What is the 1991-1999 Ford Explorer Automatic transmission overdrive failure (A4LD / 4R55E)?

The 4-speed automatics behind the 4.0L - the early A4LD and the later electronically controlled 4R44E/4R55E - are a known weak point, commonly failing in the 120k-mile range, most often losing 4th gear (overdrive). The overdrive planetary is fragile (early units used a weaker pin… Repairs typically run $25-$3,500. Severity: high.

What is the 1997-1999 Ford Explorer 4.0L SOHC timing chain cassette, guide, and tensioner failure?

The 4.0L SOHC V6 (introduced in the Explorer for 1997) uses a complex three-chain system: a crank-to-jackshaft chain at the front plus two cam chains at the rear of the engine, all riding on plastic guide 'cassettes' with hydraulic/spring tensioners. The plastic cassettes and the… Repairs typically run $400-$3,000. Severity: high.

What is the 1997-2001 Ford Explorer 5R55E Automatic Transmission Reverse Loss and Forward Clutch Slipping?

The 5R55E five-speed automatic (behind the 4.0L before the 5R55W/S arrived for 2002) commonly loses reverse and/or slips in Drive/1st as the low/reverse sprag, reverse clutch pack, and forward clutch wear. A broken tab on the pressure-regulating (EPC) solenoid in the valve body d… Repairs typically run $900-$3,000. Severity: high.

What is the 1991-1999 Ford Explorer Firestone tire tread separation and rollover safety crisis (NHTSA EA00-023)?

The defining safety issue of the 1990s Explorer: original-equipment and replacement Firestone ATX, ATX II, and Wilderness AT P235/75R15 tires (notably from the Decatur, IL plant) suffered tread/belt separation at highway speed. Combined with the Explorer's relatively high center… Repairs typically run $600-$1,000. Severity: high.

What is the 1991-1999 Ford Explorer Frame, rear subframe, and rocker/body-mount rust?

In salt-belt climates, 1991-1999 Explorers rot in predictable structural areas: the inner rocker panels, the tops of the front leaf-spring hangers (dirt packs between the hanger and inner rocker, which the factory welded only at the bottom), rear spring hangers/shackles, and the… Repairs typically run $200-$3,000. Severity: high.

What is the 1997-2005 Ford Explorer 4.0L SOHC Camshaft Position Sensor and Synchronizer Failure Causing P0340 Misfire and Stalling?

The 4.0L V6 uses a camshaft synchronizer (a gear-driven cylindrical housing that also drives the oil pump intermediate shaft) with the camshaft position sensor mounted on top. The plastic vane/'flag' on the synchronizer and the sensor's internal magnet wear or come apart, manglin… Repairs typically run $150-$500. Severity: medium.

What is the 1991-1999 Ford Explorer Camshaft synchronizer / CMP sensor bushing failure?

The 4.0L (both OHV and SOHC) drives the camshaft position sensor off a gear-driven 'synchronizer' assembly in place of a conventional distributor. The synchronizer's shaft/bushing wears or gums up with varnish, developing play and producing a distinctive squeak/chirp that is ofte… Repairs typically run $150-$500. Severity: medium.

What is the 1997-2003 Ford Explorer Intake Manifold / PCV Vacuum Leak on 4.0L SOHC Causing P0171/P0174 Lean Codes and Rough Idle?

The 4.0L SOHC V6 is notorious for lean-bank codes P0171 and P0174 caused by unmetered air leaks rather than a dirty MAF. The plastic upper intake manifold and its rubber O-ring gaskets, plus the heat-degraded PCV elbow/hose near the throttle body, crack and collapse under vacuum,… Repairs typically run $120-$600. Severity: medium.

What is the 1997-2005 Ford Explorer DPFE Sensor / EGR Failure Setting P0401 and Companion P0171/P0174 Lean Codes?

The Differential Pressure Feedback EGR (DPFE) sensor on the 4.0L/4.6L Explorer has a very high failure rate past ~60k miles. Internal corrosion makes it under-report EGR flow, so the PCM sets P0401 (insufficient EGR flow) and can hold the EGR valve open too long, producing a lean… Repairs typically run $80-$350. Severity: low.

What is the 1995-2010 Ford Explorer Power Window Regulator Cable/Clip Failure Causing Window to Fall Into the Door?

The cable-drive window regulators on the Explorer/Mountaineer/Sport Trac fail as their plastic cable guides crack and the steel lift cable frays or jumps off the drum. The window then binds, drops crooked, or falls down inside the door — the motor often still runs. The front door… Repairs typically run $120-$400. Severity: low.

