[ktjensen]

So after a year and nothing showing a failure, am just living with the cold start loud roar noise. Mentioned this a while ago. No problems yet. No other symptoms. 2006 tundra

But have read that because of computer control can just drive it immediately. The air/fuel system is all self adjusting for temperature.

Only new curious noise is a sound like diesel Mac truck jake brakes going off randomly. Again only when cold. Speculate that some valve under computer control is causing the engine to adjust air intake?

Just find the engine computer controls act weird in general. Even with the AC system turned off, the engine will rev up randomly higher at a stop sign sitting and idling. Then the engine reduces revolutions ten seconds later.

Haunted I say. Lol.






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[Big Shasta]

Some Say Vacuum Leak?

 

[ktjensen]

Some Say Vacuum Leak?

Good idea. Will need to check. No codes being displayed on dashboard. The original tubing and wires are all there at 10 years and 100k miles. So could be vacuum.


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[McGovTundra]

Good idea. Will need to check. No codes being displayed on dashboard. The original tubing and wires are all there at 10 years and 100k miles. So could be vacuum.


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Yup. You could do some carefully directed soapy water spray spooging.

 

[OldGuy43]

I'm sure this was answered if you posted this before, but the roar is due to the ECU having a pre-programmed cold-start fast idle, plus the thermostatic clutch on the radiator fan being engaged, which causes the "roar". The fan clutch should quickly cut out permitting you to listen to cold UR valve train noise at high revs.

I have no experience with the "jake brake" noise, but in my experience, ten years or 100K miles on underhood control tubing would only be a "good start" for Toyotas of the 80s. But, it is now the twenty-first century, and underhood tubing is, no doubt, sourced in the USA.

Time (UV and ozone), not mileage, is the destroyer of hoses and tubing...some would add underhood heat, but it's been compounded to take the heat since the 70s. All of the emission control tubing on my 86 4Runner was still original and flexible at 31 years and 178K miles. A couple of the vacuum switching solenoids, namely idle-up and the cold-start injector sensor, had crapped out...cold-start injector sensor just this year, idle-up VSV a few years back.

 

[ktjensen]

I'm sure this was answered if you posted this before, but the roar is due to the ECU having a pre-programmed cold-start fast idle, plus the thermostatic clutch on the radiator fan being engaged, which causes the "roar". The fan clutch should quickly cut out permitting you to listen to cold UR valve train noise at high revs.



I have no experience with the "jake brake" noise, but in my experience, ten years or 100K miles on underhood control tubing would only be a "good start" for Toyotas of the 80s. But, it is now the twenty-first century, and underhood tubing is, no doubt, sourced in the USA.



Time (UV and ozone), not mileage, is the destroyer of hoses and tubing...some would add underhood heat, but it's been compounded to take the heat since the 70s. All of the emission control tubing on my 86 4Runner was still original and flexible at 31 years and 178K miles. A couple of the vacuum switching solenoids, namely idle-up and the cold-start injector sensor, had crapped out...cold-start injector sensor just this year, idle-up VSV a few years back.

Did the injector and valve give you a code flag on obd2 ? Or did it just run poorly ?


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[OldGuy43]

Did the injector and valve give you a code flag on obd2 ? Or did it just run poorly ?...

OBD2??!! :rotf: In 1986, Dude, that truck didn't even have cup holders, let alone OBD2! There was absolute freedom from DTCs, but a two-edged sword cuts both ways. You had to find problems the old-fashioned way in those days; but now, you can just youTube it. :lol:

Others will have to confirm, but cold-start injectors are defunct 80s technology, replaced in our Tundras by a start sequence using the pre-programmed ECU and the main fuel injectors. But, in that case, the sensor failed in the normal position causing no vacuum to the solenoid energizing the cold-start injector, which, in turn, meant very hard starting or no start.

 

[Big Shasta]

The old Skool way to find a vacuum leak. with the engine running, take a small torch like the kind used for soldering copper and turn it on low but don't light it. Run it all over anything with a vacuum on it. Don't forget intake manifold stuff. If you find a leak, the idle will go up as it sucks in the propane.

The engine fan will be blowing enough air that you won't have a buildup of gas.

 

[D. Bowman]

So after a year and nothing showing a failure, am just living with the cold start loud roar noise. Mentioned this a while ago. No problems yet. No other symptoms. 2006 tundra

But have read that because of computer control can just drive it immediately. The air/fuel system is all self adjusting for temperature.

Only new curious noise is a sound like diesel Mac truck jake brakes going off randomly. Again only when cold. Speculate that some valve under computer control is causing the engine to adjust air intake?

Just find the engine computer controls act weird in general. Even with the AC system turned off, the engine will rev up randomly higher at a stop sign sitting and idling. Then the engine reduces revolutions ten seconds later.

Haunted I say. Lol. I have an 06 Tundra that does that. Kudos, on your discription of the sound. That's exactly what it sounds like, a jake brake. The darn thing only does it twice, for about 2 seconds, the second growl only about a second, then all is quiet on the western front.. I used to own a 97 road dog, that did the same thing. Cured it with a can of carb cleaner, it removes all that black carbon off the air intake. We'll see, surgery is scheduled for today.






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