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Okay so I’ve got a 98 civic ex 5 speed with an d16y8 engine. The problem started a couple weeks ago but is getting worse as it goes, some days worse than others. While at idle once the car is at running temp it idles low. Occasionally dropping so low it feels like it’s going to stall. That’s just the first part. The second (I’m thinking these two are related) is while accelerating starting in second gear until I hit close to 4000 RPM the car bucks. It’s barely noticeable in 1st but you can tell in 2-5 bad. If I slightly hit the gas it’s not as noticeable but you can still tell. I’m thinking maybe a clogged fuel filter? I wasn’t positive I wanted some feedback. Here’s some background info.
I’ve rebuilt the engine, new intake, brand new plugs wires and cap, new air filter,New o2 sensors, car put in time with a timing light, fresh oil change. I believe that’s it other than mods like sub’s, interior, things that don’t have to do with performance just adding weight. The engine was rebuilt 6 months ago.
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If the filter was plugged badly enough to choke off your pressure, the pump would be so stressed out that it should be replaced. Have you measured your fuel pressure?
When you have low pressure, you won’t get enough fuel to allow higher RPM. Usually your lower RPM (where you need less fuel volume) will be better.
This sounds like a vacuum leak or possibly a defective coil failing under load. You need to get the codes scanned to see what the ECM is seeing. You can also do a coil output test using a test light to see how far it will jump an air gap.
Vacuum leaks will be the biggest problem at low RPM and idle, and can make it idle low. When the airflow in the engine increases at higher RPM it is less of an issue. Grab a can of carb cleaner, start the engine and spray one area at a time listening for a change in engine pitch or RPM. Some of these are so fast at compensating that you may need to watch live data on a scanner to catch it, specifically the B1S1 O2 voltage and the STFT pids. I use an oscilloscope on the O2 to get the quickest readings.
I went through with carb cleaner and didn’t get anything I’ll have to borrow my old bosses scanner to see if it’s a slight change. But I’d think a vacume leak would make the idle bounce back and forth right? It’s not bouncing rapidly or anything it’s dropping pretty much as low RPM as it can without stalling and staying there. I can hit the gas a little and it might not act up for a day or it could act up soon I wrote down every time it happened and couldn’t find any correlation between temp or anything. And the coil I replaced about 3 months ago. The coil had went out. I’ll do another check on it and see what comes up. Thanks for the speedy reply.
Ran the carb test with scanner hooked up and still no change. I also tested the coil again it’s working properly. I talked to a Honda specialist shop today and was told to try resetting the valves with a feeler guage that he doesn’t think my valves are opening all the way. Any (+) or (-) feedback on that? I’m probably gonna do that and see if it helps any. I had changed the air mixture on the intake to allow more air in to raise the rpm slightly and that fixed the low rpm problem.
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