No Virginia, It Was Not The Throttle Body

[nc211]

Have you tried a new PCV valve? You can buy one for like $5 bucks, VERY easy to replace. If it's clogged up, it'll mess with the engine much like you're saying. It's located right above the 1st spark plug to the left of where you pour in new oil into the engine. You can see it in Blake's picture, right on top of that first spark plug. Simply slip the rubber cover off of it, and gently slide it out. Shake it a bit, if you don't hear a rattle in there similiar to the rattle of a can of spray paint, then it's clogged up.

I'd also suggest looking for the IACV on a parts website, to see if you can actually buy one. If you can, then you can bet the car has one, and might offer you a diagram of where it is located. I like www.parts.com for this sort of thing. Might have to dig a bit.

PCV = Pressure Control Valve.

PS: I'd check this part first, before spending the bigger bucks on 02 sensors and such. What I've learned the hardway with the LS series, is that the easiest and cheapest fix, is usually the problem to begin with. VERY frustrating indeed!

[zeebaloo]

Have you tried a new PCV valve? You can buy one for like $5 bucks, VERY easy to replace. If it's clogged up, it'll mess with the engine much like you're saying...

thanks, and thanks to blake, this is exactly the same as my engine.

Haven't found iacv for a 98 on at least two parts sites.

Today I blew about 50 bucks on some new 12k LB plastic ramps and pulled the 02 sensor, so I am already committed. It was surprisingly easy except for the part about wrestling with the carpet. I will pick up a new PCV when I get a new sensor, so we shall see.

[GEODAWG09]

Have you tried a new PCV valve? You can buy one for like $5 bucks, VERY easy to replace. If it's clogged up, it'll mess with the engine much like you're saying...

thanks, and thanks to blake, this is exactly the same as my engine.

Haven't found iacv for a 98 on at least two parts sites.

Today I blew about 50 bucks on some new 12k LB plastic ramps and pulled the 02 sensor, so I am already committed. It was surprisingly easy except for the part about wrestling with the carpet. I will pick up a new PCV when I get a new sensor, so we shall see.

My 2000 LS has a very low idle too. Only thing that helps is turning on the headlights. I am curious where the IACV is as well, but I get the feeling it may be self contained within the TB.

[zeebaloo]

Hello all ...

Still looking for that IACV :), in the meantime, I changed the O2 sensor using a generic bosch sensor, and for 10 great minutes it ran perfectly. Then of course, as this problem is intermittent, it started the hesitation again. After a few more minutes it got as bad as ever.

So ... PCV is next, however, this part had to be ordered and should come in a few days.

For those minutes, got no codes at all,then the P0172 came back again and some MIL indicators.

[curiousB]

Diagram for your car shows a valve on the intake manifold called an Actuator, Intake Air Control Valve part number 17335-50010. I am not sure its function is idle control or intake air temperature control. The drawings I looked at were a bit fuzzy. Maybe someone else on line can comment if this is the actuator for idle speed control. If it is that would explain why there isn't an IACV part for you car which is the more common nomenclature for Lexus. My car is newer so it has an IACV.

[zeebaloo]

Yes, I saw the Intake air control valve, seems to be shaped like some figure 8's and inside the intake manifold,I don't believe this is the same.

I tried the PCV valve($5.00) and a new gromit(around $6.00) and after a comedy of errors; the gromit fell into the hole, had to buy some needle-nose plyers($8.00) to fish it out, the pcv hose($16) snapped in half with the slightest movement, it does not seem to be the fix I was hoping for. The old valve did not look so bad but I changed it anyways. and the idle still surges. Also, I noticed a hose neck from the air resonator (that weird black rectangle of plastic attached to the air intake) must have snapped off at some point, I jb-welded some copper pipe to replace the neck and sealed around it.

While getting the new valve, I spoke to the service guy at the stealership, he offered to check the car out for $220 and if they repair it, to put that towards the repair. His theories were unimpressive; new plugs, maybe a bad cylinder, but, the offer was still tempting.

[blake918]

Haven't found iacv for a 98 on at least two parts sites.

That's because it doesn't have one in a traditional sense. Look at the PDFs I posted; they are specific to the '99 LS. It shows that the ACIS VSV works with the intake air control valve to maintain the idle.

Here's a real life shot of the acis vsv and vacuum tank (found it on CL):

You mentioned wrestling with the carpet to change the O2 sensor, but the manual says that P0172 could be from Bank 1 or 2, Sensor 1 which are the sensors before the cats. Which O2 sensors have you changed so far?

[zeebaloo]

Haven't found iacv for a 98 on at least two parts sites.

