scottes Posted July 28, 2018 Share Posted July 28, 2018 Hey All! Have a 2005 LGT 5MT that I've been having a bit of issues with. It started a few months ago with engine roughness, after extensive research on here and elsewhere, decided I was due for some new spark plugs. Changed them out but turned out the issue was the wiring harness that connects to the coil-on-plug. Of course after reading a bit more on here, I read about the frailty of cylinder 3's harness due to the heat. Got that fixed but the roughness/rattle has come back. Saw a pending fault for misfire on cylinder 1 on Torque so thought maybe the harness on 1 was also going bad but it appears to be well seated still. Not sure where to go from here. Here are the symptoms: 1) Most noticeable during acceleration/deceleration (applying/letting off the gas) and primarily on non-hilly roads, at higher speeds 2) Is the absolute worst when on cruise control coasting on a relatively flat surface at 50-70 mph 3) Not noticeable in neutral while coasting or while going downhill Would love any tips on next things to check for or other forum posts I may have missed to further troubleshoot! Thanks all! Link to comment Share on other sites More sharing options...
relative4 Posted July 28, 2018 Share Posted July 28, 2018 What mods & tune do you have? How many miles? What diagnostic equipment do you have? When you say roughness, are you referring to the roughness counts on one or more cylinders, or do you just mean it's running rough? I think Torque supports misfire counts, so you could start by getting misfire counts on all 4 cylinders at idle, 2500, and 4000 RPM, but even better, if you have Torque then presumably you have a dongle that can run BtSsm. A learning view snapshot from that tool would be very helpful, as would roughness counts. To clarify, "roughness" is BtSsm's term for misfires. Can you describe the rattle? Are we talking spark knock rattle or heat shield rattle? Link to comment Share on other sites More sharing options...
scottes Posted July 29, 2018 Author Share Posted July 29, 2018 Hey relative4, No mods/tune -- everything is stock. 193k miles. No diagnostic equipment besides Torque and the BAFX OBD2 dongle. By roughness I just meant running rough. Although with the cylinder 3 harness issue I was having a bit ago there were definitely misfires and P0303. From what I've read online, it doesn't appear that the BAFX dongle supports SSM unfortunately and the BtSsm dongles are out of stock:(. I'll try downloading it and running it though just to see if it works in the off chance. I ran test results on Torque and it returned all green although I didn't look closely at the numbers. I'll see if I can figure out getting misfire counts from it later today. The more I'm thinking about it, "engine rattle" may not have been the best wording for what's going on. The entire car shakes as if I'm driving over a rumble strip. I think I assumed the symptoms were caused by the engine rattling. Definitely not a heat shield rattle but possibly a spark knock rattle amplified. I don't really remember the rattle happening at a specific RPM but I'll report back on that later tonight too. Thanks for all the help! Link to comment Share on other sites More sharing options...
relative4 Posted July 29, 2018 Share Posted July 29, 2018 The best dongle is the ODBLink MX, definitely not out of stock at Amazon. Shaking like that can be misfires, fuel supply problems, engine mounts, etc. Using Torque, what are LTFTs @ idle, 2500, 4000? Link to comment Share on other sites More sharing options...
scottes Posted August 9, 2018 Author Share Posted August 9, 2018 Turned out it was the driveshaft. Thanks for the help though! Link to comment Share on other sites More sharing options...
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