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Looks like 2.5 lb*ft:
You might want to pick up a copy of the 1996-2000 service manual, where that spec comes from. Well worth the money.
I do have a copy of the service manual and just saw it in there. Thanks. I’ve got the valve installed, but it there still seems to be a vacuum leak around the valve. Can’t really figure out what’s going on. I torqued it according to spec, but not sure what’s going on.
I’ve got the valve installed, but it there still seems to be a vacuum leak around the valve.
Why do you suspect a vacuum leak in that area?
I sprayed carb cleaner around it and found it to be leaking. I tightened it to spec, but with no luck. Still leaking around the valve. And it leaks around the sides of the valve. No problems with the top. So I am not sure what it is.
I tried the old gasket just to see what would happen. Still same problem. Vacuum leak around the valve. What am I doing wrong?
I sprayed carb cleaner around it and found it to be leaking
What happened after spraying it to convince you there was a leak there? Could you explain what you did in more detail?
For example, I’m familiar with hunting vacuum leaks by watching fuel trim while releasing propane. But it’s not clear what else you did to diagnose your vacuum leak other than spray carb cleaner.
I was thinking there was a vacuum leak because when I sprayed around the IACV, the engine dropped it’s rpm’s and almost died. I took some carb cleaner and I sprayed where the IACV mounts to the throttle body. I sprayed on top with no change in engine performance. Then I sprayed at the left and right of the IACV with significant changes. I sprayed what I could at the bottom (it’s difficult to get to) and didn’t notice any change. This is what lead me to believe that the seal is not sealing properly. This is my thinking, but if I am wrong, please educate me.
Just a little history. Surging idle from 1-2000 rpm’s. Checked for vacuum leaks and found none. Disconnected IACV valve with no changes in engine rpm. Tested resistance of IACV and was out of spec. Replaced IACV. Surging stopped and idle went to normal. Soon after noticed slight hesitation when down shifting which was periodic. Checked the OBD II with a scan tool and noticed a pending code for P0505. Drove around as normal without problems. Noticed at times idle would remain at 1000 rpm’s with no load (In park and neutral). Idle at normal 700 rpm’s under load (In drive). After sitting a while with no load one day, check engine light came on (P0505). Checked for vacuum leaks and found none except around IACV.
I took some carb cleaner and I sprayed where the IACV mounts to the throttle body. I sprayed on top with no change in engine performance. Then I sprayed at the left and right of the IACV with significant changes. I sprayed what I could at the bottom (it’s difficult to get to) and didn’t notice any change. This is what lead me to believe that the seal is not sealing properly.
To make sure I understand: you sprayed carb cleaner on top an bottom, with no change in engine rpm. But when you sprayed from the sides, you did see a change in rpm.
If so, did the rpm increase or decrease? How does what you’re seeing lead you conclude that a vacuum leak exists?
If you believe there is a vacuum leak, it should show up in your fuel trims as a rich condition that improves under load. What do your long and short term fuel trims read at idle and at ~2500 rpm?
A positive fuel trim reading (> ~10%) at idle that decreases under load would be consistent with a vacuum leak.
Correct. I sprayed carb cleaner at the top and bottom with no change in rpm. I sprayed the sides, I did see a change, particularly on the left side at the bottom. That’s the side where the iacv connector is. The rpm’s decreased. I also placed my finger over the lower port in the throttle body and noticed a decrease in rpm’s, but the car never died.
Will check fuel trims tomorrow and report back. Thanks for your help thus far.
I put everything back together with the new gasket. Here are the fuel trims after five minutes each:
Idle:
Short term = 7.8
Long term = 7.8at 2500 rpm:
Short term = -7 to -0.8
Long term = -4.7Car idles fine as usually. No check engine codes or pending codes. I have not driven it around the block yet. I sprayed lightly some more carb cleaner around the IACV valve and noticed very minimal engine change, if at all. Spraying heavier amounts of carb cleaner shows significant change in engine speed.
I think this confirms the vacuum leak. Now I just have to figure out what to do with the IACV. Should I tighten in beyond the 2.5 ft lbs? I’ve tried two different IACV valves from different parts stores with the same result. I even tried the old gasket with the same result. Somebody on the honda tech forum recommended using RTV sealant, but I am against this. There must be something I am doing wrong. Any advice is appreciated. Thanks.
The drop in fuel trim under load is consistent with a vacuum leak, but the effect seems small and maybe negligible. Did you by any chance get fuel trim reading before you replaced the gasket?
BTW, you’ll want to take these readings after the car has entered closed loop ( some scanners have that as a readout). Only then is the computer adjusting fuel trim based on O2 sensor.
If you suspect a vacuum leak, one thing to try is repeat the fuel trim measurement. But this time, when idling, release propane gas (no flame, just the gas from a small handheld tank) in the area you suspect the vacuum leak. You’ll know you found it because the fuel trim will drop as propane is sucked into the intake. Propane has the advantage over carb cleaner that it won’t degrade rubber and disperses quickly.
That said, the IACV lets air in when the throttle is closed, bypassing the intake. So I’m not sure what you’d learn by releasing propane around there. That may also be something to consider when spraying carb cleaner in the same general area.
Now I just have to figure out what to do with the IACV. Should I tighten in beyond the 2.5 ft lbs?
Are you still thinking that the surging idle is caused by a vacuum leak? Anyway, I can’t recommend over-torquing ever, especially if aluminum is involved.
Somebody on the honda tech forum recommended using RTV sealant, but I am against this.
The fsm says nothing about liquid gasket as far as I could tell. Prolly not a good idea.
I agree, the vacuum leak appears to be very minor and not making much of a difference at this time. Unfortunately I did not get fuel trim readings prior to replacing the gasket.
The fuel trim readings I obtained were during closed loop. I will take your advice and repeat the fuel trim measurements after I drive the car around town for a while. I actually thought about getting a small propane tank and doing this. It will confirm what I already know, but I can use it in the future for other things. Great idea.
The surging idle that I had prior to replacing the IACV was caused by what I believe was a stuck open IACV valve. I tested it with a volt meter and it failed the resistance check. Also, I applied power to it and it failed to activate. After taking it apart, I was able to give it power and make it work, but it seemed very weak. I replaced with a new one and the surging stopped.
I am definitely not using RTV sealant. I really don’t want to over torque the bolts. I am trying to figure out what options I have at this point. The vacuum leak is definitely not enough to cause any problems at this point, but I’d like to get it resolved. There must be something I am doing wrong, I just can’t figure it out.
I read on a subaru forum where the iacv was a pain to install because the gasket was hard to seat. Something about having to drive it around and the let the coolant heat the gasket up so it could seat properly, and then afterwards you could drive it at WOT. Not sure if that applies to honda’s though.
The surging idle that I had prior to replacing the IACV was caused by what I believe was a stuck open IACV valve. I tested it with a volt meter and it failed the resistance check.
It sounds like the surging idle is fixed then, no? If so, then does the car show any problems (other than a possible minor vacuum leak) at the moment?
Yes, the surging is fixed. No signs of problems thus far, but I haven’t had a chance to drive the car around yet. When I replaced the IACV the first time, the surging was fixed, but at certain times I would notice hesitation with acceleration and on occasion it would hesitate when down shifting. Then I noticed a pending code for a P0505, and then a while later, the check engine light came on during idle.
I will re-evaluate tomorrow and report any new findings.
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