Please help with this RPM problem
01-29-17, 02:35 AM
#1
Driver School Candidate
Thread Starter
Please help with this RPM problem
Hello members
I have a weird problem in my Lexus Ls400 98, 200k mile on it.
when I start the car and it warmed if I put the gear in D and applying the barke, the car vibrate a little, but if I turn on the light ( parking light) the rpm increas a little and vibrate goes away.
when the car in gear D ( warmed) + applying the brake the rpm is 400, when turn the light on rpm goes up to 600
When the car on N doesn't vibrate and the RPM is around 650 and when I turn the light Nothing happend and no change in the rpm
What Is THIS ???
Thank you in advance
I have a weird problem in my Lexus Ls400 98, 200k mile on it.
when I start the car and it warmed if I put the gear in D and applying the barke, the car vibrate a little, but if I turn on the light ( parking light) the rpm increas a little and vibrate goes away.
when the car in gear D ( warmed) + applying the brake the rpm is 400, when turn the light on rpm goes up to 600
When the car on N doesn't vibrate and the RPM is around 650 and when I turn the light Nothing happend and no change in the rpm
What Is THIS ???
Thank you in advance
Last edited by Johnnyy; 01-29-17 at 03:29 AM. Reason: More info
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RA40 (01-29-17)
01-29-17, 08:57 PM
#3
Moderator
Hello members
I have a weird problem in my Lexus Ls400 98, 200k mile on it.
when I start the car and it warmed if I put the gear in D and applying the barke, the car vibrate a little, but if I turn on the light ( parking light) the rpm increas a little and vibrate goes away.
when the car in gear D ( warmed) + applying the brake the rpm is 400, when turn the light on rpm goes up to 600
When the car on N doesn't vibrate and the RPM is around 650 and when I turn the light Nothing happend and no change in the rpm
What Is THIS ???
Thank you in advance
I have a weird problem in my Lexus Ls400 98, 200k mile on it.
when I start the car and it warmed if I put the gear in D and applying the barke, the car vibrate a little, but if I turn on the light ( parking light) the rpm increas a little and vibrate goes away.
when the car in gear D ( warmed) + applying the brake the rpm is 400, when turn the light on rpm goes up to 600
When the car on N doesn't vibrate and the RPM is around 650 and when I turn the light Nothing happend and no change in the rpm
What Is THIS ???
Thank you in advance
Regarding the low idle RPM, there is a way to fix. The ECU controls the idle RPM targeting 750 +-50 RPM@N. But aged 98-00 engines tend to run lower than this due to the limited passages of the air at the throttle body and the air mix passages that are connected to injectors. The limitation is caused by the clogged throttle body. When clogged, the ECU can't compensate the lacking air and the idle RPM becomes lower than the target.
When it is badly clogged, you will have another problem of slow acceleration after the speed down at a tight corner or at a speed bump. I suggest you to clean the throttle body including the air mix passages that are located at the top of it. Removing the cover there unscrewing 2 Philips screws, you can see small 8-9 holes and 2 larger holes at the side. In order to clean those 2 holes, you often need a compressor though since you must apply some pressure to those 2.
Last edited by Yamae; 09-26-19 at 07:51 AM.
01-29-17, 10:41 PM
#4
Driver School Candidate
Thread Starter
Your idle RPM is lower than normal. But @400RPM, the vibration should be not so noticeable and I agree with Banshee. You seldom notice the vibration easily even @300 RPM when those mounts are OK.
Regarding the low idle RPM, there is a way to fix. The ECU controls the idle RPM targeting 750 +-50 RPM@N. But aged 98-00 engines tend to run lower than this due to the limited passages of the air at the
throttle body and the air mix passages that are connected to injectors. The limitation is caused by the clogged throttle body. When clogged, the ECU can't compensate the lacking air and the idle RPM becomes lower than the target.
When it is badly clogged, you will have another problem of slow acceleration after the speed down at a tight corner or at a speed bump. I suggest you to clean the throttle body including the air mix passages that are located the top of it. Removing the cover there unscrewing 2 Philips screws, you can see small 8-9 holes and 2 larger holes at the side. In order to clean those 2 holes, you often need a compressor though since you must apply some pressure to those 2.
