Engine stumbling at speed

[Seanz0rz]

so i took the 4runner for a very long drive today, about 130 miles, and noticed many times, sometimes getting me very scared the engine was going to die, the engine stumbles. i thought it was a transmission problem, shifting from OD to D, but it has popped up during normal driving, with out shifting.

so what are the possible causes:
spark plugs?
wires?
coil packs?
other ignition components?
fuel system(injectors, filter, etc)?

i ordered a new filter from the stealer, 34 bucks and change, and i am going to pull the plugs tomorrow and see what they look like (got dark on me fast tonight). if they look bad im going run some seafoam through the pcv and then replace them. what about possible problems with sensors? throttle position sensor, i know those can go bad. this problem is not apparent at idle, so im not sure what to make of that.

you guys have any other suggestions? anyone else ever had this happen. its all ranges of RPM, but seemed most pronounced at around 1500, when crawling through traffic at 1000, etc.

thanks in advance! sooner i can get this fixed, the sooner i can get back on the trail with you guys!

[Lee]

imo, my thought process for these types of issues is always fuel delivery > spark plugs / packs

but if you havent done your spark plugs in a while, here's your excuse!

[MTL_4runner]

Assuming no CELs....

I'd definately change the plugs if you haven't in a while but the fact that the plugs are black sounds like it's running very rich. Have you ever changed your O2 sensor on that vehicle?

Did this condition come on slowly or more quickly?

[Seanz0rz]

this condition popped up maybe 5 drives ago, about 3-4 weeks ago, all of a sudden, but its getting worse the more i drive.

no CEL's at all, ever. AFAIK, o2 sensors are origional, im going to pull the plugs right now, and if i can reach, check the fuel injectors. stealer wants over 150 a piece for the injectors, so im hoping that is NOT the problem.

i also seem to think it is a fuel problem. not really even sure where to start with the fuel system. fuel filter will be replaced next weekend, when it comes in, other than that i am unsure where to go from there.

[MTL_4runner]

Pull the plugs and see if any of them are lighter/darker than the others. If you're getting a leanout in one of the cylinders it should show on the plug. You can also begin checking resistances on the fuel injectors if you suspect them as possibly being your issue.

[Seanz0rz]

so i thought i fixed it with a new fuel filter, but apparently not. i had it happen once to me on the freeway driving back to my apt tonight.

my specific symptoms: accelerating gently (no changes in gears) from the 1600/1700 RPM area. it started bucking (about 3 times) when traveling from 1700 to 1800.

what do you guys think?

[Seanz0rz]

so im my quest to find out whats wrong, and then fix it, i took it to the dealer, see what they could come up with.

after 4 hours, they tell me plugs and wires need to be change, along with cleaning the throttle body and other parts.

they wanted 270 to put new plugs and wires. i nearly shat myself when i heard that. of course i dont have the money for that. so i took the truck back after they put it back together. today i went searching for wires. toyota wants $60 for wires. 60 bucks for wire. yes 60 dollars, for 3 plug wires......... WTF???

so hopefully i will get the ngk wires i ordered sometime next week, those were 38 out the door.

wtf is up with 60 bucks for wires? i paid 20 for 6 plugs, i already have those sitting at home. so even at 80 for parts, they want 190 to DO the work. thats not cool guys.

probably looking at changing out both 02 sensors too, esp because they dont like to throw codes.