I've got a 98 Civic Si eveyone knows it's a D16Y8 Engine. I've got a slight hesitation and i wanted a second opinion on my diagnosis. When i down shift i can hear the biscuit inside my cat rattling around inside the shell. So i disconnected the exhaust from the midpipe and stuck a screwdriver into the cat and sure enough it's all loose inside fully intacked not all broken up but the material that they use to compress around the outside of the "Biscuit" is all gone. So being that it's an OBD2a car that would mean the secondary or "downstream" oxygen sensor is seeing that the cat isn't working properly. Lastly it only happens when i drive the car normally and don't get the temp up to high, if I drive it hard for a bit the hesitation goes away or becomes less noticeable. My question is what does the computer do when it see's that the cat isn't operating properly? and whatever that is could that lead to a slight hesitation i.e pulling timing and/or reducing the amount of fuel being injected? My thinking is that once that biscuit gets hot and it would take alot more to get it hot because alot of exhaust is going around the biscuit not through it the computer would advance the timing a bit and/or add more fuel and the hestation would seemingly go away.

 

Get your computer scanned for all codes (history, pending, current) and post them up.

Your ECU does not pull timing or anything if there is a catalyst failure.

 

No codes, however i don't have access to a scan tool and i don't want to pay for a scan. Does anyone have one i can borrow?.

I have no experience with honda distributors other than changing the cap and rotor. I would like to make sure it's working properly, what is inside that i should check and how?

So what exactly does the downstream O2 sensor even do? wouldn't the computer start making changes to the fuel trims or timing maps to try and clean up the exhaust gasses if it see's the converter isn't functioning properly?

 

Can Someone point me in the direction of how to measure the ignition coil in the distributor please. also if the timing belt skipped one tooth would it be difficult to set base ignition timing and/or could that be causing athis slight hesitation i'm talking about.

 

 

That's great thanks Chris! i did search for this and didn't find anything. what do you think about the timing belt skipping a tooth?

 

If your timing belt is off a tooth ignition timing will be way off. Also, the car will constantly run rough, it would sound like its running on 2 or 3 cylinders.

A quick way to check to see if the timing belt is off is to measure engine vacuum.. if it less than spec than that's a good indication that the belt is off. Or you can just pull the covers off and have a look

 

Great thanks for the help much apreciated. Measured the Coil when i got home looks like it's not within the specs. So i replaced it with another one i had in a different distributor, but is the exact same and measured it of course and so far it runs much better.

 

Great, glad I could help