This past weekend I took the Cadillac on a relatively small road trip to Stillwater, MN for a Sunday Fun-day. It was a gorgeous spring day here in Minnesota so a group of us met for drinks on the river.
Anyhow, as soon as I pulled in to town the car developed a hard misfire. It felt like a single cylinder, but the only code being thrown was a P0300. I limped it to my dad's place and left it to be towed to the shop. Keep in mind, up until pulling into town the car ran flawlessly.
I finally got a chance to dig into it today. A quick scan showed that cylinder #2 was the culprit. I went about the usual tests: removed the ignition cassette and plug, plug was wet with (what smelled like) fuel but looked good so I assume coil died, no spark. I swapped coil packs, still #2. Hm. Alright, the coil boots look good but they may be arcing, so swap those around. Still #2. Alright... swap injectors quick. STILL #2.
At this point I'm already jumping to conclusions. The Northstar "stigma". I ran a quick compression test, had 160 psi. Ok, so nothing is hanging up. I put it back together and fired her up, letting it idle with the misfire while I set up my hydrocarbon tester. Within 3 sniffs of the overflow tank the fluid turned yellow. Great! She's blown up...
I took a few minutes to think about things, thinking there's no way the head gasket is bad when I have NO coolant in the oil, NO over-pressurization of the cooling system, and NO overheating. Then it hit me: I never swapped the actual spark plug around. I inspected it, it looked perfectly fine, so I moved on. Low and behold, swap the plug to #4 and the misfire follows. Threw in a set of OE's and she runs better than ever.
Definitely a case of me getting ahead of myself, all because I assumed the worst. Plugs were actually on my list of to-do's with this car, I just haven't gotten to it yet. I did just the front bank tonight, the rear requires removal of A.I.R. valves and other crap so I'll get to it soon, when I have time.
The lesson? Be logical! Sometimes just taking a step back and slowing down does wonders. I still can't explain why the hydrocarbon test failed, however. Since I replaced the radiator, thermostat, overflow tank and flushed the system the temps have been absolutely rock solid. I'm happy to call it a false positive, for now.
Anyhow, as soon as I pulled in to town the car developed a hard misfire. It felt like a single cylinder, but the only code being thrown was a P0300. I limped it to my dad's place and left it to be towed to the shop. Keep in mind, up until pulling into town the car ran flawlessly.
I finally got a chance to dig into it today. A quick scan showed that cylinder #2 was the culprit. I went about the usual tests: removed the ignition cassette and plug, plug was wet with (what smelled like) fuel but looked good so I assume coil died, no spark. I swapped coil packs, still #2. Hm. Alright, the coil boots look good but they may be arcing, so swap those around. Still #2. Alright... swap injectors quick. STILL #2.
At this point I'm already jumping to conclusions. The Northstar "stigma". I ran a quick compression test, had 160 psi. Ok, so nothing is hanging up. I put it back together and fired her up, letting it idle with the misfire while I set up my hydrocarbon tester. Within 3 sniffs of the overflow tank the fluid turned yellow. Great! She's blown up...
I took a few minutes to think about things, thinking there's no way the head gasket is bad when I have NO coolant in the oil, NO over-pressurization of the cooling system, and NO overheating. Then it hit me: I never swapped the actual spark plug around. I inspected it, it looked perfectly fine, so I moved on. Low and behold, swap the plug to #4 and the misfire follows. Threw in a set of OE's and she runs better than ever.
Definitely a case of me getting ahead of myself, all because I assumed the worst. Plugs were actually on my list of to-do's with this car, I just haven't gotten to it yet. I did just the front bank tonight, the rear requires removal of A.I.R. valves and other crap so I'll get to it soon, when I have time.
The lesson? Be logical! Sometimes just taking a step back and slowing down does wonders. I still can't explain why the hydrocarbon test failed, however. Since I replaced the radiator, thermostat, overflow tank and flushed the system the temps have been absolutely rock solid. I'm happy to call it a false positive, for now.