My 2004 V8 4Runner stumbles/hesitates/misses under loaded acceleration, such as a medium grade hill/highway. Most notice when traveling at 60mph and need to increase "gassing" it to maintain the 60 (or slightly greater) mph on a long hill grade highway.

This happens before it will actually downshift, and once downshifts also stumbles shortly until around 3,100 rpm's. Once it drops back to "normal" rpm's for the speed, it won't maintain the speed without an significant increase in gas, then everything repeats itself. It started the day after changing the oil (I can't imagine one has to deal with the other) at 5,001 miles.

I have a little over 5,500 miles, air cleaner is clean. I plan on taking to the dealer, but before doing so, I'd like to see what thoughts there are on what could be causing (alwys go with an educated reason to the dealer).

One other note, it has done it over a couple of gas tanks, so not likely it was a bad tank of gas. I also always run premium (Chevron).

I live in California (emmissions stuff)

Mike

 

Switch gas stations you coud just be repeatedly filling it up with the same tainted gas also try running 87, I felt on 93 is had less power and just drank more, with 87 it seems stronger, it's not a vehicle that requires premium.

It could also be that your truck does not like the 93 and the ECU is trying to adjust and is confused

 

Premium here in CA is "only" 91. I'll try the change up in octane (lower) and see if it makes a difference. I too think the issue is ECU, just who knows what's causing the problem. I did have major isues (requiring replacement) of EGR valves and cannisters (all warranty, but what a hassle). Given the dealer I went I'll never go back to, could be they re-programmed the ecu incorrectly with the new polution devices.

Mike

 

Here are my guess'es:

- BAD SPARK PLUG
- BAD COIL PACK
- BAD TPS Sensor

Is it throwing any codes?

 

What work was done on the Runner by the dealer? It sounds like they messed something up, maybe have another dealer see if they can diagnose the fault.

 

what do you mean "throwing codes?"

 

CHECK ENGINE LIGHT

 

Replaced EGR valves (twice) and Cannister. The dealer was a bunch of bone heads, South Coast Toyota, Costa Mesa Ca. Trying out a new dealer, and never going back to SC toyota.

Seemed to run pretty good until right after 5K oil change.

I'm not getting a check engine light, so, so far it hasn't thrown a code to trigger that. But it's not running correct.

Changed to new gas, 76. Didn't make a change.

 

this is a longshot as its a brand new vehicle... but how about the MAF?

mine was choking under medium acceleration at speeds between 30 and 45 all the time till i got the MAF replaced.

 

I didn't consider the MAF, since it's new. But, then again, how many new Toyota's need a whole new EGR system including cannister? I've had other issues with the vehicle, so at this point nothing would surprise me, except that anything wrong is so odd for toyota.

I noticed this morning that if I "feather" the accelerator as the stumble occurs, it will smooth out.

I wish it would trip the check engine light.

Mike

 

hmm.. i had that same feather experience with my MAF.........

 

OK, now I'm getting somewhere here. I can see the pain I'll go through to get the dealer to understand and fix for free (warranty).

Thanks for the help, and I'll let you know the outcome.

 

there wont be a pain. just tell him your truck is stumbling / hesitating and you suspect it is the MAF... they will at the very least call you with whatever the diagnosis is before doing anything, and if youre unsure (or if itll cost you money on unwarrantied work), tell them to hold off and come back here.

thats the lesson ive learned

 

Now that's funny.

Welcome to the new Toyota Corporation. Build quality and service has been getting worse since 1990.

 

listen to this guy...

I put my money on spark plug(s).

 

Even though the check engine light has not gone on, if there are any issues with MAF, plugs, etc., (or other) it would show up as a code, correct?

No check engine could just mean not enough issue to trigger this?

Thanks again for the feedback

 

You should not have to pay anything, the truck is covered under a 1st year warranty that covers anything and the 3 years 36k bumper to bumper should cover everything but general wear items, if the dealer is charging you go else where