Odd rumble only on first cold start acceleration

[003XLT]

Hi Everyone,

Thanks for all the great advise you have on here, I've solved several problems on the truck already with your help.

I'm presently stumped on what is causing this one noise. Upon starting the truck there is what sounds like a loose heat sink, PLUS a deeper rumble. I can't quite pin point where it's coming from, but my best guess is near the transmission.

By the time the car is out of the driveway the noise is gone until the next morning. Doesn't happen at stop lights, through warm starts, etc. However every standing-start will rattle whatever heat shield is loose, can't find that either.

There is absolutely no gear slipping, clunking, bad mileage or anything that would otherwise indicate a problem.

In case it helps when I bought the truck it had P0420 and P0430 codes. I reset the codes and ran Lucas fuel system cleaner and cleaned the MAF, throttle plate, and IAC which solved a rough idle and the P0420. The P0430 came back once, the FF data was:

P0430
Fuel System 1 Status
Closed Loop
Fuel System 2 Status
Not Supported
Calculated LOAD Value
57.65 %
Engine Coolant Temp
181.40 °F
Short Term Fuel Trim - Bank 1
0.78 %
Long Term Fuel Trim - Bank 1
-2.34 %
Short Term Fuel Trim - Bank 2
0.00 %
Long Term Fuel Trim - Bank 2
2.34 %
Engine RPM
1,862.75 rpm
Vehicle Speed Sensor
27.34 mph
Ignition Timing Advance #1 Cylinder
34.50 °
Intake Air Temperature
73.40 °F
Air Flow Rate Mass Air Flow Sensor
3.86 lb/min
Absolute Throttle Position
29.41 %
Oxygen Sensor Output Voltage (B1-S1)
0.79 V
Short Term Fuel Trim (B1-S1)
1.56 %
Oxygen Sensor Output Voltage (B1-S2)
0.23 V
Short Term Fuel Trim (B1-S2)
99.22 %
Oxygen Sensor Output Voltage (B2-S1)
0.87 V
Short Term Fuel Trim (B2-S1)
0.00 %
Oxygen Sensor Output Voltage (B2-S2)
0.89 V
Short Term Fuel Trim (B2-S2)
99.22 %

The noise is slowing driving me nuts, any help would be very much appreciated

 

[Number4]

Does it happen at start up or just once in drive accelerating.

Which engine do you have?

 

[003XLT]

Both when the engine first starts and right at first acceleration.

I've put it in Drive and sat with the brake on and it makes the noise, just not as loud, until you accelerate. Then it get's loud for a few seconds again then disappears.

It's almost like something has play in it that gets tightened by driving. Even moving it from the driveway to the street (2-3 car lengths) and throwing it back in park the noise is gone.

I have the 4L 4x4, couldn't figure out how to add vehicle stats to my profile.

 

[Number4]

Failing timing tensioners are known for losing pressure 'over night' which causes slack in the chains until the oil pressure builds and the tensioners function again.

This is usually more of a rattle than a rumble though.

Personally not worked on the 4.0 SOHC timing, have just read everyone here's night mare stories. Seems when the rattle occurs on the 4.0, engine death isn't far behind, if left untreated.

I'd pursue chain diagnoses to rule it out.

 

[003XLT]

The rear timing chain seems like the right area. I don't hear any noise like that in the front, guess the front chain is taking the load for the time being?

There's a definite rattle too that I dismissed as a heat shield. Would the chain being loose create that type of noise?

I'm a weekend tinkerer and my kids ride in this car. Is it hard to properly tighten the wheel nut again? Can I over tighten it?