Civic VX EGR ports / Passages cleaning
 

Hello all. I’ve been experiencing some issues with my 1995 Civic VX (California). Buckle up because I’m about to throw as much detailed info as I can about it...
I’ve had the car for about a year and had about a 75% chance of getting a code 12 CEL the moment my car warmed up to normal operating temperature. I had a dinky little Haynes and it wasn’t too much help with the EGR. I cleaned it out with no change but it didn’t seem to affect too much so I never paid much attention. Funny thing is if I turned off the car and turned it right back on the code wouldn’t pop anymore. I’ve got the stock D15Z1 engine with everything else stock (minus the down pipe and missing all the resonator boxes just before the air cleaner box)
Anyways here’s some background.. I’m moving to Arizona soon so I went through the California to federal conversion stuff (read that gem right here: can’t show links because I haven’t posted enough. Will post later.) I got my hands on an eBay bidded Canada ECU (P07-C00) for less than $50 which to my researched understanding is essentially the same as the American Federal one. I also built up the harness as exactly done in the attached forum. Lastly I got myself a brand new NGK/NTK 5 wire O2 sensor.
After finishing up I took it for a test drive and all worked well.
However, the next day I went to drive across town and as soon as my car hit that normal operating temperature I started getting some considerable bogging when I’d try to accelerate after coasting for a short time. I no longer get a CEL, but ONLY once it’s warm and after I coast at any speed in any gear for a second or two I will hit that bogging as I try to maintain that speed or slowly accelerate. If I push down harder I will break through that bogging and suddenly surge. Additionally, if I wait long enough I’ll surge just a bit as if there was no issue.
So, I did some research and got my hands on a shop service manual. I started following the trouble shooting tree but my multimeter is toast so I ordered a new one... then I stumbled on various forums with people talking about the same issue. Soooo I jumped into taking off the intake manifold to clean out the EGR ports. However I can’t find any detailed forums that go into exactly how they did the whole process. I also got lucky and found a great condition CVC valve and EGR control solenoid in a 92 VX at a junkyard so I’ll be trying those out. I’ve followed the troubleshooting steps for the code 12 in the service manual since I feel they are most likely connected.

ANYWAYS what I’m asking is 2 things. Has anyone come across a detailed forum or “how to” for drilling and plugging the intake manifold for Civic VXs? My intake manifold was severely dirty so I’m thinking that this could be the issue. But since I’m fully into it has anyone seen and fixed issues like this? I should have played around more with unplugging the EGR and the O2 sensor.. but I didn’t. Any chance it could be that ECU?
Thanks for the help!

Update
 

So... I’m going through and cleaning all that I could on the air intake. I got my hands on another VX intake that looked significantly cleaner than mine did. I’m going through and cleaning off all the gasket gunk as well as all the stuff that’s been hiding underneath the intake I couldn’t get to before.
I have another question: I’m assuming there’s a certain degree of shuddering from the lean burn right? What is a “normal” amount for the VX? I’d say mine is excessive but I’ve also never driven any other VX besides mine.

I've never owned a lean burn vehicle. But all the guys on here and elsewhere that have talked about how you can often feel when the car goes into lean burn. So I don't think it's odd that you feel it. But I suspect that what you're describing is maybe an excessive feel. I think that, given that your code 12 was for the EGR system and that it is not recurring since you clean the EGR, you must have solved that problem. But perhaps you had two problems confounded together. So you're left with this second issue for which you're not getting a code.

Some parts of your posts I cannot understand. Are you saying that you're still using the California ECU even though you've otherwise converted to a 49-state lean burn system? If so, I have to imagine that would be your problem right there.

If you have not cleaned out the EGR ports as thoroughly as you could have, or if you have some kind of intermittent failure with the solenoid or other parts of the system then that seems like a reasonable suspect.

At any rate, you should search carefully on this website using the search function in the upper left-hand corner. I searched for cleaning EGR passages I found a number of hits. A good one is this one from an old member who was always really thorough with his vehicles. He had an HX, but I would imagine most aspects of the lean burn system on the HX are the same as they were on the VX, except for the codes and the sensors. But I'm just guessing. Here is the link:

https://ecomodder.com/forum/showthre...ean-30057.html

Thanks for the reply. To clarify I have a Canada ECU (P07-C00) that, to my knowledge, is functionally the same as the Federal ECU. I’m running that ECU along with a homemade harness with a NTK 5 wire wide band O2 sensor. Once I’m past the 5 post limit I’ll post the link I followed because it’s pretty good and very detailed.

