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Not sure how to test what? Brake booster vacuum? If it takes two feet to depress the pedal for a start light, your booster is leaking. It could be the check valve or the booster itself.
Mine will hold for a month if that helps.
Plugs, although you didn't verify the gap, the precious metal tips (platinum, iridium) can break off.
What was the conclusion of the test Mike had you do?
How many miles and how is the car used?? If it does a bunch of short trips, it could have some carbon build up.
Yes sorry the Break booster vacuum. I tested it just then and the brake is fine and light don't need much force to turn on the start light.
When you say it holds for a month, what do you mean?
I will redo the the plugs in the next couple of days and report back, I'll also buy a feeler gauge to get the 1.1mm gap perfect.
The test Mike had me do, I couldn't really understand what he wanted me to do.
"Pull the inlet hose side from under intake. Disconnect the 2 wire harness. On that port disconnected no vacuum from engine should be sucking as the valve should be shut closed disconnected."
From the image I posted labelled in steps he wants me to:
1. Pull the lead here at the intake port
2. Disconnect the ONE wire harness?
3. Check to see if there's no vacuum while the car is running as the port should be disconnected thus closed?
Would you say this is correct?
Car is at 190k so 120k miles, just bought it but was a daily runner so guess it was mainly shortish trips. When I cleaned the intake while putting the spark plugs in I did notice a lot of carbon build-up on the engine valves.
I'm awaiting this TB to arrive in the coming days so I'll do all these tests and hopefully I can get somewhere. Thanks again for the reply.
Hey guys, first post here and was hoping it wasn't a problem post but alas here I am. I'll try to be as clear and concise as possible to narrow down my problem I desperately need help with.
Just bought a 2006 Lexus IS250 with 190k kms on the clock.
Finished up servicing the car and last thing I had to do was spark plugs. Removed the two ECM and ECU fuses.
Used Denso Iridium TT Spark Plug IKBH20TT they're pre-gapped from my knowledge and ready to go out the box.
Cleaned intake heads with a rag as well as replaced intake gaskets and gave everything I could see a wipe down due to the carbon sludge in the engine.
Decided to clean the throttle body while I was there as it was dirty. Used degreaser sprayed on it pretty generously (Dumb I know). Also moved the actuator, throttle body plate with my hand ever so gently a couple of times to clean the tops and the cylinder properly. Some videos say you can do this, others say dont because you could damage the gears.
Didn't replace the PCV but gave it a good clean with degreaser also and allowed to dry. Put everything back together meticulously and made sure every connector was right.
First start. Car heats up to operating temperature fine while in park. Hits around 900 rpm and says there. Idle is great. Took it for a drive and drives like a dream no worries. Here's were the problem starts.
First time starting after turning the engine off in park. I immediately get thrown the P0505 (Idle speed control system malfunction (ISC))and the engine just sounds the tiniest bit off in its idle and you can feel it in the drivers seat ever so slightly. VSC warning and engine light now flashes on the dash. (I'm guessing this just gets flashed due to the code and there's nothing wrong with the vsc system). Car drives fine, idles poor.
After some testing and troubleshooting of when exactly the code appears and after what sequence of events occur I've come to the conclusion that it happens once the car is put into park at operating temperature. I found this after clearing the codes while the acc on engine off, starting the engine and immediately putting it in drive. I can drive the car normally, stop, with the break at lights/parking but the second i put it into PARK it'll throw that code and begin to idle poorly while idling fine when stopped in DRIVE.
I've done a lot of trouble shooting which I'll now list.
Resetting the ECM so many times to relearn the new idle
Cleaned MAF sensor with MAF cleaner
Gone over throttle body and cleaned again
Small test for vacuum leak using carby cleaner
Checked harness for TB and moved wires to check connection
Disassembled the entire intake plenum again in-case of vacuum leak/gasket wrong etc
Next steps if I can't fix it:
Replace throttle body
Replace MAF
Pulling my hair out on what it could be. I've scoured this forum and google for anything that could lead me to the answer but can't seem to find it.
The ISC from what I know is inbuilt into the side of the throttle body for the IS250 correct? So is it possible I've damaged that with the degreaser or moving the plate with my hands?
The car runs fine other than idling. Also the throttle body is at 14.5% isn't that perfect? Also idle RPM isn't that erratic but I can still hear the car perform poorly and shake a little while im in the seat.
I've attached screenshots of the sensors of my car at idle, at operating temperature and in park for any of those that could help diagnose what's happening.
At this point I'm happy to try anything, even a ritual sacrifice to get this thing to be normal again
Any help would be much appreciated and I'll provide as much info as you need.
Thanks for reading!
Should always 1st go with exactly what the Trouble codes is finding.
I'll take the hint from your highlighting that I should probably pay attention to what's in the bold letters and go from there?
Love that link though, I was looking at it a week ago and thought it was telling me the same stuff but its very technical so I'll sit down and review it along with my symptoms.