Ford · Known Issues

1999 Ford Explorer Problems: 12 Known Issues

1999 model year · NHTSA recalls, manufacturer TSBs, and owner forum reports · Updated August 2026

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According to Au7o's research across NHTSA recalls, manufacturer TSBs, and owner forum reports, the 1999 Ford Explorer has 12 documented known issues, with 7 rated critical. The most serious are 4.0L OHV cracked cylinder heads and blown head gaskets from overheating ($1,000-$2,800 repair), Automatic transmission overdrive failure (A4LD / 4R55E) ($25-$3,500 repair), Firestone/Wilderness AT Tire Tread Separation Causing Blowouts and Rollovers (Recall EA00-023) ($0-$900 repair), 4.0L SOHC timing chain cassette, guide, and tensioner failure ($400-$3,000 repair), 5R55E Automatic Transmission Reverse Loss and Forward Clutch Slipping ($900-$3,000 repair), Firestone tire tread separation and rollover safety crisis (NHTSA EA00-023) ($600-$1,000 repair) and Frame, rear subframe, and rocker/body-mount rust ($200-$3,000 repair). Across all issues with published estimates, repair costs range from $25 to $3,500. at .

Frequently Asked Questions

What are the most common Ford Explorer problems?

According to Au7o's research across NHTSA recalls, manufacturer TSBs, and owner forum reports, the 1999 Ford Explorer has 12 documented issues. The most frequently reported are: 4.0L OHV cracked cylinder heads and blown head gaskets from overheating, Automatic transmission overdrive failure (A4LD / 4R55E), Firestone/Wilderness AT Tire Tread Separation Causing Blowouts and Rollovers (Recall EA00-023). Of these, 7 are rated critical and should be addressed promptly.

Is the Ford Explorer reliable?

The 1999 Ford Explorer has 12 known issues compiled from NHTSA recalls, manufacturer TSBs, and owner forum reports. 7 issues are rated critical: 4.0L OHV cracked cylinder heads and blown head gaskets from overheating and Automatic transmission overdrive failure (A4LD / 4R55E) and Firestone/Wilderness AT Tire Tread Separation Causing Blowouts and Rollovers (Recall EA00-023) and 4.0L SOHC timing chain cassette, guide, and tensioner failure and 5R55E Automatic Transmission Reverse Loss and Forward Clutch Slipping and Firestone tire tread separation and rollover safety crisis (NHTSA EA00-023) and Frame, rear subframe, and rocker/body-mount rust. Prospective buyers should inspect for these issues and factor potential repair costs into their purchase decision. Regular maintenance following the manufacturer's schedule helps prevent many common problems.

How much does it cost to fix common Ford Explorer problems?

Repair costs for known Ford Explorer issues range from $0 to $3,500, depending on the specific problem and whether you choose DIY or professional repair. The most critical issue, 4.0L OHV cracked cylinder heads and blown head gaskets from overheating, typically costs $1,000-$2,800 to repair. Au7o provides step-by-step DIY maintenance guides that can help reduce repair costs.

What is the 1991-1999 Ford Explorer 4.0L OHV cracked cylinder heads and blown head gaskets from overheating?

The pushrod 4.0L OHV V6 (Cologne) is otherwise regarded as a durable 'tank,' but the cast heads are intolerant of overheating and are prone to cracking and gasket failure, typically appearing around 100k miles or after any single serious overheat event. The root cause is usually… Repairs typically run $1,000-$2,800. Severity: high.

All 12 Known Issues

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Frequently Asked Questions

What are the most common Ford Explorer problems?

Is the Ford Explorer reliable?

How much does it cost to fix common Ford Explorer problems?

What is the 1991-1999 Ford Explorer 4.0L OHV cracked cylinder heads and blown head gaskets from overheating?

1991-1999 Ford Explorer: Automatic transmission overdrive failure (A4LD / 4R55E)#

1997-2001 Ford Explorer: 5R55E Automatic Transmission Reverse Loss and Forward Clutch Slipping#

1995-2001 Ford Explorer: Firestone/Wilderness AT Tire Tread Separation Causing Blowouts and Rollovers (Recall EA00-023)#

1991-1999 Ford Explorer: Firestone tire tread separation and rollover safety crisis (NHTSA EA00-023)#

1997-1999 Ford Explorer: 4.0L SOHC timing chain cassette, guide, and tensioner failure#

1997-2005 Ford Explorer: 4.0L SOHC Camshaft Position Sensor and Synchronizer Failure Causing P0340 Misfire and Stalling#

1991-1999 Ford Explorer: Camshaft synchronizer / CMP sensor bushing failure#

1997-2003 Ford Explorer: Intake Manifold / PCV Vacuum Leak on 4.0L SOHC Causing P0171/P0174 Lean Codes and Rough Idle#

1991-1999 Ford Explorer: 4.0L OHV cracked cylinder heads and blown head gaskets from overheating#

1991-1999 Ford Explorer: Frame, rear subframe, and rocker/body-mount rust#

1997-2005 Ford Explorer: DPFE Sensor / EGR Failure Setting P0401 and Companion P0171/P0174 Lean Codes#

1995-2010 Ford Explorer: Power Window Regulator Cable/Clip Failure Causing Window to Fall Into the Door#