HELP! Lagging Acceleration. Intermittent.

Hi All,

Ive tried almost everything I can think of and getting no codes. Sometimes the truck is fine but then all of the sudden at a start up, the truck is back to serious throttle lag like it is sucking air or something. I've replaced plugs and brought it to multiple mechanics with no resolution. I recently bought a new throttle body since my model doesn't have a separate TPS sensor to easily replace but havent dropped it in yet.

Recently, I took out all the new spark plugs and put back together and the truck ran awesome for a week. It also seems when I disconnect battery it sometimes seems great, until the issue randomly returns. Now back to the serious lag when pressing throttle. Furthermore, at high speeds the truck seems to need to use a lot more RPM's than it used to. I.e. When going 70mph I would be right around 2K or just above and now to maintain 70mph it is up around 3k RPMS.

List of thoughts.

1. Spark plugs, just replaced. Still look good as of a week ago. Mechanic also said looked good.
2. Packs or misfire, Mechanic drove with me and also tested everyone individually.
3. MAF sensor, Cleaned it, looks fine. Could this be bad without a code?
4. Fuel pump - no startup issues ever and since this happens on/off hard to say the pump works fine for a week then suddenly just pumps very weak.
5. TPS/Throttle Body - no code here. Cleaned it thoroughly, but could this be it?
6. Fuel Injectors - havent pulled and replaced yet.
7. 02 sensor? No code here either so no idea where to start.

Thanks a ton in advance, as Im trying to narrow it down but havent had luck for now 4 months.

 

1 probably fine
2 probably fine
3 not typically, if so usually a wiring harness issue not the MAF itself, could also be your throttle position sensor
4 Milage? Pump may be fine but filter may have a blockage, URD makes a very good upgrade kit which includes a remote replaceable fuel filter with a much larger capacity than stock, the stock monolithic pump/sock/filter module is frankly a bit of an embarrassment.
5 see comments on 3
6 possibly but you would expect a more consistent issue if so
7 usually pretty dang reliable and when they fail they throw codes.



Have you changed your PCV?
Have you changed your air filter?
Any modifications to the truck?
Are you manual or auto? (Trans could be slipping/having a lock-up issue)
What's your MPG average looking like?

 

Thanks for the quick response Key-Rei!

Have you changed your PCV? I have not, but will look into this today.
Have you changed your air filter? Air filter is new, looks good still.
Any modifications to the truck? No mods.
Are you manual or auto? (Trans could be slipping/having a lock-up issue) Auto transmission. 130K miles on her. It feels great when running well, any way to diagnose this? To me the way it drags seems seensor related (no codes tho), air related, or fuel related.
What's your MPG average looking like? My mpg is great without the issue, but when it starts to happen it goes real bad, like under 10mpg because I need to push the gas so hard to stay up to any kind of highway speed, or from a stop it wont want to acceleerate until I really push it.

With my 2012 taco having the throttle body and TPS all as one (or can't just replace the TPS) does anyone with a 2nd gen seen these go bad? Again, I bought a brand new one ($300) but havent dropped it in yet as trying to narrow down other potential culprits.

 

Does this lag occur while the air conditioning is running? AC running can cause a lag.

Have your mechanic take a stethoscope to the pulleys as well

Goodluck. I hope it's simple.

 

I thought it could be A/C related at first as well, but seems to happen either way.

While lagging acceleration seems to be the first sign, again at higher rpms or also really any higher speed above 50mph the truck needs more RPM's to maintain, like it is lacking power, fuel, air etc...

Thanks again everyone. PCV valve is super simple and cheap so starting there today.

 

Buy, borrow or rent a scan tool with good live data & recording capability. Track all of the related PiDs (MAF, MAP, TPS, Fuel Pressure, Fuel Trims, Spark, etc). Almost certainly, when the event occurs, you're going to see a 'smoking gun' in the data.

 

I'm almost 100% positive that you and I are having the exact same problem.

