My wifes 2001 Volvo v40 turbowith around 70 miles on it has had acceleration problems consistently. A couple months ago we noted problems with acceleration, and after taking it in the shop determined a coil was bad. Replaced the coil, and not two months later we are experiencing the same problem. Took it into another shop (could not return to the same as my wife is out of town), the they said a separate coil is bad. I am curious to know if there is a known issue with these coils with how few miles are on it, or if there is another issue. Is there something else that could be wrong that is causing these coils to fail? Or is there another issue upstream that would make it appear as though they are failing when they aren't? I have not taken it to a dealer or a reputable import shop so I am wondering if these other shops are diagnosing correctly.

I am an avid do it yourselfer and would like to diagnos as much as I possibly can to figure this out.

Other potentilially relavent variables.
We are running on regular gas (not sure if this could be a contributing factor considering plugs keep coming up fouled).
Have been through several sets of plugs throughout this process.

Any advice would be greatly appreciated.

 

Switching to mid or premium might help in the future. Poor gas could be leaving deposits, causing the ignition system to be overworked. Running through spark plugs should be a giveaway.

I would run a tank withfuel system cleaner then have the plugs changed out if they are fouled and be sure they are properly gapped. Then have the car scanned with an OBDii tool (performed free at an autoparts store). If misfiring is your problem, it more than likely will show up and the tool can tell you which coil is bad. Replacing a coil is a diy job and a new coil should only run $50+/-.

As for random coils failing, I would say ifone fails there is a good chance that another can go. The same thing happened to my brother.

 

01_fast_ride, thanks so much for the advice, it is greatly appreciated. My wife returned home with the plugs that the latest shop replaced, and they were each soiled with carbon deposits. I am curious to determine if this is consistent with your post (premium fuel, or potentially just getting a bad batch of fuel), given that they were changed out by another shop no more than two months ago.

Apparently, someone at Advance auto indicated that if a coil is going bad, the ECM will redistribute the load to other cylenders, resulting in what I have.

I have a OBD scanner and know which coil they recomended to change, and will most likely change it out. I would however like to determine if I need new wires (they recomended replacing the wires for the same bad coil), and confirm that the coil is in fact bad. I have a multimeter, is there any way to test the coil, wires, and anything else to determine what exacltly the problem is? Potentially their resistance or output while cranking?

I will make the switch to premium and keep my eyes on the plugs. Any additional information you or anyone could provide would be welcomed.

Regards

 

Two months for plug life is waaaay too short. If they were soiled like you say then my initial guess is that its either running rich or a low-grade fuel. Running rich would have caused another code so I believe that sticking with a good fuel is your best bet.

The people at Advance are usually pretty good, alot are ASE certified.

I am not 100%, but I think your engine is distributor-less, so wires aren't really a problem since they are low-voltage. I am also not positive on how to test a coil without killing yourself. Best of luck, I really hope someone else chimes in.

edit: My mistake. I looked up your engine and it has only 2 coils (not 4 like I thought). So, it is possible that the wires could go bad since they carry high-voltage from the coil to the plug. I think I saw a set for $45 at fcp. Sorry about the wrong info.

 

Status update:

Heard from someone that swapping good/bad coils and checking the gap on the plugs may be a good idea to troubleshoot. Checked the gap to the plugs (those changed by my first shop a month ago, and those replaced by the second shop this week). BOTH sets were gapped improperly. Guy at NAPA said that oftentimes shops throw in plugs that are "pregapped" at the factory without checking the specs. Once I changed the gap, performance improved dramatically and havn't gotten a cylander misfire code since. However, I noticed that the car is a bit sluggish off the line, tends to studder at idle, and I get a "system too rich" code. Also a funky smell and a sound like the engine is starved for air or something. From the research I have done thus far, could be an O2 or MAF/MAP sensor, or vacuum leak. Have no idea how to diagnose other than to replace the whole lot. Could also be a fuel delivery problem, but not sure. Any advice anyone wants to thow my way would be appreciated.

 

The ignition coil I've seen it failed but not too often... also when replace coil change the wire that runs to the other spark plugs. Since it runs on a waste spark system (2 companion cylinders fire at the same time) BTW original spark plug should not be re-gapped since it is platinum plugs may break ifbending tip to much. If checked and out of specs replace themnot too expansive. I notice volvo runs better on factory plugs... I hope that helps