Ford V10 Crate Engine Problems: Rough Idle & Power Loss

TL;DR

Your 2015 Bounder's Ford V10 6.8L crate engine shouldn't be running rough with only 27k miles after a complete engine replacement. The shop's claim that "it's a transmission problem" is highly suspect given your symptoms of rough idle, shaking during acceleration, and lack of power - these are classic engine-related issues, not transmission problems. A transmission issue would show up as slipping gears, delayed shifts, or inability to move, not rough idling when parked. The fact that they "repaired a misfire" but the problems persist suggests either incomplete diagnosis, poor installation of the crate engine, or multiple unresolved engine management issues. Before spending money on transmission inspection, you need proper engine diagnostics including compression testing, complete fuel system analysis, and verification that all engine sensors and wiring harnesses were properly connected during the crate engine installation.

Digging Deeper

Your situation raises several red flags about the quality of work performed on your Ford V10 6.8L crate engine installation. When a shop installs a brand new crate engine and it immediately exhibits rough idle, shaking, and power loss, the problem almost certainly lies with the installation process or supporting systems, not the transmission. Ford crate engines come with warranties specifically because they're supposed to run smoothly from day one.

The symptoms you're describing - very loud operation, rough idle, shaking during acceleration, and lack of power - point to several possible engine-related issues that the shop may have missed or inadequately addressed:

• Incomplete fuel injector diagnosis: They mentioned repairing "a" fuel injector for misfire, but the V10 has 10 injectors. If one was bad, others may be failing or improperly installed
• Wiring harness problems: During engine swaps, connectors can be damaged, pinched, or incorrectly routed, causing multiple sensor malfunctions
• Vacuum leaks: New gaskets and connections may not be properly sealed, creating massive vacuum leaks that cause rough idle and power loss
• Timing issues: If the camshaft timing wasn't set correctly during installation, you'd get exactly these symptoms
• Mass airflow sensor contamination: Often overlooked during engine swaps, a dirty MAF sensor will cause poor performance

The shop's suggestion that this is a transmission problem is particularly concerning. Transmissions don't cause rough idling when the vehicle is parked in neutral or park. They don't cause the loud operation you're experiencing. A transmission problem would manifest as slipping between gears, delayed engagement, harsh shifting, or complete failure to move. Your symptoms occur even at idle, which has nothing to do with transmission operation.

Ford V10 engines in Class A motorhomes are known for specific issues, but a properly installed crate engine should eliminate most of these concerns. The fact that problems appeared immediately after installation suggests the shop either received a defective crate engine (unlikely but possible) or made errors during the installation process. Given that this is a 2015 model with only 27,000 miles, the original engine failure itself is unusual and may indicate underlying issues with fuel quality, cooling system problems, or maintenance issues that need to be addressed to prevent damaging the new engine.

Your Toolkit

Before allowing any shop to convince you that transmission work is needed, you'll want to gather diagnostic information yourself or have it properly diagnosed by a more competent facility. Here are the essential tools and information you'll need to properly evaluate your Ford V10's condition:

• OBD-II scanner with Ford-specific codes: A basic code reader won't cut it - you need something that can read manufacturer-specific codes and live data. The BlueDriver or similar professional-grade scanners can show real-time engine parameters
• Compression tester: Essential for verifying internal engine condition. Each cylinder should read within 15% of the others, typically 160-200 PSI minimum for the Ford V10
• Vacuum gauge: A simple but effective tool for diagnosing vacuum leaks, timing issues, and overall engine condition. Steady reading of 18-22 inches at idle indicates good engine health
• Digital multimeter: For testing sensors, checking voltage drops across connections, and verifying proper electrical installation
• Inspection mirror and flashlight: To visually inspect all connections, gaskets, and potential leak points around the new engine installation

You'll also want to gather documentation from the shop including:

• Complete work order: Detailing exactly what was replaced during the crate engine installation
• Parts list: Including part numbers for all components installed with the new engine
• Diagnostic codes: Both current and pending codes from their scan tool
• Test results: Any compression, leak-down, or other tests they performed
• Warranty information: For both the crate engine and their installation work

If the shop is reluctant to provide this documentation, that's another red flag suggesting they may not have performed thorough diagnostics or proper installation procedures. Any reputable shop should be willing to show you exactly what they found and what they replaced.

