96 Exlporer Rough Idle Hot or Cold NO Codes or CE Light

[pmonahan]

96 Explorer Rough Idle Hot or Cold NO Codes or CE Light

Greetings,

My 1996 Explorer XLT 4.0L has a rough idle after changing the Radiator Fan Blade and clutch assy. This may be a coincidence only. At first I thought the replacement fan was warped causing an imbalance, but I disconnected the serpentine belt for a few mintutes and the rough idle persists. The idle is rough when the engine is hot or cold.

Here are the key points:

• There are no engine codes stored.
• There is no Check Engine light.
• The truck runs great other than Idle.
• The truck Starts fine.

Here's what was replaced recently as routine maintenance or to eliminate problems:

• Mass Air Flow Sensor
• Air Filter
• Fuel Filter
• Plugs and Wires
• DPFE Sensor
• Engine Temperature Sensor
• Engine Coolant Sensor
• Intake Air Temperature Sensor
• Upper O2 Sensors Bank 1 &2 (But not downstream)
• IAC Valve
• PCV Valve and PCV Grommet/Bushing
• Upper Intake Manifold (about 7 months ago, coolant leak), gaskets and O-rings
• Clean Throttle Body

Here are the tests my shop ran:

• Check for misfire
• Check for Balancer Isssue
• Double Check for Fan Balance Issue
• Check Timing, Timing Belt
• Check for Vacuum Leak
• Smoke Test Cold Engine to look for leaks
• Test EGR Valve
• Test fuel pressure

Really the only thing that has not been replaced is the EGR Valve and the Downstream 02 sensors, but neither throws a code.

One other symptom is a frequent "burping sound" from the gas cap. This could be the vapor canister or vapor canister solenoid, but I don't think that would cause rough idle.

Any ideas would be appreciated.

Thanks

Peter

 

[pmonahan]

Updated: Performed a Dry Compresssion Test

Cylinder 1 - 135 PSI
Cylinder 2 - 130 PSI
Cylinder 3 - 135 PSI
Cylinder 4 - 130 PSI
Cylinder 5 - 125 PSI
Cylinder 6 - 135 PSI

Wet results in a boost of 5 PSI

TPS measures .94V with ignition on, not running, very smooth increase as I open throttle up to 4.67 V

MAF seems to response properly when I view with my OBD2 tool.

I'm stumped. I'm wondering if timing could be off. Can the harmonic balancer shift position on the crankshaft or is it keyed ? When we changed the raditor fan, a lot of force was needed to remove the clutch assembly and the serpentine belt was still in place.

Peter

 

[lobo411]

Can the harmonic balancer shift position on the crankshaft or is it keyed ? When we changed the raditor fan, a lot of force was needed to remove the clutch assembly and the serpentine belt was still in place.

Peter

It's keyed.

 

[pmonahan]

Well, it turns out that I had TWO Dorman radiator fan blades, both of which were out of balance causing the engine to shake; presenting the same symptoms as a rough idle. I removed the (second) fan blade and the truck runs like it has a new engine in it. The first had an obvious defect that could be seen when I first started the engine and was replaced immediately.

I wanted to use a Flex-a-lite 5918 metal aftermarket fan but I discovered it won't fit.

I've spoken to Dorman and they've been really helpful. I am sending the fan blade back to them to analyze and they have a new fan blade on the way to me that was QC checked.

Peter