9/1/2003
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Shop Line September, Enginer Builder
Our installers say late model GM 2.4L engines often have a rough idle. Nothing seems wrong internally. Any suggestions we can give them?
According to AERA’s Technical Committee, it may not be an internal issue. Rough idle or misfire complaints accompanied by illumination of the "Check Engine" light may on GM 2.4L VIN T engines be the result of a missing spark plug boot spring.
See Figure 1 (left) for specifics. You can check for the presence of spark plug boot springs by removing each boot and checking for the spring presence at the boot to coil tower connection. If the spring is missing, replace the spark plug boot assembly (p/n 12132224).
Another noise-related question: What could be causing temperature gauge fluctuation and a "thumping" noise on Ford 4.0L engines?
When referring to Ford 4.0L engines (VIN X, 1995-2000), other AERA members have reported a fluctuating temperature gauge often accompanied by a knocking or thumping noise.
The noise is most pronounced when the engine is at normal operating temperatures and most noticeable in the passenger compartment of the vehicle. The noise results when coolant boils and produces bubbles of steam that are transmitted through the heater hoses and heater core.
Ford offers a coolant by-pass kit to increase the flow, which reduces steam formation in the cooling system. Refer to the chart (Figure 2) to determine the correct bypass kit.
It’s a little more specialized, but what could cause startup noise in Jaguar 4.0L engines?
The AERA Technical committee offers the following information regarding an engine noise during start-up for 1997-2000 Jaguar 4.0L engines. It has been reported that some engines may experience a rattling noise when the engine is started. The secondary timing chain tensioners can cause a noise that seems to come from another part of the engine.
Revised, spring assisted, secondary timing chain tensioners have been introduced to correct this problem, starting with engine c/n 98102106XX. In case of a customer complaint, the revised tensioners should be installed on earlier V8 engines.
The installation procedure for the revised tensioners is the same as the original style tensioner except that they must be installed in the compressed condition (retained by the clip) as shown in Figure 3 below.
The retaining bolts should be tightened to the recommended torque setting of 89-124 in.lbs (10-14 Nm) before the clip is removed to release the piston and apply tension to the secondary chain. Note: tying a string to the clip before assembling the tensioner assembly may help recover the clip if it is accidentally dropped. It should also be noted that the tensioners for left and right banks have different part numbers: p/n NCA2017AF for the "A" bank and p/n NCA2017BE for the "B" bank.
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