futuretech

LT1 97 camaro, rebuilt 383, ran 11.9 before bearing spun. Motor professionally rebuilt, same specs. Car starts and runs fine but now only runs high 12's. Lost a second. No codes, scanner says timing goes to 36 but 60' foot times of 1.7x tells me power is way off. Can this be a cam installation error or crank sensor incorrectly installed?

1994-LT1-Eric

Have you had the tuner at the numbers?

Injuneer

Wouldn’t be the “crank sensor” causing the problem. That was only added to the LT1 in 1996/97 models, to meet the OBD-2 misfire detection requirement. The PCM uses the data from the optical cam position sensor in the Opti to time the ignition and sequential fuel injection.

I’ve diagnosed a problem with the Opti being misaligned with the cam dowel pin, and the engine ran well enough with the screwed up timing that the owner didn’t notice anything unusual in the way the engine ran. But…. if the cam dowel pin is not aligned correctly, the PCM would detect a difference between the position reported by the crank sensor and the position reported by the Opti. But in that case the PCM sets a diagnostic code for the crank sensor performance. Have you scanned the PCM for codes? It was the crank sensor code that the owner was trying to solve.

The number shown on a scanner for spark advance is the value it is reading from the timing tables, +/- any programmed offsets based on engine operating conditions. It isn’t the actual timing. There is no feedback to the PCM on actual timing.

An incorrectly indexed timing set is a valid concern.