I do feel mine is excessive. Unfortunately I don’t know anyone that has owned a lean burn vehicle like mine so I can’t get anyone to test drive it. I’d be less concerned if I could at least maintain speeds. For example, If I try to maintain 55 I’ll quickly drop down so I’ll try to compensate only to have the engine sputter for a bit further dropping my speed before it suddenly surges back to life and I’ll gain speed well faster than I intend to. Then it’s a bit of back and forth from there... so maintaining 55 is more like bouncing between 50 and 60 constantly.

I saw that link and used it to clean my EGR. It looks brand new now. Early in that link he mentions he cleaned the passages themselves which would be on the intake manifold. From what I’ve found, the Civics after 96 had EGR passages on the intake manifold that were easily accessible. On my intake manifold there are 5 or so small spots that look like “welded caps” on the top of the intake just to the right of the EGR valve. I’ve seen people talking about how they drilled and either tapped those out or made caps for them, but I’ve found no good forums detailing the process.

Worst case scenario... I have two air intakes now so I could give it a shot and if I fail then at least I have another? �� if i do I’ll be sure to post about it.

Here’s a picture of what mine looks like. These are the “caps” that get drilled out and tapped or capped.

I forgot to mention, my VX has a pretty solid 35 mpg per tank average and has been steadily declining from the low 40s from when I first bought it. That seems to be related to EGRs from what I’ve read. And considering I keep getting that light... just seems to be all related.

Found a link! This ones a lot like mine. I’m at 4/5 posts and can’t post links yet.. sooo yeah

I’m gonna work on taking the same course of action as the first link. Again, my intake was VERY dirty so I’m expecting to see a good deal of carbon build up and an increase in gas mileage (hopefully!) I’ll post back when I do

Here’s the Cali to Fed conversion: https://ecomodder.com/forum/showthre...n-vx-7295.html

Here’s the intake mod link: How to clean your EGR Ports on 88-91 Crx HF - Fuelly Forums

I suspect your ECU. There were some differences between Canadian and US fifth gen Civics and some were electrical. The most important might have been that the Canadians seemed not to have the "Electric Load Detector," while the US version did (according to a guy on honda-tech who seems to have owned both CDM and USDM Civics). You have installed a Canadian ECU which will not "know" your car has an ELD. I would wonder what kind of havoc that might play with car functions. Maybe nothing, but I would seek a proper USDM ECU if this were my car.

Im going to add: connectors and grounds. A can of contact cleaner worked wonders for the Ranger

I’ve got 2 vx civics and over the years I have found that some 5 wire wideband O2 sensors are just smoother going into leanburn than others. I have one O2 that is really rough so I keep it as a spare. Once in leanburn they all seam to give the same mpg as per the mpGuino.

Regarding the egr. Pretty sure it’s for emissions not mpg. Just make sure it’s not leaking and not suck in the open position. The vx only uses egr over 2500 rpm when accelerating quickly then changing gears.At least thats how both my cars work..If you have an emissions test you may need it to pass.

If they are still available you could look at getting a MPGuino.. Should be able to hold leanburn down to 43mpg in 5th gear . When it drops out of leanburn in 5th it will go to 27 mpg almost instantly and at the same time you get that extra acceleration and power . This can be used to tell you that the leanburn is working as it should.

I think all the vx civics were built in Canada. I didn’t know that the ones sold in the U.S. had a different ecu from the Canadian vx. Hope some of this is helpful. Good luck!

Hey guys thanks for your input!
California: good stuff! I got mine for less than $50 and it was a sudden buy since it was so cheap. I had done a small amount of homework beforehand and didn’t find too much info on the differences. I actually may be able to track one down. I’ll give it a shot and see what that does.
Pio: sounds like a plan! Ill check those out since I’m in the middle of cleaning anyways.
Turbo: i suspected the O2 sensor as well. I ended up finding a great deal on the actual NTK NGK O2 sensor after I had gotten another O2 sensor (can’t remember which brand) both seem to operate the same.
Regarding the EGR I couldn’t tell you too much about it myself... but from my understanding it has a few different purposes. One being to keep the cylinder temperatures cooler by using warm recycled air (not sure how but yeah XD) and secondly it magically makes air cleaner... magically. Either way, I’ve found several posts that say those ports leading into the air intake being clogged can actually affect gas mileage although I’m not exactly sure why. My EGR valve itself is pretty clean and I have a second egr I could test once the intake is back on.
I’d love to get an mpguino! I’m planning on doing some aeromods to my civic and the mpguino would be pretty helpful with that.
Thanks again everyone. You’re helping me keep my thought train going.

