RPM's keep dropping

Tiny
CALLMEREY
  • MEMBER
  • 1993 LEXUS LS 400
  • 3.6L
  • V8
  • 2WD
  • AUTOMATIC
  • 180,000 MILES
I just finished changing my timing belt and everything was adjusted and all cams were lined-up at TDC. I ran the engine and it idles okay at 650 rpm, then I slowly step on the gas pedal to increase rpm's and when in reaches 1000 rpm's, it drops to zero. I continued stepping on the gas pedal but no power increase. I also tried adjusting the throttle sensor, but no help. Please advise on how can I fix it.
Saturday, December 16th, 2017 AT 1:38 PM

5 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,796 POSTS
Good morning my name is Roy and I will assist.

From your description it sounds like you need a throttle position sensor for the fly by wire system. Has nothing to do with the repair unless this issue was present prior to your repair.

If the proper signal is not sent to the ECM it will cause this. Just to be sure, is there an accelerator cable on the throttle body?

Roy
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Sunday, December 17th, 2017 AT 6:21 AM
Tiny
CALLMEREY
  • MEMBER
  • 8 POSTS
Lexus 1993 ls400,
i've replaced timing belt and everything is tdc lined up. I also replaced my throttle sensor, replaced all ignition plugs and wires, but eng idles ok but won't increase rpm, also I could smell raw fuel, please help me figure out this problem.
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Tuesday, January 23rd, 2018 AT 2:24 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,796 POSTS
Was this issue present before the timing belt repair?

Roy
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Wednesday, January 24th, 2018 AT 1:40 AM
Tiny
CALLMEREY
  • MEMBER
  • 8 POSTS
Thank you for your response, Roy. This issue was not present before the timing belt repair.
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Wednesday, January 24th, 2018 AT 3:37 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,796 POSTS
Good morning

Double check all your vacuum lines for any that may be cracked or broken. Make sure the plate in the throttle is clean of all carbon as well.
Also, re verify your timing marks. The mark on the back head is the hardest to see and can be off 1 tooth and cause this issue.

Roy
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Thursday, January 25th, 2018 AT 1:01 AM

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