92 LS400 acting up again? Could it be capacitors for a second time around?

[threepwood]

A while back this car was doing very strange things and a moderator here suggested I replace the capacitors in the ECM.  I did, and all my issues went away. Recently, ONLY after reaching operating temperature, the car jerks forward when you are cruising at 30mph and step on the gas then stumbles terribly trying to accelerate.  Could it be the capacitors again?  I replaced them with a kit I bought on ebay.  I guess my real question is what controls the transmission on this car, the ECM or some other board that might also have bad capacitors?  Thanks for any help.

[sha4000]

On 12/7/2020 at 5:25 PM, threepwood said:

A while back this car was doing very strange things and a moderator here suggested I replace the capacitors in the ECM.  I did, and all my issues went away. Recently, ONLY after reaching operating temperature, the car jerks forward when you are cruising at 30mph and step on the gas then stumbles terribly trying to accelerate.  Could it be the capacitors again?  I replaced them with a kit I bought on ebay.  I guess my real question is what controls the transmission on this car, the ECM or some other board that might also have bad capacitors?  Thanks for any help.

I believe the ECU controls the transmission as well. Did you use the exact replacement capacitors mentioned in the big thread on CL? Have you tried a couple of drain & fills of the transmission pan?

[threepwood]

Thanks for your response.  I did replace the capacitors with the exact capacitance rating but a higher voltage rating.  I opened up the ECU two days ago and found the 220microfarad capacitor bulged at the top, a sure sign of a serious problem.  It was a 50v cap so I do not understand why it failed so soon.  I proceeded to replace all 4 caps in that cluster on the circuit board with known good caps.  At this writing the jerking is completely gone but there is still a little stumble, however not nearly what I was experiencing before.    So I guess I need to replace them all just in case.  Thanks again.

[plexus914]

The 92 model needs 10 or 11 caps. Where the first "Ebay caps" from a no-name brand?

Here is something from the ECU/Capacitor mega-thread:

 

 

 

...make sure you use 105C rated low ESR caps from the 4 reputable Japanese capacitor companies Rubycon, Nippon Chemi-con, Panasonic & Nichicon



it is CRITICAL that the replacement caps be low ESR type and from one of the brands listed above - don't cheap out on your vital ECU!

 

1990-92 LS400 needs 10 or 11 caps as follows:

Qty. 3 of 10μF - 50v
Qty. 2 of 15μF - 35v
Qty. 3 of 47μF - 63v
Qty. 2 of 100μF - 10v
Qty. 1 of 220μF - 16v

 

 

[RacWolfy]

I would take a look at the throttle position switch first. Try to to check the easy stuff before you jump the gun ,I had my ECM redone by the guy on EBay in Van nuts it still works fine .