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Hot then cold Yes, ambient air sensors go bad. They're just a thermistor but the connections are 'tender'. You had your radiator replaced. Did they get the ambient air temp sensor correctly located?????? If the sensor is touching the radiator, your symptoms would occur.

Hot then cold Sounds like the ambient air temperature sensor is 'seeing' the radiator warm up. This sensor is near the front right lower corner of the radiator. It's 'easiest' to see from the bottom - but not at all easy to see. It could be the interior sensor but more likely the ambient. I...

Runs bad warm Sounds more like a bad O2 sensor on the driver's side. The O2 sensor does nothing until the engine warms adequately to go into closed loop. At that point the O2 sensor signals whether the mixture is correct (low/high) and the computer corrects for it. A bad O2 sensor lies and the...

LT1 flush The service manual says flush with plain water only. Pull the knock sensors and remove the lower hose at the radiator to drain completely. Fill, run, drain a couple of times and it will come out clean. Watch the analog gauge and make sure it does not get up to 260. Without antifreeze...

94 lt1 no spark Bradleywrench, I dug around in the service manual for my '95 (there are differences from your '94 and I don't know what they are) and found that there are 3 or 4 ccm fuses. Some are in the dash fuse panel (on the passenger side facing the door) and another one is in the 'under...

vacuum leak Sounds like the diaphragm in the controller is broken.

No spark Just to be sure of 'no spark', have you removed one plug wire and secured it to a spare plug that's laying on the plenum or other good ground, cranked the engine and observed no spark in the gap?? There's a thread on a 'competing' forum that says it's possible to get the opti connected...

No Spark - from left field We are related by C4's and your symptoms, so second cousins perhaps, no spark and no "Service Engine Light" when reading codes. I had a 91 Regal with your symptoms - especially the "Service Engine Light" not being on when the ALDL was connected for reading codes (if I...

SYS light Frequently the SYS light indicates a poor battery condition. My '95 SYS light would blink a few times under hard accel but threw no codes. Discovered the battery was original (this was in 2003) so replaced the battery. Haven't seen the SYS light since. Also, you can do a search (see...

Shudder in transmission I've had 3 GM cars that shuddered when under load at just high enough speed to have the TC locked up (40mph on some, 47mph on others). When slightly accelerating or beginning up a slight hill, there would be a lot of shuddering until the TC unlocked. All 3 cars were...

PKE Security Not sure for a '93 but my '95 changes from 1 to 2 (or vice versa) door open with the key in ignition when holding down the door button for about 5 seconds. Without the key in the ignition, holding down the fob door button for about 5 seconds turns the automatic lock/unlock via fob...

Security System aka PKE Congrats on buying a really nice car. If you hear the door locks click when you walk away, leave the fob at some distance and check whether the doors are actually locked. Perhaps they are. When you walk away and hear the door locks click, the horn should toot very...

Injector resistance Make sure the ohm-meter scale is set to ohms rather than khoms or mohms, unless the meter is an auto-ranging meter. 16 ohms will read as zero on either the kohms (1000) or the mohms (1000000) scale. Bad wires will usually show sparks if you view the running engine at night...

Running rough when warmed up Could the water pump be leaking as the engine warms and builds pressure? The pump is just above the Opti and could be spraying the high voltage wires with coolant causing shorting. There may be whisps of smoke or drips on the ground. But a careful exam once warm may...

A/C directional control Reading a lot of threads on this subject, it sounds like the '96 has different materials in the programmer (softer plastic) and suffers more at that distribution point. Never having seen a '96 programmer, I can't verify this. But read up on the subject and you may find...

No Start Can you hear the solenoid click when the key is turned to start? If so, it's definitely not VATS. My '95 with 90k miles had symptoms like yours (could hear the solenoid click) and it was the solenoid. It's possible to repair the solenoid (not easy) so I went for a whole...

Cooling fan control Search using the tab above to confirm this, my memory is vague. The sensor in the water pump feeds the control circuit for the digital gauge and for the fan control. The sensor in the head feeds the analog gauge (which is much less accurate, not because it's analog but...

Rotten egg odor The rotten egg odor comes from the cats working to burn off something 'rotten' that came from the motor, not from a bad cat. Since it's been running rough for a while, the cats are likely just doing their job burning off excell fuel. If the O2 sensors go bad, you may be running...

VATS NICE WRITE-UP!!!! and thanks for the credits I don't copy and paste much stuff from forums, but this one's on my hard drive. Good job.

Heater core The heater core only has 15 to 18 psi during normal operation (whatever the radiator cap pressure is) so don't over pressure it doing testing. Unless you really need heat, consider leaving it bypassed. There are other reasons than leak to bypass the core - usually a stuck door or if...