Purge vavle not sticking open. It's the one line that runs under the intake pipe. Make sure it isn't disconnected from the hard line on the body. To test the purge valve while car is on remove connector, and and pull the hose there should be no suction from manifold.
Hey Mike, I finally had some spare time to try and tackle this problem again. Sorry for being annoying, I just need some clarification on the purge valve and its operation if you have some spare time.
I was just testing it then and no matter what I did I could not get it to open while the car was running. I get the ECU decides when to open the valve by sending current but I can't wrap my head around whether its working correctly.
First I tested it by connecting it to the battery to see if it opened under 12v DC. It did, I was able to blow air through it and had audible clicks.
Then I tested the voltage across the harness that connects to the purge valve and it was 14V with engine on.
Turning the car on and having the electrical harness connected and the intake side connected ( blue side) while the engine side (black side) was disconnected I was unable to get it to open in any fashion, despite the fact 12v was opening it every go with the battery.
Am I doing the correct tests and is it supposed to function this way?
Hey Mike, I finally had some spare time to try and tackle this problem again. Sorry for being annoying, I just need some clarification on the purge valve and its operation if you have some spare time.
I was just testing it then and no matter what I did I could not get it to open while the car was running. I get the ECU decides when to open the valve by sending current but I can't wrap my head around whether its working correctly.
First I tested it by connecting it to the battery to see if it opened under 12v DC. It did, I was able to blow air through it and had audible clicks.
Then I tested the voltage across the harness that connects to the purge valve and it was 14V with engine on.
Turning the car on and having the electrical harness connected and the intake side connected ( blue side) while the engine side (black side) was disconnected I was unable to get it to open in any fashion, despite the fact 12v was opening it every go with the battery.
Am I doing the correct tests and is it supposed to function this way?
Thank you again for your time.
Yes the ECM controls the operation. Normally on a cold start it should start working. It is not meant to stay open. It will just just open slightly at a time.
The air flow path is coming from the evap canister at the rear of the car. The hose that runs under the intake pipe. Disconnect it at purge valve, and while it's working there place your finger on the port. You should feel suction. If you disconnect the electrical harness the valve should be closed, and no suction present. It's clear by your test it seems to be functioning.
Here's a good read on how it works, and its purpose.
Yes the ECM controls the operation. Normally on a cold start it should start working. It is not meant to stay open. It will just just open slightly at a time.
The air flow path is coming from the evap canister at the rear of the car. The hose that runs under the intake pipe. Disconnect it at purge valve, and while it's working there place your finger on the port. You should feel suction. If you disconnect the electrical harness the valve should be closed, and no suction present. It's clear by your test it seems to be functioning.
Here's a good read on how it works, and its purpose.
Thanks for the explanation Mike its much appreciated.
So immediately after starting the car on a cold start, I've disconnected the EVAP end of the purge valve under the intake and there seems to be no vacuum at all in the slightest. I tested with a small very light leaf and covered it as I thought there was slight suction but not even that stuck. Please see the picture to see if I'm doing it right.
I did install the new TB last night but the car seemed to reject it, its so much dirtier than mine even after cleaning it with TB cleaner. The car threw up P2103 codes 'Throttle Actuator Control Motor Circuit High' and was basically sending the rpms everywhere while idling so I pulled it and installed my old one. The TB was from a 2008 model but its the exact same TB so I thought it would be fine?
I was so dejected after seeing that honestly. I've included a pic of the TB. (Mine is sparkling compared to this one) No vacuum when starting the car, nor when at operating temperature New TB - high circuit codes when this is installed
I think you maybe chasing your tail. Correct me if wrong but.... P2103 is a bad TB control motor and/or circuit (P2103). So the P505 is not showing and cleared now?
My guess is you damaged your original TB cleaning at 1st. Now you have a 2nd bad TB replacement that has a defective control in it. I may be wrong but you still need a good replacement TB that's not defective and that's the problem that will resolve all.
I think you maybe chasing your tail. Correct me if wrong but.... P2103 is a bad TB control motor and/or circuit (P2103). So the P505 is not showing and cleared now?
My guess is you damaged your original TB cleaning at 1st. Now you have a 2nd bad TB replacement that has a defective control in it. I may be wrong but you still need a good replacement TB that's not defective and that's the problem that will resolve all.
Yep it is that code, and was throwing the cars engine all over the place so I pulled it fast so I wouldn't wreck anything else. It didn't throw the p0505 code but I'm not sure I left it long enough for the car to think its idling or even could due to the erratic nature of the dirty TB I put in.
At this point I'm just going to return the faulty TB, buy a new aftermarket TB with a year warranty (because I refuse to pay 800 AUD for a genuine one), and see if that works.
Please wish me luck, I need it :P
Thanks for the explanation Mike its much appreciated.
