Hello I have an 07 h2 and I have had a few codes thrown. I'm at 130k on my engine i bought it at 80k . My last h2 I drove to 330k before I traded it in. I changed plugs and wires because I had multiple misfires showing up.(and they hadn't ever been changed) Now the check engine light is flashing and I can't get over 45 mph. It also had a bank 1&2 catalyst code and the guy said I needed o2 sensors. I haven't read the codes again since changing the plugs and wires. I also replaced the air intake with a factory replacement and the throttle body and air filter a month ago. It acts like it can't breathe properly. Could it be my cats stopped up? Fuel filter? Or would o2 sensors cause that much of a power loss? I just drove 500 miles 2 days ago and didn't have this issue it was needing plugs and wires but after changing them it's horrible now that it's actually firing right. Any help would be greatly appreciated

 

Welcome to HF.

I MOVED this to the H2 section, because that is where H2 questions go...... crazy how that works.

A flashing CEL without providing the codes doesn't provide enough info to guess what your problem is/are.

You could start with a revisit your plugs and wire change, make sure all the wires are positioned properly and snapped on all the way at each end.

 

It does sound like your cats are indeed clogged up. If they get clogged the exhaust develop too much back pressure. Nearly the same as cannot get enough air, it cannot get the air out. However it could also very well be the O2 sensors. If those are bad or damaged your fuel economy will get much worse and yes it could pretty much cripple how the engine runs. Even if the cats are fine, if the O2 sensor goes bad the ECU will try to lean out or make the fuel/air ratio richer trying to compensate.

 

Check exhaust back pressure anything more than 0.5 psi backpressure causes all cylinders on that bank to misfire