IDLE SURGE AND/OR CODE 30 LOSS OF POWER

VEHICLES AFFECTED: ALL WITH HT4100 ENGINES

The following information will summarize the appropriate service operations for vehicles which experience abnormal distributor drive gear wear. This information supersedes Bulletin 86-641-101 which should be destroyed.

Some Cadillacs equipped with the HT4100 power system may experience abnormal or premature distributor gear wear. The symptoms of this condition are idle surge and/or code 30 or loss of power. If these conditions are exhibited, the following service procedures should be followed:

1. Remove ignition distributor as described in Section 6D of the appropriate Service Information Manual.

2. Inspect both the drive gear on the camshaft and the driven gear on the distributor shaft for evidence of advanced wear.

3. If either gear is worn, the following three actions must be completed:

A. Replace the distributor driven gear. A redesigned gear, P/N 10499163, has recently been released to supersede P/N 1979546. This new gear is identical to previous designs except that a tin plating operation has been added to improve break-in characteristics and minimize premature tooth wear. It can be easily identified by its "Silvery" appearance. GMWDD service stock of distributor assemblies has also been updated with this improved part.

B. Replace the camshaft. P/N 1628822 is used for all engines. Refer to Bulletin 84-6-229. Be sure to prelube all contact surfaces including the distributor drive and driven gears with the lubricant provided in the cam kit (lubricant available separately as P/N 1052365).

C. Remove the engine oil pan and oil pump and inspect the oil pump gears and housing for wear. Replace oil pump and clean the oil pan as required.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.