I have an LT1 car with the LTCC coil per cylinder ignition which ends up resembling the LS1 iginition. The system was already in the car when I bought it and I'm pretty sure two of the coils are bad. I am using a timing light to watch for spark and I swapped around the suspected bad coils with suspected good ones and the lack of spark followed the suspected bad coils. At best they are intermittantly working. This may sound like a dumb question but, what is the typical lifespan of the LS1 coil packs? Is there a better way to test them to be sure they are good or bad?

 

I would like to know this as well.. You said you were using a timing light?

 

yeah,.. using a timing light and you just put the clamp on whatever plug wire you want to watch.. the light flashes everytime it senses a spark so... no flashing = no spark. Moved the bad coil to 2 different spots swapping it with other coils that seemed to be working and the problem followed. easiest way I could think of.. If I hadn't swapped it around, someone could say it might just be a plug or wire but, since the symptom followed, I figure its a bad coil (two actually). I just didn't know if there's some ls1 know-how on ohming out the coils or if there's some easy way to bench test them...

 

I saw a thread kind of touching on this subject like 2 years ago. I will see if I can find it.

 

It would be very strange for 2 to die at the same time, but if you are testing them that way and it moves with them it is possible.

1) Check the connector plugs on the coils for bent prongs.

2) Are you moving plug wires too? If so inspect them.

3) How long did you test? I had a similar problem and at first it seemed the dead coil was following but later found after testing longer, all the coils on one side were firing intermittent. Turns out the coil harness on that rack has a short. I swapped on a whole new rack from a friend's truck and it fixed it, so I bought a new rail from the junkyard and kept my old set as a spare.

Are both coils on the same side? Do you have access to extra coils?

 

I just had one go bad on my 2000. It would throw a misfire code, but also start making a wierd squeaky noise when it warmed up. I ended up unplugging one at a time until it stopped. Hope that helps

You can hear it in this video,

http://www.youtube.com/watch?v=0xS-9qd2h9s

 

Sorry so long but, here's the whole story:

I could have done this the cheap way but, decided to just get all new coils since I have the money. My situation, basically, is I bought a car for its rolling chassis. I swapped my old motor and all my suspension parts from my late SS into this car. This car already had the LTCC setup installed and I wanted to keep it. During the swap out, I put in a little bit bigger cam LE 218/224 cant remember lsa right now.. and it ran decent for 3-4 weeks. I wasn't in a rush to get it tuned since its not my DD. The alternator crapped out and within a week of replacing that it started to run rough under any kind of load condition. When I ease into the throttle really gently, it revs up smooth but, if I stomp on it I will get a lot of missing and studderring as it climbs... also, if I'm cruising along smoothly in any gear and approach a hill.. as soon as add a little throttle to maintain speed I get same symptoms. I checked valve lash 3 times. I checked fuel pressure which is 40-41lbs @ idle and 39-40lbs. at 3000rpm (I was told by a friend thats good, is it?). I inspected plug wires and they are good. I changed fuel filter. I installed new spark plugs when I did the swap out. Oh, and there are no codes either. I have tuning software but not the know how to really do the job yet but, I did reflash the PCM with the stock tune to see if maybe the computer had finally adjusted to the cam and thats why it started acting weird after the 3-4 weeks of occasional driving. reflashing didn't change anything. So, the most recent check was for spark like I described with a timing light. When I say that I swapped coils, I actually swapped the 4wire plug and spark plug wire off of two that were side by side (effectively swapping the coils without physically moving them). The problem seemed to follow the coils and not stay with the cylinder. I have two suspected bad coils from this test - one is on passenger side and one is on driverside. As for this whole ignition setup, it looks as if the person who owned the car before me and installed this LTCC setup probably picked up random coils because they dont all look alike. As far as the shapes, yes they are alike but, some have a black plastic back and some have a white plastic back which makes me wonder if they are just junkyard coils or ebay junkers this guy picked up from where ever and however just to get 8 cheap coils. Well, I already went ahead and picked up 8 new coils from the parts store just to be sure they're good. My reason for this thread was to get some ideas on this problem but mainly to find out if there's another way to maybe bench test the coils out of the car with a multimeter or some other way. I haven't swapped out the coils just yet but, once I do and IF it corrects my problem, I wanted to test the old coils and keep them as spares if some of them are as they should be. Is there any resistance readings I can do or something?

 

WEIRD... I think I can hear the squeaking in your video while your still approaching from far away but not when you get close. Funny thing is, I have a weird chirp/squeak too but mine sounds a little louder. Changes with RPM, I have been thinking it is a bearing on the PS pump or ALT... makes me wonder... I doubt I would be so lucky to fix two problems in one shot... Really doing the wishful thinking now too, the chirping on mine didn't seem to start till after the ALT crapped out and I never really thought of the chirping as being connected. I'll be swapping these puppies out either tonight or tomorrow after work and I'll get back on here with the results.

 

changed em out.. no difference with the rough ride issue. what a PITA.

 

It should trow a misfire code.

 

^ you would think so... but, I'm not getting any. That would be awsome because it would help possibly narrow down the cylinder(s) I'm having trouble with or point me in a direction. I do have the LT4 KM but, this kinda occasional shudder should be registering (IMO). Might my KS be bad?

I rechecked the coils with a timing light again and all of them seem good now. maybe it was a problem or maybe it was a fluke.. or maybe there is still a problem and watching the light flash isn't a good enough check. hehe..

Also, is it possible that the tune could be responsible? I believe I'm currently running the stock tune although I have a LE 218/224 cam installed (put in the cam at time of swapping motor to this car). I just dont understand why it would run okay for a few weeks and suddenly stop being okay if it were just tune, and the car feels good when there's no load (i.e. just rolling at any speed in a lower gear at 3000+ rpm) I know VERY little about how the computer jumps around in the fuel tables but, when the car encounters some load or senses me pushing on the throttle more at low RPM (load again), couldn't it just be the fuel table, PE table, or spark advance settings not being right for this cam at particular conditions? I would think no based on, the car didn't act like this for the first few weeks. Then again, it really wasn't driven to much prior to the ALT dying.

 

Been working on an 03 tahoe. Same spark setup ( i believe ). Exact same symptoms ( idle and throttle : under load, not, ect... ). Except i chacked spark from individual packs by unplugging at spark plug, inserting smaller philips screw driver and arking off block. All coils sending spark. ( not sure on time or correct current, however still got spark ). Fast forward a week or two and am checking continuity for various applications attempting for better diagnosis. Found thermal coils on each coil pack ( for heat distribution? ) are grounded. All right heads thermal coils grounded. All left heads thermal coils are not showing continuity to ground.

 

This thread is fourteen years old. It might be better to start your own thread.