Hey Guys, My 1999 4runner limited 6cyl 4wd started surging or bucking at speed of 40 to 70 mph. It happen while under load like going up a small incline. If I let off the gas it stops. I had the tranny flushed and new filter put in. The check engine light came on once since I had the fluid changed, but hasn't come back on. the problem happens cold or hot.
Any Ideas????

Just out or curiousity, have you checked the color of the oil and coolant?

My ride used to buck and hesitate a little, but was fine when it was stil or in park/neutral and it turned out to be a cracked head.

Hopefully it isnt anything dealing with the head or headgasket but check the oil and coolant to see if its getting nasty.

Hi Scott,
I'd be very interested to hear what you find. My sister's 4runner does the same exact thing (stumbles/jerks when going up an incline at 40-70mph) and I had the check engine light scanned and it was a misfire in cylinder 2. I replaced the spark plugs, cleaned the MAF sensor and it still does it and the check engine light still comes on. I also swapped around the ignition coil packs and still get misfire in cylinder 2. After reading up on some online materials it looks like all signs point to a bad/dirty fuel injector. Hopefully this helps for you but please do let me know what you find out is your problem and or if it is even related to the fuel injector.

Thanks and good luck!
Benny

Don't get too far from the basics.
Have you checked your air filter? Seriously.
Then check your fuel pressure and fuel rail dampener.
Do you smell fuel on the passenger side of the vehicle?
If you do it's your dampener leaking.
Fuel pressure NEEDS to be in the 45 to 50# range have it checked while driving too there has been problems with the pressure while driving and ok just standing still.

:grinyes: Hey Guys, She running like a top again. I changed the air filter, fuel filter, plugs and wires and she is happy again. I had the code pulled on the check engine light and it was missing on cylinders 1 and 2.

Thanks