Extremely loud boom and jerk when shifting into drive or reverse!

[ArashB]

Extremely loud boom and jerk when shifting into drive or reverse!

Greeting, I recently cleaned the throttle body on my Previa (~240km/150miles) but after reinstalling it, shifting has been a nightmare at stand still... but the van still performs really great otherwise. This condition gets worse when the engine is warm\hot.
Also after going through drive and reverse a number of time, what sounds like a detention, reduces greatly.



I even installed a different throttle body but still have the same problem.

After much researching Ive come to a few conclusions.

1. Vacuum leak at the throttle body (I used the old gasket and added a bit of sealer the second time around) or the large intake hose may not be clamped hard enough.
(To test this I will be buying a propane extension hose [and fire extinguisher] and see it seeps in to change idle sound)

2. One of the sensors locking clip broke (light coloured) and it may not be pushing in all the way or I may have damaged the wires connecting one of the adapter. (can i disconnect any to see if the connects are in tact?)

3. I may have pulled the "kick down" throttle cable too hard initially when I was amateurishly trying to get the throttle body off its screw bolts. It is currently adjusted with the 1mm spacing.

4. I currently have the battery disconnected (over a few hours) incase the old idle rpm settings in the ecu need to be reset.

My father should be coming to town soon so that I could connect a scanner and get some readings to help hopefully.
Thanks for reading.

p.s. I read this on the Zen Adventures site... maybe it could help diagnose my problem.
http://i.imgur.com/VbnNLHW.jpg

[tbkilb01]

I had a extremely loud boom and jerk once, when I shifted into gear, If I remember correctly, it was 1st and reverse! It happened early on, before 150k I needed new SADS coupling. No boom no jerk since, sounded like a Loud clap! Does engine idle as before? Happened as go into 2nd or 3rd?...luck

[eggvan]

I had a problem with a very harsh shift between drive and reverse on my '95 S/C. The culprit turned out to be a sticking throttle valve cable. Since you mentioned pulling on the TV cable, your problem could be related. When the TV cable is stuck open, it increases the hydraulic pressure inside the transmission, which can cause harsh shifting at low speeds. The S/C Previas have a different throttle body position and therefore a different cable layout, but the basic idea is the same.

[ArashB]

Yes thanks you, I had found out that the main culprit was a sticky cable but also later that it had a broken supporting sheath... cleaning it up and re-positioning it better, the problem was 90% solved but I still have the same trans pressure symptoms.

Im thinking of refurbishing the original throttle body with its cleaned idle air control valve to see if that is contributing to it.



@1 minute in the shifting gets worse

I had a extremely loud boom and jerk once, when I shifted into gear, If I remember correctly, it was 1st and reverse! It happened early on, before 150k I needed new SADS coupling. No boom no jerk since, sounded like a Loud clap! Does engine idle as before? Happened as go into 2nd or 3rd?...luck

Thanks, I had damaged the idle air control valve (because I had to drill the screws out) on the original throttle, so I put in another throttle and the idle feels much lower. No problems for 2nd or 3rd.
I will be shifting the car on ramps and checking the shaft to cover all my bases.