2006 Pontiac Torrent with P0300 and P0351

robertg927

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Hi,
A couple of weeks ago after I had been driving the car around town for an hour or so. I first started noticing that there was what seemed to be a random misfire as I was taking off from a stop light and it seemed to get less random and worse the more I drove. When I neared home, I have to go up a steep hill on a gravel road to get to my house. The car really started missing and then the check engine light started flashing as I neared the top of the hill. As the road leveled out and there wasn't such a load on the engine, the check engine light stopped flashing and the misfire seemed to stop and I was able to make it home. I put my scan tool on the car and although the check engine light wasn't on, I did get the P0300 and P0351 codes. The problem seemed to mimic a bad coil from my experience with older cars in years gone by. So I went down to my local parts store and bought a new coil and installed it. I've now driven the car for about a week, but as I was driving it on Saturday, I started getting the same symptoms - random misfire that got worse the longer I drove, the flashing check engine light as I drove up the gravel road, which then stopped once the road leveled out. Where should I look next for the problem? I'm suspicious of the new coil. Is there a way to test it? I did check the spark plug wires while replacing the coil and they looked fine - they had been replaced recently when I swapped out the engine a few months ago.

Thanks!
 

melsg5

Staff member
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If you google the P0351 code it indicates problem either with the primary or secondary circuit. You have to test plug wires with an ohmmeter. In addition vacuum leaks appear to cause this code also . Did you install new plugs and checked the gap when you replaced the engine? Follow the suggestions on the established OBD code sites such as repairpal.com or obd-codes.com.
 
G

G-987787

I installed new wires and new plugs and the gaps were correct. But here's an interesting update: I went through the diagnostic procedure outlined in my AllData DIY subscription and I came to the part where they suggested that I cut and splice the wires going into the coil. So I cut the coil circuit #1 and #2 wires and swapped them and then swapped the spark plugs on the coil so coil #1 is now feeding plugs 2 and 5 and coil #2 is feeding plugs 1 and 4. When I plugged the harness back in, it seemed that there was a tension on the plug from the weight of the harness, so I took a zip tie and supported the harness so it wasn't pulling on the plug (it seems like there is a wiring harness support plug missing). I've been driving it for a couple of weeks now and have had no more problems, so I think there must be a short in that connector.
 

robertg927

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Plugs and wires were new and plugs were gapped correctly. I followed the troubleshooting steps from alldataDIY and cut the coil circuit #1 and #2 wires and switched them. I also switched the plug wires, trading wires 1 for 2 and 4 for 5. When I put the connector back on the coil, it seemed that the wiring harness was putting some tension on the connector and it looks like maybe a harness support clip is missing, so I tied the harness with a zip tie to relieve the tension from the connector. I've now been driving the car for more than 2 weeks and haven't had any problems, so I suspect there's a slight short in the connector.
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robertg927

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It's been over a week and the car is still running good and there aren't any codes - the problem must be in the connector. I'm going to order a new one and splice it in and switch the coil circuit wires back so as to not confuse the next owner.
 

melsg5

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Sounds like a plan.
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