 

How’s your brakes? Could be having a caliper hang up or a leaky rear drum cylinder causing the drum to lock up.

 

Thanks again everyone for the responses. Break are good to go.

@Shauniscool123 that sucks but also good to hear Im not crazy. Have you tried any fixes so far? I drove out this morning and scooped a PCV valve for $4 so going to replace today and will report back. Seems like an easy start - also read that PCV valve failure will also cause power problems, which is the easiest and most general way to describe my ongoing issues, albeit intermittent.

 

I replaced my PCV cause OEM is cheap on that, sparkies are all new, also cheap at dealer. Filters are new, brakes are new, all fluids new, I run 88 octane. I literally have no idea what it is. Possible going out fuel pump is my guess. But only a guess, I've driven with Livedata before with no results. I work for Honda so I have lots of stuff at my disposal, no results or lights.

 

Interesting, ok maybe we can point this thread at fuel pump. Has anyone experienced intermittent fuel pump issues? Everything I have read seemed to indicate it would just fail and I would get a no start. My start is perfect, but maybe fuel pumps could become weak?

I dont want to throw money at the fuel pump without knowing due to cost. Thanks again everyone!

 

Agreed. I dont wanna throw a fuel pump at mine either, especially cause the part alone is like $500 something dollars.

 

How's the battery terminals? Even if they look clean, the posts could be badly oxidized. Get a battery brush and clean the terminals and posts. While the battery is disconnected, check continuity from the negative terminal to all over the place. Test the fuel pump resistor. Use the erase codes function of your obd reader. Even if there are none, sometimes it'll chase away the odd gremlin. Run a can of jectron or similar good quality cleaner with a tank of premium. Then drive it hard, like up a long hill on a hot day.

 

I have an intermittent acceleration lag that starts after an oil change and lasts 600-800 miles. I'm 90% sure it is the VVTi actuators (or one of them). I searched for the longest time before finding a thread online about this. I'm guessing the actuators in my truck get too (internally) leaky with new clean synthetic oil. Eventually I'll get irritated enough to replace them.

https://www.tacomaworld.com/threads/oil-control-valve-location.270960/page-3#post-15726418

 

This for sure is not what I'm experiencing.

 

Thanks again everyone. @Waasheem Terminals are good and I checked the resistor. I am starting to think more and more it may be a fuel pump that works sometimes then is starting to fail at other times. I am going to take it back to a mechanic and have the pressure test the fuel system and see what we get. Hopefully when they have it acts u[ and doesnt run perfectly fine.

@JKD Agreed with Shauniscool, nothing related to oil changes for me. It seems totally random, low fuel, new fuel, great one day or for weeks then for a several days it is total sh*t.

Ill report back after I get a status on fuel pressure etc....

 

Definitely let me know what you find. I'm half expecting my fuel pump to go out at some point.

 

@Key-Rei If I find fuel pump needs replacing - do you suggest replacing with URD suggestion above? Looks like a good deal and even cheaper than the Toyota fuel pump etc.. Am I missing something in the replacement with this kit? Looks like around $200 for a better setup than the $350 plus Ive seen for the standard in tank pump. Thank you!

 

I swear this sounds like another VVTi issue.

I want you to check your fuel trims. Both long term and short term. If those appear okay (under +-5.5%) then the issue is in your VVTi solenoids. You would not be the first guy who has defective ones and you would not be the last. The giveaway for me is the lag at acceleration and the trash fuel economy.

 

The price on the URD one can vary depending on which option you choose for the fuel pump.

I have been more than satisfied with mine (I chose a Deatchworks 255lph e85 rated pump) and it has been running 3 years with zero issues.

I try to only run ethanol free whenever I have the option, but I wanted an e85 pump for flexibility and reliability should I ever choose to put e10 fuel in or go full bore and do an E85 tune. Which will probably never happen.

The price is pretty cheap as it's not a very complex system.

A fuel pump motor, some connectors and hoses the filter and that's about it.

But yes I recommend the kit even if you don't need one right now it's good peace of mind.