Hesitation at 2000 rpm 3fe (1 Viewer)

Joined
Jan 20, 2015
Messages
107
Intermittent problem
truck runs great nice power....then decides to start hesitating from 2000rpm to 2500 rpm sometimes a backfire..... then takes off like a rocket once it hits about 2500 rpm.
also when this hesitation starts it will start idling badly.
it will do this if cold or hot.....

things checked
1. TPS....ok
2. IAC....ok
3. MAF....ok
4. O2.....ok
5. all sensors on water pump replaced...
6. all vacuum leaks fixed....
NO CODES CEL flashes like it should with no codes
i have FSM and have been going through them one at a time.
when it wants to run nice it runs perfect like new truck.....

HELP!!!!!
 
Joined
Dec 8, 2006
Messages
9,850
Location
New Jersey
10. EGR Valve: OEM part# 25620-61120 The EGR valve and modulator (flying saucers mounted on top left of intake manifold) both have rubber diaphragms inside that become brittle with age and heat. They tend to disintegrate and the resulting particles can clog vacuum lines. A faulty EGR system will yield poor acceleration under 2100 RPM and feel like a turbo kicked in above that range. They are also a good source for vacuum leaks. Both the valve and modulator should be replaced at the same time and all hard vacuum lines should be cleared out with a solid strand wire and some WD40. The vacuum system can have a profound effect on brakes as well. Make sure it’s in good shape.
11. EGR Valve Gasket: OEM part# 25627-61021
12. EGR Modulator: OEM part# 25870-61020
 
Joined
Jan 20, 2015
Messages
107
10. EGR Valve: OEM part# 25620-61120 The EGR valve and modulator (flying saucers mounted on top left of intake manifold) both have rubber diaphragms inside that become brittle with age and heat. They tend to disintegrate and the resulting particles can clog vacuum lines. A faulty EGR system will yield poor acceleration under 2100 RPM and feel like a turbo kicked in above that range. They are also a good source for vacuum leaks. Both the valve and modulator should be replaced at the same time and all hard vacuum lines should be cleared out with a solid strand wire and some WD40. The vacuum system can have a profound effect on brakes as well. Make sure it’s in good shape.
11. EGR Valve Gasket: OEM part# 25627-61021
12. EGR Modulator: OEM part# 25870-61020
Smog delete about 5 years ago...
 
Joined
Aug 18, 2014
Messages
105
Location
Boise, ID
Maybe my google isn’t great, but the thread I get is from Twilly saying they are no longer produced, and the substitute doesn’t fit. The other sites listed say oos.
 
Joined
Jan 20, 2015
Messages
107
10. EGR Valve: OEM part# 25620-61120 The EGR valve and modulator (flying saucers mounted on top left of intake manifold) both have rubber diaphragms inside that become brittle with age and heat. They tend to disintegrate and the resulting particles can clog vacuum lines. A faulty EGR system will yield poor acceleration under 2100 RPM and feel like a turbo kicked in above that range. They are also a good source for vacuum leaks. Both the valve and modulator should be replaced at the same time and all hard vacuum lines should be cleared out with a solid strand wire and some WD40. The vacuum system can have a profound effect on brakes as well. Make sure it’s in good shape.
11. EGR Valve Gasket: OEM part# 25627-61021
12. EGR Modulator: OEM part# 25870-61020
hey john i think i found it...........there are 2 vacuum lines on the top of the throttle body...........i had them open......i closed them off and it has not stumbled since. nice power through the whole rpm range....
 
Joined
Jan 20, 2015
Messages
107
ok problem not fixed..................soooo intermittent
very odd..........
i noticed it does not do it in 1st gear only second and third....right when it shifts to second it boggs down a little until 2500 rpm then takes off as it should....
 
Joined
Sep 5, 2005
Messages
370
Location
ATL
Sure it’s not your transmission kickdown cable? I say it, given what sounds like an issue only at the shift point. This is where my issue was (92 3fe), solved by slightly tightening the cable.
 
