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Severe Engine Missing................Another Very Interesting Story

Mar 9, 2009
Not long after I installed the TH700R4 in my '71 my daughter and I went to the coast for a one day father-and-daughter outing. After about 100 miles my engine began missing REAL bad every time I put it under a heavy load. As long as I drove it real easy my engine ran great but the moment I gave it a heavy throttle it began missing REAL bad again. On the way back from the coast it ran great for the first 100 miles and then it began missing again REAL bad under a heavy load. So it seemed heat had something to do with the severe missing but I couldn't imagine why heat would cause it. Over the next year I noticed it NEVER missed until it had at least 100 miles on it so it never missed during my usual day-to-day trips. It was only the longer trips in which I exceeded 100 miles when it missed. As I live in the mountains and have to pull a 15 mile long 6% grade coming home it missed REAL bad as long as I had logged at least 100 miles on it before pulling the steep grade. I couldn't understand why it had to have at least 100 miles on it before it missed so I was baffled. Why 100 miles? Why not 25? Or 50? Or 75?

One day when I was pulling the 6% grade after driving over 100 miles it was missing REAL bad and wondered if my lockup torque converter could somehow be involved. And I wondered if I was mistaking the bad missing for "shuddering" (rapid locking and unlocking) of the torque converter's lockup clutch. Hmm. A few days later I went to the local gas station to fill up and noticed my torque converter didn't lock. When I got back home I traced the lockup solenoid's wire back and found I had connected it to the IGN terminal on the fuse block and now that IGN terminal was DEAD. Hmm. As the ignition switch powers the IGN terminal when the key is ON I immediately suspected the ignition switch as it was still the original switch. I replaced the ignition switch and the severe "missing" stopped. It was the torque converter's lockup CLUTCH that was causing the severe "missing". And why the 100 miles? The longer I drove it the hotter the ignition switch got and it just happened to take 100 miles of driving to get the switch hot enough for the internal contacts to quit contacting. I took the old ignition switch apart and sure enough the contacts were burned blacker than black.

Since then I installed a 6-terminal BUSS fuse block on my firewall and use that to power my lockup clutch and it has never given me any further problems. Interesting story, huh?


  • 1971 Corvette Accessory Fuse Block .jpg
    1971 Corvette Accessory Fuse Block .jpg
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