Cliff's Notes: Suspected bad coil pack on cylinder #5 since no effect on idle when disconnected. Swapped for coil pack on cylinder #4 and yet it is still cylinder #5 that has no impact on idle when disconnected.

What could be causing this?

The CEL has been on/off intermittently for some time showing only misfire codes P0300 & P0301 - P0306 (random + each individual cylinder). It seems to run fine for a while, then the same symptoms return. Acura dealer gave stock diagnosis of "bad gas", which proved to be false.

Yesterday the CEL started flashing constantly, car runs rough & sounds like a V8 or bike with a big cam at idle ("glug, glug, glug"). I immediately turned around & took it back home. Still strictly the misfire codes, so research led me to believe it could possibly be a bad coil pack.

When I pulled the electrical connectors from the coil packs one by one at idle to test them, each one had an obvious impact on idle except cylinder #5 (front center). However, when I swapped the coil packs between cylinder #5 & #4 to confirm that was the issue, it was still cylinder #5 that had no effect on idle when disconnected.

What are your thoughts?

Previous post with some other history is here --> https://acurazine.com/forums/3g-tl-problems-fixes-114/p0153-p2a03-random-misfire-909227/ However this seems to be a different / unique issue so I started a new thread.

Thanks for all of your help!

 

Did you actually check spark plug in cylinder #5 if it was tightened and not coming loose?

 

@justnspace - I did so 2-3 months ago as part of the diagnosis then, but by the time I had the car up to temp to check the coil packs, it was too hot to mess with the plugs * I had work.

That's definitely my next step, but I thought it was worth asking if that symptom may point to anything else so I can get a game plan together today to hopefully fix it tonight.

Thanks for the quick reply!

 

if spark plug in cylinder #5 is tight, your next step is a leak down and compression test.

these two tests will let you know if something is wrong with compression.
if something is wrong with compression, the car has been over-rev'd or over heated or has had water sucked up.

 

Thanks, man. I'll report back as soon as I have some more info.

 

Don't just check to see that it is tight; physically take the plug out and look at it. Maybe the electrode broke off the plug.

It could also potentially be a bad fuel injector, assuming that the compression/leakdown test is good.

 

Is yours a manual or auto? A lot of guys bend valves by over revving on manuals. If the dealer diagnosed it as bad gas(and meaning youve went a few tanks since then) then take it back and they should diag if for free really. If you have a dead cylinder #5 that has no effect on how it runs, check the wires going to the ignition coil to make sure you have power and ground to actually send spark. Misfires are easy to determine the cause, its just a case of having the right tools to diagnose correctly and the know how. Also check your wires to your fuel inector, constant power and flashing ground on a test light. Do this last because you'll have to pull your intake off. PM e if you have additional questions. Im a mechanic, so i deal with this every day

 

I presume the manual guys are over revving during downshifts. Because, on upshifts, mine at least, has a 6800rpm hard limiter. I wish they could have put a soft limiter on as well.

 

on upshifts, software protects the engine components. fuel gets cut off.

on a downshift, a software protection is impossible
its called a mechanical over-rev.
the hardware is going way to fast for each other. and BAM! they collide.

 

Yeah, I realize there's no way to protect against a mechanical over-rev, but damn you gotta be beating the piss out of your car to over-rev it. I know pretty much what speed each gear tops out at. At least 1-3, which are the gears I normally use for spirited driving.

 

^have you been following my engine rebuild thread?

a friend over-rev'd my car and ive been rebuilding it.
It's likely he didnt know the gearing.
I remember him trying to find the sweet spot for third gear.

I know, since its my car and I am familiar with it. I know top of third gear is already at 90mph.
I believe he put it into 4th and accelerated, which would have put us somewhere in the 100mph range....
and i think he stuffed it back into third, thinking it would pull harder.
butt, he exceeded the mechanical RPM range for that gear and boom! my valves are all bent!!

 

Sorry, to hear that. It makes sense him not knowing what speed is safe for each gear, but that still doesn't really take the sting out.

