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post #1 of 7 (permalink) Old 03-01-2017, 02:52 PM Thread Starter
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Misfire solutions

Here's where I'm at with this one... Misfire cylinder 6 on 1996 3.8. I can feel the car lacking some power at the line, but power picks up at around 2500 rpm. I have changed the plugs, wires, coil, and ran seafoam through as to clean up my injectors. Pulled the cables to reset the system, but still im getting p0306 from the computer. Next I plan to do a propane enrichment check around the plug to check for cracks. It's cylinder specific so I doubt vacuum line as it would lean out the bank, rather that pointing to that one cylinder. Any other ideas for this one?
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post #2 of 7 (permalink) Old 03-01-2017, 03:20 PM
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I had this problem with a 3 liter last month- replaced the plugs, wires, coil pack, and even two injectors- nothing. Gave up and sent it to the repair shop. In the end the problem was a faulty NEW spark plug.

Try swapping the number 6 plug with another cylinder and check if the misfire follows it.

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post #3 of 7 (permalink) Old 03-02-2017, 07:45 AM Thread Starter
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I'll give it a shot and see if it work, thanks!
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post #4 of 7 (permalink) Old 03-26-2017, 08:31 AM
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One other thing that can cause misfire is a leaking intake manifold gasket. From what I understand, the coolant passage portion of the gasket can leak coolant into the combustion chamber and cause misfire.
If you have the old plugs, compare #6 to the rest and note if it looks as if it had been 'steam cleaned'. The coolant flash to vapor will make any deposits on the plugs get 'steamed' away.
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post #5 of 7 (permalink) Old 04-03-2017, 02:29 PM Thread Starter
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Ok here's where I'm at with this. Brand new plugs, wires, coil pack. #6 looked just like the other plugs, no big difference. Also did silencer delete, k+n box filter, cleaned the maf and the throttle body. CEL still came back on for #6. Car still feels sluggish, especially when I start it up. Anything else I should look into before I hand it over to the shop?

Possibly related to this, possible not. Car has no heat and does not hit operating temp. It gets just below the N on the gauge, and fluctuated there and lower, especially at highway speeds. I noticed that it drops very fast when I turn the heat on. I flushed the coolant, new thermostat from the Ford dealer here in Rockland county, flushed heater core (was very clean) and purged the system with a funnel. I cant tell when the fan comes on when Im driving, so would a bad temp sensor do all that? Sorry for the lengthy post but this one's driving me up the wall.

96 Thunderbird LX 3.8L
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post #6 of 7 (permalink) Old 04-03-2017, 03:16 PM
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Quote:
Originally Posted by tmwalsh View Post
One other thing that can cause misfire is a leaking intake manifold gasket. From what I understand, the coolant passage portion of the gasket can leak coolant into the combustion chamber and cause misfire.
If you have the old plugs, compare #6 to the rest and note if it looks as if it had been 'steam cleaned'. The coolant flash to vapor will make any deposits on the plugs get 'steamed' away.
tom
a leaky head gasket (HG) would cause coolant to go into the combustion chamber. I don't recall an coolant passages in the intake manifold (except some wierd cars with coolant going into the throttle body to make sure the intake air is adequately heated) so a "intake manifold gasket" leak would cause vacuum leaks NOT coolant leaks into the combustion chamber.

Suggestions (all can be done with loan a tools except maybe the pressure test which will also need a small compressor).
- Vacuum Test: test for vacuum leaks or some issue with your
- Compression test: tell you condition HG or wear of engine in general -- if rings are worn (is the block worth a HG job on)?
- Pressure test: with rocker arms off, will definitely tell you if you have leaky valves.


Other thought: did seafoam go into the tank or did you suck that into the intake tract? If sucked into the intake, that is known to gum up your O2 sensors which isn't going to do any favors for your drivability.

My nickel guess is the HG.

See my tests in trying to resolve my own bucking/surging at partial throttle issues with a 5.0; different engine but it may give you some ideas.

Issue Solved - engine bucking/surging at partial throttle

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post #7 of 7 (permalink) Old 04-06-2017, 12:19 PM Thread Starter
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Success! I had to drive it a bit after everything I did at once but things seem to have greatly improved (plugs, wires, coil, cleaned maf and tb, silencer delete, k+n). I cleared the codes and the cylinder code as disappeared, only lean bank remains... Intake manifold gasket will be sunday's project. Power has come back a bit as well. I filled the tank before so I'll see how my efficiency is affected once I run it all through. Also installed a new Kenwood BT318U and 4 speakers in the usual spots, sounds great and got it all online for under $200. Thanks for the help everyone

96 Thunderbird LX 3.8L
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