I know everyone on here say to use only ac delco or original gm coil packs,...but do people ever have any luck with Denso or aftermarkets,...the price point is crazy variable,..on ebay you can get 6 aftermarkets for the price of one ac delco.
Coil Packs
- Thread starter Shaw520
- Start date
Blckshdw
Moderator
I replaced one of mine with whatever store brand Advance Auto had (BWD or something), about 6 years ago, because one of mine failed and that store was within walking distance. Has worked fine for me all these years. 
Mooseman
Moderator
My swapped in engine had a Standard newer coil in the #4 spot (usual one to fail) and it failed a few months later. Used a spare from the old engine.
Delphi is another brand option which should be a good bet. I think any well known brand, except Standard, should be good. I checked the listings on RA and weird one is Airtex/Wells which has only a couple of bucks difference between their economy and standard replacement part numbers. Go figure.
If it were me, I'd go with the Delphi.
Delphi is another brand option which should be a good bet. I think any well known brand, except Standard, should be good. I checked the listings on RA and weird one is Airtex/Wells which has only a couple of bucks difference between their economy and standard replacement part numbers. Go figure.
If it were me, I'd go with the Delphi.
Mooseman
Moderator
My goose chase continues,...new coil pack, new iridium plug,.. still getting a misfire code cyl #4,...probably going to be a clogged injector due to the vehicle sitting for a yr prior. I can feel a studder at an idle (rough idle),... but seems to clear just off an idle.
Mooseman
Moderator
Mooseman, unfortunately I have an old school compression checker the is incapable of reaching the plug threads,.. and although it will be my last resort, based on how well it runs just off an idle I don't feel there is a compression issue, (wishful thinking I know). So I ran some live scans with my Torque Pro / OBDII scan tool and I now leaning towards an intake leak on cyl 4. So the code is ALWAYS cyl 4 misfire and never differs,.. some real time monitoring of the misfires while driving have proved that the misfires are ONLY occurring during idle. Injector Pulse Widths all seem within relative, even during idle, so I think I can rule out injector issue. Zero cyl 4 misfires as soon as the throttle is applied and while underway. I did hear a high pitched whistle today at about 2k rpm, next step is to remove intake plastic cover and spray some carb cleaner around the intake mating surface while idling. Below Ive attached screen shots of IPW (injector pulse width) and CM CUR (cyl misfires current)
Mooseman
Moderator
The IPW is just telling you what the PCM is sending to that injector. No way for it to know if it's receiving it and spraying fuel, except to say if it's misfiring. But that could be due to a number of things.
You have to find a way to do a compression test. Maybe check with a parts store for a loaner tester.
You have to find a way to do a compression test. Maybe check with a parts store for a loaner tester.
seanpooh
Member
- Jan 24, 2012
- 461
At the shop:
If the misfire is at idle after warm up, it's the valves. When you're on the throttle, the valve are smacking the head making a complete seal. At idle with no load however, there's a leak between the valves.
A misfire after a cold start is injectors.
It's just our rule of thumb for diag until we have to dig deeper.
If the misfire is at idle after warm up, it's the valves. When you're on the throttle, the valve are smacking the head making a complete seal. At idle with no load however, there's a leak between the valves.
A misfire after a cold start is injectors.
It's just our rule of thumb for diag until we have to dig deeper.
So,..this may still be an injector issue,...which is what it feels like,...even when the misfires are occurring and I unplug the #4 connector the rpms still drop slightly,..possibly meaning a lean cond at idle. BTW,.. I just went outside and sprayed carb cleaner around the intake mating surface to the head, (well the best I could anyways, hard to get in there even with the straw), and no difference in idle.
This would make sense sean,... Im experiencing very little misfire when cold,..much more prominent when warm. thank you
seanpooh
Member
- Jan 24, 2012
- 461
Getting to the injectors isn't too bad... If you have time. Swapping two of them would indeed narrow your assumption.
And I have to elaborate more on the misfire at cold. Misfire after a cold start is present because the PCM/ECM isn't following a fuel trim until it warms up. When it does warm up, the misfire goes away since it's goes into it's "learned" trim.
And I have to elaborate more on the misfire at cold. Misfire after a cold start is present because the PCM/ECM isn't following a fuel trim until it warms up. When it does warm up, the misfire goes away since it's goes into it's "learned" trim.
seanpooh
Member
- Jan 24, 2012
- 461
I'll get an SI document for you.
