1999 RX300 rough idle and low vacuum after warm up
05-07-19, 10:21 AM
#1
Driver School Candidate
Thread Starter
1999 RX300 rough idle and low vacuum after warm up
I have a 1999 RX300, once the engine get to operating temp it gets a real rough idle and I assume is losing vacuum because the break is real hard to push, idle jumps between 500 and 700 I guess. When the engine is cold it idles as smooth as can be. Give it any gas at all and it runs smooth. Even when warn with a little bit of gas to get the RPM's up to about 1K the brakes work good. Its only an issue when warm and when you take your foot off the gas. Its the kids car, we have had it for two years and this just started. 174K miles.
It had no gas cap (KIDS), bought an autozone cap and cleaned the area for it to seal real good. Filled it with fresh gas and gas treatment. Cleaned the idle air control valve, it turned but was a little rough. After a good cleaning its moves easily but you can feel its a little rough, but no real resistance. The vacuum hose to the air box was off, connected it. I could not hear any vacuum leak. And like I said it runs perfect till engine is to full operating temperature. It does have a CEL, but the code reader come back with error trying to read codes. I will try and take it to autozone so they can try and read them. I disconnected the battery to clear the code, daughter drove off and after about 10 minutes she said the CEL was back on and brakes were hard to push, but not as bad as yesterday.
Its runs so good with just a little gas I cannot believe it would be electrical, I guess it could be fuel, or a vacuum leak that only happens once the engine is hot. Any temp valves to open vacuum ports? Could I adjust the idle to force it up higher so the brakes work good, if so how, It has never stalled, but shakes a little with the rough idle.
Any other suggestions, I have read so many threads my head is spinning.
Thanks Chris
It had no gas cap (KIDS), bought an autozone cap and cleaned the area for it to seal real good. Filled it with fresh gas and gas treatment. Cleaned the idle air control valve, it turned but was a little rough. After a good cleaning its moves easily but you can feel its a little rough, but no real resistance. The vacuum hose to the air box was off, connected it. I could not hear any vacuum leak. And like I said it runs perfect till engine is to full operating temperature. It does have a CEL, but the code reader come back with error trying to read codes. I will try and take it to autozone so they can try and read them. I disconnected the battery to clear the code, daughter drove off and after about 10 minutes she said the CEL was back on and brakes were hard to push, but not as bad as yesterday.
Its runs so good with just a little gas I cannot believe it would be electrical, I guess it could be fuel, or a vacuum leak that only happens once the engine is hot. Any temp valves to open vacuum ports? Could I adjust the idle to force it up higher so the brakes work good, if so how, It has never stalled, but shakes a little with the rough idle.
Any other suggestions, I have read so many threads my head is spinning.
Thanks Chris
05-07-19, 04:23 PM
#3
Driver School Candidate
Thread Starter
Well finally got the codes read. Autozone could not figure out how it was still running with so many codes. But the "P1349 Variable Valve Timing System (Bank 1)" is the root cause of the rest. Ordered Dorman OE Solutions Part # 917-211 and Dorman OE Solutions Part # 917-214 off Amazon $45 each. In to days I will know if that is the issue, but looks like it. And that great DIY post on here makes it look real easy. Can't wait.
Chris
Chris
05-09-19, 07:45 AM
#4
Moderator
Well finally got the codes read. Autozone could not figure out how it was still running with so many codes. But the "P1349 Variable Valve Timing System (Bank 1)" is the root cause of the rest. Ordered Dorman OE Solutions Part # 917-211 and Dorman OE Solutions Part # 917-214 off Amazon $45 each. In to days I will know if that is the issue, but looks like it. And that great DIY post on here makes it look real easy. Can't wait.
Chris
Chris
Salim
05-09-19, 05:25 PM
#5
Driver School Candidate
Thread Starter
The new ones looked exactly like the old ones. Took me about 20 minutes tops. The front one came out easy, I was able to get vice grips on the rear and get it out pretty easy. The two caps for the filters, not that looked like a pain. But I got lucky compared the procedures I read and the filters remained attacked to the cap so when I took the cap off the filter came with it. No more CEL not more code, got it to full operating temp for 20 minutes and no problems.
