usoff89

iTrader: (2)

Yes, the caps can be bad and not show any sign.

SC93

thx for reply..

uhh..look in my garage...1965 mustang. guess i am a wussy

great car..original owner.

drone6

Going to Hijack my thread back.

Just kidding - we are all having similar issues, so appreciate the input from everyone.

So, I received the MAF/AFM assembly today. Instead of replacing the whole assembly, I just took the sensor off and put into my engine. Well, things improved greatly, engine still seems to sputter, rpms jump at idle from 600 to 1000 and then back. But, I can actually drive as long as I don't stomp on the pedal. If I do, the rpms go up but the car doesn't move like it should. If I'm gentle on the throttle, especially if I start in L, 2 and the D - then everything is fine. If start in D, it sounds like my transmission/exhaust is about to die every time the car shifts, but it keeps going.

I went ahead and replaced the whole assembly, as that was the only factor unchanged at this point. Still works as I describe above.

One thing is clear, my OEM MAF was bad, and so is the one I bought (not OEM) from ebay - so that is going back to the ebay seller.

The used assembly and sensor are staying in the car as things have improved.

But, now what? I have no lights on the dash, but the engine sputters.

Any suggestions?

SC93

time out...

i put my board under a super bright light and looked at the base of each cap with a jewelers
eye glass. on two caps at the base was a very tiny deposit (orange in color) about the size of
fine ball point tip. took a tooth pick and prodded the deposits and they were not liquid in nature
but very hard. can the leakage from a cap form a solid hard residue, both caps looked
perfect in shape and color.

SC93

[QUOTE=drone6;8095663]Going to Hijack my thread back.

Just kidding - we are all having similar issues, so appreciate the input from everyone.
================================
drone... it does appear that i have kind of taken over a bit and i apologize and as u mentioned
our probs seem to be similar.

i all your posts here on this thread, i don't see any reference to the possibility of a faulty ecu
module. have u discounted this as a potential problem area.? if you haven't read my original
thread "faulty ingntion coil questions" it covers a lot of the issues u r bringing up. i thought i
had finally solved the poor performance problem by replacing all the old plugs (90kmiles service
w/o a change) but the improved performance lasted about a week and the erratic performance
recurred .

as u can tell i am hot on rebuilding my ecu with new caps and hope this solves it all but i still
have the maf in my mind as being the culprit. so my new caps will be here next week and
should have them installed ( by an experienced electronics tech) shortly thereafter and then
i can report back and maybe if it solves all, u can also consider this route.

===================================

cowboy..still trying to get a clear close up of my board but i guess the quality of my digital camera
not up to snuff. the flash seems to reflect off the shinny board and "whites" out the pic.
it has been raining continuously here for past few days and when it lets up i will carefully
lay the unit on a dry surface in the daylight and try a close up this way.

side note...cowboy i c u use a kind of shorthand approach in your posts (no caps) and that is
the way i usually send emails and such. i also do a lot of abbreviation and my question here
is am i going overboard and breaking forum rules by being so grammatically incorrect??

cabin shot of ecu location and pic of plastic cover plate below:

SC93

Caps Inventory of 1993 Lexus sc400 ECU Module (10 total):

3 10mf 50v ....... ordered 3 10mf 50v

2 15mf 35v ....... ordered 3 15mf 63v

1 47mf 63v ........ ordered 3 47mf 100v

2 100mf 10v....... ordered 3 100mf 35v

1 220mf 16 ....... ordered 2 220mf 50v

1 fat one located under housing case i coluld not read and did not want to take
back cover off. will report it's values later after tech repairs.

cowboy...some i ordered have higher voltages and you said this was ok, or actually
better. am i ok from what you can see from above??

anybody have an idea which ecu cap might be responsible for speedometer function.
my speedo is totally whacko and i found orange deposits under a 10mf and 100mf cap,
both 10v. any relation there to speedo control???

LScowboyLS

the back board is not removable, and that fat 47uf under the housing is a bear even for me to change, so just skip it, you will still be changing 90% of them - I change it when I do one, but I don't enjoy it! - ugh!

the LS owners are lucky, they don't have that buried cap!

higher voltages are fine as long as you ordered the exact caps from my links section - other caps or even those caps from a different source is an iffy proposition, due to quality and counterfeit concerns, as well as ESR and ripple current rejection.

