: 93 with a miss

09-26-12, 07:43 PM
Have a 93 with northstar with 40 K miles. Car started developing a miss when driving, feels like it's chugging going up hill and you can feel the car shaking a little. Hear it at idle
Never when cold but intermittant when operating temp. Not neccesarily tied to operating temp when warm.
Never went away when driving but did stop after shutting off and restarting.
Local shop read codes, said fuel imbalance between banks. Replaced O2 sensors, plugs, wires, and cleaned injectors and egr. Took for a long test drive and was fine. I picked the car up and on the way home car started with the same symptoms.
I think the dirty O2 sensors and plugs were not the root cause, but result of problem.
It's back at the shop, any ideas?

09-27-12, 09:51 AM
I had something similar, when cold it ran ok, but I got up to operating temp driving between say 42-60 mph it would surge, chug and just feel like it was missing, part of that was the torque converter but a simple tap of the brakes would make that part go away....but when the torque converter kicks it will MAGNIFY any miss you have in your ignition system. Also she was a dog out of the hole, like you were starting in 2nd gear but when you count the shifts it was all 4.

My friends told me it was spark, replaced plugs (delco), wires (delco) found a coil that was bad replaced with napa cheapie, fuel filter, replaced PCV, verified proper fuel pressure, fogged the throttle body to check for vacuum leaks, seafoamed it all the way to the Cat convertor, cleaned the throttle body and EGR and none of those things seemed to work. Last weekend we were doing more research and talking with a Northstar guy and he suggested based on what I had already done to replace all 4 coils, replace the MAP sensor and possibly a Throttle Position Sensor. So I bought everything he recommended for roughly 150$ and she absolutely SCREAMS now, I had forgotten what torque steer even was :D

The MAP sensor is under the intake cover drivers side, the Throttle position sensor is beside the throttle body closer to the front of the car, I did have to remove the dogbone motor mount assembly to get to those stupid star headed bolts, it took me about an hour and my goodness what am impressive car it is now! Dont forget to let the computer relearn, there is a procedure to relearn the idle but I could not get into my diagnostics (another problem) So I just followed the directions in the owners manual for when you disconnect the battery and let the computer run thru its own relearn process.

I do not know which one did it, but the MAP sensor looked pretty bad so that would be my guess, or it may have been a combination of all. I have no chuggle, I dont even notice the torque convertor kicking down anymore other then a drop in RPM's, no shaking no nothing just smooth as silk now

09-27-12, 10:17 AM
I would suspect the coils first. Very common on a Northstar to have a coil fail.

10-05-12, 09:38 AM
just as a note, my mileage has went from a 17.1 average to 20.6 :yup: and thats with me putting my foot into her a lot more then I ever did before