Rough idle for 3.0 - Ranger-Forums - The Ultimate Ford Ranger Resource


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Old 09-03-2014
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Rough idle for 3.0

Cant track this down and was wondering if anyone could help. got a Dead cylinder on 5 only swap plug towers between 1 and 5 on coil pack and runs good smooth idle swap back and just as good. let it sit and back to dead cylinder. Checked for spark and all plugs firing. Compression tested on 6 5 4 123 to 126 psi. Pulling my hair out on this one.
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Old 09-04-2014
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Does it do it when the coil pack is cool, or when it warms up from the engine heat?
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Old 09-04-2014
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3.0's are known for valve seat/head issues that cause similar misfires. but before calling it that, there are a TON of things you should check or change. start with the plugs, then wires, then the coil pack itself. sometimes they just take a **** and start acting all screwy. after that check to see that your idle air control valve is clean and your mass air flow meter. any check engine lights or codes?
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Old 09-04-2014
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no codes and it acts up when the coil is cold
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Old 09-05-2014
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I read on another forum from a member that frequents here as well that the 3.0 coil pack has 4 wires to it. One is the battery power (red), and the other three are the ground wires for two cylinders within the coil pack. These ground wires are controlled by the PCM/ECU to "fire" two cylinders coil pack (one spark is useless to one cylinder, as it would be on its exhaust stroke) based on the crackshaft or camshaft position sensor signal. Since the engine runs, these sensors are good, and unless you have some sort of spuratic vacumn leak, it would point to the coil pack.

What you can try is to wiggle each of the three ground wires to see if the fault is the wiring connector or one of the wires. Otherwise it could be a weak coil within the coil pack, which means the entire unit has to be replaced.

Got a buddy with the same engine you could do a swap with to verify the coil pack is the culprit? I'm not one to keep tossing parts at a fault until it's fixed; eventually you get it fixed, but that method is way too too costly.

Last edited by bucko; 09-05-2014 at 06:01 AM.
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Old 09-05-2014
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Thanx ill try that and really appreciate all the help here. Ill get back when i have found out more.
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Old 10-12-2014
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In case anyone was still following this it was blown head gasket. Number 6 cylinder water jacket blown.
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