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Discussion Starter · #1 ·
99, 2.7L ~ 130,000 kms..

Engine at curb idle runs rough. The CEL is back on and getting a code 0303, which I think is a misfire detected in cylinder 3. I have installed new plugs and problem is still there. Next I put in a new IAC motor. Still there. With the engine running I started unplugging the coil pack wires one by one. You can hear and see a noticeable drop in the idle on all including number 3, although not as pronounced. I swapped cylinder 3 and 5 coil packs and no difference. I'm stumped. Last time I took it to the dealer they had to swap out one sensor at a time until they found the bad one, not the same problem at that time. I'm not made of money and can't afford to replace the sensors until I find the right one. Can anyone suggest any voltages to measure or any other things to look for. Under normal driving conditions the car is fine, it accellerates fine, only when stopped at the lights does it act this way.

Appreciate any pointers,

Max
 

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Discussion Starter · #3 ·
PCV valve is good, lots of suction, hose is new. Swapped coil packs tonight and still no change in idle when unplugging the coil wire off pack number 3. Unplugging the wires off the other cylinder and the idle drops noticeably. Swapped the plug in # 3 no difference. With the coil out and plug in the coil pack you can hear the spark plug sparking with the engine running so I know the coil pack is getting the signal to fire. The plug also shows evidence of firing. My arm felt the spark too! So I know the coil pack is good, the plug is good and the wire is good. What should I be looking for next?

Max
 

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Like I said in the earlier post - it could be a clogged or bad fuel injector - that's harder to tackle because you have to remove the intake manifold to get to it. Unless you are really good at turning a wrench you may want to find a good mechanic. A cheep fix you can try is adding some fuel injection cleaner to your gas.
 

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As jgams said(twice) could be clogged fuel injector. The other issue could be low compression in that cylinder. The only way to eliminate things is a compression check on all cylinders (valve or ring problems) and if that turns out good is to start looking at the fuel injectors. Also could be an intake leak at that particular cylinder. If you're not comfortable with doing the checks yourself or you're not qualified...then your alternative is an independant mechanic or the Dealer. Sorry that there's no easy diagnoses/fix.
 

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Discussion Starter · #6 ·
I did put some Seafoam into the intake and the gas tank today. Didn't do anything. I have talked to the mechanic who rebuilt the motor and may have to take it to him. He is an hour away so I am trying as much as I can before having to make the trip.
 

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Bad fuel injector. Its a bit of work to get them out, but try swapping the injector to another cylinder. After that, if you end up getting a P030X with the "X" being that cylinder you moved the injector to, then you know for sure. I doubt its clogged, its probably on its way out though. And yes, P0303 is a misfire on cylinder #3. That being the case, focus your attention specifically to that cylinder. You've already checked the coil and plug. Other items are the fuel injector, the intake manifold gasket around that cylinder, a leaky fuel injector o-ring. Since the #3 is in the middle of the cylinder head, I wouldn't think that the intake gasket would be at issue. And as far as the o-ring, if that were the case, you'd probably smell and see gas leaking from it since the fuel is under pressure. Bets on the fuel injector.
 
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