Intake leak?
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Intake leak?
'98 4.6 auto, 150k miles. Getting consistent p0303 code- misfire in cylinder 3. Misfire is worst at low rpm, above 2k it's almost gone.
Put in accel coil packs and new plugs. Old plugs were clean - grey tan color. Plug wires were metered and #3 was replaced with new to test - no change. Fuel injector and its plug were tested and checked out ok. All changes were done one at a time and the computer was cleared and parameters reset.
Any history of air leaks around cylinder 3? Anything else that will trigger the p0303 code?
Also, carb cleaner sprayed around the intake area caused the engine to almost die at one point but we couldn't duplicate it a second time. It seemed to react when sprayed around the front of the engine - not near cylinder 3.
Put in accel coil packs and new plugs. Old plugs were clean - grey tan color. Plug wires were metered and #3 was replaced with new to test - no change. Fuel injector and its plug were tested and checked out ok. All changes were done one at a time and the computer was cleared and parameters reset.
Any history of air leaks around cylinder 3? Anything else that will trigger the p0303 code?
Also, carb cleaner sprayed around the intake area caused the engine to almost die at one point but we couldn't duplicate it a second time. It seemed to react when sprayed around the front of the engine - not near cylinder 3.
Last edited by sirnose; Aug 31, 2003 at 06:08 PM.
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From: So. California
I think you are on the right track with the air leak idea. The only other thing I can think of is to swap another injector with #3 and see if your misfire moves. I don't recall seeing any threads about intake runners w/ air leaks but there is always a first time. Let us know how you make out
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We fired the injector with a separate control box and you could here it clicking with a regular rhythm meanwhile the engine still had the same irregular misfire. That doesn't mean the injector isn't partiallly clogged but the kicker was when the carb cleaner was sprayed around the engine. I just don't have the time to take the truck off the road for more thorough testing.
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No, haven't had a chance to do a compression test. The misfire comes and goes all the time and my experience with compression problems is they don't just visit - they move in for good.
Nobody else has any ideas? Where's the miracle cure when you need one. This is making it tough to sell the truck.
Nobody else has any ideas? Where's the miracle cure when you need one. This is making it tough to sell the truck.
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Joined: Aug 2001
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From: Monument, CO
I'm with pestco1,
Try moving the injector to another cylinder and see if the misfire follows the injector. Also inspect the injector seals on that cylinder. Just because you are spraying the carb cleaner at the front of the engine does not mean it is not getting to cyl #3 under the intake. As you can see these engines are wide open under the intake manifold. It's not that far for that carb cleaner to travel under the intake to the #3 cylinder. But I would move that injector first and determine if that is the cause or not.
Try moving the injector to another cylinder and see if the misfire follows the injector. Also inspect the injector seals on that cylinder. Just because you are spraying the carb cleaner at the front of the engine does not mean it is not getting to cyl #3 under the intake. As you can see these engines are wide open under the intake manifold. It's not that far for that carb cleaner to travel under the intake to the #3 cylinder. But I would move that injector first and determine if that is the cause or not.
