liquidtouch

97 Tacoma 3.4L 340000km. timing belt recently done. new plugs wires and fuel filter. burns no oil. mobile 1 synthetic. good compression. good alternator with dual gel. isolated start/run batt.

Every now and then(20min - 30min) while im driving usually while rpms are steady for a bit at 2200-2400 engine will miss or stumble for what seems like .5 sec.

even rarer it will stumble on soft acceleration.(usually 5 mins after every second or third cold start)

Ron Helmuth

don't throw parts at it without gathering a variety of opinions-I will say check your MAF sensor it may need cleaned. Also the Throttle position sensor seems likely it has reached it's mileage limit. Just guessing from your description of symptoms- I am no mechanic and not pretending to be.

t4r.org is Runner specific-many of which use your same motor- but this forum has good to better advice also. Welcome.

terminator

iTrader: (1)

Woodruff key issues maybe? Mine was damaged during a timing belt install when I had the engine swapped and didn't show for a while. Mine would act like a stutter box you hear at the drag strip when I would hit passing gear. Turns out the idiot that did the work at the engine shop didn't torque the balancer down properly and wore the woodruff key enough to cause this. I understand it's a fail safe thing the engine does as to not damage itself internally. The problem is you have to remove all of the timing parts/water pump to check it out.

Cpate81

Could be bad gas (water in gas)...Try some water remover.

liquidtouch

Thanks guys,
Done the fuel and oil treatments. as well as injector cleaner. run premium gas. woodruff is tight and fine. no codes or check engine light. MAF is clean and moves freely. About to test TPS resistance values. will be checking O2 values as well.

liquidtouch

all tested ok
any other ideas?

brian2sun

Coil packs maybe, you can test them too.

chuckd

Did you ever get this figured out? Mine stumbles pretty badly at part throttle accelerating but is fine at higher rpms and constant speed.

YodaPala

one of my spark plugs backed out and cooked the stem of the middle coil pack. I replaced this and havent had a problem since.

toy4mud

What do you mean cooked it? I have a 2000 4runner with 3.4L v6 and have been having similar problems. The missing I experienced was under hard acceleration. I could get up to 65 and stay steady there, but it took babying as giving too much gas would start the hesitation. I changed my plugs and wires and the problem went away. Since I changed them I've put about 1,800 miles on them. I drove from Ohio to Iowa and it was great the whole time. As of 5 days ago the problem is back, and it's worse. I can't accelerate quickly without stumbling/missing. I don't want to start buying random parts to find out it was a waste. I replaced the fuel filter, air filter, and pcv valve the other night, and its still bad. It doesn't seem to miss at idle, but hammering on the gas makes it sound like its running without a cylinder or two. Any ideas? I checked resistance on the ignition coils and it seemed within the limits.

tommytuttle

I have a similar problem replaced two coils, and MAF, Fuel treatment etc.

Thinking of trying new plug wires.

toy4mud

i just noticed this tonight. The brakes have been a little funny about the same amount of time the engine has been acting up. I went to church tonight and the truck wouldn't start on the first key turn. I noticed the pedal went all the way to the floor when it stalled right after starting. I started it again and went out under the hood. I started looking at the brake booster lines. the large hose that connects to a round stem with a base on the front of the booster moves. It looks like its cracked on the front of the booster. I wonder if this could be the cause of my problem? Maybe anyone else that is having this problem they cant trace could go check thier booster? Would this vacuum leak make the truck run bad?