Bucking coming off from stop

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MaximaGuy

Joined
Sep 20, 2003
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Location
Austin, TX
The Highlander in my sig has 190K and recently there has been a bucking coming off from stop or WOT.

The things that are up-to-date

a) Air filter and cleaned MAF
b) Coolant flushed out with OEM fluid
c) At 140K both the pump, belt and plugs changed
d) Always used good gas

Leaning towards a clogged cat or a worn out fuel pump but then it could be the coils as well though there is no codes in the system

Any suggestions would help
 
Originally Posted by HangFire
Busted motor mount(s)? Or is this definitely engine trouble? Usually you get codes with real engine trouble.


The front and top mounts were changed as well, the one that takes the highest wear is the one near the radiator and that was replaced as well.
Engine trouble no way, it runs like a champ
 
Here in TX we have 10-15% ethanol and it is a good cleaning agent, wonder if at all anyone replaces the fuel filter ever.
 
Will it buck the same if you try to move using the Reverse gear?

Try this next time to isolate the problem to the engine.
 
Does it have a telescoping style rear driveshaft? My 4Runner had a bucking/squatting under acceleration from a stop, and it was the driveshaft binding. Problem went away after greasing the driveline.
 
Originally Posted by cjolson140
Does it have a telescoping style rear driveshaft? My 4Runner had a bucking/squatting under acceleration from a stop, and it was the driveshaft binding. Problem went away after greasing the driveline.


The driveshaft is a 2-3 piece sealed units and mechanic said there is no play and are in good condition.
Suspect the MAF, will order it online or call the dealership and go from there.
 
Originally Posted by HoosierJeeper
x2. I've never had luck replacing a MAF. Can get a new Denso one from Amazon for $50, my LR3 loves them.


Sorry, meant cleaning...never had luck cleaning one
 
Have someone assist you in the vehicle and you stand to the side of the vehicle (for safety). Have them put on the emergency brake and step on the regular brake firmly. Put it into gear and while holding the brake bring the vehicle's RPM up to 1500 RPM and see how much the engine rocks then do the same in reverse. If there is more than a couple inches of torquing going on you have a bad mount somewhere.

Failing that is could be torque converter slippage that could be a problem. A good scan tool can tell you how many RPM it's allowing it to slip in gear at idle. If it's slipping too much or not enough this can cause a problem.

Is it better when the vehicle is cold or hot?
 
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The key word in the OP is "bucking." I've experienced both a broken motor mount and a bad MAF sensor at different times. Bucking is totally different than the knocking thud experienced from a broken motor mount. People posting in this thread need to research the definition of bucking. Maybe even watch a few cowboy bull riding videos.
 
Originally Posted by StevieC
Have someone assist you in the vehicle and you stand to the side of the vehicle (for safety). Have them put on the emergency brake and step on the regular brake firmly. Put it into gear and while holding the brake bring the vehicle's RPM up to 1500 RPM and see how much the engine rocks then do the same in reverse. If there is more than a couple inches of torquing going on you have a bad mount somewhere.

Failing that is could be torque converter slippage that could be a problem. A good scan tool can tell you how many RPM it's allowing it to slip in gear at idle. If it's slipping too much or not enough this can cause a problem.

Is it better when the vehicle is cold or hot?


Absolutely sure there is no mounts issues on the vehicle that can be ruled out.
Its better when cold and hot is flares up - cannot say much since the last 2 weeks here in TX its been raining and all vehicles behave differently when there is too much precipitation in the air, the heavier the air the vehicles somehow for some reason have more HP and less of vacuum leak behavior which can mess up the A/F ratio
 
Not sure about Toyota but Ford had a "Mode 9" IIRC that allowed one to see individual misfire counts per cylinder. It was quite common for the Modulars to "buck" when they'd hard miss under load but not trip a CEL. Going into this data you could see if one cylinder had significantly higher misfires than another and could then change out that coil, resolving the problem.
 
Can you see fuel trims? If so can you tell me the following:

What the short term fuel trims and long term fuel trims are for idle in gear (wait a few minutes) and in park at 2,000rpm and if possible when the problem is occurring just the S/T FT's. (Be safe about this)
 
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Check O2 sensor and related parts affecting fuel mixture? Bucking from a stop was common with carburetors set on the lean side, including new ones of certain vintages. The Honda PR guy we dealt with circa 1980 humorously termed the phenomenon "the Honda Hop."
 
The O2s have always been on my mind - they don't really last beyond 150K, they may never ever throw a code but then its served well if they do their job for 100-150K.
One of the reasons not to invest much into an old vehicle is you never know when the vehicle can get totalled in an accident, ploughing in too much money the ROI is depreciating given that the older cars aren't getting fixed rather written off. Its a $500 bill which I shall put into, the MAF is ordered.
 
Replaced the MAF with OEM MAF and the bucking is gone. Thank you all for suggesting the right fix.
The O2s are next in line for replacement.
 
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