2001 Volvo v70xc with 188k miles on it,

my car has been shaking recently between 1,000-3,000 rpms, and got a po301 code when I had them read. Doing that led me to believe that I should replace coil pack and all the plugs, which had no effect on the shaking. I think the compression is fine because it only does the shaking 50% of the time, other times it drives just fine. I think it may be a wiring issue but I'm not sure, anyone have any ideas????

thanks, dave

 

P0301 is a misfire code for the #1 cylinder. As noted typical solution is to replace the plugs and then the coil packs. With that said, from time to time the problem can be the connector into the coil pack so you may want to inspect for cracks. Considering your suggestion that the problem is intermittant, I'd agree with your assessment that it may be a wiring problem. Other possible causes for shaking can be the torque rods (motor mounts), wheel balance, axles but those don't go away...

 

My 2004 C70 is doing the same thing, got a P0301 code. Check engine light is either on solid, or sometimes blinks. Seems like it only vibrates and has low pick up in the first gear, maybe second but not as noticeable. It's got 117K miles on it and I'm HOPING it's just plugs. Timing belt replaced within past year; transmission replaced (ouch) just a month ago.

 

likely causes are 1) plugs - try going with OEM Volvo. More expensive after market does not always equal better performance. 2) Coil packs. Before replacing, try swapping coil 1 (the 301 refers to cylinder 1, which is by the timing belt side of the engine) with coil 3. If you get a 303 error, blame the coil, if you still get a 301, look closely at the coil's connector for cracks or corrosion. 3) if you are not in the habit of running premium (ie 93 octane) try running the next tank or two on premium and consider throwing in a bottle of injector cleaner (such as Techron) when you fill up. Brand name premium gasolines have better detergents and can clean up injectors in just a tank or two.