Civic Forumz - Honda Civic Forum - DIY: EG Intake Manifold Swap

I had posted something of this nature for the VX owners out there as a low-buck solution for helping that 1.5L of VTEC-E Fueled Japanese Fury breathe more like a track star and less like a trombone player with emphasema. I'll lay it all out for you VX owners out there step by step. My camera is toast right now though, so the pics aren't going to make it up, sorry folks. Ok, on to the good stuff.

Parts you'll need:

-1992-95 DX intake manifold (I pulled mine off my totaled DX in the junkyard, an LX/CX/Si should all work too)
-1992-95 LX throttlebody (Look for the MAP sensor on top of the throttle body, that's the one you want)
-1992-95 DX intake manifold brace (just pull it with the intake manifold)
-The rubber hose that runs from the airbox to the initake manifold is larger on non-VX models, so you'll need that too.
-New throttlebody gasket
-New intake manifold gasket
-Coolant and distilled water
-1 M10 (10mm) bolt
-Plastic fittings (Canadian Tire)

Tools you'll need:
-Basic hand tools, spanners, ratchets
-Gasket scraper/drywall spackle tool
-Breaker bar is nice.
-Rags
-Drain pan
-Masking tape
-Marker
-Elastics
-Cling Wrap
-Zip Ties
-Drill & Metal bits

STEP 1: Pulling the old manifold

-Drain the coolant via the plug in the bottom of the rad

-Unhook and unbolt the throttle cable from the throttle body

-Using pliers, loosen all the spring clamps holding coolant and vacuum lines to the intake manifold as you pull them off, take some masking tape and the marker and label both the plug on the manifold and the corresponding hose

-Relieve the fuel pressure via the bleed screw on the fuel filter

-Unbolt the fuel rail, and remove the fuel feed line at the banjo bolt on the fuel filter, replace the banjo and cover both the bolt on the filter and the fuel line banjo with cellophane and an elastic to protect them from dust grime etc.

-Slowly and evenly remove the injectors from the intake manifold, leaving them seated in the rail. The injectors are held in via the clamping force of the rail being bolted to the manifold, so they wil fall out if you're not careful. Cover each injector in cling wrap and an elastic to keep it safe and zip tie the rail assembly up and out of the way to the driver's left of the engine bay by the brake booster.

-Unplug the TPS, MAP Sensor, IAC, and any other electrical

-Unplug the EGR valve, and remove the PCV valve at the block

-Remove the nuts that hold the manifold to the cylinder head. And work some body origami and reach down between the manifold and the firewall to reach the bolts that hold the manifold brace to the block. There is an extra bit of bracing here that you can throw out. It's used to hold up the stock mid-pipe. I'm assuming that if you're going this far, you've got some headers.

-Make sure that everything is disconnected and slowly pull out the manifold as not to damage anything.

STEP 2: Prepping the new manifold

-Make sure you thoroughly clean all of the gasket surfaces on the manifold and the block.

-Using the old manifold as a guide, mark all of your vacuum lines and coolant lines on the new one so that when it goes in there's no guesswork.

NOTE: There will be one vacuum line that has no home on the new manifold. You'll have to drill a small hole and put a fitting in the hole for that line. GO SLOW, it's a cast piece, so very liable to crack, just take your time and keep the bit speed up.

-Clean the gasket surface of the throttle body and using a new gasket install it on the manifold. The new throttle body will have a Fast Idle Air Valve (FIAV) on the bottom, not the bypass that the stock vx one does. We'll keep that in mind for later.

STEP 3: Installing the new manifold

-Hang the new manifold gasket from the studs on the block. (PS, if you broke a stud/lost a bolt, I believe that they are M8x1.25 hardware. If you broke the stud, turn it out with some vise grips and just replace it with a bolt)

-Wrestle the new manifold into place, and start by bolting down the brace to the block in the back, use the beefier brace with the DX manifold, as it will suppor the increased weight.

-Starting in the middle, bolt down the manifold and torque the nuts to spec, work evenly in both directions.

-Connect all your vacuum lines

-Connect your throttle, and have a buddy help you make sure you have wide-open.

-Plug in all your electrical, excepting the EGR valve. Because well...you no longer have one. Yes, your emissions will suffer, and yes your exhaust temps will be higher, again, I assume you have some headers. Now this should throw code 12, but so far, over a month post swap with both around town and serious highway kms, no code...go figure.

-CAREFULLY, replace the injectors, refasten the fuel rail and replace the banjo and banjo bolt on the fuel filter.

-Push the PCV valve back in

-Now, the FIAV. The DX manifold has the side mounted IAC as well, so the return from that will meet up with the VX coolant return line. There is also a coolant feed line that comes off the block that will work to feed the new FIAV. The coolant exit for the FIAV is the feed for the IAC, so no problems there. But you will have one coolant feed line, that should go into the paired valve cover breather and coolant line to the driver's right of the valve cover.

Block that line by cutting the rubber hose 2-2.5" above where it exits the manifold. Jam that M10 bolt you bought in there, right up to the head if possible, but at least until where the shank meets the threads. I cut mine down to 2 threads above the shank so I could bury the mother. Use a spring clamp or some $2.99 Canadian Tire fuel line clamps to make sure it doesn't leak and zip tie it to something rubber so it won't rattle, get caught in your throttle linkage, or wear throgh anything else metal.

STEP 4: Finishing up

-Refill with 50/50 coolant or a water wetter mix, but MAKE SURE to use distilled water, not tap. Tap water is full of minerals and ions that can damage the internal water passages of your engine as well as your water pump. Spend the couple dollars and do it right.

-Set your idle. I think for the VX it's 750 +/- 50 or somewhat, double check a manual to make sure.

-Check for leaks. The sources could be gaskets, coolant lines etc. Keep an eye out and roll with a small can of mixed coolant for the first few weeks until it really settles in. I had to replace one clamp on the FIAV because it had a slow leak. Other than that no problems.

-Fasten the new airbox tube, use a gear clap to hold it fast to the manifold and the stock spring clamp is fine for the airbox.

That's pretty much the rundown. It took me about 2 hrs to do the swap in my driveway by myself. I would rate the difficulty at about a 7 out of 10, just because of all the integrated systems involved and if you break something like an injector or sensor it can get pretty expensive. Just make sure you have EVERYTHING with you when you start so you're not stranded half way. Best of luck.

If you have any questions, just PM or post. My internet is a bit dodgy so it may be a while before i get back to you, but I'll do my best.