Hey guys,

I've been troubleshooting a misfire for a couple of weeks now swapping coil packs in/out like a mad man (and resetting ECU). I'm on my last swap out right now, but I can tell its still not running smoothly, just haven't seen the CEL yet.
My mistake may have been buying a Delphi brand coil pack as a replacement (amazon prime 2 day shipping got the best of me). Does anyone have experience with using aftermarket coil packs?
I've even used a multimeter and the resistances looked pretty consistent, does anyone have tolerances for our coil packs impedance?
Trying to avoid the mayhem of switching 2 coil packs around, any other ideas?
Other details: spark plugs < 2k miles, standard NGK Iridium. 2002 S at 253k miles. Misfires register very sporadically, sometimes I can get 6 or so drives in without any.

 

Another easy way to check the coil packs: When you unplug them one by one if the car bogs down your good to go if not bad coil pack.


Have no experience with aftermarket coil packs but also haven`t read any thing bad about them. I have oem in mine they work good.

 

I have used aftermarket coils and they work just like oem until you hook up a lab scope they show different characteristics, not that it maters. I have aftermarket coils in my TL for 2 years now and all good.
Heres a video so you can understand how to find the bad coil.
If that didnt work out for you take a look at all the coil boots for this

If you see this then thats your bad coil but first do the power balance test.
Make sure they are not full of oil as that can also cause a misfire.
Hope it helps, Let us know what you find.

 

Other things besides a bad coil can cause "misfiring". Check the codes again and tell us what they are.

Have ya checked for a vacuum leak, checked fuel pressure, inspected wiring connections and grounds, cleaned TB/intake and EGR passageways, etc........ ???

 

So you dont have a cel for misfire but you are replacing parts for one? If you have had one what cyl was it for?

Have you adjusted your valves? They can cause it. Fuel injectors will also cause it.

 

Thanks for the feedback. I have pulled the coil pack wires to look for rpm drops and I noticed a drop/stutter on all of the packs. The misfires are very intermittent. However, I have identified one coil pack that when removed makes my engine run smoother than the others, but I still had a misfire CEL occur multiple times with it. I may leave that pack in and buy another for swapping, because I suppose one could have been damaged during swapping, even though i was careful.

I've pulled codes a few times, but of course I've been moving packs around so it may not be helpful. First pull: Cyl 1,3,4,5. 2nd: Cyl 4,5. 3rd: Cyl 2,3,4,5,6. Clearly cyl 4 and 5 are the common element here, but I read elsewhere (01tl) that the reported cylinders aren't necessarily the root of the cause.

I cleaned my entire intake manifold/egr less than 20k-ish miles. Valves haven't been adjusted in a long time. Maybe this weekend I can get around to checking wiring, fuel pressure, and vacuum leak. May run some seafoam for fuel injectors.

 

I'm with fsttyms on this one. The exhaust valves get tight, and will cause a misfire that's random and hard to pin down. You're usually ok till about 125,000 to 150,000 miles.

 

In that case, a valve adjustment may be consuming my weekend.

Just to clarify: If a coil pack is bad, you can typically tell by unplugging it? Or are some coil packs only bad intermittently?

I guess since my engine hasn't been running smoothly at all the past few days, and all packs have an effect on the RPM, packs must be fine.

 

I am having this exact problem and could use all the advice I can get.
Please post as to what u find.


I would add that when misfire started it was while I was in park - warming up the vehicle .
Just happened to be sitting there longer than usual as it was pretty cold that morning and then misfiring started.
then engine light. (codes 0300, 0301, 0305.)
Immediately replaced plugs , checked coil packs and harness, checked for clogged evaporator drain hose and inspected the area on and around the PCM for any signs of moisture .



Tomorrow i guess ill pull the EGR valve .

Thanks in advance for any ideas.

 

A coil pack can go bad if it is intermittent there is possibly a deeper problem.
Valve Adjustment Tip: Double check all work before putting everything back together. If needed you can also clean out the iacv valve and intake while everything is out

Unplug every coil one by one to see which if not multiple might have issues.

 

THANK YOU Nicks2001tl !

why did i not try this first? I guess the multiple cylinder codes threw me off. I knew she was missing on only one by the way she ran and sounded. apparently that is enough to throw any or all cylinder misfire codes as well as the 0300 multiple. Learn something every day.
( next time Ill just ask here first.)
Last 2 questions , (hopefully) What if anything causes these to go bad other than mileage. ? I am at 165k should I carry a couple spares or replace them all?

Thanks again .

 

I replaced all my coils at 125,000 miles and haven`t had any issues since. 145,000 now. Starts crisp in the winter months.

 

The factory OEM coils are actually very durable....unless mishandled.
I've only ever had to replace one so far in a 2000 TL with 180K. Many other things can cause the "Misfire" codes to come up, so check the other simple stuff before replacing all of the coils.

 

plug replacement is the number 1 killer of coil packs for us
easily damaged despite caution,,die some months later!

exactly which ngks are you running- 8 dollars each?

for fun have the battery and system tested for free at parts stores
a weak batt cell will really mess with the car--it did mine

you cleaned the IACV rod and chamber and TB parts when the manifold was off 20k ago?