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We are having an issue with a 1988 22RE idle taking about 6 seconds to return to base idle. We have isolated it down to a dashpot issue by removing the small vacuum restrictor/filter? that is attached to the underside of the dash pot. Once removed from the vacuum line the slow idle return is gone and all seems well. Do these little things go bad? The FSM makes no mention of it or even gives it a proper identification, though it is shown in some TB section drawings. Can someone ID this and explain its function? I'm sure it is supposed to be there. Thanks!
Last edited by westfalia; Apr 17, 2022 at 12:54 AM.
Try removing the black rubber filter section on the bottom and reinstall just the upper section. It slides off. If it still works, then the filter inside is clogged preventing air flow. Mine was clogged and I cleaned it with Dawn liquid soap and water.
Thank you for that link. It was very helpful, but sadly they do not mention what to do if the VTV fails the test. Replace? Clean? Are those even available? BTW, what does VTV stand for? Vacuum Time Valve?? We did take out the fuzzy filter in the black holder and it was not significantly clogged. I'll do both tests and see what happens. Thanks again for the link.
EDIT: Never mind, I found out what it is called. It is called a Vacuum Transmitting Valve (VTV).
Last edited by westfalia; Apr 18, 2022 at 05:09 PM.
Still available but it is not cheap at my favorite parts dealer. Toyota Parts Deal!
The foam part is not available there.
Toyota 90925-01014
Valve, Vacuum Transmitting1979-1992 Toyota 9092501014
Thanks! The filter on the valve is clean, but still not sure if the valve is functioning correctly. Seems to be, but the diag. instructions are vague. I have no way to correctly measure the actual volume of air through the valve in either direction.
No. since it's not designed to retain vacuum in either direction measuring would be difficult.
I put a new return spring on the throttle body, that helped. You might also check the throttle plate shaft and see if there's excessive play in the shaft at the bushings. Maybe it's binding there.
No. since it's not designed to retain vacuum in either direction measuring would be difficult.
I put a new return spring on the throttle body, that helped. You might also check the throttle plate shaft and see if there's excessive play in the shaft at the bushings. Maybe it's binding there.
Good idea. With that said, the TB functions perfectly when the TVT is removed. Idle returns back to correct level in a about a second per spec. I’ll keep my eye open for one in a junk yard and swap to see if that changes. I guess I could just put the black filter on the line and delete the TVT.
. With that said, the TB functions perfectly when the TVT is removed. Idle returns back to correct level in a about a second per spec.
The dashpot and the attached VTV are solely part of the emission system. During deceleration the combustion can get unstable do a combination of factors. The dash pot and VTV slow it down a bit to prevent a spike in HC and CO.
Apr 17, 2022 | 12:52 AM
