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Old 07-26-13, 10:32 AM   #16
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I'm going to pull the ECU this weekend and look for leaky capacitors.
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Old 07-26-13, 10:44 AM   #17
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Sounds exactly like my tps issue, had a brand new tps that was no good from toyota. took a year to figure it out until i hooked up a datalogger and seen no tps signal.

i used to be able to drive however long i wanted.... even 8 hours and it would not have issue. As soon as i started and restarted vehicle i got the light throttle jerking you speak of..... while trying to cruise it would buck back and forth but soon as i mashed the pedal it went away.

bet its tps....
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Old 07-26-13, 11:59 AM   #18
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Quote:
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Sounds exactly like my tps issue, had a brand new tps that was no good from toyota. took a year to figure it out until i hooked up a datalogger and seen no tps signal.

i used to be able to drive however long i wanted.... even 8 hours and it would not have issue. As soon as i started and restarted vehicle i got the light throttle jerking you speak of..... while trying to cruise it would buck back and forth but soon as i mashed the pedal it went away.

bet its tps....
Where did you take it that had the OBD-I datalogger? I would like to look into doing that.
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Old 07-26-13, 12:29 PM   #19
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does your check engine light work properly, do you see it come on for a second and go away when you key on.
when you jumper the ports to read it, it should blink slowly even if there are no codes, if not then thats not a good sign.
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Old 07-26-13, 12:43 PM   #20
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does your check engine light work properly, do you see it come on for a second and go away when you key on.
when you jumper the ports to read it, it should blink slowly even if there are no codes, if not then thats not a good sign.
Yes, it comes on with key-on engine-off and when I jumper E1 and Te1 it flashes repeatedly showing no codes. I even induced a code (unplugged MAF) to make sure the CEL was working correctly and it threw the corresponding codes related to the MAF being unplugged.
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Old 07-27-13, 12:17 PM   #21
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Quote:
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Where did you take it that had the OBD-I datalogger? I would like to look into doing that.
At the time a friend who worked at a local tire shop had the solus scanner that the whole chain passed around. Another friend picked up a snap-on scanner and it has the obd1 toyota adapter.

by what your saying, sounds identical to the issue i had. The super light throttle makes your car buck but if you get in it it "seems" fine? bet if you got a new tps on there youd noticed a world o difference.
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Old 07-28-13, 12:22 AM   #22
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Quote:
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At the time a friend who worked at a local tire shop had the solus scanner that the whole chain passed around. Another friend picked up a snap-on scanner and it has the obd1 toyota adapter.

by what your saying, sounds identical to the issue i had. The super light throttle makes your car buck but if you get in it it "seems" fine? bet if you got a new tps on there youd noticed a world o difference.
The TPS tested in spec and adjusting it even 1/8 of an inch makes a very noticeable difference in idle and shifting RPM. I believe it it in working order. I'm at a loss for words on this one.
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Old 09-04-13, 12:30 AM   #23
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Cleaning the IACV once more seemed to solve the issue
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Old 09-08-13, 06:40 AM   #24
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hi guys i am having the same problems with my 93 sc400 has about the same mileage 117k and i did everything swint did my self. only thing i got mine with the idle problem its just getting worse every day i disconnect my MAF SENSOR and it runs much better i have a check engine light and a traction light when i disconnect it. I take it to the Lexus dealer and they are telling me to start with replacing my transmission like am stupid or i have money like that they r just throwing parts at cars. O I have too throttle plate in mine one is open all the time and the other is close until i rev it out is that normal? i love this car would love to fix the problems.
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Old 09-08-13, 08:09 AM   #25
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I am still leaning towards three things: bad coils, IACV, and or ignitors...

Here is a great DIY for really cleaning the IACV. I would do this first. While you are at it, replace the bearings, and then put back together.

http://www.clublexus.com/forums/perf...acv-sc400.html
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Old 09-08-13, 09:55 AM   #26
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Quote:
Originally Posted by Swint View Post
The TPS tested in spec and adjusting it even 1/8 of an inch makes a very noticeable difference in idle and shifting RPM. I believe it it in working order. I'm at a loss for words on this one.
you just tested with a volt meter? Get someone with a datalogger.... pay em 100 bucks and save your headaches.
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Old 09-09-13, 12:32 PM   #27
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Ok I will try that this weekend thanks
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