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Discussion Starter #1
Hi all, my trusty old van (183,000 miles) registered a P0303 just before smog check. So I pulled plug #3 and it looks fine. Did a cranking compression check--it has 110 lbs in it, others have 120. Changed the plug and wire with the plug/wire from another cylinder. Changed the distributor cap for good measure. It took a week, but still gives me a P0303.

If I pull #3 wire it runs like it has a miss. With the wire connected it runs fine, although I do believe gas mileage (16 mpg city w/ac on) and power might be a bit down. I poured a bottle of Lucas fuel cleaner in it in case it is an injector. It often does take a couple minutes for a noisy tappet to shut up.

It only pulls the P0303. I'd guess cleaning/replacing the injector for #3 would be the next step.

I'm kind of out of ideas. Any suggestions for what might be causing this?

Thanks!

Dan
 

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A fuel injector swap with an adjacent injector may move the misfire code to the swapped injector cylinder. This may prove a plugged or malfunctioning injector. Fuel demand increases under heavier engine loads.
A cranking cylinder compression test may not catch a leaking valve. 110 may be low. How does that compare to the compression readings in other cylinders?
A static cylinder leak-down test with compessed air in the spark plug hole and both valves closed may be a better test. Air escaping the tailpipe would be an exhaust valve as air escaping the throttle body would be an intake valve. Air heard at the oil filler hole would be leaky rings/piston.
If this is an intermittent misfire then duplicating the conditions under which it misfires would make diagnosis more helpful.
Leaky valves/seats tend to show up more at idle and lower engine speeds while weak or broken valve springs (you mention a lifter noise) would occur at higher (cruising) speeds.
 

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Discussion Starter #4
ImperialCrown said:
A fuel injector swap with an adjacent injector may move the misfire code to the swapped injector cylinder. This may prove a plugged or malfunctioning injector. Fuel demand increases under heavier engine loads.
A cranking cylinder compression test may not catch a leaking valve. 110 may be low. How does that compare to the compression readings in other cylinders?
A static cylinder leak-down test with compessed air in the spark plug hole and both valves closed may be a better test. Air escaping the tailpipe would be an exhaust valve as air escaping the throttle body would be an intake valve. Air heard at the oil filler hole would be leaky rings/piston.
If this is an intermittent misfire then duplicating the conditions under which it misfires would make diagnosis more helpful.
Leaky valves/seats tend to show up more at idle and lower engine speeds while weak or broken valve springs (you mention a lifter noise) would occur at higher (cruising) speeds.
Crown,

It initially would only set off the code when I let it idle for long periods, which would point towards leaky valves/seats. I'm hoping to wait until Thanksgiving to dig into it. How do the bottom ends hold up on these 3.0 engines? Would I be wasting my time by just putting remanufactured heads on it without reringing it? The first 100k miles it did not get maintained so well. The last 85k has seen regular oil changes every 5k with 10/40 dino of whatever is cheap.

Thanks!
 

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Discussion Starter #5
It appears to have been the injector. Cleaned it up on both ends with some carb cleaner and moved it to cyl. #2. No codes and seems to run a bit smoother.

Thanks for the help!

Dan
 

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A bottle of Techron in your tank every 7 to 10,000 miles is recommended. I have over 200,000 miles on my Grand Caravan and use the Techron every 7,5000 miles or so. Never had a fuel problem at all. Knock wood!
 
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