That's because it doesn't have one in a traditional sense. Look at the PDFs I posted; they are specific to the '99 LS. It shows that the ACIS VSV works with the intake air control valve to maintain the idle.

Here's a real life shot of the acis vsv and vacuum tank (found it on CL):

You mentioned wrestling with the carpet to change the O2 sensor, but the manual says that P0172 could be from Bank 1 or 2, Sensor 1 which are the sensors before the cats. Which O2 sensors have you changed so far?

Thanks, Somehow I glossed over the PDFs.

Was under the impression that PO172 was only for drivers side before the cat (B1S1). This is what I changed. That installation went smoothly. I had to pull up the carpet under the brake and gas pedals. I am getting a little intimidated to pull apart the intake to expose the Intake air control valve, but maybe I can change a part of the VSV ACIS circuit.

They mention testing it with a Lexus hand held tester, do you recommend I buy one of these things? I only have an OBD2 reader.

I have to say, I am starting to think I had multiple issues going on. The surging idle and the hesitation on accel. Maybe they are unrelated as sometimes I notice that idle is more steady, but I still get the hesitation problem, and now during the hesitation sometimes a misfire or two.

Yes, I am still driving it to test it out and for short trips.

[blake918]

Thanks, Somehow I glossed over the PDFs.

Was under the impression that PO172 was only for drivers side before the cat (B1S1). This is what I changed. That installation went smoothly. I had to pull up the carpet under the brake and gas pedals. I am getting a little intimidated to pull apart the intake to expose the Intake air control valve, but maybe I can change a part of the VSV ACIS circuit.

They mention testing it with a Lexus hand held tester, do you recommend I buy one of these things? I only have an OBD2 reader.

I have to say, I am starting to think I had multiple issues going on. The surging idle and the hesitation on accel. Maybe they are unrelated as sometimes I notice that idle is more steady, but I still get the hesitation problem, and now during the hesitation sometimes a misfire or two.

Yes, I am still driving it to test it out and for short trips.

The manual says that P0172 can be the left or right side, but since you also have a P0133 code, the driver's side before the cat is where I'd start my testing. If you peeled up carpet to change the O2 sensor, you changed the sensor after the cat since the sensors before the cat plug in underneath the car (and takes all of a minute to change). I'd try to take care of the trouble codes p0133 and p0172 before chasing after the components under the intake since I'd bet they have their own set of trouble codes.

I don't think that us mere mortals can buy those Lexus scanners! I hear they are quite costly too (in the thousands). Most of the sensors on the car (like an O2 sensor) can be tested with a basic multimeter.

COMP.pdf

INSP.pdf

CI__P0171__P0172_.pdf

CI__P0133__P0153_.pdf

[zeebaloo]

The manual says that P0172 can be the left or right side, but since you also have a P0133 code, the driver's side before the cat is where I'd start my testing. If you peeled up carpet to change the O2 sensor, you changed the sensor after the cat since the sensors before the cat plug in underneath the car (and takes all of a minute to change). I'd try to take care of the trouble codes p0133 and p0172 before chasing after the components under the intake since I'd bet they have their own set of trouble codes.

I don't think that us mere mortals can buy those Lexus scanners! I hear they are quite costly too (in the thousands). Most of the sensors on the car (like an O2 sensor) can be tested with a basic multimeter.

It was under the car, but the wire came up thru the bottom of the car into the cabin where there was a gromit and an electrical connection.

Maybe it was one of the MILs that told me it was B1S1,but I can check the other too.

Thanks Blake, I now have more to check out.

[zeebaloo]

The manual says that P0172 can be the left or right side, but since you also have a P0133 code, the driver's side before the cat is where I'd start my testing. If you peeled up carpet to change the O2 sensor, you changed the sensor after the cat since the sensors before the cat plug in underneath the car (and takes all of a minute to change). I'd try to take care of the trouble codes p0133 and p0172 before chasing after the components under the intake since I'd bet they have their own set of trouble codes.

I don't think that us mere mortals can buy those Lexus scanners! I hear they are quite costly too (in the thousands). Most of the sensors on the car (like an O2 sensor) can be tested with a basic multimeter.

Thanks Blake,

Here's an update. After all the work so far, I am now only getting p0172's consistently, no more p0133s. i looked thru the trouble-shooting notes in one of the PDF, among other things they said to check the ECT (engine coolant temperature sensor). This was one thing I hadn't done yet, so I changed the ECT ($30) with one I got from pep boys. The old one fell apart in the socket so I had to change it. I don't know if it was broken before. Still getting the surgy idle, but I think the accel. has improved, I will have to test it over time.