Hello everyone! Just a small update. Went ahead and cut into those weld today. I can definitely see how those little ports can clog up super easy. I went ahead and cleared off the welded caps of my newer cleaner intake and these are relatively clean. I’d be shocked if my original intake manifold had these passages clear. Here’s a shot of what it looks like. There’s no real easy way to get tools in there and the welds are very well done so each cap has taken me awhile. I tried using a dremel but my cut off discs weren’t working very well against the welds so I switched to a small angle grinder and the welds are no match. I’ll be cleaning them up with the dremel sander bits afterwards but so far they don’t look TOO bad. The small section where the cap sits doesn’t look the best for tapping.. so I might drill it out some more so I have more material to tap.
Getting a tiny bit late for power tools so I’ll be doing some cleaning and hopefully finishing it tomorrow. If I get the chance I’ll cut into my original manifold and check out those ports.

I suggest if you can't get it fixed update to a OBD2 engine setup... before/OBD1/1.5 stinks..(practical joke with cars)

I know your in California but its from a same yr or newer model it's acceptable.. did you do the muti meter tests and is it show 5V all the time?

Progress update: I got all the caps drilled out and I used about 2 and a half cans of carb cleaner on the inside of those ports. None were filled up but I got a TON of carbon out of there. Keep in mind this is after I used 2 cans initially just cleaning it up. There was all kinds of black gunk coming out of there.
I worked on tapping those holes today. I ended up going with a smaller bit and used that small platform those caps were sitting on instead of drilling them out (like I was planning) I figured if I screwed something up big time I’d at least have a back up plan.. haha
I went out and bought 7 10x1.5 16mm bolts. I then cut them down to be about 5-7mms then straightened out the threads, slapped some gasket maker on them, and threw them in. They seem to be holding well. I will likely slab gasket maker all over just to be sure since I my dremel didn’t wanna fit very well.
*worthy mention for the clueless ones like me: the sides of the ports were a bit tricky. I think the port opens up VERY slightly the further down the port extends. I will have to retap one of the sides for a bigger bolt because there was too much wiggle room in the bolt.

Also: is it even possible to go from obd 1 to 2? I’ve heard of conversions going from 2 to 1 but not the other way. Also.. multimeter was done for and I was inpatient. I wanted to do the caps on the intake manifold anyways so once it’s all back together I’ll be able to shoot some wires.

Next step it scraping all the gasket off my manifold and the cylinder. I’ll let everyone know if it makes a difference.

Update!
Got some gaskets I was waiting on and threw everything back in. Started up but was idling VERY high. Took it around the block a few times and tried adjusting the idle a bit. Once I got to normal operating temp I noticed that studder when trying to accelerate from a constant speed was LARGELY reduced. I was able to maintain speed and accelerate slightly as well. Seems to work great!
I got my hands on a federal ECU and I’ll try that out to see if there’s any better outcome.
I installed an external coil and I hadn’t put a boot on one of the connectors and I popped my coil somehow. Once I fix that I’ll do some more testing and see how that turns out gas mileage wise and over all performance (to include the original problem)

Problem is completely gone. In case you suspect this issue is the same with your car here’s my summary of the issue:
First of all get your hands on the helm manual. I went through all the trouble shooting steps for a code 12 (since that’s what I was popping with my California ECU. I ended up getting my hands on another black box and cleaned out all those components real good and swapped the two boxes. I also got another EGR valve and did the same to that.
After my multimeter showed me it was toast I went ahead and pulled off the intake manifold and drilled out the caps over the small welds covering the egr ports. Unfortunately I haven’t gotten to the original one, but from how dirty it was... I’m certain there is at least one port clogged... anyways! The new intake manifold I pulled was in great shape and was really clean. I used carb cleaner to clean out those ports and got a ton of junk out of them.
Next I threw everything back on (keep in mind I was cleaning grounds and everything else in the engine bay since I had easy access anyways. Engine started up and was idling around 2000 which is definitely not normal. Either way, problem was still present but HUGELY reduced. 2nd gear was the most significant at that point.
Next morning my car was dead (turned out to be a bad solder on my external coil)
Today I threw in that federal ECU and that made the last bit of difference. There was no hesitation whatsoever maintaining a consistent speed and the ecu would come out of lean burn easily when accelerating quickly.
After a bit of digging it turns out the Canadian engines have different timing adjustments which seems to be what was causing my stutter and it explains why 2nd gear seemed worse than the rest of the gears. So as it turns out that would answer another question I had earlier on.. the C01 and A01 ECUs are not the same!
In the end I suspect I was getting two issues that compounded each other. The ECU was the main cause but the egr ports and general passages within the intake manifold caused bogging and combined lead to a significant lag on acceleration.
Sooo lessons learned: do better homework and clean your intake manifold.
Thanks everyone for your help. Next step: aeromods! Looking into a belly pan and similar mods

Glad to have helped. And you have a much cleaner and fitter engine for all your problem solving efforts. Cheer.