urdrwho Posted August 18, 2011 Share Posted August 18, 2011 My son picked up a 95 Legacy with 165,000 miles on the engine. It runs well, idles well, has a lot of power, no smoke from the tailpipe. In the process of tuning up some items - things that are new PCV Ign. wire Fuel filter Evey once in a while, for no rhyme or reason it will throw a code #3 misfire. I haven't looked at the plugs yet. I've read that even though it is one coil that the coil is actually a split coil. Is that true. The coil is a pricey little thing and costs almost as much as the four coil packs for my caddie. So I'm not ready to replace the coil as a just in case item. It has been a while since a Subbie resides in our house and I am not up to date on their wants and needs. Is there a usual culprit for the #3 misfire? Other than the intermittent code, the car runs great --- problem free. Link to comment Share on other sites More sharing options...
I Donated broknindarkagain Posted August 18, 2011 I Donated Share Posted August 18, 2011 Read though this link. Do all of the stuff in the "MPG FAQ". Have you done a compression / leak down test? -broknindarkagain My Current Project - Click Here COME AND TAKE IT "The only thing necessary for the triumph of evil is for good men to do nothing." Link to comment Share on other sites More sharing options...
urdrwho Posted August 18, 2011 Author Share Posted August 18, 2011 Thanks for the links and ideas. Haven't done a compression test yet. That will be done if nothing else is apparent. IF this puppy fails compression testing, it is heading out the door. But with all the pep the car has I am not suspecting any burnt valves, piston, etc. problems. There is a hill that is one mile, no switchback turns and is a decent angle. The car will run like crazy up the hill without throwing any codes. The car may run for a while, on the highway, up the hills, etc. without throwing a code. It is not possible to duplicate the thrown code. Went on the same path it last threw a code and nothing. I forgot to add that the air filter is new. I haven't gotten around to cleaning the TB or the MAF wire. Read though this link. Do all of the stuff in the "MPG FAQ". Have you done a compression / leak down test? Link to comment Share on other sites More sharing options...
chicagozer Posted August 19, 2011 Share Posted August 19, 2011 Mine throws the same code, but we race it and it seems to happen only when a couple of our drivers get friendly with the rev-limiter. Swap plugs and wire on #3 with another cylinder and see if the code moves. Link to comment Share on other sites More sharing options...
urdrwho Posted August 19, 2011 Author Share Posted August 19, 2011 New wires so I am guessing it isn't the wires. Plugs? Haven't checked them yet. Today we were drving all day, from town stuff to 60 MPH highway. Didn't throw the code until the end of the day. We were going down a hill int he country at about 45 MPH, hit a bump and bam....on comes the light. And we were just remarking that it didn't throw the code all day long. Since it is a recent engine transplant (car lot did the transplant) I am guessing at a loose wire but which one? Before going electrical gremlin hunting I'll check out the plugs. When it throws the code you can't tell any difference in running before or after the code. I have a 90 Jag XJ40 that throws a code, very intermittent and always on just the first start of the day. Never again. You clear the code and it won't appear for weeks or months. I know what the Jag code is but it doesn't make any sense. Can't figure it out. The trouble with computers is that it only takes a milli-second for something to be off and the computer throws a code. Back in the day before all the codes we never knew that for a split second the engine world wasn't as it was intended. I'll keep looking. http://legacygt.com/forums/images/smilies/spin.gif Mine throws the same code, but we race it and it seems to happen only when a couple of our drivers get friendly with the rev-limiter. Swap plugs and wire on #3 with another cylinder and see if the code moves. Link to comment Share on other sites More sharing options...
I Donated broknindarkagain Posted August 20, 2011 I Donated Share Posted August 20, 2011 You may want to check the upstream o2 sensor. It sits right below the right side axle...and the wires have a habit of rubbing on the axle and shorting out. I've seen misfires caused from that -broknindarkagain My Current Project - Click Here COME AND TAKE IT "The only thing necessary for the triumph of evil is for good men to do nothing." Link to comment Share on other sites More sharing options...
chicagozer Posted August 20, 2011 Share Posted August 20, 2011 Also look at the crank angle sensor and the camshaft position sensor connectors. If it's vibration related maybe something's loose there and that's what the ECU uses to detect misfire. Link to comment Share on other sites More sharing options...
I Donated broknindarkagain Posted August 20, 2011 I Donated Share Posted August 20, 2011 No, the Knock Sensor is used to detect misfires. The crank and cam position sensors tell the ignition WHEN to fire. They can't tell if its misfiring With that being said...a faulty crank or cam sensor can cause a misfire since it will be telling the ignition to fire at the wrong time -broknindarkagain My Current Project - Click Here COME AND TAKE IT "The only thing necessary for the triumph of evil is for good men to do nothing." Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.