Took a look at the manual, it turns out you're right. The o2 sensor for bank 1 and 2 seem to be before the cabin, under the engine somewhere, the diagram in SF-86.pdf does not show much. So what in the world was I changing??? b1s2... doh! I must have got that impression from another tutorial on how to do it.

So, I will test/change those.

One other question, for a shot in the dark as someone recommended I changed the PCV valve. This turned out to be some trouble because what I wrote before. However, I am looking at the pcv and how it sits in the engine block, it is not fitting too tight, actually, I can twist it around and get it out quite easily.

Is this supposed to be this way? I replaced the gromit and the valve and even the pipe. The gromit,seemed to go in about 98 percent of the way, couldnt get it to seal by itself, then I popped in the valve which sort of mushs in. Maybe I should have sealed in the gromit with some sealant before poping in the valve. What do you think? am I introducing a vacuum leak?

[joe913]

Hello all ...

Still looking for that IACV :), in the meantime, I changed the O2 sensor using a generic bosch sensor, and for 10 great minutes it ran perfectly. Then of course, as this problem is intermittent, it started the hesitation again. After a few more minutes it got as bad as ever.

So ... PCV is next, however, this part had to be ordered and should come in a few days.

For those minutes, got no codes at all,then the P0172 came back again and some MIL indicators.

Check out the attached file for help troubleshooting and locating parts. Good luck!

SFI__SF__file.pdf

[zeebaloo]

Here's an update. After putting the PCV valve back on and changing the ECT,I noticed a definite improvement. I disconnected the neg. terminal of the battery for half a day to clear all codes and memory (which I am assuming clears the computer memory). I drove the car on saturday night and it drove GREAT! like when I first got it, nothing went wrong. stopped, started, everything fine. I was convinced the problem was solved. Even the CEL was not coming on. But, the next day, after a short drive the problems came back again. Pause after initial acceleration and now some coughing noise like the TB door is opening and shutting rapidly, repeatedly.

But ... the acceleration is sometimes very good and if I were to guess, now the TB doesn't go into limp mode. A smell of gas as if the car were running way too rich. I will continue to trouble-shoot this, but its quite strange that it worked so well for one night, then went back to the kr@pper. It makes me wonder whether the mechanic was right that I need a new computer.

[blake918]

Thanks Blake, Here's an update. After all the work so far, I am now only getting p0172's consistently, no more p0133s. i looked thru the trouble-shooting notes in one of the PDF, among other things they said to check the ECT (engine coolant temperature sensor). This was one thing I hadn't done yet, so I changed the ECT ($30) with one I got from pep boys. The old one fell apart in the socket so I had to change it. I don't know if it was broken before. Still getting the surgy idle, but I think the accel. has improved, I will have to test it over time.

Took a look at the manual, it turns out you're right. The o2 sensor for bank 1 and 2 seem to be before the cabin, under the engine somewhere, the diagram in SF-86.pdf does not show much. So what in the world was I changing??? b1s2... doh! I must have got that impression from another tutorial on how to do it.

So, I will test/change those.

One other question, for a shot in the dark as someone recommended I changed the PCV valve. This turned out to be some trouble because what I wrote before. However, I am looking at the pcv and how it sits in the engine block, it is not fitting too tight, actually, I can twist it around and get it out quite easily.

Is this supposed to be this way? I replaced the gromit and the valve and even the pipe. The gromit,seemed to go in about 98 percent of the way, couldnt get it to seal by itself, then I popped in the valve which sort of mushs in. Maybe I should have sealed in the gromit with some sealant before poping in the valve. What do you think? am I introducing a vacuum leak?

No problem! I just looked at my PCV, and it fits tight but not extremely tight--I can pull it out with out having to clamp on to it with a pair of pliers and pulling with all of my might (which is what I had to do the last time I changed it), but it is also not at all loose. I'd say it's just right (the PCV and its grommet are about 8 months old). Personally, I can't see a PCV that's 98% as your problem.

I will continue to trouble-shoot this, but its quite strange that it worked so well for one night, then went back to the kr@pper. It makes me wonder whether the mechanic was right that I need a new computer.

There's nothing odd about that. All of the check engine lights I've had (and I've had plenty on my 99) have done the same thing. When I had oil control valve problems, I'd ride around with the OBDII scanner in the driver's door map pocket to clear the codes when I wanted 30 seconds of peace since bad oil control valves wreak havoc on the idle. When you fix the problem, the cel will turn itself off shortly after you fire it up. Have you had a chance to check out your O2 sensors?

