Hello All,

Just put about 600 miles after finally repairing a coolant leak on the car, now the CEL came on which read PO 420. This car doesn't give me a break. 145K on the odo and seems to run quite well.

I've done some research (thank you Klaus) here on the BB and also on Google and I'd like to do some diagnostics myself. I suppose I can check for exhaust leaks by hooking up my vacuum blower (from my shop vac) duct-taped onto the tailpipe and feeling around. I've used that approach on my 240 and it works quite well. Is there an easy way to check for intake leaks too. About 1K miles ago, I did replace all the PCV components, and I think I did a stellar job, but you never know.

Also, on my 240 I've learned how to backprobe the O2 sensor with my voltmeter and check the voltage swings. Is this something I can do with the sensors on this car. I don't have a scanner and am looking for the DIY approach.

Rich, my mechanic friend says the car needs an "Italian tuneup". I've cleared the code but haven't driven it many miles to assure myself that the PO 420 won't come back. I suppose the Italian tuneup wouldn't hurt.

Any thoughts on all this.

Marty Wolfson