It bucks ,stumbles,hesitates

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vipergrhd

vipergrhd

10 Year 15 Year
Joined
May 29, 2007
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66
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no.california S.F.O BAY AREA (EAST BAY)
only when engine is cold.after engine reaches operating temp.it is fine,no check engine light coming on.it has been an issue for quite some time and have no time to take across the street (toyota) to be diagnose. done the tune-up thing wires etc.seafoam for the fuel system but still happening.it currently has 206k and a 3.0l v6 mostly stock.just need some input from someone that have run into this similar issue.Thanks in advance.:D

John:idea:
 
Pull the cold start injector out and see if it's cruddy.

Also check the temp sensor that feeds the ECU.

Check the adjustment of the TPS.
 
thanks

I don't think the timing belt would cause this issue,its been happening since the first timing belt replacement.i like the cold injector suggestion and the coolant temp sensor.follow up question would be if the cold injector is not doing it's job wouldn't that affect the starting when cold and does the cold injector still fires after the engine fires up? :confused:

John:frown:
 
The cold start injector fires for awhile until the engine starts to warm up, then the ECU shuts it off. Properly tuned and running right, you can easily tell when it shuts off as the engine idle will drop noticibly. What can happen is the little nozzle part of the injector can get gummed up and partially clogged, I think you'll be surprised how dirty it will be if it's never been cleaned, after that many miles. Some carb cleaner should take care of it, just do it outside, that stuff is potent.

There are 2 copper gaskets on the fuel banjo fitting, and a paper gasket under the injector. You might want to get new ones before taking it out, it would suck to have it leak when you put it back together.
 
clean terminals

batt.terminals are clean,no engine or head job was performed so i'm assuming that all grounds are in it's place.owned it since 5k.how bout the coil/igniter any ways of checking this parts to see if bad?i'm just avoiding to spend 130 bucks to get it checked out at toyota,i would rather used it to buy other stuff.:frown:

John
 
You may want to do some checking with an ohm meter to see how all the ground wires are working... test from the bat to the engine, frame and to the body. Just cause they are on doesn't mean they are good... :cheers:

As for the coil/ignitor I'd find another running truck to swap with and see if it fixes it. There are a few tests for the coil in the FSM, check in the FAQ thread.
 
mass airflow

went and check FAQ but did not find any info on testing mass air flow sensor.is it possible that this could be the cause for my hesitation?:idea:

John
 
KLF said:
Pull the cold start injector out and see if it's cruddy.

Also check the temp sensor that feeds the ECU.
Click to expand...

I think I like this idea. If it runs fine after warm up then it's probably not a ground issue. Cold start time switch, or cold start injector. Pull the connectors and snap them back on.
 
unlikely

that my timing belt is off a tooth or more to cause this issue,first it only happens when cold and this thing bucks like a wild mustang if you don't let off the gas pedal and sometimes it's just flat on it's face gutless.i'm on my second timing belt already and my hunch
leads me towards inputs to the computer reason being not getting the proper output to the coil or injectors,i have no scanner to check each individual component to see which one is acting up or reading wrong.i might just take it across the street at Toyota dealer to get it checked.will let you guys know what they find.:hhmm:

John:confused:
 
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