mcgrad96

I know a lot has been posted about this but right now I have not found my particular symptoms so here goes. Occasional "bucking" under most any conditions while driving... but just one buck as opposed to multiple. It will just hesitate for one quick hit and, when it does, both the speedo and the tach will bottom out simultaneously with the single hit (lights or radio does not go out... just those two gauges). This will happen once or twice a day OR only once a week, depending on its mood. Even less occasional is that the car will stall out. this will happen under the same random conditions as the bucking (acceleration, coasting, slowing down) but both NEVER happen at a stand still... only while in motion. When it stalls, it will turn over but WILL NOT start again unless I pull the key completely out of the ignition and reinsert it. When I do this "reset" it will ALWAYS start back up, EVERY TIME and be "fixed" until it happens again. I am convinced these two things are the same problem but I have not figured it out. Also, there has been occasional rough idling after warm up which seems more like bad fuel to air mix as opposed to missing spark only because when I rev it even slightly it feels smooth and seems to have all it's power, then when you take back down to an idle, it's rough. sometimes turning the A/C on and back off fixes the rough idle... this is also random. thanks in advance for the help. Jim

dicer

For your Volkswaggon problem posted above


https://www.clublexus.com/forums/ls400/656360-all-my-crazy-lexus-issues-solved-ecu-leaking-capacitor.html[/url]

RugbyDad

Lol, took a page right out of pures handbook eh?

I'd have to agree though. Randomness seems to always point to ecu caps. Although I ain't as well versed in diagnosing finicky problems as some of the other members are.

RA40

iTrader: (6)

Welcome to Club Lexus.

Those symptoms are within the listed for the ECU caps. As well, there can be other maintenance required that also contribute to a poorly running engine.

When asking for assistance, please list year and miles on car as well.

mcgrad96

Sorry, my car is a 97 LS400 with 140k on it. Unfortunately, (or fortunately, depending on how you look at it) I have replaced all the capacitors on the ECU already. I have also rerouted/added the vacuum lines pertaining to the power steering valve and the extra vacuum nipple on my intake manifold (see other threads). Additionally I have cleaned the throttle body and MAF sensor. I have no check engine codes currently BUT the transmission temperature sensor code has tripped twice... once was at the same time the car "bucked" on me (coincidence?).

The gauges cutting out with the hesitation lead me to wonder if it's in the ignition switch... I know the metal parts under the dash seem pretty rusty and I have several electrical components that are not working (steering wheel adjustment out... motors good and switch good; seat memory buttons out; hot/cold blending and recirculating doors not moving even though the doors that direct of flow air are working between defrost, floor, dash, etc.) All that to say, could some moisture in the car from past exposure be causing some bad electrical connections? I did spray electrical cleaner in the key hole of the ignition and, although the bucking still happened occasionally I went over 500 miles before it stalled again where previously it stalled twice in 90 miles of driving.

AHJ

This may be a long shot but get your alternator/generator checked. There is gadget that can be hooked up to the battery and will analyse your car's charging system.

My car was diagnosed with a bad diode and fixing it seems to have cured a few other ills - idle is rock steady now and misfire CEL codes have not reoccurred for over two weeks.

Yamae

These statements are the key to solve the problem. The reinsertion of the key means that the ECU needs the start-up reset.

I suspect an unstable 5V DC supply to the processors. I would observe it while driving using an equipment which can detect any glitch.