98 Honda Accord has no cat. conv. everything else is new. What can I do. Would not having a cat. make this code come up? I've been driving car for about 6 mths.. Car has been studdering on accel. and low RPMs.

 

That is the exact reason for the code to pop up. This shouldn't cause the car to shudder on acceleration.

 

Wouldn't it cause a shudder if the code caused the car to go into "limp mode"?

 

Im not sure whether the rear O2 sensor has the authority to put the car into limp-home mode. The rear sensors only job is to measure whether the cat is working.

 

Personally, my 99 has had the P0420 code for 8 years now, and never once has it caused the car to shudder or hesitate, nor go into limp mode. Not having a cat would be your #1 reason for the code, #2 would be having a bad O2 sensor if you did have a working cat.

 

limp mode locks out VTEC ..... no shudder, just no power and it won't go over 4000 rpms.

 

OK. Just making sure. I've never had a car go into "limp mode" before, but I have heard of plenty of members talking about it. So the shudder is probably coming from somewhere else then. Let's try to help.

How old are the spark plugs? What kind of plugs are in there (brand)?
How long since you checked or changed the distributor cap & rotor?
Check the spark plug wires for damage. Manually look at each wire. Then, in a dark garage, have the engine running and spray a mist of water over the wires. If you see any sparks or light coming from anywhere on the wires (arcing), you got a plug wire problem.

 

Good stuff, Jon. Arcing seems to be more visible if the engine is COLD before you try it.

The studdering might even be from EGR problems?

 

I wanted to start with the easy tests first .
I didn't realize arcing was found best if engine is cold first. Good advice. I learn something new every day