I recently purchased an '88 CRX-si and am having trouble passing emissions testing. It fails on high CO, and there are no trouble codes. It runs great and got 35mpg average on the trip from Florida where I bought to back home in Ohio. It does have a pretty bad vibration/shudder at idle, although it idles at the correct 750rpm. It doesn't really fell like a rough idle - more like if it had a lightened flywheel. It's basically stock, with the only engine mods being a DC header and HKS exhaust. It also has a polyurethane front engine mount (all others are stock rubber). It has a new O2 sensor, distributor cap, rotor, and wires. The spark plugs are NGK's in good condition. Ignition timing is the stock 18 deg.
The only thing I haven't verified is the Cat, but I'm pretty sure that's not the problem, as it seems to be lighting off correctly. I believe high CO means an overly rich mixture, and it does smell rich coming out of the exhaust, but the plugs look perfect. I'm planning on running some Seafoam through it tonight, and maybe swapping the injectors out for a set I know is good. Other than that, any ideas? I've never used PU engine mounts before, but could that be causing the idle vibration, or do you think it's related to the reason it's not passing emissions?
Thanks in advance,
Jim

 

I could really use some help with this, guys.

 

The PU mount absolutely will cause increased vibration. It is one thing if the vibration is just standard engine vibration, but quite another if it is a "bouncing idle" problem. Bouncing idle implies that one or more of the idle control devices is not functioning properly. This shouldn't really cause you to not pass emissions though, as idle is tuned pretty lean from the factory.

As for the emissions issues, I would first start with a new O2 sensor, and then entertain a new cat if the o2 sensor was not enough, especially if you are not getting a CEL. Are you driving the **** out of the car before taking it in to be tested? or are you driving it 2 minutes from your house to get tested? it takes about 10-15 mins of driving to get a cat up to temperature in 70degree weather, so you may need to adjust those times in Ohio this time of year. Last, is your test a speed range test where they put it on a dyno? or are they just sniffing at idle?

As a side note, I would never let seafoam touch any car I own. You might as well plan to buy a new cat and new o2 sensor for sure if you seafoam it. There is no "magic sauce" that is going to fix your problem. The problem is mechanical or electronic.