95 LT1 Rough Running, need help!
Thread Starter
Racer
Joined: Aug 2008
Posts: 388
Likes: 116
From: Jackson Michigan
95 LT1 Rough Running, need help!
Please help me diagnose my problem. Car is running rough, misfiring on acceleration. Idle a bit rough. I checked fuel pressure, and it goes to 42 with key on, not running. Turn key off, and it drops to 20 instantly, then down to zero within 5 minutes. I realize this isn’t right, but not sure why it’s doing this. While running, pressure is about 38. When I pull the regulator vacuum line, it jumps to 42, so I think the regulator is OK. Checked all injectors with stethoscope while running, and all are clicking steadily. Next, I used my temp gun to check the header temps while warming up from cold start. All but #2 quickly heated up to 175 to 200, while #2 was staying around 95. So, I’m guessing I either have a fuel or spark issue on that cylinder. Could the rapid decay in fuel pressure be a leaky #2 injector? What should I check next? Any guidance would be appreciated.
John
John
Thread Starter
Racer
Joined: Aug 2008
Posts: 388
Likes: 116
From: Jackson Michigan
Another data point
I lifted the fuel rail/injectors out of the intake, leaving the fuel lines connected. Key on shows 42 psi, with no leakage on #2 or any other injector. After key is on for about 3 seconds, fuel pressure drops rapidly (key still on). Also, no fuel smell on dipstick. Now I’m thinking fuel pump check valve may be faulty, but that doesn’t explain the #2 cylinder issue. So, looks like plug wire, plug, or cap might be next suspect. Unfortunately, the headers are making it almost impossible to pull that plug, or hook up my inline spark tester…
Another update:
While the injectors were out, I switched #2 and #4 to see if the problem followed the injector. Started it up and #2 header is still about 100 degrees, while the rest are over 200 degrees.
John
Another update:
While the injectors were out, I switched #2 and #4 to see if the problem followed the injector. Started it up and #2 header is still about 100 degrees, while the rest are over 200 degrees.
John
Last edited by WhiteC1; May 24, 2023 at 02:42 PM.
Thread Starter
Racer
Joined: Aug 2008
Posts: 388
Likes: 116
From: Jackson Michigan
Another update
As mentioned in the previous post, I switched injectors, and cylinder #2 doesn’t seem to be firing properly, as evidenced by the header temperature being about half of the other cylinders. I hooked up a spark tester in-line with #2’s spark plug, and it appears to be firing consistently. I’m not sure what to check next. Any suggestions? Maybe a compression test on that cylinder? Hard to imagine the Opti causing such an issue, although it didn’t want to start right away. Had to try several times. Fuel pressure was about 32 psi while cranking, and about the same running. Engine off, key on, pressure goes to 42 psi, then after prime stops, pressure drops like a rock to about 5 psi immediately.
John
John
