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Ronnie Helmo · **Posted:** Sat Mar 20, 2010 9:34 pm

Thank you guys. I will do exactly that tomorrow. Where is the FCV? And how do I unplug it? Thanks fellas.

RJM · **Posted:** Sat Mar 20, 2010 9:46 pm

Follow the battery side boost hose down to the engine, brings you right to the FCV. Unplug it there.

geordi · **Posted:** Sat Mar 20, 2010 9:51 pm

Just to confirm this for you: From the front of the vehicle, the drivers-side hose leading from the intercooler to the engine (which drops down, crosses under the battery tray, and then comes back up to connect to the engine) the FIRST part that it connects to is the FCV. The plug is easily accessible. Squeeze and remove.

CRD Joe · **Posted:** Sat Mar 20, 2010 10:26 pm

What is this and why are you unplugging it?

geordi · **Posted:** Sat Mar 20, 2010 10:59 pm

CRD Joe wrote:

What is this and why are you unplugging it?

http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=51190

That is why he is unplugging it, for some reason he started a new thread - this one.

The Flow Control Valve (FCV) is a butterfly valve in the end of the intake stream just before the engine that closes off when the computer commands it to. There are two times the computer might command the intake to be choked off, which is generally not needed for any diesel. The first is when the engine is shut down. Supposedly, closing the FCV at the moment of shutdown stops the engine from doing some "harshness" that I have never felt. My diesel Jetta had a similar device, and oddly enough, it also was located just before the EGR entry into the intake air. When I removed both the EGR and the FCV from my Jetta, I noticed no harsh shutdowns at all. Ditto for the CRD, it shuts off when I tell it to... The engine just stops.

The second reason that the computer would command the FCV to close is the one that I believe is the "real" reason it exists: By choking off the incoming air supply (that the engine's cylinders are demanding at a constant velocity and volume) while the EGR valve is open... The FCV closure forces more of the filthy non-burnable exhaust gas to replace the burnable oxygen supply. This has some supposed "benefit" to the engine or the environment by minutely reducing a non-polluting gas (80 % of our air is nitrogen anyway) that might have possibly contributed to acid rain formation 30 years ago when the fuel had 10 times the sulfur in it that it does today.

Our diesels, with the use of biodiesel or even just ULSD (all we can really get these days) are basically incapable of contributing in any meaningful way to anything that might create acid rain. Of course, acid rain hasn't occurred in decades in the environment... Or the grannies at CARB would be shouting it from the rooftops.

Short story: You can safely unplug and disable that stupid FCV without doing ANYTHING detrimental to your CRD. If you do not have an SEGR device, there is a small chance that the CEL may be illuminated someday when the computer figures out that it isn't changing the airflow anymore. I have both an SEGR and a tune from GDE. Both remove the EGR from operation for the protection of your engine.

I think we can all agree, the replacement of 4500 lbs of steel, aluminum, rubber, and plastic (a new car) b/c the engine was destroyed by soot contamination is far worse than the tiny increase in nitrogen output by killing the EGR.

CRD Joe · **Posted:** Sat Mar 20, 2010 11:16 pm

Im going to get a GDE Hot tune. I wonder how they deal with this in their tunes.

Sir Sam · **Posted:** Sat Mar 20, 2010 11:17 pm

Unplugging the FCV WILL result in a CEL.

CRD Joe · **Posted:** Sat Mar 20, 2010 11:23 pm

I already have that with my MAF unplugged.

kdlewis1975 · **Posted:** Sun Mar 21, 2010 12:16 am

The gears are apparently stripped in mine and it doesn't work anymore. The shutdowns are noticeably harsh. I have an engine mount that's either loose or toast. So, it does provide a useful function. Unfortunately, it helps the EGR too. Either a tune or SEGR is needed to keep the FCV's function while knocking out the EGR.

Sir Sam · **Posted:** Sun Mar 21, 2010 12:25 am

CRD Joe wrote:

I already have that with my MAF unplugged.

I was just pointing out per Mr Laforge's post that unplugging the FCV will definitely cause a CEL.

geordi · **Posted:** Sun Mar 21, 2010 12:37 am

Sir Sam wrote:

CRD Joe wrote:

I already have that with my MAF unplugged.