 

Sorry to hear this that sucks
Sounds more like the death shift 1st redline 2nd reline 3rd reline back to 2nd accidently instead of 4th
Did it jump the timing belt (was it off a few teeth)? or float the valves and hit ?

 

Sorry about your car, Justn.

 

I skipped the leak down and compression test as I knew already what had happened.


Utah, as i tore down the engine i saw piston strikes!
as you know, you cant see the bent valves as its generally the stems that bend



https://acurazine.com/forums/3g-tl-problems-fixes-114/justnspace-vs-j32-j37-915065/






I swapped to 3.7l heads.
so, I have a 3.2 short block(2006 TL) with 07-08 3.5l type-s cams inside 3.7l heads(07-09 MDX)

 

Wow, justnspace, that's rough! But at least you're making the best of a bad situation...

OK, the plug in cylinder #5 was in tight & although a little darker than I'd expect for ~10k miles on it (which would make sense if it's not sparking, right?), it seems fine. The coil pack is apparently OK (based on the previous cylinder switch I did). So now I'm following the chain backward from there...

@NBP_BALLER:
- What's the best way to test the ignition wires with a multimeter?
- Can I simply probe one of the 3 slots in the connector & ground it or what?
I have the same question on the fuel injectors, too -- but that seems to be far less common on these cars & it looks like I'd be taking the top off the engine to get to that stuff. I've tried searching here + online in general & can't seem to find anything specific to our cars. Forgive me if I'm missing something obvious here... (P.S. Maybe I'm tired or just not used to these forums, but I couldn't figure out how to PM you....

It is a manual but I rarely redline it & I never aggressively downshift to have caused a mechanical over-rev. Bent valves always seem to be the first diagnosis when I share that it's a 6MT with P0300-306 codes.

Compression + leakdown testing seems like it would come after all that, but it's hard to imagine what would cause that kind of serious issue on a car with barely over 120k miles that isn't driven hard.

Thanks again to everyone for their help with this & good luck on the rebuild, justnspace!

 

You can test coil packs with a digital multimeter. You measure the resistance, but I can't seem to find the values in my manual.

It also mentions the ignition coil relay. The #2 15A fuse is for the relay, and the relay itself is "under-dash". It goes on how to test that.

 

UPDATE: On a friend's advice, I went ahead & replaced the #5 spark plug while I was in there (even though it looked fine visually), took the EGR valve off for a peek (nothing noticeable there, either) then reset the ECU so I could read any fresh, hopefully more specific codes that popped up & cranked it over.

Lo & behold! Smooth idle + no CEL. Let it get up to temp, still running smooth so I took it on a 10 mile spin. No problems to report & all is well.

I'll keep everyone in the loop to be certain this is indeed the fix, but it proves the point yet again -- always start with the simplest, most obvious, easiest & cheapest options then work your way up from there!

Thanks again to each of you for your support + guidance in helping me work through this!

 

I always swap plug to the left and coil to the right and mark them, that way if the misfire moves, I know what caused it, and if it doesn't go away then I can rule the plug and coil out. Maybe you put the plug in too tight and cracked it internally. Ive seen it before. Not often, usually ppl snap plugs in half on the porcelain. Hope your prob is fixed!

 

What gas do u put in that poor engine. Those heads look crusty?

 

Not top tier gasoline I bet lol

 

UPDATE: !!-HELP-!!

CLIFF'S NOTES: In addition to the misfire codes, the car will now -- only occasionally -- run extremely rough & blow white smoke **on warm starts only**. It is also losing coolant with no visible leak... Is it possible this could be something other than a head gasket?! Such as the intake manifold being cracked or the gasket there? These CELs / problems only occurred *after* my 105K TB / WP service at the dealership.

For a bit more detail to bridge August's post to now -- About 350 miles later, the CEL popped back on -- and has been intermittently more on than off since then. Again only the misfire codes (one for each cylinder + random misfire. That's been the case for at least a couple thousand miles.

