Engine - Knocking Noise After Cold Start
Article No.94-14-4
07/13/94
ENGINE - 1.8L - "KNOCKING" NOISE FROM ENGINE AFTER COLD START - VEHICLES WITH ENGINE I.D. NUMBERS BEFORE 794954
FORD:
1991-93 ESCORT
LINCOLN-MERCURY:
1991-93 TRACER
ISSUE:
A "knocking" noise may be heard after initial cold start. The noise may either remain constant or go away after the vehicle reaches operating temperature. This may be caused by carbon build-up on the "squish" area of the piston face or cylinder head.
ACTION:
Using Carburetor Tune-Up Cleaner, remove carbon deposits from the combustion chambers. If the carbon cleaning procedure fails to permanently eliminate the "carbon knock", replace all four pistons (4) with revised pistons which allow for increased clearance in the "squish" area.
BEFORE YOU BEGIN:
There are several causes of engine noise. TSB articles have been released addressing some of these concerns. Hydraulic Lash Adjuster (HLA) noise and the noise from carbon build-up sound similar, however HLA noise generally stops after the first 5-10 seconds of engine operation.
To eliminate the possibility of HLA noise, refer to the following TSB articles:
^ TSB 93-24-14
^ TSB 92-18-5
^ TSB 92-17-6
CARBON CLEANING PROCEDURE
1. Bring engine to normal operating temperature, then turn engine off.
2. Obtain a two (2) ft. (0.61m) length of 1/8" I.D. vacuum hose for use as a feed tube for the carbon cleaner.
3. Connect one end of the feed tube to the canister purge vacuum port on the upper intake manifold, Figure 2, and place the other end of the feed tube in the can of cleaner.
4. Pinch the feed tube with clamping pliers to prevent suction during engine start-up.
CAUTION:
FORD CARBURETOR TUNE UP CLEANER MUST BE FED INTO THE ENGINE THROUGH THE CORRECT VACUUM PORT AND THE FEED RATE MUST BE SUCH THAT AT LEAST 20 SECONDS IS REQUIRED TO EMPTY A CONTAINER. A FASTER FEED RATE MAY RESULT IN LIQUID ACCUMULATION IN THE ENGINE CYLINDERS, RESULTING IN HYDRAULIC LOCK UP AND POSSIBLE ENGINE DAMAGE.
CAUTION:
PROVIDE A SEPARATE FEED TUBE FOR THIS PROCEDURE. DO NOT USE ANY OF THE VEHICLE VACUUM HOSES FOR FEEDING CLEANER INTO THE ENGINE. DETERIORATION OF THE VEHICLE VACUUM HOSES MAY RESULT.
5. Restart the engine.
WARNING:
AN EXCESSIVE AMOUNT OF EXHAUST SMOKE WILL BE PRODUCED IN STEP 6 OF THIS PROCEDURE. USE AN EXHAUST HOSE TO VENT THE SMOKE.
6. Allow the idle to stabilize, then:
a. feed cleaner into the engine by releasing the pliers while maintaining engine speed between 1500-3000 RPM until 1/2 of the cleaner is used.
NOTE:
REGULATE CARBON CLEANER FEED RATE BY PARTIALLY KINKING THE FEED TUBE.
b. Allow the idle to drop and engine should stall. If it doesn't, turn engine off.
7. Let the vehicle sit for at least six (6) hours, or up to 24 hours. This allows the cleaner to saturate the carbon in the combustion chambers.
8. Flush the remaining carbon from the engine by repeating Steps 1 through 6, using the remaining cleaner. DO NOT let the engine stall.
9. Remove the feed tube and reconnect the canister purge vacuum line.
10. Take the vehicle on a 3-4 mile (5-6 km) test drive, using the full RPM range to remove any remaining cleaner or carbon from the engine.
NOTE:
INFORM CUSTOMERS THAT ONLY QUALITY UNLEADED 87 OCTANE FUEL SHOULD BE USED (REFER TO TSB 91-8-13). USE OF PREMIUM (HIGHER OCTANE) FUEL IS NOT RECOMMENDED AND MAY CONTRIBUTE TO RAPID CARBON BUILD UP IN THE ENGINE.
If the carbon cleaning procedure fails to permanently remove the "carbon knock," piston replacement will be necessary.
PISTON REPLACEMENT PROCEDURE
1. Check the engine I.D. number to verify the build date of the engine, Figure 1. If the engine I.D. Number is before 794954, it has the old level pistons.
2. Remove all four piston and connecting rod assemblies. Refer to the appropriate model year Service Manual, Section 03-01A for removal procedure.
NOTE:
MARK ALL CONNECTING RODS AND CAPS TO IDENTIFY CORRESPONDING CYLINDER LOCATION.
3. Inspect the cylinder bores for damage.
a. Measure cylinder bore diameter, bore taper and cylinder out-of-roundness for standard size pistons. Refer to the appropriate model year Service Manual, Section 03-01A.
b. Oversize pistons are available if cylinder bores are damaged, or if measurements are not within specifications.
NOTE:
IF CYLINDERS ARE WITHIN SPECIFICATIONS AND OVERSIZE PISTONS ARE NOT REQUIRED, DO NOT BREAK THE GLAZE OR HONE THE CYLINDER BORES. THIS WILL DISTURB THE PRODUCTION BORE FINISH AND COULD CAUSE OIL CONSUMPTION.
NOTE:
NEW CYLINDER HEAD BOLTS ARE NOT REQUIRED WHEN REPLACING THE 1.8L CYLINDER HEAD. THE ESCORT/TRACER SERVICE MANUAL INCORRECTLY STATES THAT REPLACEMENT IS REQUIRED. REUSE THE ORIGINAL CYLINDER HEAD BOLTS UNLESS VISIBLY DAMAGED.
4. Remove the pistons from the connecting rods and install the new revised pistons and new piston rings. Refer to the appropriate model year Service Manual, Section 03-00.
5. Reassemble the engine. Refer to the appropriate Service Manual, Section 03-01A for reassembly procedures.
OTHER APPLICABLE ARTICLES:
92-17-6, 92-18-5, 93-24-14
WARRANTY STATUS:
Eligible Under The Provisions Of Bumper To Bumper Warranty Coverage For 1992-93 Models, Basic Warranty And Powertrain Warranty Coverage For 1991 Models
Parts Block
OPERATION DESCRIPTION TIME
941404A Clean Carbon Only 0.6 Hr.
941404B Clean Carbon And Replace 8.3 Hrs.
All (4) Piston/Ring
Assemblies
DEALER CODING
BASIC PART NO. CONDITION CODE
6108 56
OASIS CODES: 497000