Also there's more injector testing by commanding the fuel pump along with injectors and watching psi and such but it's all with a Tech2.
Also there's more injector testing by commanding the fuel pump along with injectors and watching psi and such but it's all with a Tech2.
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Wow,...very helpful sean,...thank you.
I just downloaded those 2 files,....Doesnt look too terrible,... all stuff I can handle,... before doing all that it would be wise to do the compression test to eliminate fuel issue,.. but guessing by how well it runs above an idle, I dont think ring to cyl compression is going to be an issue,...sounds more like a #4cyl valve not seating properly at idle, which would make sense given the vehicle sat for a yr before I acquired it.
Edit to ad; If im going to spring for a new compression checker, would it make sense to spend the extra coin and get a leak down tester,..will this better enable me to pinpoint if its a valve or cyl?,.. Can you actually hear the air escaping through the exhaust/intake?
I just downloaded those 2 files,....Doesnt look too terrible,... all stuff I can handle,... before doing all that it would be wise to do the compression test to eliminate fuel issue,.. but guessing by how well it runs above an idle, I dont think ring to cyl compression is going to be an issue,...sounds more like a #4cyl valve not seating properly at idle, which would make sense given the vehicle sat for a yr before I acquired it.
Edit to ad; If im going to spring for a new compression checker, would it make sense to spend the extra coin and get a leak down tester,..will this better enable me to pinpoint if its a valve or cyl?,.. Can you actually hear the air escaping through the exhaust/intake?
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seanpooh
Member
- Jan 24, 2012
- 461
Well... I've seen some guys who modified their compression testers to be leak down testers. And you hear the air leak, google Eric the Car Guy. However, if you do the dry and wet test, it will eliminate the piston rings. At the same time with a leak down tester, you need to get the specific cylinder at true TDC but pinpoint the issue immediately. You have lots of options to take.
Wow,..you were just reading my mind,..I was just watching the video where eric the car guy did that,... think Ill try that at no cost just to rule out or pin point the problem. Getting #4 at TDC on the compression stroke I can do.
Question 1; Im 100% certain my issue is in the #4 cyl, so,..if its an intake valve im sure I'll hear the air through the throttle body,....but if its exhaust what are the actual chances of hearing such a small leak way back at the tailpipe after muffler/cat/ect ? .. I would think slim to none,..I did see where someone suggested removing the closest O2 sensor for a better listen. (thinking about a way to ad smoke)
Question 2; Without a regulated leak down tester,...should I regulate my shop air down to 100psi.?
Thank you Sean,...you've been very helpful
Question 1; Im 100% certain my issue is in the #4 cyl, so,..if its an intake valve im sure I'll hear the air through the throttle body,....but if its exhaust what are the actual chances of hearing such a small leak way back at the tailpipe after muffler/cat/ect ? .. I would think slim to none,..I did see where someone suggested removing the closest O2 sensor for a better listen. (thinking about a way to ad smoke)
Question 2; Without a regulated leak down tester,...should I regulate my shop air down to 100psi.?
Thank you Sean,...you've been very helpful
And then this happens,.. torrential rains have been dousing the east cost for the past 20 hrs or so,.. been driving on wet, and even some flooded roads, on and off all day. Now since Ive been working on my TB and chasing this #4 misfire, I always have my Torque App going,..and usually I can feel the misfire while idling at a light or stop sign whatever..... well in these super wet conditions my misfire is gone!,...strangest thing, not one misfire in the past 6-8 hrs of driving in very wet conditions.
In the old days misfires occurred during wet conditions due to old wires ect.
I'll just let you guys ponder this for a while,...as I am.
In the old days misfires occurred during wet conditions due to old wires ect.
I'll just let you guys ponder this for a while,...as I am.
jsheahawk
Member
Possible scenario; Due to the varmint chewed history of the engine compartment, (I replaced the entire engine harness when I got the truck), I wonder if one of the wires going to the #4 injector has a nick in it and the water created a better connection,...but why then does it only misfire at idle,...shouldnt the voltage be the same at all rpms,...or does the voltage increase slightly with engine rpms?
Mooseman
Moderator
I'm kinda getting the same thing. Mine has a very slight misfire on #4 but it's not enough t set a code but I see it in Torque. Only does it when the engine is idling on a warm restart. If it's in gear, nothing. Can't even feel it. Swapped the coils, nada, stays at #4.
Another misfire thread
Another misfire thread