93 4.9 Intermittent Knocking on Acceleration.
Senior User
Joined: Feb 2000
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93 4.9 Intermittent Knocking on Acceleration.
1993 w/156,000m 4x4
Where would be the best place to start. I have checked codes and replaced TPS, Map. I have changed the oil and oil filter.
Do exhaust leaks sound like internal knocks?
Could the problem be a flaky knock sensor?
Thanks,
WHaynes
Where would be the best place to start. I have checked codes and replaced TPS, Map. I have changed the oil and oil filter.
Do exhaust leaks sound like internal knocks?
Could the problem be a flaky knock sensor?
Thanks,
WHaynes
Posting Guru
Joined: Feb 2001
Posts: 1,728
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From: Keweenaw Bay, MI
93 4.9 Intermittent Knocking on Acceleration.
What octane gas are you using? It could be a pre-ignition knock, especially if your timing is advanced a little more than the base setting and you are using low octane gas.
Senior User
Joined: Feb 2000
Posts: 175
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93 4.9 Intermittent Knocking on Acceleration.
It is intermittent....when it does do it uphill(4th gear/more load[Almost feels like a timing issue]) but if I am accelerating hard in 3rd or higher it is noticebale. I was playing around with the EGR a week or so trying to test it, perhaps it is getting stuck. I will try and pull the codes again to see if there is anything that shows up.
What does an exhaust leak look like/diagnosis?...I shined a light onto the manifold side but did not see any teltale black exhaust marks.
Thanks,
WHaynes
What does an exhaust leak look like/diagnosis?...I shined a light onto the manifold side but did not see any teltale black exhaust marks.
Thanks,
WHaynes
Junior User
Joined: Apr 2002
Posts: 75
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From: Port Gibson NY
93 4.9 Intermittent Knocking on Acceleration.
if you think your hearing an exhaust leak and can't find any evidence of it on the exhaust manifolds or the pipes, you might want to check the air injection rail that runs along the top right side of the cylinder head. there are 6 smaller tubes that come off the larger one, they have fittings that screw into the cylinder head above each exhaust port. it took me 3 months to find the leak on mine. it was the last tube at the back. couldn't hear the leak at idle or when taking off easy, but under heavy acceleration the leak was there to hear.
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