Then about 4 times in the past 3 weeks (but only intermittently & on warm starts only) the car will bog down hard & blow white smoke. I immediately shut it off, let it cool down a little & reset the ECU. Then it seems to be fine... for a while.

Occasionally I have also (both separate from & once at the same time as the smoke) watched the temp gauge start to rise & have had to add 1-1½ quarts to the radiator. The immediate guess at a diagnosis based on these facts alone would point at the head gasket, correct?

BUT -- is it possible these same symptoms could be the result of a cracked intake manifold or bent IM gasket or something else entirely? If so, what's the best way to inspect / confirm this?

Correct me if I'm wrong, but a head gasket going bad on a TL with only ~128,000 miles on it is highly unusual, right? That's why I'm exploring what else could possibly cause these symptoms, as on a gut level it just doesn't seem right the head gasket is the issue.

Thanks for all of your help, guys!

from_zer0

 

Anyone?

 

it sounds like a head gasket to me, like you said, not really common problem tho. i wouldn't suspect the intake manifold. you could have a pressure test done...

 

Might be easier just to swap a new engine in rather then beat your head trouble shooting and trying to replace every single part along the way. A replacement engine should be in the ballpark of $1000.

It does sound like a head gasket problem, but, although I could be wrong, it seems like there is other issues occurring. I can't imagine a head gasket causing that many issues. It is highly unusual for the head gasket to go on these engines, so in my mind, it seems like the gasket going was a result of another problem.

If you're capable of replacing the head gasket, an engine swap would be pretty simple. Best of luck and let us know what direction you choose to go with!

 

That's the short block, not heads. The top of the pistons look crusty. That's normal, as combustion occurs above the piston tops. If the heads looked like that, it would be because of not changing oil. Ever.

 

Hey, thanks for the help + insight, TacoBello. I appreciate it.

It opens up some other questions though:

1). Is this the general consensus / opinion of the group here? It seems completely off the wall that a problem like this would occur so early on in the life of such a reliable car that would call for a full-on engine replacement...

2). Is a replacement j-series engine really only $1,000? If so, where? And what would it cost to have that shipped / installed?

3). Why is this happening?! LoL! I did intensive research up front, had the car thoroughly inspected by an Acura dealership & it ran just fine for 15,000+ miles before even starting to hint at acting up (w/ random misfire CEL that the dealer blamed on bad gas)...

Thanks again for all of the support from this community as I work to get this sorted out!

 

What year vehicle? If it's a 3.2 from 04 - 06, engines are cheap, I'd say 400 - 800 depending on mileage and source. There is much debate, but if I recall, you can use a 3.5 from the Odyssey or MDX with the 04 manual, and they are cheap too.

If you need an 07+ 3.5 - you're looking probably closer to $2K or more.

I don't recall what R&R book time is on an engine - a google search shows it as 17.2 hours, which would be nearly $2K at shops in the $100 - $120 /hr range.

A new engine probably only makes sense once you have confirmed that is the problem and can DIY it.

 

:::UPDATE:::

So I've exhausted my other options & taken the car to a shop I can trust. Pressure test was good *but* there is some oil in the coolant. I should know by tomorrow if that stems from the intake (*fingers crossed!*) or the head(s). This leaves 2 key questions in my mind:

1. What should a reasonable repair cost be if it is intake related?
   
2. What should a reasonable repair cost be if it is the head(s)?

Also, if I have to go ahead & get this work done, is there anything else at all that I should have taken care of / done while the engine is apart?

Let me know as soon as you can, as I'll be making some decisions tomorrow!

Thanks!

from-zer0

 

update?

 

What was the outcome? I am currently on the same boat and really hoping my valves are okay...

 

make sure radiator is good, it could be mixing fluids due to a leak.

 

Thanks csmeance I will have a look at the radiator today. If i were to find a leak , would you recommend doing a coolant flush before or after finding the leak?