Exhaust System Splash Shield - Knocking Noise

91olds02

NUMBER: 91-T-96

CORP.REF.NO: 806601R

DATE: April 1991

SECTION: 6F


SUBJECT: EXHAUST SYSTEM WATER/SLUSH SPLASH SHIELD, NEW PART NUMBER AVAILABLE


MODELS/YEARS: 1986-91 EIGHTY-EIGHT
1985-91 NINETY-EIGHT


THIS BULLETIN CANCELS AND REPLACES DEALER TECHNICAL BULLETIN 90-T-128 WHICH SHOULD BE DISCARDED.

On the above vehicles, it is possible to have a condition of the exhaust pipe contacting the intermediate heat shield, which is located between the exhaust pipe and the floor panel. This condition could occur when water or slush is splashed onto the underside of the exhaust pipe. The rapid cooling and resultant contraction may cause the pipe to bow upwards making contact with the shield above it.

It is possible that the knocking noise could be transmftted to the engine through the exhaust pipe. This could be picked up by the ESC knock sensor, which in turn, would signal the ECM (by lack of voltage), causing it to respond with retarded ignition timing, thinking the engine has a detonation condition.

Figure 1:

CORRECTION FOR 1985-1988 VEHICLES:
1. Order shield from GMSPO (Part Number 25533711) which consists of two pieces.
2. Install the shields with three stainless steel clamps and the existing front bracket (See Figure 1).

Figure 2:

CORRECTION FOR 1989-1991 VEHICLES:
1. Order shield from GMSPO (Part Number 25533711).
2. Notch both the front and rear halves of the shield (See Figure 2) to clear the cross brace welded to the exhaust pipe. Install the shields with three stainless steel clamps and the existing front bracket (See Figure 2).

Parts are currently available from GMSPO.

WARRANTY INFORMATION:
Labor Operation Number: T5179
Labor Time: 0.3 hour (1985-88 vehicles) 0.6 hour (1989-91 vehicles)
Trouble Code: 92