I need help with a problem on my 1988 T/A. When coming to a stop, with the clutch engaged, at 1000rpm in any gear there is a strange symptom, as follows: It feels as if someone took all the plugs out of the engine, then put them back in and this only lasts approximately 1 second. Another way to describe this is that the first time it happened, I actually thought someone hit me from behind. It is as if all compression is lost for 1 second, then it returns and all is normal. There is nothing obvious happening under the hood. I am a mechanic, have been for many years and this one just plain stumps me. Also, there are no error codes.
This is a 305 TPI 5 speed with no modifications. Anyone who has knowledge of this symptom please clue me in as to the cause. Thanks, Rick

 

Pull the distributor and look at it... possibly a point broke off or something?

 

TPS need ajustment ?

 

Nite-One-Three,

Welcome Aboard!

A complete loos of ignition or fuel delivery? Does the engien accelrate normally, or otherwise run normally?

If so, it could be a symptom of that transition point from a fully closed throttle to the IAC becoming active below 1,000 RPM. If the IAC, pintle, and air passages in the TB are clean, you may want to check IAC pulse counts in the idle position. It should be in the 20-40 range. If the throttle stop was inadvertently adjusted in an attempt to change idle RPM, or the TB is dirty around the IAC passages or throttle plates, the lag could be solely from the IAC system. It's amazing just how little varnish and dirt it takes to almost completely "kiil" the IAC's response.

This is the little difference between a "dead" IAC and a very responsive one (same one after cleaning):

 

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