SC300 Revving like I was tapping on accel
05-06-08, 11:52 PM
#1
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SC300 Revving like I was tapping on accel
Thanks in advance for any advice you may have; I am really stumped.
My 1992 SC300 engine is accelerating by itself on a regular cycle about every two seconds. It's a lot like when you first turn on the car and it idles high for a second then drops back down. Only then it idles high again and drops back down again. It does this whenever the car is running, so I obviously don't drive it.
The day that it started to get really bad I noticed that the battery light came on and the ABS Break light. It hesitated on startup like it was having a battery problem, but then kicked in and all was well (the lights went out and the car drove fine for a while). I parked, ran an errand, came out, started it up again and everything seemed fine. About five minutes later, the engine accellerated on its own to the point that I had to keep the parking break on at a stoplight to keep from rear-ending someone until I could pull over.
Any suggestions?
I recently got the car back from the guy who owned it before me: he is a Lexus master technician and an absolute saint. I had taken it to him as a last resort after getting the car back from a local tech shop. It was running choppy and he was able to tune it up and make it run fine. I would prefer not to bother him again as I am sure that his kindness is often taken advantage of.
The thing about it is that I have felt like this revving thing is just the logical extension of the problem we have been having since we got it back. Granted it was nothing like it is now, but it seemed to be revving before this started. It kinda sounded like the engine belonged in a big muscle car the way it idled.
Any ideas, suggestions, or questions would be greatly appreciated. Thanks again for your help,
jase
My 1992 SC300 engine is accelerating by itself on a regular cycle about every two seconds. It's a lot like when you first turn on the car and it idles high for a second then drops back down. Only then it idles high again and drops back down again. It does this whenever the car is running, so I obviously don't drive it.
The day that it started to get really bad I noticed that the battery light came on and the ABS Break light. It hesitated on startup like it was having a battery problem, but then kicked in and all was well (the lights went out and the car drove fine for a while). I parked, ran an errand, came out, started it up again and everything seemed fine. About five minutes later, the engine accellerated on its own to the point that I had to keep the parking break on at a stoplight to keep from rear-ending someone until I could pull over.
Any suggestions?
I recently got the car back from the guy who owned it before me: he is a Lexus master technician and an absolute saint. I had taken it to him as a last resort after getting the car back from a local tech shop. It was running choppy and he was able to tune it up and make it run fine. I would prefer not to bother him again as I am sure that his kindness is often taken advantage of.
The thing about it is that I have felt like this revving thing is just the logical extension of the problem we have been having since we got it back. Granted it was nothing like it is now, but it seemed to be revving before this started. It kinda sounded like the engine belonged in a big muscle car the way it idled.
Any ideas, suggestions, or questions would be greatly appreciated. Thanks again for your help,
jase
05-07-08, 04:52 PM
#4
vaccum leak or idle surge which can be caused by the IACV... Check for leaks by building a pressure tester....if there are none (there most likely is), then you know u have a faulty Idle Air Control Valve......
hope this helps
hope this helps
05-07-08, 05:24 PM
#5
i took my IACV off one time to tinker around in it, theres really not much you can do in there except mess things up. I don't think you can repair, only replace.
Sounds like a vacuum or a faulty IACV or even the TPS sensor. These are the answers that get thrown at everyone with any idle problem, and for good reason.
when you disconnect your IACV electrical plug, your idle should jump up and down repetitively, at least mine did. It is not random either, it has a steady beat to it. kind of sounds like what you are experiencing.
Sounds like a vacuum or a faulty IACV or even the TPS sensor. These are the answers that get thrown at everyone with any idle problem, and for good reason.
when you disconnect your IACV electrical plug, your idle should jump up and down repetitively, at least mine did. It is not random either, it has a steady beat to it. kind of sounds like what you are experiencing.
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