggests MAF first.... any ideas? I will add that I was getting 18-20mpg with each tank, and my only concern before this was that it cranked slightly longer than I'd expect when starting, warm or cold

 

You don't say what engine you have, but with your MPG, I assume it's a 2.7. Now.....Take off the Throttle Body and clean it with throttle body cleaner "ONLY" and then clean the IAC (Idle Air Control). Get some Q-Tips and get Hot! Then I would replace the TPS (Throttle Position Sensor), $50 bucks. Be sure to use OEM only as Aftermarket parts don't play well with Tacos. Even the MAF. And don't ever touch the MAF with your fingers and use MAF cleaner only. Then clear the codes and see.

 

Fyi he says 3.4L in the title

could be fuel related, but cleaning the IAC and checking the TPS is also good maintenance. The TPS failing will throw different codes.

 

Thanks for the input ya'll. i'm going to look for vacuum leaks again before testing the fuel pump somehow. Anyone have a recommended way to check fuel pressure on a '98 3.4L?

 

Also most of the codes talk about the 02 sensor....and it looks super old..... seeing that makes me think 02 sensor but everybody's pointing somewhere else.

Bypassed brake booster to eliminate gross leak at booster. No change.

Removed fuel return line at left engine bay - ran engine til it died, no fuel came out. Ran for 10 -12 seconds.

 

In an attempt for you to diagnose your issue there are a few things you need to understand. There is one code, P0125, that needs to be fixed first. If the powertrain contgrol module (PCM) does not get the signal that the engine is warm enough it will not enter closed loop mode. Closed loop mode is where the various input sensors actually modify how the motor runs. Up to the moment the PCM enters closed loop it is running in open loop. Open loop is nothing more than the motor running on programed in settings, so much fuel, so much spark advance for a given throttle input, etc. If the coolant sensor is telling the motor it is -40* outside, which for some manufacturers is the default temp for a bad sensor you can imagine how the motor will run.

Sounds vacuum leakish to me, look at the intake hose, It is probably original, 20+ years and is stiff. Look for cracks in the bellows, splits where it attaches to the throttle body and MAF. MAF's are HPYER sensative to false air, a vacuum hose with a 1/16 ID will trigger a too lean condition.

Do you have a scan tool?

 

Thanks Glamisman, All I have is a code reader at this time. The intake tube is a K&N set up for cold air intake, which appears to be this one: https://www.knfilters.com/cold-air-...Yyykc1sODpsp4t-BgBcGxi9zMxj7nNSeYG4x_5idTFIw_

I've had it apart 2x for examination and I put sealer on the threads to the fitting it has for a vacuum hose as seen in the pic. I'll double check it now again tho.

As it is now, it barely starts and gasps for more when I throttle it, and I can somewhat keep it running but it dies quickly at idle. So if it's in an open loop of any kind it's not one that works to keep the motor running at all.

I'll report back after checking the intake tube/K&N/clamps once more.

Thanks!

 

Ok, got a helper to start and try to keep motor running while I sprayed connections with carb cleaner and both manifold plenum gaskets etc. Same. Just won’t stay running.

 

It is starting to sound more like a fuel pump to me all the time. Checking pressure on these isnt easy but there is a plan B. Take the fuel filter off under truck and see if it is clear first by blowing through it, there will be resistance because of the fuel in the filter and after that clears it should blow through pretty easily. Timmy the toolman has excellant videos. https://www.youtube.com/watch?app=desktop&v=N-lhZIWOkyU

As a go no go type of test I have attached a nylon hose to the inlet side of the filter line, put it in a barrel/bucket/container and had someone crank the motor for 1 second. You will know if you have 45 psi ish and enough volume. Most people that I know do not have access to a fuel pressure gauge, O reilly will rent you one or you can get a below par one at harbor freight but then you are hoping that the fittings fit and lets be honest, you will be doing this once, maybe twice in your lifetime.

 

Copy, thanks again. I changed the filter late yesterday and it was clear, but an old filter, so it was time anyway. I'll undo an end or the hose somewhere and crank the motor over to find out if the pump is moving any kind of pressure.

 

Update…. Been busy with work n fam events, and luckily have something else to drive, but fuel pump (denso) and related parts all finally here today. So out comes the pump looking like this…. Turns out a car quest pump was installed at some point and apparently they come with the wrong rubber cushion for the bottom of the pump. With no keyed seating of the rubber cushion, it wiggled out of the metal framework and allowed pump to dangle and eventually vibtrate/slide off of the hose and thus no longer sent fuel out of the tank…. So, correct cushion arrives tomorrow from Toyota dealer.

 

Verify that the connection hose from the pump to the pipe is fuel submersable... regular fuel injection line is not submersable.

How much for the Bronco?

 

Good idea, it seemed kind of weak- I’m going to use the new hose that came with the Denso pump. Bronco belongs to a customer of mine…it’s been a long road to get it done and we are close.

 

It’s done. Thanks everyone. Started right up and cleared codes. Here’s the correct cushion for pump and how nearly it fits.

 

Yep, that looks right, the other hose looked like external FI hose and didnt look like the submersable stuff.