I was just pointing out per Mr Laforge's post that unplugging the FCV will definitely cause a CEL.

Then why don't I have one? The light isn't burnt out, and while I have an SEGR and the GDE tune, I don't think that the SEGR did anything to the programming or sensing for the FCV. And like I said, I've had mine unplugged for months now. I originally unhooked it as part of the diagnostics trying to chase down my intermittent power loss issue, I've just never plugged it back in.

Literally, I have seen or felt ZERO difference from having it connected or not.

I guess, YMMV.

kdlewis1975 · **Posted:** Sun Mar 21, 2010 1:26 am

geordi wrote:

Sir Sam wrote:

CRD Joe wrote:

I already have that with my MAF unplugged.

I was just pointing out per Mr Laforge's post that unplugging the FCV will definitely cause a CEL.

Then why don't I have one? The light isn't burnt out, and while I have an SEGR and the GDE tune, I don't think that the SEGR did anything to the programming or sensing for the FCV. And like I said, I've had mine unplugged for months now. I originally unhooked it as part of the diagnostics trying to chase down my intermittent power loss issue, I've just never plugged it back in.

Literally, I have seen or felt ZERO difference from having it connected or not.

I guess, YMMV.

...FCV never worked right in the first place? It's just odd that operability or inoperability made a difference in your case.

Because the circuit Turbo Tim designed for the SEGR tells the computer that the EGR is opening as it asks when it in fact isn't, the FCV has no reason to actuate when the engine is running. The SEGR circuit is supposed to allow the valve to shut during stutdown when the transmission is in nutrual or park.

RJM · **Posted:** Sun Mar 21, 2010 11:05 am

Sir Sam wrote:

Unplugging the FCV WILL result in a CEL.

X2

Goglio704 · **Posted:** Sun Mar 21, 2010 11:40 am

x3 on the CEL being set with the FCV unplugged - at least in stock configuration. The shudder at shutdown is also noticeable, but not objectionable. If you don't notice a difference at shutdown with it unplugged, it must be stuck.

Sir Sam · **Posted:** Sun Mar 21, 2010 2:45 pm

Goglio704 wrote:

The shudder at shutdown is also noticeable, but not objectionable. If you don't notice a difference at shutdown with it unplugged, it must be stuck.

x2

Ronnie Helmo · **Posted:** Mon Mar 22, 2010 8:05 am

All,

That fixed it. Well, the valve is not making any noise now but I do have a CEL. Would anyone happen to know the approximate cost of a FCV? Any online suppliers? Thanks in advance.

europachris · **Posted:** Mon Mar 22, 2010 8:16 am

Ronnie Helmo wrote:

All,

That fixed it. Well, the valve is not making any noise now but I do have a CEL. Would anyone happen to know the approximate cost of a FCV? Any online suppliers? Thanks in advance.

I bought one for $319 this past August from ebay seller g-ordus. Pickin's were pretty slim for FCVs at the time, that was about the best price I found.

Chris

RJM · **Posted:** Mon Mar 22, 2010 8:49 am

Shop around online, they range anywhere from $260 to $400+ It won't hurt to run it short term without, but IMO the rough shutdown may bugger your motor mounts.

RJM · **Posted:** Mon Mar 22, 2010 9:13 am

geordi wrote:

Sir Sam wrote:

CRD Joe wrote:

I already have that with my MAF unplugged.

I was just pointing out per Mr Laforge's post that unplugging the FCV will definitely cause a CEL.

Then why don't I have one? The light isn't burnt out, and while I have an SEGR and the GDE tune, I don't think that the SEGR did anything to the programming or sensing for the FCV. And like I said, I've had mine unplugged for months now. I originally unhooked it as part of the diagnostics trying to chase down my intermittent power loss issue, I've just never plugged it back in.

Literally, I have seen or felt ZERO difference from having it connected or not.

I guess, YMMV.

Something ain't right there, I would tear into it and take a look. Are you getting crappy mileage?

Sir Sam · **Posted:** Mon Mar 22, 2010 12:27 pm

RJM wrote:

Shop around online, they range anywhere from $260 to $400+ It won't hurt to run it short term without, but IMO the rough shutdown may bugger your motor mounts.

For the record the 02-04 did not have an FCV, and I don't see any of those people screaming about motor mounts.

FCV

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