My 2005 R53 with 147k miles has started to develop a cough that I am having trouble diagnosing. I am the original owner and it has been my daily since I've owned it. The strange thing is it's not throwing any codes and the "service engine soon" light has not been on at all but the cough is becoming quite prevalent. Normally only happens under acceleration at just under or at 3000 revs. It is usually a quick cough (only once or twice) and then revs normally past that. I replaced spark plugs several months back and put in stock NGKs - they were replacing some very worn down plugs that were way past their prime. Plug wires and coil pack are original. There is corrosion and even pitting on some of the coil pack posts (been thinking of replacing the coils and wires but did not just want to start randomly throwing stuff at the problem without some more advice first). The fuel filter has not been cleaned or replaced (something else I've been considering). I also hear a strange "chirping" sound coming from the back seat area (can easily be heard with one or both seats down). I suspect that it might be the fuel pump but not sure. If I can manage a reasonable recording I will try to post it but not sure if it will be easy to hear the chirp or not.

I'll start with this until someone asks for more information. Any thoughts?

Thanks in advance,
Tim

 

Could be the coil, the 3k hiccup is associated with that. Be sure to pull the wires and see if the electrodes are rusty, but even if not I am still thinking the coil is bad.

 

Thanks coop. I guess I've never heard what I have called the 3k hiccup before. Maybe a good correlation if it's that well known... Would you expect it to NOT throw any codes under this situation?

I have pulled the wires at the coil and the #3 is a little rusty as I guess is common. The #1 doesn't look rusty so much but it actually looks like there has been pitting on that post. Should I stick with the stock coil pack as a replacement? I have read some not so great things about the MSD coil pack and not sure about the WMW screamin' demon. Any advise on picking a replacement?

Thanks,
Tim

 

with the original coil and wires it is for sure a good maint item to replace before trying other parts to fix a problem.

 

The coil problem does not throw codes that I am aware of. Way can chime in more.

 

Replace coil and wires with oem. Need replaced after that many miles, just as a preventative maintenance thing. You don't need anything fancy, oem is plenty good enough on a daily driver.

 

Update 5/Jan/2018:
I replaced just the coil pack first with a basic Prenco replacement unit. Didn't realize I was going to have to find bolts for it but got that done for now with a trip to the hardware store. The results after a a quick round-the-block test yesterday evening and then the typical commute to work today were not good. Pretty much no change. Today, I got the replacement wires from Way Motor Works today and the quick round-the-block test was a big . Tried repeated, hard accelerations from about 2k to 4k in 2nd, 3rd and 4th gears and not once did it cough or hiccup. Not gonna call it quite done yet (more testing required) but I think we may have a winner here solving my hiccup problem. My tip: try the WMW performance wires first!!!

Tim