[Matthew99]

I didn't read through all the posts but I wondered if you have encountered all these issues with the same tank of gas? I had a camry once that did all that you mentioned in your first post, so I did a lot of troubleshooting and parts replacement. In the middle of it my wife asked if it could be bad gas, because she had just filled it up, and I laughed at her. Well, $800 later I was still stumped and thought what the heck, I'll put in some fuel treatment ($5) and fill it up with premium (normally put in 87). I had only run out a quarter tank through all the issues.

It worked! I felt like such a fool. So watch out for Holiday Gas Stations and be advised that your problem could be a fuel issue. (I wonder if there was water in it?)

Good Luck z!

[zeebaloo]

Thanks,

I changed the gas several times and tried one of those fuel treatments to "clean out the injectors", it just cleaned out my 10 bucks.

No updates yet, ran out of spare time these last few days, I will update when there is some news.

[zeebaloo]

Hello all,

...

Latest Update. I finally found some time to change the upstream o2 sensors. I went with the non generic type because they were in a cramped spot and I didnt want a dodgy wiring job to be hanging in that tight space. They each cost me $111 and I had previously bought some plastic ramps. It was quite a struggle to get the old ones off. On one, the connector was stuck and the second one was on so tight it took a very long wrench to finally twist off.

And the result ...

No luck, the problem still persists. The surgy idle and occasional sputtering - mostly when the car is warmed up.

As before, sometimes for brief periods of about 20 minutes it runs perfectly, then goes to the kr@pper again.

So to recap, changed the throttle body, cleaned the maf, changed the radiator (because I broke it :) while working on it), changed the pcv, changed the engine coolant temperature sensor and now changed the upstream and one of the downstream o2 sensors.

I will continue to trouble-shoot. because I really enjoy driving that car when it runs well.

[maxed_out]

Hey Zee, way to stick with it.

I'm going out of the box here. My 91 did some similar type things. Really knocked me on my a%# for a while. Yes I smelled gas too. Turned out that I had a corroded gas line that was allowing the car to suck air thus throwing off the computer+mix+sensors. When I eventually talked to the Lexus techs they said they have seen this problem before. I bought a new gas line and filter. It was a bear of a job but everything settled down after that.

If the codes are suggesting any type of lean condition you might want to do a visual on the entire fuel rail from tank to engine. I live in the NE where they use salt during the winter and the corrosion was located right where you'd expect to see salt water hitting the body.

It might be worth a look.

max

[curiousB]

... Turned out that I had a corroded gas line that was allowing the car to suck air thus throwing off the computer+mix+sensors. .....

Sounds strange because the fuel pump is in the tank so that means the fuel line is under positive pressure not under vacuum. As a result a leaky fuel line wouldn't draw air, rather it would spring a fuel leak onto the ground... I could see it undermining fuel rail pressure (fuel pressure at injectors never high enough). That could be easily tested with a fuel pressure gauge.

[cardona6569]

I suggest to take to a really good mechanic or to the dealer. The Lex scanners are better because they were made specifically for your car from the factory. I know it cost a lot. You could also have a bad vvt-i, they have to do a lot with the iddle. CCF

Hey Zee, way to stick with it.

I'm going out of the box here. My 91 did some similar type things. Really knocked me on my a%# for a while. Yes I smelled gas too. Turned out that I had a corroded gas line that was allowing the car to suck air thus throwing off the computer+mix+sensors. When I eventually talked to the Lexus techs they said they have seen this problem before. I bought a new gas line and filter. It was a bear of a job but everything settled down after that.

If the codes are suggesting any type of lean condition you might want to do a visual on the entire fuel rail from tank to engine. I live in the NE where they use salt during the winter and the corrosion was located right where you'd expect to see salt water hitting the body.

It might be worth a look.

max

[fireboy]

To further beat a dead horse, I bought a manual (a non-hyperlinked set of pdfs) for the ls400 (1998-2000) and did a search on "iac","isc", "idle air control" and "idle speed control", nothing turned up. Maybe it could be part of a graphic and not searchable, but it seems that it is just not mentioned. This is what led me before to believe that it may not have one. So if someone has a picture of this, it would really help. :)

All of the photos so far have not been of a 98-00 LS 1UZFE VVTi engine, so here are some pics of my engine, and maybe someone can point to it on there. After rummaging through my PDFs, I did find some relating to this. I kind of thought it might not have one either since I couldn't see it either, but it looks like it's hidden if I'm looking at the PDF right.

I had my starter replaced on my '91 (300k mi)and this problem developed; very annoying but I persisted with my shop and finally the shop determined problem to be vacuum leak at intake manifold. Replaced gasket of intake and all fuel injector ports for good measure. No longer have problem. I had thought the computer was faulty but shop owner never thought that, he always said it was vacuum problem.