Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Bad coils

I bought a 2004 Nissan sentra a few weeks ago, at the time, the owner told me it had a bad coil that sometimes caused slow start ups. However, whenever I went to start it up, I had no trouble before buying it, and the mechanic I had inspect it said there were no problems.

However, after buying it, I did run into the “slow” start up a couple times, and worse it also started to run roughly, so I decided to replace the coil myself. Bought the correct part number put it in where the bad coil was diagnosed at a local mechanic. This solved the problem of the rough ride, however it still had a slow start up. I’ve left it alone for a few months, figuring that the slow start up is just something I have to live with, however now the coil seems to be bad again and its riding rough. Someone suggested that the slow start may be due to a fuel line problem, since the slow start resolves if I prime the engine by turning the key almost all the way a few


I figure a coil shouldn’t go bad within 2 months, so there must be something else going on with this car, and I’m wondering where I should start investigating…

First step is scanning for codes. AutoZone, Checkers, etc. will do this for you free. The odds of the problem being coil caused are not high at all.

However, based on your comment about priming the engine this sounds like a loss of residual fuel pressure. This is (most often) caused by the check valve leaking off in the fuel pump and this requires replacement of the pump.
You can install a fuel pressure gauge, run the engine for a minute, and then note if the system maintains fuel pressure after it’s been sitting for a while.
Other less likely causes of fuel pressure loss would be a leaking injector or fuel pressure regulator.

Thanks, I’ll let you know how it goes!