Strange result testing with noid light - any insight?
Thread Starter
2nd Gear
Joined: Jan 2024
Posts: 2
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Strange result testing with noid light - any insight?
Hi, working on my son's 94 Corvette LT1 base. He complained of rough running and thought it might be his injectors. I checked each one for ohms and they were all in spec and nearly the same. I then tested the harness with a noid light and got a strange result - only cylinders 7 and 8 lit up the noid light, with a regular pulse. None of the other cylinders lit up at all. Any ideas on what would cause this? I researched about the TPS possibly causing a no fire if it was stuck open, but then I wouldn't be seeing 7 and 8 light up, would I? Same thought on ICM - I understand they would all not work if that was bad. No codes. Hoping it's not the ECM. Started reading about potential VATS issues but again don't thing I'd see any firing of 7 and 8 if that were true. It was running when I started testing, just running rough according to my son. Thanks in advance.
Le Mans Master
Joined: Sep 2013
Posts: 6,192
Likes: 750
From: near the thumb in the mitten
94-97 lt1 are SFI aka Sequential Fuel injection. Each injector is independently turned on. Is there 12v to the other injector connectors? Using a spark tester is there in spark at all cylinders?
vats fault will keep security light on dash on.
vats fault will keep security light on dash on.