So immediately after starting the car on a cold start, I've disconnected the EVAP end of the purge valve under the intake and there seems to be no vacuum at all in the slightest. I tested with a small very light leaf and covered it as I thought there was slight suction but not even that stuck. Please see the picture to see if I'm doing it right.
I did install the new TB last night but the car seemed to reject it, its so much dirtier than mine even after cleaning it with TB cleaner. The car threw up P2103 codes 'Throttle Actuator Control Motor Circuit High' and was basically sending the rpms everywhere while idling so I pulled it and installed my old one. The TB was from a 2008 model but its the exact same TB so I thought it would be fine?
I was so dejected after seeing that honestly. I've included a pic of the TB. (Mine is sparkling compared to this one) No vacuum when starting the car, nor when at operating temperature New TB - high circuit codes when this is installed
Is there a reason for the depin of the purge valve connector?
I was mainly having issues where i put my car in gear and rpms drop briefly while gear engage into reverse or drive, or press window and rpms drop. Like use high beams and rpms drop. issues with my power and mpg. I am getting like 8 mpg when i give gas city. Also delayed shift into 6. I am thinking my Throttle position sensor is bad or not receiving enough power., or maf is not recieving enough power or bad. I get battery and alternator tested and voltage regulator is bad on alternator. I replaced my original oem denso alternator with a car quest premium alternator, and i disconnected the ecu box to do the repair. During repair i noticed my idler pulley bearing was bad, and i replaced it with a cheap part..the four seasons idler pulley. i noticed this pulley had some play in it, compared to the $75 pulley i declined from advance auto. I also replaced the belt. After repair of alternator, my lexus is250 165k miles started with the rough idle EXACT SYMPTOMS AS THIS THREAD immediately after replacing the alternator. I can feel the shake as well. The symptoms are all the same as yours, start at 2 rpm and go down slightly to like 1.3. And weird electric noise from engine. i still have the issue where i use my power window or turn on lights and the rpms drop.
After two days, I throw codes finally...like a bunch.. maybe because of bad battery...maybe because i raced a motorcycle on a bumpy road .. not sure..U0126, u0124, u0123, u0073. ALSO I threw code "C1201 for a brake booster sensor and performance", and Idle control P0505..
I got a new battery today, and it cleared the codes when replacing battery. I have a New PCV valve coming in mail.. The car still idles weird, and the rpms drop when i use a window. Maybe i shoulda gotten a denso alternator.. does anyone else have rpms drop when using car window, or moivng their seat forward or back?
anyways i just got a denso MAF sensor like one hour ago, and it idled high initially, so i idle reset, with turning on car with no brake depress, then press brake all the way and wait 10 second. then remove foot, shut off car, then press foot and turn on car. let idles creep down to like 1.5... throw ac on and it goes down to 1.3 and then put in reverse and get tht b on highway, drive for 10 min.. MPG HIGHER and when i get home and put in park solid af no weird idle. however i can still feel a little shake. maybe my idler pulley that was cheap was not a good buy. I also noticed my other bearing on the belt tensioner was squeaky and had play. but i could not afford the part. anyways when i idle warm with no ac its around 1.05 rpms in park. and when i put ac on its like .8 rpms. When i put it in reverse my idles dip down and act weird. in drive they hold but still act a little weird. is it relearning idle on the ECU? It feels like it shouldnt be doing that in reverse.
I think my problem could be when i disconnect my battery the car does not like the aftermarket alternator when it relearns its idle and it started to do that after i replaced the alternator to a non denso.
This guy claims he has a fix, but it really doesnt seem to fix as i can see his rpms flutter right when he moves camera on the gauge. and the comments seem to have the issue after their alternator was done. maybe ill swap mine to a denso..
Update: The replacement aftermarket TB came. I noticed it had an ever so slightly bigger resting opening than the original denso that came with the car.
Popped it in the car, reset the ecu using the fuses and battery and started it up cold.
RPM in park immediately starts going up and down between 2k and 3k revs non stop. So stopped the car.
I set the car in drive after starting it again which stopped the weird idle fluctuation and waited for it to reach operating temperature. The idle in DRIVE never went below 1000RPM.
Put the car in PARK and the idle would not settle below 1700RPM, which I think is a by-product of the the TB reading its idle position as 16.86% rather than the stock TB reading 14.509% but just speculating here.
Then it threw the codes once in park and idling.
Takeaways:
I think the crappy TB response from the aftermarket TB is as a result of poor workmanship on the part and not the car.
The problem is not the TB and instead I need to look further.
I'll be taking out all of the spark plugs today and reseating them. Removing the anti-seize as much as I can from the threads, removing the di-electric grease, re-checking the PCV hose and PCV function. Inspecting the intake and all connectors thoroughly again.
I just want to get this fixed. At least we've eliminated one of the options I'd say.
What a nightmare.
09-19-22, 07:45 PM
