OK, the roadster has been laid up for several months while I put fenders on it. Engine is a 1994 from a Camaro or Firebird with a 4L60E trans. Factory style wiring and ECU. Today I took it for a short spin, went two blocks and got gas then up the road a bit. About 1.5 miles up the road, engine temp about 160-170 it started to miss. Run...die...run...die. Finally got it's act together and ran right. Got home and checked the light (it's in the trunk...to lazy to run a wire up to the dash). No Light! Which I can assume no codes. Started acting up just about the time it goes into closed loop. Any ideas?

 

a no fuel issue or low fuel pressure issue will not throw a code. check/change fuel filter and check contents for water or crud. test fuel pressure.

 

Good call. I was thinking along the same lines. Things seem to have correct themselves and I can't fine a "smoking gun". I think the fuel injection god just poked me in the eye and left no trace. I'll take it up the road again tomorrow and see if it happens again.

 

Been a while and the problem still exist but with a new twist. Car runs just fine for ABOUT 2-3 miles, check engine light comes on and starts to misfire. About a block later the light goes out and it's running smooth again. Get home and pull the codes and always the same, low coolant temp. Using EEHACK I can watch the coolant temp and it's within several degrees of the dash gauge. Sensor seems to be working correctly. Any ideas?

 

there are two temp sensors one for the gauge and one for the computer, one under #1 cylinder and one at the water pump.

 

check 20 and 12 here 4th Gen LT1 F-Body Tech Aids

 

Yes, two sensors, that's why I mentioned the EEHACK and gauge were within several degrees of one another. I can watch the EEHACK temp climb smoothly and then go into close loop. Mystery as to why it would stumble, throw a code then turn off the check engine light and smooth out.

 

OK, put the EEHACK on the ALDL and watched the coolant temp. At first it read about 100 degrees and then it flipped to 43 degrees. Still warming the engine it flipped again to 125-135 degrees and then want back to 43 degrees. Each time it goes to 43 degrees it sets a code. Finally it would not move from 43 degrees so I assumed the sensor had died. Went to replace the sensor and got to thinking I've done this before. Looked back at my receipts and yes, I did replace it. So this is the 3rd coolant temp sensor. Got it from Auto Zone, Duralast. Why would I have two sensor failures?

 

a grounded sensor wire I believe will cause it to go max one way or the other, I think -43 degrees.