I just replaced the EGR VSV on my 1997 Camry 4-cyl by going in from the top. Took me three days -- somewhat like Ahab's combat with the White Whale, although fortunately, I did not get dragged off to my doom tangled in vacuum hoses and wire harnesses. I think I know enough now that I could probably do another one in 2 hrs.
Before you start this project, get yourself a flexible-shaft magnetic pickup tool. I come from multi-ethnic origins, and there is a family story about some friend's kids being prompted "Say something in German" to my grandma, to which one child replied with the worst Serbian curse word. "Where did you hear such a thing!" "Oh, Daddy says that all the time when he is fixing the car and drops the wrench." You are going to drop wrench sockets, the VSV bolt, etc into the engine compartment, and there are two places to sweep to get them back -- in this pocket formed by an engine mount bracket right under the middle of the intake manifold, and also on the crevice on the front side of the steering rack. I payed 10 dollars for this tool at a well-equiped hardware store. You have that tool at hand, so you don't have to say any "German" words.
The other thing to do is park the car with the steering wheel turned left so you can lie down on the ground and peer in through the passenger wheel well to get an idea of the location of the valve. I did a lot of looking, wearing one of those LED headlamps, squinting past the various brake and power steering hoses in the way, but I didn't bother with lifting the car and the jack stands required if you do that. But it helps to identify some landmarks because the rest of this is done by feel.
The next step is to remove the bolt holding the VSV to the firewall side of the cylinder head. Others have recommended removing the electric connector first, but you are going to get bruised and scraped attempting this, and you will give up in frustration. The release tab (on the passenger side of the connector when the VSV is bolted down) requires goodly amounts of pressure, and separating the connector requires a firm pull, and you simply can't get your hand in there to do this, at least not without going in from the bottom with the car up on jack stands and the passenger-side front wheel removed.
I ended up using six inches of extension on an ordinary socket ratchet with the specified 12 mm socket. After dropping and losing and recovering stuff a bunch of times, I ended up using electric tape to hold the extension and the socket together -- perhaps higher quality tools snap together more firmly and don't have this problem. Getting the wrench, extension, and socket in position underneath the intake manifold is not too difficult -- the challenging part is locating the bolt completely blind and doing it entirely by feel -- if you don't have a helper peering in through the wheel well, do some more looking down there to get "the lay of the land."
Where you are aiming for is a spot along the cylinder head in the gap between the paired intake runners. There is a bolt you can see that attaches the valve train cover or such thing to the cylinder head, and below that is a triangular indentation in the aluminum head that you can probe with your extension, and right below that is a kind of ledge of aluminum that has a round island of aluminum into which is fastened the mounting bolt. Again, peer in through the wheel well with a good headlamp or flashlight to get a picture in your mind, and recreate that picture by probing with the wrench extension when working topside.
I ended up rounding the bolt with a 12-point socket because I got confused and set the ratchet for tightening. My poppa once scolded my for not knowing the right-hand rule for tightening and removing screws and bolts, but these days I rely on "righty-tighty lefty-loosy" that I learned on the TV "Millionaire" quiz show, but you have to set the ratchet before diving into the engine compartment not to get turned around. I found a 6-point socket but with only a 1/4" drive in my motley collection of tools, but after having strained to tighten and rounded the bolt, the loosening was a pleasant surprise that happened without much trouble. Maybe that bolt is tapered to "cam out" on overtightening so you don't strip the threads in that aluminum.
Of course I promptly dropped the bolt into that pocket formed by an engine mount bracket and the engine block, hence the magnetic retrieval tool -- I put a bend in the stiffening wire of the tool and dipped the errant bolt out from the wheel well.
Upon removing the mounting bolt, you can reach in from topside and maneuver the VSV to where you see it -- I was able to get two hands on it to remove that stiff electrical connector, and I removed the two vacuum hoses -- one took some plier persuasion to twist off. The vacuum modulator has three hoses topside -- two to the thottle body, the third one I blew into to find which vacuum connection at the VSV is modulator. I also blew into the vacuum hose pulled from the EGR valve proper to identify the second hose connection to the VSV that is the EGR valve.
Having the VSV removed, you can get at the terminals easily with alligator clips, and I used a 12 V DC HO-scale model train power pack to test the valve. It tested OK, but interestingly enough, I had to blow hard in the modulator hose to get it going when checking vacuum connections, so maybe there was some blockage there.
The vacuum "logic" of the VSV is that deenergized, that is with no juice applied, there is a vacuum connection from the modulator straight through to the EGR valve. It seems that the "default" operation of the VSV is to allow the modulator to operate the EGR valve. When you apply 12 V, there is a click. Now there is a "dump vacuum to vent" connection between EGR and this little air filter thingy on the VSV, and the vacuum connection to the modulator is blocked. This energizing the VSV dumps or vents the EGR valve vacuum to prevent the modulator from causing EGR to happen, and the modulator line is blocked to prevent a vacuum leak in the system.
