Results 1 to 7 of 7

Thread: Recommended strategy on a bad valve

  1. #1
    Forum Newbie
    My Van(s):
    1993 Previa Alltrac LE
    Join Date
    Dec 2017
    Location
    San Antonio
    Posts
    3
    Rep Power
    0

    Recommended strategy on a bad valve

    I have a 93 Previa Alltrac LE and I love it. It has been dealer maintained until about 3 years ago when I decided the dealer route wasn't really buying me anything more than a good mechanic with a solid knowledge of Toyotas could.

    About two weeks ago, it started running a rough, most notably at idle and the mechanic I took it to, who had had it about a year ago for a repair, seemed to think it was a bad valve. He gave it the once over, tuned it, cleaned the injectors replaced the distributor cap and the wires but really didn't fix the issue. Again, he felt the problem was a bad valve. I hadn't even opened the engine access under the passenger seat, or done anything more than a brake job on this Previa, even though I'd say I am mechanically inclined and even worked as a mechanic for a couple of years in the mid-1970's but things are WAY different now and although I could easily service my 79 Hilux, I never even thought about any engine work on the Previa.

    Local estimates here in San Antonio are $3k-$6k for a motor replacement and my dilemma is that I love this vehicle and don't want to give it up but don't want to drop $6k to get it fixed. 285k miles. New tires. Completely new A/C system about 3 years ago. Replaced the rack and pinion 4 years ago. So, the vehicle is in good shape, until this valve problem. Pretty sure that it is a bad valve. There is a distinctive "chirp" on acceleration. I can pull the #2 spark wire with absolutely no effect on idle (still very rough). The "flap" test on exhaust has the paper being pulled back and forth and the engine idles. Diagnosis: Bad valve on #2.

    So, here is the question: I don't have a lift rack (wish I did). I have basic tools, socket wrenches, torque wrench, other basic stuff, so am I nuts to try to drop the engine out and either have the head rebuilt, buy a head or just find a good used engine, if that is possible, and go that route? I read multiple posts here about head gasket replacement and it looks fairly gnarly for a casual mechanic. I have a two week break coming up and I think I can drop the engine in a couple of days, if it doesn't take special tools or skill. I can methodically disassemble almost anything, my concern is getting the head re-installed correctly and not missing something essential when I reassemble.

    I hate to give up my Previa but I don't want to get 1/2 through this process and find that I am stuck. Sorry for the lengthy post. I just need a go or no go here. You don't know my skill level (not sure I do) but I am will to give it a go if you feel someone with intelligence, some experience and perhaps $2k to invest could do the job in his own garage. I have jack stands and a floor jack (how high should they go?) and time...

    Go, or no go?

  2. #2
    Van Enthusiast
    My Van(s):
    1989 4x4 manual dlx 1987 4x4 manual cargo 1987 2wd 5 speed 1986 2wd auto LE 1985 2wd 5 Speed LE
    Join Date
    Feb 2017
    Location
    abq, nm
    Posts
    106
    Rep Power
    1

    Re: Recommended strategy on a bad valve

    Go!

  3. #3
    Van Fan
    My Van(s):
    1991 Toyota Previa 5spd
    Join Date
    Dec 2015
    Location
    Michigan
    Posts
    85
    Rep Power
    1

    Re: Recommended strategy on a bad valve

    I replaced the engine myself early this year. It was the first time I ever attempted changing an engine. It took me 3 months to replaced the bad engine with a jdm replacement. I only worked weekends however. It was a big challenge, no exaggeration. Why not just purchase a JDM engine, instead of trying to fix your tired, high miles engine? Mine turned out fine, and is running great. Whole thing was $795 delivered.

    https://forum.miata.net/vb/showthread.php?t=630410

  4. #4
    Forum Newbie
    My Van(s):
    1993 Previa Alltrac LE
    Join Date
    Dec 2017
    Location
    San Antonio
    Posts
    3
    Rep Power
    0

    Re: Recommended strategy on a bad valve

    Quote Originally Posted by Kurtanius21 View Post
    Whole thing was $795 delivered.
    So, some questions about this. I have flip-flopped on the "whole engine" idea a couple of times. I don't mind doing it, it probably isn't a whole lot more work than dropping the engine and pulling heads, etc... but my concern has been the quality. You don't know what might be lurking in a "used" engine...I'll do some more research.

