Silvertune

At the title states I have a 1997 Accord EX, it's the 5 speed car, turned over 155k three days ago.

Maintenance is fully up to date. Timing belt, BS belt, water pump 15k ago. Cap, rotor, wires and plugs 3k ago. New fuel filter and a can of Techron went in a thousand miles ago. The engine was seafoamed and the oil has been changed as of yesterday. No check engine codes. I'm averaging 29 MPG in the middle of MN winter with warm up time and lots of city driving so everything seems decent on paper.

The first problem I have happens at low RPM's. From about 1200 to 2500 while accelerating the car bogs hard and misfires randomly. The misses so bad you can feel it as the car jerks a bit. At 2500 RPM's the misfire goes away and the car jumps what feels like a good 20 horsepower without me having adjusted the throttle input what so ever. I understand this should be the first Vtec stage but why a valvetrain event would make misfire go away I am not sure, unless the tune dramatically changes here or something. I'm at a loss for the cause of this issue. The belts are all timed correctly and the ignition system is entirely new, but perhaps there is something I am missing with the distributor? I am tempted to replace it but I am not sure if the rotor timing is set-able on them. I come from Mitsubishi where the rotor timing isn't adjustable.

The second problem I have is a nasty vibration. You feel it through the whole car. It is worse at low RPM's, get's faster as I accelerate. Goes away when I let off the gas but comes back albeit lightly if I engine brake from higher RPM's. I thought it was bad engine mounts so I changed the front and side mounts but it changed nothing with the vibration so I don't know if it is a bearing failure somewhere in the drivetrain or what. CV axles look great and seem tight.

The next problem is another vibration though this one is audible. At 1800 RPM's religiously some harmonic is making something vibrate very loud. It sounds like exhaust rubbing the frame or a bad mount but as stated above the mounts are new and I have checked the whole exhaust. It is bolted down and rubbing nothing. It comes from the belts area in the engine bay, the noise happens upon acceleration, deceleration or dry rev, same intensity regardless of throttle input. Is this a worn out harmonic balancer? I can't think of anything else it could be at this point. I have literally sat under the hood and made it do it's thing and I can't figure it out.

The next issue is rev hang. I have driven a great many cars and nothing rev hangs like this accord. I let off the gas and push in the clutch to shift and the RPM's will maintain the level I let off at for a solid second before starting to drop. Then they will drop incredibly slowly. This is worse than my friend's Mkvi GTI with a nearly 40 pound flywheel. The car idles at 800 RPM's which seems high but all vac lines are hooked up and there are no leaks. The throttle body does not hang up, it shuts directly in conjunction with letting off the pedal. Is it possible the EGR is stuck open but not throwing a check engine light? The light does work, I have checked that.

If the car were running inefficiently I'd be more pissed off, I love this car but driving it is becoming more and more painful due to the above issues. Any help offered is greatly appreciated.

poorman212

You are sure the bulb for the CEL works....correct? Key to on and it should light up for about 2~3 seconds as the pump primes.

Clean the egr ports on the intake manifold.....assuming this is a 4cyl.

Clean the tb, both sides and edges of the butterfly and be sure the cable and spring are moving correctly.

Did you do the timing belt? Was the tensioner replaced? Is the engine mount on the belt side on properly and good?

MAD_MIKE

Possibly a lean misfire from partially clogged EGR ports, you will need to clean the EGR manifold. There is a writeup in the Accord FAQ at the top of the forum.
Since it's load dependent it may be related to the clutch/pilot bearing.
An axle issue would not really change with load, no load, engine braking.
Possibly the timing belt was set too tight? Do you have a long enough stick or ratchet extension to place on the belt tensioneer nut on the timing belt cover? Place the other end to your ear and see if the noise is directly coming from the timing belts. With the undertray removed lock the wheel so as to see the harmonic damper, look for the damper bolt being tight, check the bonding rubber band between the hub and pulley of the damper, overtightened belts.
Could be the TB shaft is gummed up a bit, unhook the throttle cable and verify it is not hanging up either. Accord FAQ on the IAC/FITV for cleaning and checkout.
If EGR was stuck open your car would either not idle, or idle badly(stumble).