Joined
Jan 20, 2015
Messages
107
Sure it’s not your transmission kickdown cable? I say it, given what sounds like an issue only at the shift point. This is where my issue was (92 3fe), solved by slightly tightening the cable.
Sure it’s not your transmission kickdown cable? I say it, given what sounds like an issue only at the shift point. This is where my issue was (92 3fe), solved by slightly tightening the cable.
No its not.....tried to adjust it.....very odd..backfires sometimes....after backfire it runs nice...thinking could be clogged exhaust? I dont know
 
Joined
Sep 5, 2005
Messages
370
Location
ATL
Fuels system ok? Possible filter/sock clog? Re: vacuum lines, if you saw that had an effect, have they all been replaced (remedying leaks through hose cracks)?
 
Joined
Jan 20, 2015
Messages
107
Fuels system ok? Possible filter/sock clog? Re: vacuum lines, if you saw that had an effect, have they all been replaced (remedying leaks through hose cracks)?
put vacuum gauge on and checked out perfect vacuum 21in no fluctuation, also checked for exhaust clog....no clog. ruling out fuel pressure because at 2500 rpm it takes off as it should with plenty of power........im breaking down and bringing it to toyota service tomorrow......lol....
 
Joined
Jan 20, 2015
Messages
107
UPDATE:
took cruiser to toyota service
3 days later they could not find anything (i really dont think they looked)
gave back cruiser no charge
upon getting cruiser back i removed iac valve adjusted valve closed reinstalled it
truck idled perfect 650........turned off engine....restarted.....idle now up to 750.....shut off restarted....850....again idle now at 950.....that is where it stays....
bad iac?
also when i tap on the top of the air flow sensor box lightly with screw driver vehicle almost stalls then idles up to 1500 and slowly returns to 950...is this normal?

also hooked up vacuum gauge.......runs 20.5 inches of vacuum no leaks......

anyone have any ideas?
 
Joined
Aug 26, 2007
Messages
165
Location
Baton Rouge, LA
Air flow sensor is a possibility. I had luck cleaning mine with alcohol after taking the plastic top off. Cut the silicone bead and pry it up. DO NOT TOUCH THE SCREWS. The air flow sensor would throw a check engine light. Also check you grounds. Every ground.
 
Joined
Jan 20, 2015
Messages
107
Air flow sensor is a possibility. I had luck cleaning mine with alcohol after taking the plastic top off. Cut the silicone bead and pry it up. DO NOT TOUCH THE SCREWS. The air flow sensor would throw a check engine light. Also check you grounds. Every ground.
No cel.......no code flash......
 
Joined
Dec 5, 2010
Messages
626
Location
Northeast PA
Maybe I missed it, but did you check your intake tube? They often crack at the flex sections, and will cause intermittent issues (since it's sealed in one position, and open in another position).
 
Joined
Jan 20, 2015
Messages
107
Maybe I missed it, but did you check your intake tube? They often crack at the flex sections, and will cause intermittent issues (since it's sealed in one position, and open in another position).
Yes I should pull them off and check them..but I replaced them about 6 months ago. They were used but in good shape. But I will check. Thanks
 
Joined
Jan 20, 2015
Messages
107
Air flow sensor is a possibility. I had luck cleaning mine with alcohol after taking the plastic top off. Cut the silicone bead and pry it up. DO NOT TOUCH THE SCREWS. The air flow sensor would throw a check engine light. Also check you grounds. Every ground.
What grounds? The ones on the air flow sensor plug?
 
Joined
Jan 20, 2015
Messages
107
UPDATE:
Problem found and repaired
IAC valve has rubber 0 ring gasket
Gasket was hard and brittle not sealing causing a intermittent vacuum leak.
Whew!
My 3fe runs like new.
Such a great feeling. Thank you all for your very appreciated posts.
 

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