Regarding the low idle RPM, there is a way to fix. The ECU controls the idle RPM targeting 750 +-50 RPM@N. But aged 98-00 engines tend to run lower than this due to the limited passages of the air at the
throttle body and the air mix passages that are connected to injectors. The limitation is caused by the clogged throttle body. When clogged, the ECU can't compensate the lacking air and the idle RPM becomes lower than the target.
When it is badly clogged, you will have another problem of slow acceleration after the speed down at a tight corner or at a speed bump. I suggest you to clean the throttle body including the air mix passages that are located the top of it. Removing the cover there unscrewing 2 Philips screws, you can see small 8-9 holes and 2 larger holes at the side. In order to clean those 2 holes, you often need a compressor though since you must apply some pressure to those 2.
thank you so much Banshee & Yamae.
Yamae , you exactly explained my problem.
I cleaned the throttle body and top cover 4 months ago, but maybe I need to clean it again. I will also order motor mounts, I think they are really bad. I have replaced the transmission mount a month ago and most of vibration gone.
Now there is another problem, when car is warmed and I press gas at stop , white smoke come from exhaust,
(if I don't give it gas there is a little smoke from exhaust like vabour, I see many cars have this vabour , I don't know if this is normal or no)
I had oil leak from valve cover gasket and fixed both side a month ago, then I was about to change the oil and the guy in the shop told me there is a leak in the oil pan gasket, I decided not to change the oil and just topped it up because I don't know if it is really leaking or old oil. When I park the car every day I don't see any oil under the car.
Can oil pan leaking cause car to smoke a little?
odorless smoke , coolant never change its level since Jan 5t, + oil level didn't change.
Actually I don't think oil pan is leaking, I will check tomorrow again before I change the oil.
01-30-17, 07:14 AM
#5
It's fairly rare for the oil pans to leak as they are essentially glued on with an RTV type substance called FIPG. Usually front crank seals leak and saturate that area with oil.
Check your power steering fluid. If you search much on smoking LS400's, you'll see that 99.9% of the time it's a leaking ACV on the power steering pump. Remove those vacuum hoses on the ACV and see if they're wet inside.
Check your power steering fluid. If you search much on smoking LS400's, you'll see that 99.9% of the time it's a leaking ACV on the power steering pump. Remove those vacuum hoses on the ACV and see if they're wet inside.
01-30-17, 07:35 AM
#6
Driver School Candidate
Thread Starter
It's fairly rare for the oil pans to leak as they are essentially glued on with an RTV type substance called FIPG. Usually front crank seals leak and saturate that area with oil.
Check your power steering fluid. If you search much on smoking LS400's, you'll see that 99.9% of the time it's a leaking ACV on the power steering pump. Remove those vacuum hoses on the ACV and see if they're wet inside.
Check your power steering fluid. If you search much on smoking LS400's, you'll see that 99.9% of the time it's a leaking ACV on the power steering pump. Remove those vacuum hoses on the ACV and see if they're wet inside.
i have replaced the ACV valve last month, and the steering fluid doesn't leak, also, I change the crank seals and cam seal.
I don't know why it is still smoke white when I press the gas.
Thank you for your information
01-30-17, 07:39 AM
#7
Driver School Candidate
Thread Starter
It's fairly rare for the oil pans to leak as they are essentially glued on with an RTV type substance called FIPG. Usually front crank seals leak and saturate that area with oil.
Check your power steering fluid. If you search much on smoking LS400's, you'll see that 99.9% of the time it's a leaking ACV on the power steering pump. Remove those vacuum hoses on the ACV and see if they're wet inside.
Check your power steering fluid. If you search much on smoking LS400's, you'll see that 99.9% of the time it's a leaking ACV on the power steering pump. Remove those vacuum hoses on the ACV and see if they're wet inside.
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09-29-19, 09:51 AM
#8
Racer
Bump.Very useful thread,added to my lexus bookmarks on comp.Thanks again Yamae!
Anybody have a good throttle body thread link they can post?
Anybody have a good throttle body thread link they can post?
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