bama_boy95

alright guys I've got the 98 coupe DX that's comes with a d16y7. it drove fine for the longest time until about a few days ago it started backfiring and hesitating to go any faster than a creep. it eventually got to the point where it was so bad I could go more than 5 seconds without any kind of problem. so I compiled a laundry list of things that it could be, read a ton of threads on here. I cleaned the iacv(thinking it was a vacuum leak) which did help engine responsiveness a bit but not much because manifold is cracked. then I unplugged my upstream o2 sensor and it turns out the sensor slowly went out of spec and the ecu just never realized. since then I've got pretty bad gas mileage but it idles great! I'm sure like 80% percent of the people here would have figured it out asap but this is for the other 20% still experimenting. I hope this helps!

86azms3

Check all the easy stuff, ignition system, fuel, air. Do a compression check.

Did you replace the o2 sensor? And if the crack is bad enough, you need a manifold.

bama_boy95

not yet, I have it unplugged for now but I may wait till I get a new manifold/exhaust to replace the o2. and no I'm saying I fixed the issue, lol I just don't really know where to post solutions I have found to problems I've had. I'm new so I'm just trying to get familiar with this.

86azms3

Start with the manifold and 02 sensor. I know it's expensive, but it needs to be done. I had to replace mine too.

bama_boy95

I will. now I just don't know If I should get a whole new exhaust or a manifold. do aftermarket manifolds bolt up to the original exhaust?

Former User

You have not posted a solution. Your car troubles have just begun based on the way you choose to address issues.

bama_boy95

okay, sorry. it was back firing and idling bad when braking and taking off, I unplugged the upstream o2 sensor and now it hasn't backfired or idled bad since then. fuel efficiency is bad because of cracked Mani. I will replace the manifold and o2 soon.

Former User

Pull the CEL codes.

Don't replace the O2 sensor until you replace the cracked manifold. There's a possibility that the main problem is the bad manifold and not the O2 sensor.

Also, if you haven't done an ignition system tune up in a while, do that too.

bama_boy95

I did an ignition tune up in around jan-feb. and I know, I'm waiting till I get a new manifold and then replace the o2. if I do it now it'll just foul out soon enough and I'd be wasting money. thank you for the replies. and the only cel I have is for the o2 sensor that I unplugged

tony_2018

So...you have a solution or are you looking for a solution?

oneheadlight

I think that's the part that everyone is missing. Believing that the ECU will always illuminate the check engine light is not true whatsoever. Honda was sued by the EPA for not programming the ECU to correct emission standards. That included on adhering to the OBD-2 standard. They were able to appear to pass the EPA's tests, but in reality, the computer would not report all failures. Since Honda had been found guilty of violating these standards, warranties were extended on Civics. (the time has expired by now..)

The result today? An ecu that WILL not illuminate the CEL when emission related components go bad. I have a 96 and the same exact thing happened to me as it did to the OP. The o2 primary sensor went bad. How do I know? I tested it with an ohmmeter (multimeter set to ohms) and it was clearly bad, did not test within the specs. Did the CEL light on mine? nope. I actually did come on this site and people were demanding I compression test the engine because they believed the engine was gone. No that was not the issue no matter how they didn't want to hear it. It was the o2 sensor, and now the engine is running well. Always the simple things.

This is a reminder to those out there, check with a multimeter, don't rely on the ECU to tell you, especially the 96's. If no one believes me, google it. EPA knows.. they won the lawsuit.

So back to the original point. Yes you disconnecting it was a good sign that it's most likely the issue. But if the manifold is cracked, which was a common issue , then replace that first, and check your o2 with a multimeter (get a service manual on how to test the o2). You're going to have to go "old school" and test things manually, just to make sure if you suspect an issue.

White_EG1

So you're saying the OBD1's weren't the main concern?