91 Q has a bad miss!

[PopPop]

My 91 Q has a bad engine miss. You can really notice it once the engine is fully warmed up and at idle. You can feel the engine thump every 30 seconds or so. Placed hand behind exhaust and you can here and feel the miss. Checked ECU codes and 55 flashed so no codes in computer. Also checked coils and wiring harness conections since I done spark plugs last month. This miss has been going on for about a week now and since this problem started. Car has shut down on me in the morning after a 5 minute warm up. Started rate back up but, this is the first time Q has cut off on me in the morning. Help with ideas too get me started in the right direction!

[Q45tech]

Use the Consult and do a power balance test to identify the missing cylinder.It appears you recently changed plugs [exact oem replacements ?].

Ohm injectors and look at their individual current rise time.

[Q451990]

The mis is only every 30 seconds or so? Sounds like an electrical issue... a dead miss will feel like a bouncing every second or two at idle. I would re-check all of your electrical connections. OBDI is very forgiving, so not finding a code doesn't mean everything is working...

Heath

[PopPop]

Thanks for the information you provided for my problem. I'll give your suggestions a try this week.