Hey guys. I need some help here. I have a 99 4Runner with the 3.4 and about 225k miles. All of a sudden it's "stumbling" when sitting at idle. It runs fine then "stumbles" for a second then runs fine for about 20 seconds then "stumbles" again. Also on acceleration when you first start out it seems to miss right at first then runs fine. Once you are moving it runs fine. It only does this when you are moving very slowly, especially when backing up. It actually seems like it's going to die when you are backing up it's so bad.

I've replaced the fuel filter and it fixed it for a minute, at least long enough for me to drive it. Then when my wife drove it about 20 minutes later she said it's still doing the same thing. We are going on about a 500 mile trip here at the end of the week so I'd like to get this figured out. Also, no check engine light is on.

Thanks for all your help.

 

How old are the plugs and wires?

 

plugs, wires, clean the maf. Other wise check for codes in the history.

 

X3 on plugs and wires.

 

All of the above and clean throttle body, too.

 

Plugs were replaced this summer. I haven't had a chance to do wires yet. I'll pick some up today and do that along with cleaning the MAF and throttle body tonight and let you guys know.

 

maf can do this when dirty

 

FIXED. Replaced the wires, had the originals on it at 225k, and plugs. Running great now.

 

Whew, those were some old plugs! :O

But yeah, had this problem a year and a half or so ago, got them plugs and wires swapped out for some new ones, ran great!

 

plugs and wires.. it happened to me quite a bit

 

BUMP

I have exact same problem 99 4runner 3.4, stumbles/hesitates in reverse and idling in drive. Seems normal once up to speed.

Replaced: MAF, Plugs, Wires, Tested Coil packs they in spec, No engine code. Any ideas?

 

FIXED

For anyone else... It was a bad coil. Even though it tested to spec with the multi-meter it was somehow still bad. Oh well, 350,000 KM and runs good again!

 

How often is it recommended to replace the coils? And is there a difference between the coils for a 96 and a 2000?