Rep Power: 0

Hi, I have a 2001 civic EX MT Em2 civic. I recently bought the car which had bad piston rings so I swapped in a 2005 ex motor. The car had poor acceleration problems before I did the swap and after so I'm kind of just scratching my head trying to figure out what's wrong. The pcm is throwing only a P1298 Code for the ELD and I was wondering if dropping in a new one would fix the acceleration issue.

 
Rep Power: 222

Cat/muffler clogged?

 
Rep Power: 0

Not that I can tell. Wouldn't there be a code that comes up if a cat is clogged? There does seem to be an exhaust leak somewhere, possibly before the cat. Checking fuel trim data from OBDII scanner shows negative % data when throttle is applied.

 
Rep Power: 222

Not necessarily, and if the rings needed to be done then it must've been burning oil pretty bad.
you can either loosen the bolts where the manifold meets the head or remove the primary o2 and see if the acceleration is better

 
Rep Power: 0

Yeah, the previous engine burnt about 3/4s of a quart of oil within a 37 mile trip home after purchasing it. I replaced the ELD and now have no codes stored or pending, however am still having the acceleration issue. I'll try unbolting the downpipe from the cat to see if there's any performance gain tomorrow.

 
Rep Power: 367

primary o2 sensor is much easier

 
Rep Power: 224

 
Rep Power: 99

This is the easiest way so long as you have an oxygen sensor socket handy.

Also, a more technical way, you can purchase an exhuast backflow gauge and see what the reading is. This is what i did to see if exhaust backpressure could explain a lack of power. It can also help isolate where the restriction might be.

However, you mentioned there may be an exhaust leak. This would eliminate backpressure as the cause.

 
Rep Power: 0

Finally getting back to this thread a month later lol. Turned out to be a clogged cat. Loosened one of the downpipe bolts and I immediately felt an increase in power. Thanks to all of you for giving suggestions to diagnose this. Unfortunately a new cat with downpipe included is $600 since I couldn't source one from any near junkyard, my solution was to just hollow out the cat.

 
Rep Power: 0

As for the P1298 code I just threw in a spare ELD that I had laying around and it cleared the code.

 
Rep Power: 222

The money you would've gotten from scrapping the factory cat would've paid for a new one