Dah808kine

I know this is my first post but I can't seem to figure this out and would greatly appreciate the help... so here is the symptoms

I have a 92 sc400... it has its temperamental problems as all sc400s do I'm guessing lol. I just bought the car about a month ago and have noticed that when I get the around 45-50 maybe even 55 mph and cruise on that speed the trans will skip 4th and go into o/d and basicly I'm guessing bogg and cause the engine to shake... reason I suspect the trans is because anything after 55ish mph the the car runs fine... no shakes what so ever cruising at 60 no problem. If I were to accelerate past 45-55 in 4th it will shift properly but enough pressure has to be applyed the to peddle. Also I noticed if I'm going up a hill it won't kick back down out of o/d onto 4th it will just bogg again Enless the peddle is firmly pressed kicking it down a gear. But isn't the trans spose to know when it needs to drop down a gear? Also, say I'm going up a hill and it starts to bogg again if I let off the peddle and then apply the pressure again it will kick it down to a lower gear wich stops the bogging/shaking. Could it be a torque converter problem because I think thats going bad. When I come to a stop the wants to jerk/shake. But if the ac is on and the engine is at a higher idle it will no longer jerk or shake. Wich leads me to believe mayb the idle is off... causing all symptoms... but I'm not a trans guy and with it having a electonicly controlled trans makes it even more difficult for me... (shoulda bot a sc300 w/ standard trans woulda been easier... lol) the electronic trans thing makes me feel like there's alot to go wronge with it... because electronics fail to easily... but anyways any help would be appreciated ty

P.s if anyone could point me in the derection of a thread involving how to check the ecu capacitor leakage problem would be greatly appreciated to... p.p.s srry if this is a repeat of another thread.. if so plz point me in that direction as well thank you!

Biddles

iTrader: (2)

The ECU is located under the passenger's carpet. Pull it back you'll see a big black plastic box, that is the ECU's housing. Just 3 10mm bolts hold it in if I remember correctly. After that pop the ECU out, it may be a pain to crack open you might want to run a razor down the crack a few times as it is sealed, then it should pop apart with a little effort.

Looking at capacitors won't really tell you for sure if it's bad, as mine had no signs of damage, but sending it in for repair fixed my issues. So just because you don't see any burn marks or leak spots doesn't mean that it's a good unit. Tanin Electronix has the best price, a great reputation, and insanely fast turn around time. I sent my unit in on a Monday, and had it repaired back at my house on Thursday...

Duck05

Biddles gives great advice. Even if this does not totally resolve your issue, having the ECU checked out and rebuilt is good peace of mind for our cars.

I have had a rebuilt installed and sent the original out to be rebuilt as a spare.

Good luck on getting your issue worked out. Welcome to CL.... Post pictures of your car....

Dah808kine

Thanks for the advice guys I'll be sure to do that hopfully that's the issue... since I'm having dash light problems as well the check engine light and trac off light comes on and off on it own, when I put it in diagnostic mode there is no code... so thinking it might just be an ecu problem... might I ask where u got the spare rebuilt ecu Duck? Or would u know where I can purchase a rebuilt one?

sc4hunnit

sometimes buying used ecus can be tricky. You never know what you're really getting into. I was fortunate to find a forum member to sell me working ecu for my car. Just, if you can, try and test the ecu in your car before you buy it!

Tabaka

iTrader: (8)

Where vendors are you guys choosing for ECU repairs?

Dah808kine

Ok so I believe I've gotten to the root of the problem... I THINK it may be a problem with a shift solenoid. From my understanding solenoids can go bad over time... I think that might be a costly repair but that only bcuz I'd have to take the trans in to be taken apart correct? Or are the solenoids under the oil pan? And accessible? Cuz if that's the case and can do that myself under the car.. but it's a whole other situation if I gotta pull the trans....

Dah808kine

Never mind I've found a DIY for the solenoid replacement and it's fairly easy. If anyone wants to do this as well I'll leave a link for your viewing needs. It has pictures and detailed description. I'll also lyk if this has solved my problem.. also this would be a good thing to replace for any high miles AT on its next service.
http://https://www.clublexus.com/for...placement.html