'93 V6 has a jumpy idle...sometimes

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I just recently picked up a '93 Camry 3VZ-FE Auto with a blown Head Gasket for $500. Replaced the gaskets, milled the heads, and replaced the plugs.

I also advanced the Timing to ~15*BTDC, and turned the gear in the MAF lean about 6-7 clicks. When the car is warmed up and I come to a stop, the idle jumps -50/100 rpm and the whole car shakes when it happens. I thought it was originally from advancing the timing too much and turning the cog in the MAF, so I set it all back to stock (I marked the original position of the cog, set timing to 10*BTDC.

It still did it, although it was MUCH better than before. I decided to run some seafoam through the intake. I got Seafoam Spray and sprayed it through the TB, let it sit for 10 min, idled it for another 10. Then, I used the regular Seafoam Liquid through the Brake Booster vacuum line. Let it sit for 10, idled for another 10. Idle is much smoother now, but it still jumps about 25-50 RPM.

Again, this is only when it's warm. All of the vacuum lines by the TB are routed correctly. I was thinking it was the IACV that was making the idle jumpy, but wouldn't that have gotten cleaned when I ran all of the Seafoam through the TB/Intake? Where exactly is the IACV on the 3VZ-FE? And more importantly, would that cause this issue? Keep in mind, the car runs GREAT when it's not idling, and the jumpy idle happens about 50% of the time I come to a stop. Otherwise, it's smooth as butter.

[Jason.MZW20]

The 3VZ-FE uses a stepper type ISCV. Basically, there are 4 solenoids that open the ISCV in steps. The ECU can combine them to provide a wide range of adjustment. IMO, this is one of the downsides of the 3VZ as the rotary ISC is a simpler design with less to go wrong.

The ISCV is mounted on the throttle body on the underside of the TB. One of the solenoids may have failed and the ECU is using others to make up for it, or it's gunked up and the ECU uses more adjustments to keep the idle somewhat stable.

You'll have to remove the throttle body and inspect the ISCV.

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Bump...

I removed the ISCV, took it apart and cleaned all of the carbon off. It STILL has a jumpy idle. The thing is, it hardly, if ever, does it when im in drive idling at a light. It only seems to happen in neutral and park.

I also replaced the PCV Valve, and ran more intake cleaner through the passenger side vacuum hose runnong to the brake booster coming off the Intake Plenum.

Im at a loss right now. Timing is at 17* BTDC. I may try to hook up our Mac Mentor scan tool tomorrow at work and see what happens

[BMR]

ISCV???... is that the same thing as the IAC? NM, I googled it up and yes, it is.... right?

That's weird. My Camry had the exact same idling problem, even the part where idle RPM wouldn't "hunt" in neutral, but would in gear. It would also stall ocassionally when coming to a stop in gear. Removing, disassembling, and cleaning the IAC til it was squeaky clean totally fixed it. Oh, and my timing is at +15 degrees and MAF is 2 clicks lean. It was at 4 clicks, but I recently put new O2 sensors in both banks, and it seems to run better at 2 clicks instead of 4 now.

[Jason.MZW20]

Well you may have to swap out the ISC. You'll probably have to get the entire throttle body from a junkyard (via car-part.com) if you don't have any close to you.

I use ISCV for the 3VZ because Toyota refers to the ACIS system as IACV (Intake Air Control Valve, not Idle Air Control Valve) in the repair manual. Gets confusing.

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I pulled a whole IM/Plenum/TB assembly from a '94 V6 at a local junk yard. Gonna take it all apart, clean it, maybe polish it. Also pulled a pair of valve covers. Gonna replace all of the hoses and vacuum lines when I remove the current setup and replace with this.

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Well, I figured out the problem.

I replaced the ISCV and the ACIS plate, and I still experienced the same thing.

I was stumped, looking for vacuum leaks or something. Turns out my I/M Plenum bolts were LOOSE. I could turn them by hand and take them out. I tightened them up and BOOM, smooth as butter idle. I feel so stupid lol. The night I finished my head gasket job, I had been working on it for 6 hours already, and it was past midnight. I think I just was rushing myself and forgot to torque them down.

Oh well. Now I have a spare upper/lower I/M, fuel rail, injectors, throttle body and valve covers. Deciding on what to do with them. They're already getting hot tanked right now so I just need to decide what color I want them!