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Automotive Industry

Service Slants

Motor, Jul 2004 by Savasta, Bob

Jeep

Rough idle, MIL illuminated, DTC set. Some 1999-2004 Grand Cherokees, 2000-01 Cherokees and 2000-04 Wranglers, all with the 4.0L inline Six, may exhibit a rough idle for about 30 seconds following a 10to 20-minute soak in hot ambient temperatures (greater than 90°F).

According to Jeep, the problem can be aggravated by high ethanol content in the fuel, is more prominent after stop & go driving and is due to heat from the exhaust manifold migrating to the area around the No. 3 injector. This leads to vapor forming in the injector and causes a misfire in the No. 3 cylinder, which results in DTC P0303 being logged in computer memory. Installing a new insulating sleeve (Part No. 5602H371AA) around the injector should lower its operating temperature sufficiently to prevent a recurrence of the problem.

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Begin the repair by cutting the insulating sleeve with a razor blade or XActo knife so you have two equal sleeves about 1 in. long. Install one sleeve around the No. 3 injector, with its slit facing the upward side of the fuel spritzer (see illustration). Install the other sleeve with its slit facing the downward end of the injector. To complete the fix, make sure the sleeves are Hush with the intake manifold surface and that the injector is rotated to the 2 o'clock position (as viewed from the driver's side of the vehicle) so the wiring doesn't twist and cause undue strain on the harness connector.

GM Truck

Exhaust pop or snap. A slew of General Motors sport/utes and pickups (complete list below) may produce a loud, irritating popping or snapping sound from underneath the vehicle at idle or immediately after engine shutdown.

The good news hure is that GM service engineers have found the source of the noise: moisture trapped between the layers of the muffler. This moisture tends to turn to steam as it's super-heated by the exhaust gases. That in turn leads to the expansion of the inner shell of the mufflcr, which deforms and expands against the outer layers and case. Its this contact that results in the popping or snapping noise.

The bad news is that GM doesn't have a remedy for the problem, at least not yet. Replacing the muffler or other exhaust components won't result in a fix, so don't waste your time or your customer's money. GM is actively working on a solution, and should have one shortly.

The Following vehicles can be affected by the problem:

1999-2004 Chevy Silverados and GMC Sierras

2000-04 Chevy Suburbans & Tahoes and GMC Yukons & Yukon XLs

2002-04 Cadillac Escalades & Escalade EXTs

2003-04 Cadillac Escalade ESVs and Hummer H2s

Ford

Fluttering noise on shutdown. Ford wants you to be aware that some: 2000 Focus models (build dates 9/2/99 through 10/1/99) can produce an irritating fluttering sound from the engine bay when the engine is shut off. Powertrain engineers have traced the problem to the natural resonance that sets up in the PCV valve and hose when vacuum to the valve is abruptly terminated at shutdown. A new-design PCV valve (Part No. YS4Z-6A666-AA) and hose (Part No. YS4Z-6758-BA) are now available to address the noise complaint. Figure about .2 hour labor to complete the parts swap.

Lincoln

Battery warning light on, DTC set. Some 2003 Town Cars built before 7/1/02 may illuminate the battery warning lamp on the dash and store DTC P1246 (generator load input failed) in PCM memory. Lincoln engineers say the condition typically occurs when the vehicle is started, then placed in gear and immediately driven, without allowing the engine to return to normal idle. Problem is, under those circumstances, the PCM strategy is set up so it won't command the alternator to charge, which causes the warning light to go on and the code to set.

A revised PCM strategy is now available to correct the anomaly. You'll find the software update in WDS release B28.3 or higher. After the reprogramming is complete, make sure you fill out an Authorized Modifications Decal and affix it adjacent to the VECI decal.

GIVI Truck

Headlamp saver. If the low-beam headlight socket corrodes or shorts out on a 2002-03 midsize GM sport/ute (full list below), the General has good news: A replacement socket (Part No. 88987884) is now available to eliminate the problem. Previously, the entire headlamp assembly had to be replaced if the socket went.

To install the new replacement socket, begin by removing the headlamp assembly. Now cut the old, damaged socket from the wiring harness. Using a few wire splice sleeves (Part No. 12089189 or equivalent), splice the new socket into the harness. Cover everything up with electrical tape, then install a new bulb into the socket. To complete the repair, install the replacement socket into the headlamp assembly, then the headlamp assembly back into the vehicle. Total elapsed time for the surgery should be about .3 hour.

Trucks that can benefit from the new low-beam socket are Chevy TrailBlazers and TrailBlazer EXTs, CMC Envoys and Envoy XLs and Olds Bravadas.

Toyota

Vibration under brakingl Toyota says that 1996-2000 4Runners are prone to giving off a pretty nasty vibration under braking at speeds above 40 mph. Not surprisingly, excess lateral runout in the front rotors is the most likely cause for the complaint.

Automotive Industry

Service Slants

Motor, Jul 2004 by Savasta, Bob

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