CarTalk.com Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

Please Help

Hello,
I own a 2001 Nissan Sentra 1.8 liter GXE. In March, I replaced two sensors. 1 (one) O/P Crankshaft sensor and 1 (one) O/P Valve Timing Position Sensor. In May, while driving, the car started to hesitate and what I would describe as choking. The engine was running roughly and there was a vibration felt while sitting in the drivers seat. A friend looked at the car and tested the ignition coils and it was determined that one was bad. (We loosened the screws and lifted the coil from it’s housing and noticed that while the engine was running there was no change or interruption.) When we tested the other three coils, there was engine disruption. So, I purchased a new ignition coil for $81.00 and installed it. The car was running great again. Until recently when it started to hesitate while driving and the rpm needle fluctuated at random times.

Thinking it might be another coil, I tested them by switching them. This time I had another friend helping me. Whatever we did, messed the car up even more. Now it will not start easily and stalls out. It is running extremely rough and I’m really not sure what to do. I know I should have let a professional deal with it, but I’m a single Mom on a very tight budget and it seemed so straight forward.

Do you think switching of the coils could cause this. I tried to put them back in their original spots, but unfortunately, I can not remember exactly where they were. They all look the same except for the one I purchased in May.

Please help me, I don’t know what to do. I’m afraid to drive the car now. Actually, I won’t drive it until I can get it back to running well.

Thank you very much for your help.

Christine

If one coil was bad, you certainly could have another one bad at this point. You could also need a set of plug wires if it has them. If the wires were bad, messing with the coils could have made it worse. You can test coils with an meter but I think at this point it might be best to have it diagnosed.

You may have bad wires or plugs. You got fixed on the ignition coil but sometimes both are bad and replaceing one may help but disconnecting and reconnecting stuff may have caused other problems. Are you absolutely certain that you did not cross a wire from one cylinder to another? You can go online and check the correct wiring. I have worked on cars for 32 years and it has happened to me. It can get confusing if you do not work one wire at a time.

I agree with Bing. When one coil-on-plug coil fails, most shops will want to replace all of them because of the likelihood that the others will fail soon, one after another.

Unplugging a coil while the car is running is not a good idea. The computer does not like that. OK to unplug a coil and then restart the car, though that may result in a check engine light.

When you say that you tested them by switching them, what do you mean exactly? Is there any chance that the wires that attach to the coils got crossed? If that happened, then the coils are not firing at the correct time and that will make the car hard to start and it will run terrible if at all. Those wires carry a trigger signal to the coil at each cylinder of the car in a precise time and sequence. You must make sure that each of the wires is connected to the coil on the correct cylinder. Hopefully it will be apparent based on the origin and length of the wires.

Coils can be killed by aged spark plugs and new plugs can be done in by a failing coil. My opinion is that any coil replacement should involve new spark plugs and no way would I remove the spark plugs and not run a compression test at that time.

Weak compression can do a spark plug in which in turn can ruin the coil. Odds are the compression is fine but I’m a believer in verification.