Expert: Robert Summers - 9/25/2009

Question
Hi
  I have a 87 S10 2.8 liter TBI, auto.   It has always ran like a champ! Until it suddenly started sputtering.  It will turn over, but all it will do is sometimes idle harshly but with no MIL light.  I have found that if I unplug the Temp sensor, it will crank and run smoothly (at a high idle) for about 15 seconds.  During this time I can rev the engine, but as soon as those 15 seconds are gone, it dies.  Then it's back to a really rough idle, and if I floor the gas. it will die.  I replaced the temp sensor.  I did notice that if I disconnect the map sensor's vacuum line it idles better, but dies once again once I touch the gas.  One more thing, no MIL light at all till I start unplugging sensor.  Can you give me an idea?

Answer
Hi Brian. well it could be a heat sink problem in the ign control module. try changing it, and the other thing it could be is a bad coil. even though you don't have a service engine soon light try putting a scan tool on it and see  if you have any history codes...also watch the voltage on map sensor, high voltage would mean bad ign module.... hope this helps