Cleaned Iacv And Now Won't Idle

[shilferty]

After having low idle when warmed up in warm weather, I removed and cleaned IACV - removing #1 throttle body to get at screws, following instructions from this forum from GoldenGateSilver Sport.

All went well, IACV rotor assy was very dirty and sticky. Now it turns freely. I reassembled everything, several times now, because this 99 ES300 with 120,000 miles on it suddenly won't maintain any idle.

It runs smoothly with pedal depressed, and as foot is released slowly off gas pedal, all is normal, looks great, until the last couple millimeters of pedal travel when rpms decrease to around 300 rpm.

I can't find any vacuum leaks using carb cleaner. I even tried some propane to see if it would indicate one - Nada!

I made sure brass washer/spring was reinstalled - correctly I think, between black assy and metal assy of IACV - with round black plastic lip pushing the brass washer into the metal assy. The 0-ring is in place.

Any suggestions?

BTW - another, smaller, very thin brass washer appeared while I was removing the throttle plate assembly from the engine, and I'm not sure where it came from. Inner diameter is enough to go around rotor of IACV, but outer diameter is not enough to hold it anyplace in IACV assy. Since nobody else mentioned it, I assume it is NOT from the IAVC. The housing that the throttle body assembly attaches to looks like one ear that a screw goes to is not quite flat - the machining that left the rest smooth is still rough there. I am assuming that this very thin washer was used to make up that difference and keep the throttle plate assembly from warping when screwed into this ear.

[shilferty]

I still need help.

I got my ES300 to idle by increasing tension on the accelerator pedal cable where it attaches to the throttle bodies, and can be adjusted. The bracket holding the adjustment arm was very loose, so tightened it. There was some slack on the cable, which I assume is normal. I took out the slack, but moved the throttle very, very little, so it now idles at around 900 rpm in Park.

Today I cleaned the #2 (left) throttle body, aired out IAVC and TPS connectors with compressed dry air (from spray can used for computers). I also cleaned the MAF sensor, just in case.

I'm now warming up the car completely to dry out all wires and connectors, in case any carb cleaner got into them (Note - I did NOT use any water while looking for leaks, to make sure connectors and wires were not subject to shorting out).

With throttle cable adjustment, car now drives fine, but I still want to find out what happened so I can release the tension from the cable and get it back to spec.

[shilferty]

NEW SYMPTOM: Drove to store 5 miles away. On way back, on highway, I put on the cruise control. Activating cruise caused gas pedal to jump down a little, 1/4 to 1/2 inch. That has never happened before. Repeated several times to make sure it was doing same thing consistently.

I assume that something in the system decided the throttle bodies needed to be opened more.

Although, I could I have gotten carb cleaner into the TPS while cleaning the Throttle Body, I just took it off and inspected it - clean and dry. I disconnected the TPS, Trac Off & Check Engine lights came on, acceleration was slow and would not shift into overdrive at 60 mph during test drive.

Reconnected TPS and reset Trac Off lights by pulling EFI Circuit Breaker for 30 sec.

Thoughts?

Steve

[shilferty]

:) It seems to be fixed. I sure hope so.

After putting TPS plug back and resetting Trac Off & Check Eng. lights, I test drove the car. Parking in garage, I pulled accelerator pedal out and idle did not drop below 600 rpm - before it would drop to 400 or below. I loosened the accelerator cable at the adjustment bracket on throttle plate assembly, and rpm stayed at 600 rpm. Test drove it, and rpm stayed about 600 rpm with A/C on, in Drive or Reverse. Test drove it without incident.

Two things that might have happened:

A. My drying out of connectors and wires actually worked.

B. The Engine Control Module has been slowly resetting the idle speed.

Although I have reset the EFI fuse several times, the idle stayed low until this last drive.

I'd still like to know what happened, but at least it is working.

Steve

[homemechanic]

do not use carb cleaner, soap or water on sensors and electronic parts. use electronic parts cleaner! it cleans and dries quickly.

by the way, did you put in new gaskets for the iavc and throttle body?

[shilferty]

Thanks for the reply and advice!

I did not use any new parts, although I obviously could (should) have used new gaskets. Doing it on a holiday weekend with wife taking other car to work, limited some of my options. The throttle body gasket seemed fine, although I ended up adding some gasket seal to it because I was afraid it had a vacuum leak. The IAVC seal to the throttle body is quite intricate and easily stretched out. I used a little threadlock liquid to hold it in place until it was screwed back into place. There are no vacuum leaks anyplace, so I assume everything was reassembled properly.

After driving quite a bit over the past two days, it seems to be driving close to perfect. The idle is now 500-600 rpm, while I think it used to be 700-800. That may may have been a bit high, but it was always very, very smooth. Using cruise control, there is still a bit of a jump in the gas pedal. Otherwise it is back to the beautiful Lexus drive, even at over 120,000 miles.

Based on my experience, I would not disassemble the IAVC to fix the low idle when warmed up, until I did some other things first. The symptoms started showing up first showed up two years ago, but other issues including replacing the O2 sensors kept me from concentrating on that issue - I assumed it was related to the other issues.

This year, the only problem I've had is the low idle when warm. Rather than worrying about stripping screws, losing o-rings, or messing up seals, I wish I had simply:

1. Removed the dual air hose from air filter to the throttle assembly.

2. Sprayed some carb cleaner/throttle plate cleaner into the hole in the bottom of the right Throttle Plate Assembly.

3. Reassembled and checked it out.

If necessary, I would do this 3-4 times and I think this would have fixed the problem for a year or more. Ten minutes of work, almost zero chance of problems. It would not completely clean the IAVC assembly, the only part that needs to be halfway clean is the rotating valve. Mine was very sticky and hard to turn. As long as the electrical control can rotate it easily, the rest of the IAVC should work fine.

Steve

[shilferty]

Final results: After a couple more days, my Lexus runs beautifully. Engine control module seems to have corrected everything. Idle is 600-650 rpm, no jump when activating cruise control, starts great warm or cold.

Thanks for all the help and all the previous posts for showing how to do this.

Steve