Low RPMs idle speed?

JLEEW1207

MEMBER
2004 TOYOTA TACOMA
3.4L
6 CYL
2WD
AUTOMATIC
240,000 MILES

My truck randomly stopped working not too long ago. I changed the mass air flow sensor and fuel pump and it seemed to do the trick but when I would start the truck the rpm would drop so low it almost died and then it goes back up. It idles fine in park but when I put it in reverse it would do the same thing and try to die but the rpm wouldn't go back up. It would sit at about 200 RPMs. When I'm in drive and not moving it would also idle at about 200-300 RPMs. I just changed my fuel filter, and it stopped it from almost shutting off when started and when I put it in reverse. But it still idles low when in reverse. Is it supposed to idle low in reverse and if not, what could be causing it? I really appreciate the help.

Sunday, January 29th, 2023 AT 1:29 PM

3 Replies

KEN L

MASTER CERTIFIED MECHANIC
51,598 POSTS

This can be caused by one of two things, either you have a vacuum, leak or the throttle bore needs to be serviced. Here are videos on how to service the throttle bore and ISC motor:

https://youtu.be/JZoEb_hyWC8

To see if you have any vacuum leak use this guide when the engine is cold only:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Please go over this guide and report back.

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Sunday, January 29th, 2023 AT 6:51 PM

JLEEW1207

MEMBER
2 POSTS

I cleaned the throttle body. It was really dirty; I think that it could have definitely been the problem. But I think I made a mistake along the way. When I turn it on it idles up above 2,000 RPMs and then shuts off. I put a code reader on it and it's throwing code P0122. I tried looking up how to fix it and it said to buy a new position sensor but is there a chance I put it on wrong or? Again, I really appreciate your help.

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Monday, January 30th, 2023 AT 1:29 PM

KEN L

MASTER CERTIFIED MECHANIC
51,598 POSTS

You did a good job cleaning it. I would double check the electrical connectors to see if a pin is rolled over/pulled out if not it sounds like the throttle bore went bad. With that many miles a new throttle bore is not out of scope for the repair. Let me know what you find and thanks for the images.

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