Cleaned Throttle Body now High Engine Idle?
05-17-07, 09:17 PM
#1
Pit Crew
Thread Starter
Cleaned Throttle Body now High Engine Idle?
94' GS with 145k
Alright, here is the story. Lately, from a cold start, I'd begin to drive off and the accelerator pedal would feel like it was sticking for just a moment, and then would break loose and feel okay. Did some searching on the forums and found that a cleaning of the throttle body would do the trick. So a couple of days ago, I pulled out the airbox, moved the MAF, disconnected the large intake hoses to where I could get a clear view of the throttle. Did as instructed in the postings.... spray tb cleaner, scrub with toothbrush, wipe clean with paper towels. Repeated until all appeared to be mostly clean and free to operate without trouble. Re-assembled intake, MAF, tubes & airbox. Let the engine warm up for a few & then go for a drive. Been driving for a couple of days now and the sticky throttle problem is a thing of the past.
The bad: Ever since then my idle is high. Typically I'd get the 1500RPM for a minute or two when starting from cold, and then it would settle down to the usual 700 or so when the engine temp rose a bit. But..... now, it never settles down, idles right at about 1250 rpm (annoying). If I'm at a stop light I feel like I have to hold the brakes down firmer to keep the car from running away from me. And shifting from P to R or D is more rough, due to the unwanted rev of the engine it sounds like the transmission clunks in and out of gear, it sucks.
Any ideas on what I may have tampered in the TB cleaning process? Everything appears to be back in place, firmly, without any leaks. I see an idle control sensor mounted near the body of the throttle, but don't see how I could have messed that up, and doesn't appear to be adjustable.
Please & thanks, sorry for rambling but I NEED HELP!
Mike
Alright, here is the story. Lately, from a cold start, I'd begin to drive off and the accelerator pedal would feel like it was sticking for just a moment, and then would break loose and feel okay. Did some searching on the forums and found that a cleaning of the throttle body would do the trick. So a couple of days ago, I pulled out the airbox, moved the MAF, disconnected the large intake hoses to where I could get a clear view of the throttle. Did as instructed in the postings.... spray tb cleaner, scrub with toothbrush, wipe clean with paper towels. Repeated until all appeared to be mostly clean and free to operate without trouble. Re-assembled intake, MAF, tubes & airbox. Let the engine warm up for a few & then go for a drive. Been driving for a couple of days now and the sticky throttle problem is a thing of the past.
The bad: Ever since then my idle is high. Typically I'd get the 1500RPM for a minute or two when starting from cold, and then it would settle down to the usual 700 or so when the engine temp rose a bit. But..... now, it never settles down, idles right at about 1250 rpm (annoying). If I'm at a stop light I feel like I have to hold the brakes down firmer to keep the car from running away from me. And shifting from P to R or D is more rough, due to the unwanted rev of the engine it sounds like the transmission clunks in and out of gear, it sucks.
Any ideas on what I may have tampered in the TB cleaning process? Everything appears to be back in place, firmly, without any leaks. I see an idle control sensor mounted near the body of the throttle, but don't see how I could have messed that up, and doesn't appear to be adjustable.
Please & thanks, sorry for rambling but I NEED HELP!
Mike
05-19-07, 01:59 PM
#4
Pit Crew
Thread Starter
Well, I did another (thorough) cleaning on the throttle body again last night. Did not solve the problem. If anybody has any ideas, I'm interested in avoiding a trip to the auto repair shop.
Thanks...Mike
Thanks...Mike
12-09-07, 08:30 AM
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12-09-07, 10:16 AM
#7
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I don't know if the Lexus computers do it (they should) but here goes.
Most automotive computers are designed to allow for changes to operating parameters. The manufacturers know that settings are not going to stay within spec. So, after a setting (like your tps) changes, and stays that way for a certain number of complete cycles (car on, drive for X amount of miles and turn off, I think it's 3-5cycles) The new settings are stored in the computer as the default settings and your idle was adjusted to that.
Now that you've cleaned the TB and gotten the settings closer to spec, the parameters have changed again. You can either manually adjust the TPS, or it will reset itself and normalize after a few more complete cycles.
It would be better to adjust it manually, because the cleaning is not a gradual change like the accumulation of dirt. And it is affecting your gas mileage...
BUT! now you know a little bit more!
Most automotive computers are designed to allow for changes to operating parameters. The manufacturers know that settings are not going to stay within spec. So, after a setting (like your tps) changes, and stays that way for a certain number of complete cycles (car on, drive for X amount of miles and turn off, I think it's 3-5cycles) The new settings are stored in the computer as the default settings and your idle was adjusted to that.
Now that you've cleaned the TB and gotten the settings closer to spec, the parameters have changed again. You can either manually adjust the TPS, or it will reset itself and normalize after a few more complete cycles.
It would be better to adjust it manually, because the cleaning is not a gradual change like the accumulation of dirt. And it is affecting your gas mileage...
BUT! now you know a little bit more!
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