LScowboyLS

MAF issues where the car improves greatly with it unplugged tend to generally be either an air leak after the MAF, which defeats its air volume measurement, or else ECU capacitors.

drone6

Visually I don't see any parts with a leak leading to the intake. Any other way to check for a leak?

I'm going to try and pull the ECU today and take a look. Also going to check out the local junkyards and see if I can get an ECU for cheap.

LScowboyLS

a junkyard ECU will also need its capacitors replaced, so that is only a good plan if your capacitors have leaked so badly that the main lower board has become irreparably damaged from the corrosive effects of the leaked electrolyte.

make sure to disconnect the negative battery cable before disconnecting or reconnecting the ECU, and always wear all cotton clothes and bare feet any time the ECU is open or out of the car. (for static protection)

take very high resolution pics of the caps inside and Yamae or I can examine them and spot any leakage, as we have seen it so many times before.


a smoke machine is ideal, but most people don't own one, sometimes you can hear an air leak or vacuum leak, you just have to play detective, some people spray carb cleaner at joints and were tubes connect and listen for changes in engine rpm, some people use the smoke coming off of a burning cigarette

drone6

There are a few guys on ebay that offer a ECU rebuild service for about $100-150. Has anyone worked with one of these guys with good results?

SC93

[QUOTE=LScowboyLS;8096070]the back board is not removable, and that fat 47uf under the housing is a bear even for me to change, so just skip it, you will still be changing 90% of them - I change it when I do one, but I don't enjoy it! - ugh!

the LS owners are lucky, they don't have that buried cap!

=================================================

assuming i tell the electronics tech to forget the 47uf cap under the casing, what would u estimate
to be a reasonable period of time to do the job, i.e., how long would it take you?? he worked as a
tv repairman for quite a few years. also, i don't want to insult the guy but do u think it would be a
good idea to give him a copy of your procedure solder type, cleaning, etc., or would u just let it
ride??

usoff89

iTrader: (2)

Cowboy has mentioned it alot. Anybody selling a rebuilt ecu has most likely hacked it up, or it wasnt done right. Also they have not used the COREECT caps for the ecu. Not a good idea!

LScowboyLS

I could do a good job on it in 3 hours, much faster than that and some corners are being cut!

the physical soldering doesn't take that long, it is the safe removal of the corrosive electrolyte, the desoldering, the component hole making, the inspection under magnification when you are done, etc.

maybe carefully take some of the flux I recommended and do a some cleaning on any leakage with some q-tips before the solderer ever gets it

and make SURE to check his work against your diagram for correct placement and size of each cap, correct polarity, and nice joints on both sides of the board - tell him you want the new caps 1/4 inch up off of the board (then you can see if he used enough flux, by inspecting the joints)

SC93

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

.. happy camper at this moment.

got ecu caps yest (per coyboy rec... digi -key) and took unit to service tech.

don't want to shaggy dog but here is the followup :

1) he had no probs with 9 cap install but as cb mentioned, 47uf under housing super b**ch.

2) cb..the guy is a perfectionist ...i said if u can't get to it, forget. he took extra time and said he
had to melt some solder covering hidden screws?? and went ahead and replaced the "hidden
cap" he said it was bigger than the original so he bent it slightly so it would seat in.

3) final job looked great...board was clean and solder joints very professional. total tab was
$50.... i was embarrassed too low... doubled his charge.

3) i had asked him to measure uf of all the old caps but he just commented that two were totlaly trashed.

4) installed refurbed unit, reconnected neg cable, plugged suspected "bad" maf in and started
car and it responded immediately.

5) no error codes. took to road and speedometer registered normally for first time in many
months. car responded at all speeds. smooth shifts low to highway speeds. no stalls and
tachometer looked correct from start to run temp.

currently happy s a pig in mud but...been bit before assuming problem is solved only to find
it rears it's head at a later time.

fingers crossed on this one... if the same probs reccur , i will probably be too embarrassed
to report back.

Thx cb for your help and professionalism re the ecu dilemma that a lot of members have but
do not address. bottom line as u say...10-12 yrs, chances are it is going or gone. my case
was 20 yrs in hot FL....way overdue .