When you put the new VSV in, you are going to have to get the hoses straight -- putting the VSV hoses in reversed will not operate the correct way. It is easy enough to test which hose is modulator and which is EGR valve by blowing on the tubes and feeling where air comes out. Also, the modulator is connected to the "passenger side" or "connnector side" of the VSV, and it has the longer vacuum hose that has been bent into a kind of shepherd's crook, and the shorter vacuum hose is the EGR valve connection to the connection on the driver's or little airfilter thingy side of the valve. The open hood has an EPA Emission Control decal showing the vacuum hose routing, and there is a kind of cartoon of the valve that shows enough detail to confirm these connection.
The other strange thing is that I thought, well, the VSV works, and if it fails, it is because there is some crud in it causing an intermittent condition. I squirted spray can carb cleaner in it, and then the valve failed -- the solenoid would buzz instead of click, and the inside spool was stuck in a position where all ports were blocked, hence the P0401 Insufficient EGR code. Before someone takes me to the wood shed for putting carb cleaner in something that gets wrecked with carb cleaner, the next day, the valve started working again. I am thinking that maybe the way this valve fails is that insulation or plastic gets baked from engine heat to coat the spool inside the valve, and that the failure in intermittent is that it takes heat (or solvent) to liquify that coating to make it sticky to get the valve to fail.
Getting the new valve installed is an even better opportunity for German practice than taking it off. It is easy enough to put the vacuum hoses the right way from what I have outlined, and you may as well click the electric connector in place while you have the valve angled to where you can see it. I routed the modulator vacuum hose over the electric line. I suppose you could just leave the valve hanging there, but once the vacuum connections have been removed, they tend not to stay on when you put them back on, or at least until vacuum and engine heat bakes those connections on. There was a suggestion to use an alternate bolt hole on the intake manifold to remount the VSV, but I didn't see anything on my 97 Camry that was within range of the short leash of the electrical connector.
Next, all of one evening and an hour and a half of the next morning were spent on the quest to get the bolt through the mounting bracket and screwed into the proper bolt hole.
What finally worked was to use electrical tape to not only tape my socket to my wrench extension, but also to get the bolt held firmly to the socket. There may be magnetic sockets to do this, but I used electric tape. You also have to get the bolt taped straight into the wrench socket or you are going to have trouble getting the bolt threads started into the bolt hole. Make sure the electric tape holds the bolt firmly or you are going to say things Grandma doesn't want to hear from a young man. Once you get the threads to take in the bolt hole, you can angle off the wrench extension to leave the bolt behind in its thread hole without getting electric tape stuck to the bolt.
Here was my five hours worth of work question -- we are back to Herman Meilville's whaling analogy of maniacal persistence. How to you 1) position the VSV, 2) get the bolt threaded through the bracket hole, and 3) get the bolt thread started in the mounting bolt hole.
What I finally came up with was that you get the VSV in some semblance of the final position by looking through the wheel well to see where you are and then going topside to jockey the VSV into position. As mentioned earlier in this thread, there are constraints on four sides, and you have to maneuver the VSV with two attached vacuum lines and one electric cable, and the VSV is bulky, with the mounting bracket sticking one way and that air filter thingy sticking another way, wanting to get hung up on the wrong side of a flange on that engine mount bracket that catches your dropped bolts and sockets.
I started with the taped up socket extension, socket, and bolt without attaching the ratchet -- once you get the bolt through the bracket and threaded into the cylinder head, coming back with the ratchet attached is easy. I also practiced with this rig and without attempting to thread the bracket, in the blind and completely by feel, locate the bolt hole and thread the bolt into it. If you have the bolt taped the least bit off center, this will frustrate catching the threads, and you have to know this now before even attempting to thread the bracket. This exercise will also get you a feel and also a topside look through the gap between the intake runners of where the bolt hole is located. When you feel around for it, it is on an island -- you have to feel for the bolt hole in that island, and you have to feel for the exact angle that gets the threads to grab.
Once you have this feel for putting the bolt in blind, you are ready to thread the mounting bracket and thread the attaching bolt hole. And you can jockey the VSV to where you can sort of see the mounting bracket in that gap between the intake runners, but in moving the VSV around, be sure you don't pull off one or the other vacuum hose -- they tend to slip off at this point and you are back to having Grandma want to wash your mouth out. With the bracket hole threaded, and with your training on how to locate the cylinder head bolt hole blind, you are ready to probe for that bolt hole, capture the threads, and now you can breathe a sigh of relief before getting the ratchet out and tightening the bolt. Do one final visual inspection from down below that the two vacuum hoses are in place. I had also threaded the passenger-side modulator hose over instead of under the electrical cable as having less interference, but your mileage may vary.
As a final test, I went topside and blew air through the EGR line and verified that air came out the modulator line, verifying that the hoses were connected and that the valve was in its deenergized pass-through condition.
Were I do this again, I might go the the hardware store that sold me the magnetic pickup tool to look over their assortment of inspection mirrors in a variety of sizes -- if I could get a view topside of where I was sticking the bolt, finding the bolt hole could be done without all of that probing and checking from below. Following what I have described, it is possible to change the VSV without jackstands or without scraping and bruising your hands and arms.
op2:
