ASK RAY

MISFIRING LT1

Q: I have a 1994 Z28 with 33,000 miles that had a failed original OptiSpark distributor (non-vented). I replaced it with a Dynaspark and followed all the instructions, especially the vacuum-line routing.

I did not notice the miss with the old distributor, but the engine did sit idle for about six months before I got around to installing the Dynaspark.

Here is my problem: With the engine warm I have an intermittent miss, what I would call a misfire. It only occurs in drive at idle (about 620 rpm) and with a warm engine. Above idle it is gone, and the car runs okay otherwise.

I noticed if I remove the vacuum hose from the distributor, the miss goes away. So, I did a vacuum check with the vacuum hose disconnected and found this: At idle in park it reads 18 inches, in drive 16 inches. If I reattach the vacuum hose, I get 12 inches at