    So, a couple of questions: How much stuff did you have to transfer from old engine to new? Was the engine an exact match? How high do you need to lift the vehicle to clear the engine? What tools did you end up buying/borrowing? Were there any tools beyond the "standard" set of rachets, sockets, screw drivers, etc that you needed (a "specialty" tool)

    I am willing to give this a go, I just don't want to come to a dead halt because I didn't have something that I needed to complete the job. The plan is to do this in my garage (residential) so just trying to prep for the project.....

  5. #5
    Van Addict cvtroger's Avatar
    My Van(s):
    95 Previa LE S/C
    Join Date
    Jun 2014
    Location
    SF, Cali
    Posts
    349
    Rep Power
    1

    Re: Recommended strategy on a bad valve

    Quote Originally Posted by Kurtanius21 View Post
    I replaced the engine myself early this year. It was the first time I ever attempted changing an engine. It took me 3 months to replaced the bad engine with a jdm replacement. I only worked weekends however. It was a big challenge, no exaggeration. Why not just purchase a JDM engine, instead of trying to fix your tired, high miles engine? Mine turned out fine, and is running great. Whole thing was $795 delivered.

    https://forum.miata.net/vb/showthread.php?t=630410

    NICE!

  6. #6
    Van Addict cvtroger's Avatar
    My Van(s):
    95 Previa LE S/C
    Join Date
    Jun 2014
    Location
    SF, Cali
    Posts
    349
    Rep Power
    1

    Re: Recommended strategy on a bad valve

    For the money's worth, I'd just get an engine replacement.

    I'll have to find my thread, but I rebuilt my engine from the ground up. Everything in the Engine is new. I spent a few thousand, but the motor and transmission run great and I have not issues. But I probably went the most expensive route.. and my outlook was that I am keeping the Previa forever, so I didn't shortcut or cheap out... Everything is Toyota OEM.. which was forced onto me because many of the guys on these forums are OEM purists.

  7. #7
    Forum Newbie
    My Van(s):
    1993 Previa Alltrac LE
    Join Date
    Dec 2017
    Location
    San Antonio
    Posts
    3
    Rep Power
    0

    Re: Recommended strategy on a bad valve

    So, I got the 1993 Previa manual on Ebay and that, plus the other videos I have seen, have helped me to feel a little more secure about the whole process. I have about 6 full days available to me and I hope that, plus a couple of weekends will allow me to get it all done. I still have unanswered questions that I could use some help with. I plan to start this whole shindig in a few days....

    My biggest concern isn't with disconnecting everything and even finding a replacement engine, it is getting the engine out, once everything is disconnected. From what I have seen, it looks like you need to raise the engine a bit in order to get the engine mounts off but what I can't quite tell is if it is a straight shot down from there. I have seen a couple of pictures that show the engine/tranny at an angle (front to back) and resting on a floor jack. I also saw one that had a hydraulic lift in the vehicle and then lowered it with straps. I looked through the lift options at Harbor Freight for ideas and it looks like a motorcycle lift might work or a transmission lift but I'd have to see where I could rent one. But, getting it down and then getting it back up is my biggest worry. How is this accomplished? And, is it a straight drop down once everything is disconnected and the motor mounts are removed?

    But going back to my other questions that went unanswered:

    How much stuff did you have to transfer from old engine to the replacement? Was the engine an exact match? How high do you need to lift the vehicle to clear the engine? What tools did you end up buying/borrowing? Were there any tools beyond the "standard" set of ratchets, sockets, screw drivers, etc that you needed (any "specialty" tools that were absolutely required)

    I'd love to get some answers on those questions.....

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •