Miss/vibration
Thread Starter
Instructor
Joined: Oct 2006
Posts: 233
Likes: 3
From: Franklin indiana
Miss/vibration
I have a 90 convertible that I bought with the GM HOT cam, headers, true duals. The engine sounds flat, like it isn't firing on all cylinders. It also has a Carolina clutch and aluminum flywheel. It has supposedly new MSD wires and cap. When it is lugged at all, it vibrates and kind of chugs. You can't drive in 5th or 6th at any low speed at all. The PROM was burned for the setup I have now. Could the flywheel not being balanced properly cause this, or is it some kind of ignition/injector issue? It has LT1 injectors, and I'm not sure about them. Sometimes it takes a few seconds to start, like it might be flooded, also runs extremely rich. Thanks for any help.
Safety Car
Joined: Sep 2003
Posts: 3,599
Likes: 24
From: Orange County NY
St. Jude Donor '10-'11-'12-'13
Was it running like this when you bought it? An out of balance flywheel wouldn't cause it to run like that. From what you describe, it could be anything from an ignition / electrical component issue to any number of mechanical issues (causing it to run rich). If the plugs are really carbon fouled, that could cause the symptoms you are describing. Time for new plugs, but they wouldn't get that way unless something else wasn't right, so you still need to troubleshoot.
Racer
Joined: Dec 2004
Posts: 470
Likes: 0
From: Phoenix Arizona
I have a '90 vert, had almost the identical problem, rough idle, minimal power, and would chug while driving 45mph. Actually had two problems:
1) O2 sensor replaced
2) Injectors replaced, removed originals and replaced with Bosch 24#
Car runs great now! Hope this helps
1) O2 sensor replaced
2) Injectors replaced, removed originals and replaced with Bosch 24#
Car runs great now! Hope this helps
Thread Starter
Instructor
Joined: Oct 2006
Posts: 233
Likes: 3
From: Franklin indiana
When I got it it wasn't running well, it had had a much larger cam in it, and the chip was burned for that. I got one programed for the current setup, and it missed and backfired after it went into closed loop. I changed the O2 sensor to a heated one, and it is driveable. I have cleaned the plugs (not bad), cleaned the cap (looks new), checked timing, set TPS, checked firing order. I do have the stock injectors, thinking about putting those in. Also, when I stop, it takes a while for it to idle down. I didn't think being out of balance would do that, but you can feel the vibration until you put the clutch in.
