Persistent, intermittent surge / hesitation 2001 Tacoma FIXED!!

Trying to track down a gremlin, need help.

Have a 2001 tacoma 3.4L w 195k miles. Recent work within last 6-8 months includes, replaced coils, plugs, gas cap, vaccum lines, purge solenoids on evap canistor, New MAF, cleaned throttle body and new fuel filter.

I run E-free gas. No error codes. 18-19mpg. No overt loss of power. Injectors I could get a screwdriver on "tested" fine.

Truck will hesitate as if the gas line was pinched for a second or two then a "thump" as the engine seemes to catch back up. This occurs mostly in mornings when engine is cold, but will continue throughout a day of driving under gentle throttle.

New fuel pump w sending unit and Fuel pressure regulator are up next.

Local shop no help because its not throwing codes and they can"t "replicate"

Anyone run into this? Fixed it?

 

Can you clarify what you mean by "Injectors I could get a screwdriver on "tested" fine"?

Had a friend who's truck had similar symptoms (hesitation to accelerate, but only between 2-3k RPM). Swapping injectors and changing out IAC (with new OEM one) solved the issue. Not sure whether it was the injectors or the IAC, but the symptoms are gone.

 

Meaning when I touch the screw driver to the top of the injector while engine is running I can hear the raPid clicking of the injector. Not a fool proof way to test, I know.

Truck doesn't actually hesitate to accelerate under throttle, and Idle is still smooth, no major fluctuations. It's like if you were jogging w a harness on and someone yanked on the harness for a hot sec then let you keep running.

 

When you cleaned the throttle body, did you remove the IAC? If not carbon run down into the IAC and cause problems

 

Didn’t see mention of tps.

 

Local mechanic said TPS tested fine when I had it in ways back. No, didn't remove IAC. Will trouble shoot that.

 

I had an aftermarket TPS that tested fine. Same intermittent skip/jerk/miss at highway speed and in acceleration. Replaced a bunch of ignition related stuff. Then noticed TPS reading on scan gauge jumping all over at idle from 9-3 and to 14 or so. This with it set properly at 10 for idle. Put new OEM in and fixed it. I’d be surprised if IAC was culprit, usually an idle issue thing with it being stuck in one position or another. Maybe 3.4l is different.

 

Hmmm, I'll have to check to see if its OEM or Aftermarket. Obviously have a few things to run down and recheck.

 

I had a similar issue and it ended up being fixed after putting in a new set of OEM coils and plugs. This was for the 3RZ though.

 

UPDATE.... Just threw in the new MotorWest injectors and Beck Arnley Fuel Regulator. All went as expected. Test drove afterwards and it threw P0120, TPS circuit A. cleared the code and will drive for few days to see if that keeps coming back....

 

Needed a new TPS. Standard Motor Products to the rescue! Runs cherry now. New TPS, Injectors and Fuel Regulator.