Cleaned MAF and 'idle up' valve - now high idle and reverse stall with AC on

[GreenLantern]

Background:


Before I cleaned the MAF and adjacent 'idle up' valve, my car idled at a perfect 650rpm while the car was stopped and in "D". In addition I didn't have any issues with the car wanting to stall out or idles dropping out while the A/C was on and car was reversing.


I checked all the lines, everything looks good. I'm basically idling about 90-100 rpms higher in drive now (roughly 730-760 rpms). Mileage is more or less the same. I used CRC MAF cleaner of course and don't know what could be causing this other than I fouled the MAF and/or idle up valve. I did the "disconnect battery" trick for an hour and even removed the EFI fuse. Both didn't do a darn thing.


Any pointers are much appreciated!


Lesson of the month: If it ain't broke, leave it be! I had no issues with idling or mpg performance, rather I just wanted to do more tinkering or preventative maintenance.

[maestro123]

No idea if it's related, but I've read a few threads on black flakes in the coolant causing high idle for Supercharged Previas. Here's an example:

http://www.toyotavantech.com/forum/s...t=black+flakes

[GreenLantern]

Thanks but I already have a coolant filter in place. No codes, no issues prior to the maf and idle up valve cleaning.

I have another coolant filter I plan to swap in as it's been a few years so it's quite possible something may be coincidental.

[cvtroger]

My friend's previa does the same thing and I can't figure it out as well.

It seems that her AC has a higher load demand and at idle, sometimes it shuts of the motor. When she first told me about it, it was after starting up her van (when it was cold) and if you put it into gear, the motor dies. But it is fine either when the van is warmed up or/and the ac is off.

[TheMAN]

I bet you it's the A/C idle up valve that's bad... you can't clean this without ruining it.... what you can clean and I bet you did clean was the IAC valve (idle air controller), which is attached to the throttle body
this is a common thing that goes bad in this era of toyota... I replaced mine and it's better already

[HotRodPrevia]

Hey folks, did the OP get the problem fixed with replacement MAF or IAC? I am curious because we have been having a similar problem.

[GreenLantern]

No, the problem never got fixed even after cleaning the MAF a few times as well as the IAC + TB once.

Sometimes the adage about "if it ain't broke, don't fix it" is a wise one to follow.

[GreenLantern]

I bet you it's the A/C idle up valve that's bad... you can't clean this without ruining it.... what you can clean and I bet you did clean was the IAC valve (idle air controller), which is attached to the throttle body
this is a common thing that goes bad in this era of toyota... I replaced mine and it's better already

Just saw your response. Yes I did clean this out with MAF cleaner when I cleaned the Mass air meter. Ouch, this part is betwen $165-$200 new! There's a guy on ebay selling them for $88 each but I don't like to take chances with used parts. Any plausible explanation why cleaning this idle up vacuum valve screws it up?

[cvtroger]

I took one apart awhile back. There is a thin rubber piece, possibly overtime that gets stiff and rips or even the cleaner might rip it.

I can't quite remember, but I will definitely try to find one this weekend because I'll be hunting previas.

[HotRodPrevia]

Green Lantern, so are you driving the van in this condition? Ours is parked now...The last few things well try is the bypassing the MAF, perhaps a test pipe to see if either cat is clogged...after that ?

[GreenLantern]

yes, I am driving the van with my condition. No real issues other than bogging and stalling when the A/C is engaged at a stop.

The OEM vacuum switching valve is part number 17650-76010 but costs over $160! Lots of OEM and aftermarket ones for other Toyotas for $30-$60 so I was wondering if these valves are more or less the same, just different mounting positions and tube connectors.

Does anyone know if they can be adapted to work?

[timsrv]

I usually grab these type parts from salvage yards (usually $5 - $20). It's just a simple vacuum switching valve. Some will allow flow when 12v is applied, others will prevent flow when 12v is applied. Then there are some that will do other things like switch between multiple vacuum lines and/or vent to atmosphere. Sometimes the more complicated ones are harder to find A/M. The one in your last picture however is just a simple on/off VSV. The only thing you need to know is whether it's N/O (normally open) or N/C (normally closed). Armed with that info you can purchase one from anywhere and make it work. You will likely not be able to mount the same and you will probably need to modify the electrical plug. When I get parts like this from salvage yards, I take a test battery in with me so I can test function. If I'm taking one that doesn't match the electrical plug, I'll cut the salvage yard vehicle's harness and take that too. Then it's just a matter of splicing that connection into the vehicle's harness. Tim