Engine Hiss
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Amateur
Joined: Dec 2010
Posts: 42
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No I noticed it was running rough when stopped at a redlight a few weeks ago. It has plenty of power while driving just starts to studder when at a redlight. The hissing noise sound like its losing pressure or something. Gonna change the cap and rotor this weekend and see if it helps at all.
Hall Of Fame
Joined: Jul 2006
Posts: 12,204
Likes: 10
From: Gainesville, Ga.
if the AC has been on, a hissing sound from the AC system is normal.
if it's not AC, then its likely from the cooling system. a little bit of blowoff from the radiator cap into the overflow tank is normal. cap is something like 16 psi. if you have a coolant leak elsewhere, it might be making some noise. any coolant on the ground?
if it's not AC, then its likely from the cooling system. a little bit of blowoff from the radiator cap into the overflow tank is normal. cap is something like 16 psi. if you have a coolant leak elsewhere, it might be making some noise. any coolant on the ground?
Hall Of Fame
Joined: Jul 2006
Posts: 12,204
Likes: 10
From: Gainesville, Ga.
vacuum leak? that could explain a hissing sound when running, but not when engine is off.
if you suspect it might be something serious, you should rent a compression tester from the parts store and check it to rule out major problems. you can check it while you replace the plugs.
Registered User
Joined: Mar 2013
Posts: 4
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From: Fort Deposit Alabama
Chech your EGR valve. I had a problem very similar to yours. EGR valve was opening to early. Possibly the Temp sensor for ECM. I unlugged the vacuum line to the EGR valve and problem went away. Truck is parked now while I replace the Dash and entire instrument panel. I will trouble shoot the rest after this.