Salim, You have to research after market parts, look at reviews etc. Most are as good as OEM, its not like Lexus has their own plant to manufacture this valve, and who ever makes it for Lexus sells it under another brand name and part number is my bet. These Dorman parts were truly an exact match, I compared them closely especially the part that goes in the engine. Maybe what I pulled out was not the original parts, I do not know. I read about other parts where the part in the engine looked a lot cheaper plastic, but those people said they worked well. I spent a little more and got the ones many people were very happy with and did question the quality. Time will tell, but if the part fails it fails. If I put back in a bad part with no clue why it was failing and that caused my daughter to get stranded somewhere down the road, my wife would kill me. So that factors in it as well.
Either way it looks like its fixed. have to get some miles on it to be sure.
Salim, You have to research after market parts, look at reviews etc. Most are as good as OEM, its not like Lexus has their own plant to manufacture this valve, and who ever makes it for Lexus sells it under another brand name and part number is my bet. These Dorman parts were truly an exact match, I compared them closely especially the part that goes in the engine. Maybe what I pulled out was not the original parts, I do not know. I read about other parts where the part in the engine looked a lot cheaper plastic, but those people said they worked well. I spent a little more and got the ones many people were very happy with and did question the quality. Time will tell, but if the part fails it fails. If I put back in a bad part with no clue why it was failing and that caused my daughter to get stranded somewhere down the road, my wife would kill me. So that factors in it as well.
Either way it looks like its fixed. have to get some miles on it to be sure.
11-15-22, 10:17 AM
#6
Hello Bigfoot123, if you are still around, can you report back about this solution? Did it work? I am experiencing exactly the same issue, except my car is not throwing any codes. 1998 Harrier. The same as an RX300 for all intents and purposes. Previously my mechanical timing was out and I got codes for both solenoids and was hoping that correcting the timing would be the fix. No such luck though.
11-29-22, 07:31 AM
#8
I have confirmed that my issue is definitely VVT related. If I unplug the coolant sensor, I never get the poor idle issue. This confirms it is not something that is actually temperature related. I suspect my system is able to advance the cams, but not retard them, hence the choppy idle after driving for a while. I had something similar tuning a Honda back in the day where the ECU kept the VTEC solenoid engaged and the car drove really poorly at low rpm with the higher overlap/lift (and yes, I know the VVT only changes overlap). I guess after parking for some time, the oil pressure in the mechanism bleeds off and the cams revert to the base position. With the sensor unplugged, the ECU never tries to advance the cams.
New solenoids are on the way.
New solenoids are on the way.
12-18-22, 07:51 PM
#9
To follow up on my last post, I have now replaced both solenoids and my issue has been resolved. Smooth running at all rpm and more torque/power. I expect fuel consumption will improve also. It is interesting that I didn't get a cel for this though. My vehicle is a JDM Harrier, so I guess there is a difference in the codes the ECU will throw.
Before changing the solenoids, I was getting a rattle from the engine at 2250 rpm plus or minus maybe 50 rpm. I did a lot of research on this, on here and other sites. I found several persons with the same issue but there was no conclusive answer. A failing timing belt tensioner was put forward by most persons as the cause, but nobody reported back that they solved their issue. Well, since changing the solenoids, this sound has gone away, at least so far. I assumed the issue was unrelated as I didn't see anyone post this as a consequence of a failed solenoid.
Before changing the solenoids, I was getting a rattle from the engine at 2250 rpm plus or minus maybe 50 rpm. I did a lot of research on this, on here and other sites. I found several persons with the same issue but there was no conclusive answer. A failing timing belt tensioner was put forward by most persons as the cause, but nobody reported back that they solved their issue. Well, since changing the solenoids, this sound has gone away, at least so far. I assumed the issue was unrelated as I didn't see anyone post this as a consequence of a failed solenoid.
Last edited by mhay; 12-18-22 at 07:57 PM.
12-18-22, 07:55 PM
#10
I didn't get any codes either.
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mhay (12-18-22)
12-19-22, 08:35 AM
#11
Moderator
12-19-22, 10:17 AM
#12
My issue was VVT too. Maybe they start to go bad and engine performance is affected before the problem reaches a threshold detected by the ECU
12-19-22, 11:01 AM
#13
Bigfoot mentioned codes on his car, so that is what I was referring to. The code I would expect would be due to cam phasing, i.e. the commanded cam position and the actual position differ by some amount. Anyway, just glad it is sorted now. The poor idle was really getting annoying.
12-19-22, 09:23 PM
#14
Moderator
Bigfoot mentioned codes on his car, so that is what I was referring to. The code I would expect would be due to cam phasing, i.e. the commanded cam position and the actual position differ by some amount. Anyway, just glad it is sorted now. The poor idle was really getting annoying.
Salim