njmatt

Hello,

I have a MY04 with 148,000 miles. Recently, I have noticed that the car seems much more sluggish at lower revs (2000-4000rpm). When applying additional throttle throughout this rpm range, it feels as if the car is bogging and does not want to accelerate. The engine sound gets louder, but it does not rev up and accelerate as it should. Also, I frequently experience shaking when applying moderate throttle (30-60%). This is mainly noticeable at highway speeds in 5th and 6th gear at 3000-4500 rpm. The idle is also a bit rough at times and occasionally makes small "popping" sensations, although it is not consistent with motor revolutions (pops every 1-3 seconds inconsistently). However, Once the engine enters vtec, most of the shaking goes away and the bogging seems to disappear. The problem does seem to become more noticeable after the engine has warmed up, and is based on the amount of throttle being applied, especially the shaking. I have not experienced any sort of check engine light, making this a lot harder to identify. The motor is 100% stock.

So far I have done the following:

1. MAP sensor whack
2. Cleaned IACV
3. Reset ECU and reprogrammed idle (this seems to help with the problem for a few minutes, but then it comes back)
4. Performed a valve adjustment. Most were in spec, a few were just slightly too tight.

I've been looking into this issue for the last two weeks and so far my remaining theories are...

1. Clogged catalytic converter? I do have a reduced exhaust note and the fact that the problem gets worse as the car warms up seems to point to this.
2. A coil pack not firing properly.
3. A bad MAP sensor or TPS?

I would greatly appreciate any advice you all have to offer. Just looking for a bit of guidance to make sure I'm going in the right direction to get this sorted out.

Thank you!

PaGEmaZt3r

Hey man, I was having the same issues. Especially the weird popping noise from the exhaust. No cel either. I bought and installed brand new coil packs and it got rid of it.
I'm assuming they were starting to fail but not enough to pop a misfire code.
If you have that many miles and have never changed your coils I would start there, considering you did the map whack, valves, etc. already.

njmatt

Thanks for your input!

I actually just had to replace one about 3,000 miles ago. It was causing a CEL and a complete misfire, but replacing it solved my problem and it ran perfectly until now. I will look into getting a new set soon as I'm not sure if the previous owner ever replaced them all.

spets

Also, change the spark plugs themselves if you haven't yet.

PaGEmaZt3r

No problem, idk if it's true but I have heard that when one goes bad it causes the others to fail as well. At 150k they should all be changed anyways. And like Spetz just said I would change the plugs to if you haven't already.

Slowcrash_101

Might be your fuel injectors, also change your PCV valve. Anyway, when the car is first started up it goes into closed loop mode, and it does it when it's in VTEC as well, only when it warms up does it go into open loop mode. So it could also be your O2 sensor or your spark plugs. As for the shaking, it could be pitted CV cups, have you done your axle nut TSB?

njmatt

Yes, I recently installed a new differential with a low mileage one (old one was going out) and checked the axles and properly torqued them while I was at it. However, it feels like the shaking is coming from the front of the car because I mainly only feel it with my feet, on and near the pedals. It also seems to be transmitting through my shifter.

I'm going to check my o2 sensors as well. Correct me if I'm wrong, but doesn't the o2 sensor tend to go out along with the catalytic converter? Just wondering if anyone could give some input on how to determine if a cat is clogged up. It's weird that I barely have any exhaust noise especially after it warms up.

Slowcrash_101

The front O2 sensor before the cat doesn't have much to do with the cat, the secondary one just makes sure the cat is functioning properly. If you don't have the CEL for the secondary cat it's not that, but a lazy primary O2 can give you a rough running engine, so can fouled spark plugs, but that usually throws up a CEL. You said your problem only happens when the car is warm, not when it's cold or in VTEC right? If that's the case then there's chance it is a sensor or something that functions while the car is in open loop mode that isn't giving accurate signals. Maybe if you posted a video of the symptoms we would be able to help pinpoint the problem.

MR.T

easy test for the cat. pull your primary O2 out and hang it safe and out of the way with a ziptie. if you notice an immediate difference it could be a clogged cat...stole this from billman by the way. if it seems to be doing fine in vtec, i'm not sure if that's your issue, but it's an easy way to check.

S2kPowa

I have similar issues Recently changed my transmission after that everything went downhill, When installed my new transmission i broke pressure plate bolt 3rd day or so I get massive vibration at idle and also when i accelerate vibration is there. I can feel it in gas pedal, brake clutch etc, My dashboard vibrates my doors vibrates even my rear view mirror vibrates when i press on gas, After I broke P Plate bolt I drove car like that for 500 miles, After i changed everything clutch pressure plate fork , throw out bearing, Vibration is still there. Cant figure out what it is , Changed plugs already, checked timing, Next thing ill do is change coils and coil harness.
Today after i floor it my car started to bug out i got scared shut it off , So it seems my engine soon will take big dump/ or something is about to fail , after i shut car off it seems to work same. but no bugging out , People telling me its megan engine mounts i know its not, I drove on them for 3 months before clutch change had no vibration. I have no check engine lights etc only p0411 due to faulty ecu , air pump
I Also notice power loss as well.
This sucks because I got turbo install this Saturday...


I hope you can figure out what it is,