The Process

Here's a systematic approach to diagnosing your Ford V10's problems without immediately jumping to expensive transmission repairs. Start with the most likely culprits and work your way through the possibilities:

Phase 1: Initial Assessment

1. Document baseline conditions: Record exactly when the symptoms occur - during idle, acceleration, cruising, or all conditions. Note if problems are worse when cold or hot
2. Scan for codes: Use a quality OBD-II scanner to pull all current and pending diagnostic trouble codes. Don't clear them yet - you need this information
3. Visual inspection: With the engine off and cool, inspect all visible connections, vacuum lines, and gaskets around the new engine installation
4. Listen carefully: The "very loud" operation you mentioned could indicate exhaust leaks, vacuum leaks, or internal engine problems

Phase 2: Engine-Specific Testing

1. Compression test: This is critical for a new crate engine. All cylinders should be within specification and within 10% of each other. Low compression indicates internal problems
2. Vacuum test: Connect a vacuum gauge to a manifold vacuum port. At idle, you should see a steady 18-22 inches of mercury. Fluctuating readings indicate valve or ignition problems
3. Fuel pressure testing: The Ford V10 requires specific fuel pressure (typically 35-40 PSI). Low pressure causes exactly the symptoms you're experiencing
4. Mass airflow sensor inspection: Remove and visually inspect the MAF sensor. Clean with appropriate MAF cleaner if contaminated

Phase 3: Installation Quality Verification

1. Verify timing marks: Ensure the camshaft and crankshaft timing marks are properly aligned. Incorrect timing causes poor performance and potential engine damage
2. Check all electrical connections: Verify that every sensor connector is properly seated and secured, with no damaged pins or corroded contacts

Phase 4: System Integration Testing

1. Test drive analysis: If safe to do so, perform a controlled test drive to determine if symptoms occur during specific operating conditions
2. Monitor live data: Use your scan tool to watch real-time engine parameters during operation, looking for anomalies in sensor readings
3. Temperature monitoring: Verify that the new engine is reaching proper operating temperature and that all cooling system components are functioning
4. Transmission function test: Only after ruling out engine problems, test transmission operation by checking shift points, engagement, and fluid condition

Throughout this process, document everything you find. Take photos of any questionable connections or components. Record all test results and diagnostic codes. This documentation will be valuable whether you end up working with the original shop to resolve their installation issues or need to involve another facility or pursue warranty claims.

When DIY Isn't Enough

While many diagnostic steps can be performed by a competent RV owner, some aspects of your situation require professional intervention, particularly given the warranty implications of a new crate engine installation. Here's when and how to escalate beyond DIY troubleshooting:

Immediate Professional Help Needed If:

• Compression test shows low readings: If any cylinder reads below 120 PSI or varies more than 15% from others, you have internal engine problems that require immediate professional attention
• Metal particles in oil: Check the oil on the dipstick and oil filter for metal particles, which could indicate bearing or internal damage
• Coolant contamination: Any signs of oil in coolant or coolant in oil suggests head gasket problems with the new engine
• Timing chain issues: If you hear rattling from the timing chain area, especially on startup, stop driving immediately

Dealing with the Original Shop:

Before writing off the shop that did the installation, give them one more opportunity to make it right, but with specific demands. Present them with your diagnostic findings and insist on:

• Complete re-diagnosis: Not just checking for codes, but comprehensive testing including compression, fuel pressure, and timing verification
• Written explanation: They need to explain in writing why they believe this is a transmission problem given the symptoms
• Warranty coverage: The installation work should be warrantied, and a properly installed crate engine shouldn't exhibit these problems
• Second opinion allowance: If they're confident in their diagnosis, they should be willing to pay for an independent diagnosis at another shop

Finding the Right Specialist:

If the original shop remains uncooperative, you'll need to find a facility with specific Ford V10 and RV experience. Look for:

• Ford dealership service departments: They have access to Ford technical service bulletins and specialized diagnostic equipment
• RV-specific repair facilities: Shops that regularly work on Class A motorhomes understand the unique aspects of chassis-mounted engines
• Certified engine rebuilders: Facilities that specialize in Ford engines and have experience with crate engine installations
• Independent shops with Ford certification: ASE-certified technicians with Ford-specific training and equipment

Legal and Warranty Considerations:

Document everything because you may have several avenues for recourse:

• Ford crate engine warranty: The engine itself should be covered by Ford's warranty if there are internal defects
• Installation warranty: The shop's workmanship should be guaranteed, and poor installation voiding the engine warranty could make them liable
• Consumer protection: If the shop took payment for services they didn't properly complete, you may have legal recourse
• Insurance claims: If the original engine failure was due to negligence or defective parts, your RV insurance might cover some costs

Don't let the shop pressure you into transmission repairs when the symptoms clearly point to engine problems. A transmission that shifts properly but has an engine that runs poorly will still exhibit the rough idle and power loss you're experiencing. Get a proper engine diagnosis first, and only consider transmission work if that diagnosis conclusively rules out all engine-related causes of your symptoms.