I have a 99 Honda Civic VP and I am losing rpms for about 2 seconds every time I step on it to pass someone. Is there anything I can upgrade to stop this hesitation and accelerate smoother?

Oh and its automatic, 290k miles and idols hard. I've heard upgraded sparkplugs, CAI, cat back exhaust, and replacing dizzy would help but I wanted a second opinion.

Sounds like you need a tune up. You can pull your plugs to see if you are running lean or rich. I don't know that I would go with expensive plugs - like platinum or double platinum, etc - I would stick with what works best for your car. Different imports tend to have their norm of what works best. I'd suggest getting on a honda forum and ask for help getting your car to run efficiently before you go after modifications. Mods can potentially make it run even worse and you might end up chasing all sorts of issues. You could start with the sensors that are inputs for the computer that control your fuel/air mixture. especially the oxygen sensor and coolant temp sensor (probably near the intake manifold). Try cleaning your intake plenum and throttle body and idle air control sensor but I'd research how to properly clean the IAC in case your setup is sensitive or not? They are sometimes super expensive. You can also remove the ground wires where they connect to the body, wire brush the seat and reconnect. Check your cables pos/neg for corrosion and address properly. There are a lot of things to consider. Keep in touch, Best regards,

Do not upgrade any part until your get this problem fixed. It could cause more harm than good or just do nothing and waste your money.

Thank you guys. I wasn't expecting such in depth, helpful answers and I will definitely follow your advice. I do have a check engine light for an o2 sensor in the cat and another code for the throttle body. I had never removed a throttle body before and I followed a youtube video step by step but either there is a bolt that I just cannot find or it is fused to whatever it is housed on. I bought throttle body cleaner and a cheap toothbrush (suggested by video) but I am had trouble removing the throttle body itself. As far as the o2 sensor in the cat, I don't have emission checks where I live and considered removing it but I have read that you get lower gas mileage. Would it be smart to look for a new cat and replace it entirely or should I just have the sensor replaced in a shop? I'm pretty sure its the original from 290k miles ago. I was also considering replacing the timing belt, there is a log book that has been kept up and it is recorded that the timing belt was changed at 219k miles and they arent as expensive as I was led to believe but I'm sure labor on something like that is a little costly. Unrelated but you guys seem to be very informed and I cannot find anything to confirm this but I found two replacement front doors for my 99 civic vp sedan but it is coming from a 99 civic ek sedan... the guy swears they will fit and it is a steal of a deal but a little bit of a drive. Does anyone happen to know if they will match up? Sorry for asking so much I'm just excited I have found people with real knowledge about these things. Thanks again!

Ok man the throttle body on your car is held on by 4 bolts one at each corner. Once your remove the throttle body you will need to replace the gasket for it. If not it could cause a vacuum leak which could results in another check engine light for a lean condition on bank 1, meaning more air than fuel is being delivered to the cylinder so the pcm will try to compensate by adding more fuel. This will result in decreased fuel economy. I would not remove the 02 sensor or cat, just simply It would cause a huge decrease in fuel economy. As for the o2 sensor causing the car to bogg down, I don't think that's your problem just because the o2 sensor's sole responsibility is to monitor and measure the exhaust before and at the cat. If an o2 sensor is not reading properly then it would cause a rich or lean condition and a code for rich or lean and low or high o2 sensor circuit input and a lose of fuel economy. The cat could cause the car to feel like it's losing power, if it's melting down inside the catalyst. I would replace the o2 sensor and cat to keep fuel economy at its peak if your worried about the fuel economy. The timing belt on those car should be repacked around every 90k to 100 miles, if your unsure when it was replaced last then go ahead and get it done. A timing belt job on a honda consist of replacing the timing belt, balance shaft belt, waterpump, camshaft and crankshaft seals (to avoid an oil leak behind the timing cover) timing belt tensioner, and all yor drive/ serpentine belts. If your timing belt were to slip or break it would result in the valves opening to soon and hitting the pistons, the damage could result in bent or broken valves damage to the pistons and cylinder walls. If this happens then you would need to replace the engine. Rebuilding the engine would cost more in parts and labor than a replacement engine.

Okay so tune up, clean throttle body and replace the gasket, replace timing belt and everything that goes along with that. I'm not insanely concerned about losing gas mileage unless removing the cat will make a huge difference in gas mileage I may just cut it off.

I heard removing the cat will keep the check engine light on but you can do something to the computer to trick it into thinking its still there

Not having the o2 sensor in place at the cat will have a decrease I fuel mileage

You can buy an aftermarket test pipe to take the place of the converter that has the o2 sensor port and yes it will cause a permanent check engine light.

You can trick the pcm into thinking the cat is still there but that is a job for a tuner. If you don't know what you doing when playing with the pcm setting you could ruin the pcm. But first fix the problem with the vehicle stumble on acceleration before any aftermarket mods are performed. Do u know what the p code is for the throttle body that you said you had.

I will get it re-checked saturday and post the codes here. The guy at autozone said he see's both of my engine codes pretty often but they aren't the best people to take advice from. Although there is a surplus of civics in my area so Im sure hes seen a good bit

Does the fact that my car idols hard point to the throttle body or would you think that is another problem in itself. It doesn't sound that bad its more of my interior shaking or vibrating pretty hard. The engine SOUNDS decent enough but my dash, mirrors, and steering wheel didnt used to shake at all. I guess we'll see after cleaning it.

the vibration that you're feeling is due to the front motor mount bwing broken.I would recommend replacing all the motor mounts. Another thing that you should get done if it has not been done and if you hear a tapping noise coming from the valve cover would be a valve adjustment. The rocker arms and valves have a specific adjustment called valve lash which is the gap between the valve stem head and rocker arm. Overtime the valve lash will become greater in out of specification which could cause your valves not to open up enough.

I'm starting to get the feeling it would be cheaper to buy a used car with less miles. This is my first car so it has personal value to me. I will definitely get the tune up and start looking into a new timing belt asap but I feel like I'm going to end up putting over 2500 into this car that as is is probably only worth 1k. I do appreciate the help a lot I promise you didn't just waste your time. Seeing as I plan on keeping this car all of that information will be put to use but I'm starting to think the cheaper route may be to get another used civic considering most of them are selling for 1500 - 3500. This car also has very expensive body damage (quarter panel smashed in, both front doors are damaged, rear bumper severely damaged where the quarter panel got smashed in) but it has been and still is a reliable car I'll likely end up completely repairing it over time now that I have a garage to work in and the financial capabilities

Did u get your codes?

Clogged catalytic, because it's less pressure in high speed (low rpm) and back pressure in low speed. But, bad catalytic also caused by age or poor combustion.