Starting problem
Thread Starter
1st Gear
Joined: Oct 2020
Posts: 1
Likes: 0
Starting problem
Hey guys, my '93 LT1 has been running fine for months, no lights, issues, anything. Then suddenly the other day i started it, and it initially ran fine, RPMs might have been slightly high but no biggie, but then suddenly the RPMs started dropping suddenly and the idle was pretty rough. I kept giving it gas to try to keep it running, but despite that the RPMs kept dipping until it died on me. Now, when i try to start it it either cranks but doesn't turn over, or occasionally it'll start but do the same thing as before. I changed out the spark plugs hoping that might be it, and on the old ones i noticed on cylinder 8 the plug was pretty white, as if it wasn't getting enough fuel. There might have been another plug like that, but the rest were pretty dirty, lots of carbon buildup. I tried the paperclip trick on the OBD1 and no codes have come up from what i can see. Can you guys maybe get me pointed in the right direction?
Drifting
Joined: Nov 2015
Posts: 1,332
Likes: 397
From: Clay New York
Dare I say....optispark? Check to see if the plugs are firing, if nothing or intermittent you're headed in the right direction. If you've got a good solid spark then I would suspect something in the fuel system. This should keep you entertained for a bit.....
Last edited by ls777z; Oct 18, 2020 at 05:01 AM.
Le Mans Master
Joined: Oct 2004
Posts: 6,314
Likes: 508
From: South-central Missouri
FUEL...AIR...SPARK
Fuel pressure for the "LT1,4 should be very close to 40-41 psi in all operating parameters.
The fact that one plug is "white", whereas the others are sooty(?), suggests one (or more) injectors has failed. Measure the resistance across each injector (when they are at operating temperature, if at all possible!!).
Spark is another item too that needs to be verified. Unfortunately, the Opti-Spark distributor in the earlier LTs were not vented and were prone to issues. The symptoms, as is777z points out definitely points to the Opti. (And, if that turns out to be the problem, replace it with a new one that is vented (very important).
Conclusion: One plug being "white", coupled with the rough idle, hard starting, and dying points to multiple issues. Take them one at a time and resolve/test/verify each "fix" before moving onto the next issue.
Good luck!
P.
Fuel pressure for the "LT1,4 should be very close to 40-41 psi in all operating parameters.
The fact that one plug is "white", whereas the others are sooty(?), suggests one (or more) injectors has failed. Measure the resistance across each injector (when they are at operating temperature, if at all possible!!).
Spark is another item too that needs to be verified. Unfortunately, the Opti-Spark distributor in the earlier LTs were not vented and were prone to issues. The symptoms, as is777z points out definitely points to the Opti. (And, if that turns out to be the problem, replace it with a new one that is vented (very important).
Conclusion: One plug being "white", coupled with the rough idle, hard starting, and dying points to multiple issues. Take them one at a time and resolve/test/verify each "fix" before moving onto the next issue.
Good luck!
P.
