328 slowdown light

I am bedeviled by this problem. Would appreciate anyone's thoguhts on this.

1. Month ago sat in the emissions test line with the engine idling for about 25 minute. SD light came on briefly just before the test then went out right after I revved the engine. This was the first time that I had ever seen the light come on. Car has 32K miles with about 3k put on by me over two years. Passed the emissions test with no trouble.

2. Week later when driving on a small hilly road near my house at about 30 MPH light came on again but went out.

3. Tightened all plug wires. One appeared loose. Problem seemd to go away.

4. Came back the other day as in 2 above. Let it sit then drove on the highway up to 100 mph and then home. No problem but later smelled gas in the garage.

5. Drove it today and SD light came on as in 2 above. Flickered and then went out aftef driving for . 25 miles.

I don't believe that it is a plug wire but it is also not a complete bank going out because there does not seem to be a loss of power. Could it be just a plug that is not firing for some reason? Appreciate any suggestions.

Hi Russ,

one of the easiest ways to tell plug condition is to simply pull them out for a 'plug read'. All 8 should look the same and be a brownish grey color. I'm pretty sure the Champion plug site has a 'plug chart' that can help you identify plug condition if you're not familiar with what perfect plugs should look like.

Missing, be it plugs or something else can make a cat light come on or blink....however, if plug condition looksperfect a blinking cat light sometimes indicates a temp controller is going bad.

Regards, JRV

Thanks guys. All this has been very helpfull. Moments ago and after the car had been sitting awhile I started it up and headed down the road. Within a tenth of a mile the light came on and this time I believe that I could detect a miss in a cylinder. Recall this problem first surface when I was in line for emissions and it idled for over twenty minutes which may have fouled a plug or two.

At any rate my tool kit does not have a plug wrench and NAPA and Shucks do not have a plug wrench. They do have an 18 mm socket which will accept the plug but it does not have the rubber insert to protect the plug from breaking. I am worried about breaking the porcelin and having a piece drop into the cylinder. Any thoughts on where to get a proper sparkplug socket. I will call Ferrari of Seattle tomorrow but suspect their price will leave a bad taste in my mouth.

Russ,
I have seen several posts in the past on another site, and it was often times the spark plug extenders failing (there is a thread on this presently). I would most definitely inspect them very carefully (while removing the plugs), and if any of them have burned or scorched marks (which would show they are shorting), then I would consider replacing them all. Of course plug inspection should tell you which one is specifically giving you trouble.

You could also remove the distributor caps, complete with the wires and test for continuity and resistance. You may find one intermittant or with excessive resistance. I know one person had a problem with their wires and simply removed them all from the distributor caps, trimmed them back every so slightly, then reinstalled them, puncturing them freshly with the set screw. Fixed his intermittent "miss" problem. You should also inspect the caps themselves for cracks or wear..same with the rotors.

Thanks guys. All this has been helpfull and I will work with everyone's suggestions this weekend.

Looking for more suggestions. Here is the latest.

1. Recall the problem of a blinking SD light first occurred after about 20 minutes of idleing going up to the emissions test. Passed test with no problems. Light stopped blining on the way home.

2. Later the light began coming on more and more, usually after about 10 minutes of running at up to about 50 MPH.

3. Sometimes will come on and then go out for a while. If I take it out of gear and idle the light goes out as expected.

4. One time after I got home and parked in the garage, came out later and smelled raw gas but could detect no leaks.

5. Pulled plugs. All but one looked alike, not gray-closer to black. Running rich?

6. The odd plug had some liquid on it which was not gas??? At least it did not smell like gas.

7. Bought a simple current tester which I put on each plug wire at idle and got a current reading at each plug.

8. At idle I smelled the tailpipes and the left pipe (facing forward) seemed to smell of gas. Don't know if that is normal.

9. I have not run the car fast on the higghway because I do not want to go to far from home.

Any clues in the above, Have not checked distributors because I am not sure how and with current on each plug wire-at least at idle-seems like the problem lies elsewhere.

Could this be a mixture problem. Runs too rich putting gas into the CAT. If so, how do you check and how do you cure.

Many thanks for any help.

This morning I took the advice of Dave Handa and others and lifted the panel on the passenger side of the "trunk" which has attached to the underside numerous relays, grounds etc. When I looked it over all of the fittings appeared to be tight. However following Dave's suggestion I unhooked each connection and sprayed it with contact cleaner. Put it all back together and now after putting about 100 miles on the car-fast, slow, highway, backroads etc. the SD light after coming on briefly when the key is turned promptly goes out and I have not gotten so much as a blink since the fix.

Thanks again to everyone who had a suggestion. I printed them all out and now have a nice file on the slow down light.