Does your engine surge until warmed up? It's really annoying, and 9 times out of 10 I've found the FITV (Fast Idle Thermo Valve) to be the culprit. I had promised a few people on here a full write-up due this weekend, so without delay, here it is:
How-To Check and Fix Your Fast Idle Thermo Valve
First up is actually finding your Fast Idle Thermo Valve (which will be referred to as the FITV for the rest of this article). It is located directly on the bottom of the throttle body. The one pictured and outlined in red is from an SiR2 B16A. This is a top view of the engine bay.
Here is another picture of the location of the FITV, again outlined in red. This is more of a side view so that you can see the entire part. If you are still using a stock airbox and not a cold air intake, your view of the FITV may be partially blocked.
Now you will need to remove the intake (be it a cold air like mine, or the stock airbox). Just unscrew the hose clamps and pull it to the side, I didn't even remove mine completely. NOTE: If you will notice, I also removed my strut tower bar for easier access to everything and to allow the intake tube to be pushed aside.
On the inside of the throttle body, I have circled the FITV opening in red. Once the intake tube is out of the way, you will want to start the car. Let it warm up to operating temperature, then put your finger over this hole. If it still has suction once warmed up, then the FITV is the culprit of your idle problem and the idle will drop to normal while the hole is blocked.
Pictured below is the FITV still attached to the throttle body. The hoses circled in red allow coolant to flow through the body so the FITV will know if the engine is warmed up or not. The hose closest to the firewall (one on the left) is easy, use pliers to squeeze the clamp together and push it on down the hose a little. Then use your fingers or a flathead screwdriver to push the hose off. Some coolant will leak out at this point, its okay though. Just push the hose aside and try to keep it high up in the engine bay to prevent an excessive amount of coolant leak. The hose closest to the engine (one on the right) will be much easier to remove once the FITV has been removed, as the intake manifold makes it a hassle to push this hose off.
Now you will need to remove the three 10mm bolts that attach the FITV to the throttle body. These are located on the bottom side of the FITV. In the first picture below are what the three bolts look like, so you can be absolutely positive you arent removing the wrong part. In the second picture I have circled in red the locations of the three bolts on the underside of the valve. The two on the same side will be closest to you when standing on the passenger side of the car, while the one by itself will be closest to the intake manifold.
The blurry picture below is just what the FITV will look like once the three bolts are removed. Notice I left the hose running to the block connected until I unbolted the FITV as stated above. Now is the time to remove this hose.
Now that you have the FITV in your hand, you will want to remove the two screw nuts that hold the flat steel plate on one end of the valve. The wax carrier is located under the cast aluminum cap with the hose nipple...however we wont be removing it.
Pictured below are the screw nuts that must be removed. You can either use a socket or phillips head screwdriver. I suggest using a socket though, so as not to strip the screws.
Once the end plate has been removed you will see a white plastic screw-in ring inside the FITV, pictured below in the first picture with an arrow pointing to it. Sometimes these can become loose, or even completely backed out. This is whats causing our idle problem. The ring limits how far the piston inside the valve body can travel (shown in the second picture below outlined in red), which in turn limits how much air can bypass the throttle plate to allow the engine to idle higher until warmed up. Just use a flathead screwdriver to screw this bad body back in until snug. No need to tighten the hell out of it, because if you break it you'll have to get a whole new FITV from Honda. They say these are set from the factory and cannot be adjusted, basically that just means you can't buy internal parts for it. Just get this ring good and snug so it won't go anywhere.
And there you go kids. Just put the end plate back on and secure it with the two screw nuts. Then reinstall the FITV reverse of removal. Be sure to reconnect all the hoses and put the hose clamps back where they belong. I would leave the intake tube disconnected once you get the FITV bolted back in and the hoses reconnected though, start the engine and let it warm up to make sure the hole inside the throttle body doesn't have suction once the engine is warmed up.
Contributed by EE_Chris: "Since you may have introduced air into the coolant system, make sure to re-bleed the coolant once everything is back together. Air bubbles in the coolant can trick the ECT sensor which will cause a surging idle."
If everything is good and she purrrrrrs like a kitten once warm, shut the engine off and reconnect the intake tube and strut tower bar (if applicable).
If however you are still surging once all this work is completed, then the source of your idle problems lies someplace else. Most of the time on Honda engines, idle problems are caused by vaccum leaks, be it from a defective FITV, IAT sensor, poorly set idle adjustment screw, faulty TPS sensor, etc.
I hope this article has helped in some way, for further questions/comments leave them here or send a PM my way.
Since you may have introduced air into the coolant system, make sure to re-bleed the coolant once everything is back together. Air bubbles in the coolant can trick the ECT sensor which will cause a surging idle.
Re: surging problem with JDM swap (please help...)
(sorry for offshooting topics. My noob options are limited.)
I put a 97 JDM LS swap into my 95 integra with a p75 ecu, and on start-up, the engine instantly idles to about 3.5k, and after a minute starts pouring out white smoke. For some reason, the JDM TB doesn't have a FITV, just a straight connecting pipe between the 2 coolant lines. The TB port circled in your photos leads to my IAC solenoid, which BTW remains open at all times. If I disconnect the IAC electrical connector or seal off the port, the engine idles at 2k (smoothly at first, and then roughly after a minute) and also eventually barrels out white smoke. Any ideas?
Thanks in advance,
(I've already pressure tested and milled the head, and replaced the IM. Solid compression across all 4 cylinders, IAT sensor and IAC solenoid sensor also test fine. Only thing left untested is the ECU and the TB+TPS/MAP. No codes.)
1990 Acura Inetgra LS (OBD0 for now)
wiseco 81mm 9.1 pistons, eagle rods
ARP bolts throughout
Omni race valves, super-tech dual springs/tit. ret., gsr cams
AEM cai, RS-R exhaust,
some other little things here and there
You could always just bypass the FITV, and block it off.
Than connect those coolant lines..
Any idea how to unbypass it. I can't find where the coolant lines are supposed to come from. I think it is the cause of my idle problem. The people who did the swap bypassed it and it has never idled since i got it.
ok so i guess im retarded because i couldnt locate the FITV, although a while back i took the IACV off and douched the **** out of it with carb cleaner and also cleaned out the harness with contact cleaner. it ran like a brand new swiss watch, then the next morning went back to its regular bull ****. i read on another board that the idle surging can be due to an exhaust leak. i do in fact have a leak in the flex pipe, and the flange between the header and collector. but to say that it is fixed after cleaning the IACV means something to me, maybe a bad IACV or maybe bad wiring.
94 Prelude Si
looking for winter car to start the buil [img]http://images.honda-tech.com/set1/smile/emwink.gif[/img]
you dont actually have to take off the FITV to get to the white plastic screw.. i spent a long time trying to remove the 3rd bolt on the FITV underside and so i gave up on that method.. you can access the flat plate quite easily by pushing aside a few hoses.. as mentioned above, use a 9mm socket instead of a phillips head to take off the bolts
Thank you for fixing my '90 accord after about two years of this problem getting progressively worse. Thanks to this fix my car is running perfectly now and luckily I don't do much stop and go driving so this problem didn't wear down my engine too much. Does the original poster have a paypal account?
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