senorbob999

hi, im a newbie member to the site but i have a lot of mechanical knowledge of gen 3 ls1 engines but for some reason i cannot figure this problem i have now. here the scoop.

i have a 2001 silverado with a 4.8L V8. the oem ignition coils on my truck recently had problems. 3 of them were bad. so instead of just buying 3 new coils i thought id rather buy a whole new set. I have the delphi (square looking) coils on my truck. the delhi coils are the coils that require the 10.5" long spark plug wires. I checked online and i found serveral froums that say that when you upgrade the ignition from the delphi type to the ac delco type that you get more horse power and a little nit more fuel economy. the ac delco type ignition coils are completely different from the delphi type. they are barrel shaped and have a different ignition coil harness and a different mounting plate. i found a new set of OEM take offs on ebay and i bought them from my truck. the donor coils came off a 2004 tahoe. i went to my local autozone and asked the supervisor there (he's a freind). he said that he didnt see why i couldnt swap the coils out, all that i would need are the ac delco wires and mounting plate.

when the new set of coils arrived it took me about 2 hours to change them out and install the new ones in. i removed the factory delphi coils and installed the new set of ac delco coils. i also used the ac delco ignition coil harness and it plug right into the plug with no problems. after installing i turned my truck on and everythign seemed ok. the idle was aabout 200rpm more but i read online that it was normal. then after about 20 minutes of driving the check engine light came on. i did not feel any power loss of difference in the trucks performance. when i stopped i got my ecu tuner (that has a trouble code reader) and it gave me 8 trouble codes, all 8 coils set of the check engine light. the code reads :primary and secondary wire malfuction" i reset the codes and drove off. then again 20 minutes later the check engine light came on again. again i got the same trouble codes. ive looked all over online to try and find a solution to this problem but the only think that i can come up with is that i might need to use the delphi ignition coil wiring harness with the new ac delco ignitoon coils. i just wanted to ask if anyone has ever tried this before successfully? camro and corvette guys do this swap all the time and they dont get check engine lights!

any help is greatly apreciated in advanced!

thanx

BrownBoy

iTrader: (10)

*bump* for an answer.

I plan on doing this swap soon, can someon chime in here?

senorbob999

i went to my local chevy dealership and i talked to a tech there for about 15 minutes. he said the ignition coil wiring harness for the delphi type coils (square type) and the ignition wiring harness for the ac delco type (barrel type) coils are almost identical except for 2 things. the colors on the wires are different and the ac delco harness uses a little more power than the delco type. he said that camaro and corvette guys come to the dealership all the time to buy the ac dlco coils and harness and bracket. he said that i should try installing the ac delco coils with the delphi coil harness. he said that he strongly suggests i disconnect the negative battery before any attempt. he said once it was installed to turn the truck on and leave it on for 20 minutes without running it, just leaving it in idle. he said that maybe what caused my check engine light to go off was not giving my truck and the ecu enough time to get used to the new coils and the greater amounts of power they produce. he then said that if i still get the check engine light that i should once again try to the 1st setup of the ac delco harness and ac delco coils but disconnect the battery and run the truck for 20 min in idle. he says that if that still doesnt solve the problem that i may have to come into the dealership and get my ecu re-programmed to accept the ac delco coils. but he said that he heard that camaros and corvettes do the swaps on thier ls1's and they dont get the check engine light on. i will attempt to try to instakk the coils again on my truck tonight if not them i will try agian this weekend (its 24 degrees at night when i get home so i might have to wait for my day off!). i will post any results asap.

but if any ls1 guys or gen 3 or gen 4 truck guys have successfully done this swap then i ask please share your info with me. tell me what im forgettoing to do or what im doing wrong. any help is much aopreciated.

thanx

69LT1Bird

iTrader: (1)

Are you sure you don't have any wiring issues. It is hard to believe that 3 coils would fail at the same time.

The myth of of the increased horsepower and mileage is just that, a myth.

Verify that the new harness is exactly like the stock harness, pin for pin. Trace each wire.

The coils received 12 volts, have a ground and get a 5 volt reference from the PCM to fire, they are not too complicated. I have never heard of a reflash or relearn procedure for a coil swap.

senorbob999

the 3 oem coils on my truck had over 200K on them and 3 were just about to go out. i got a set of low low mileage ac delco type online. the harnesses for both types of coils look the same but have different color wires. the delphi type have 2 black wires, 1 brown wire, and a white wire. the ac delco type have 1 pink wire, 1 black wire, 1 brown wire, and a redish pink wire. the plug is the same for the coils. i was going to attempt to do the install mentioned in my last post last night but is just got to damn cold.

ive also never heard of getting a ecu tuned for different coils but i just wrote what the tech at the dealer told me. he might not of understood me 100%.

anyways tonight i will try the ac delco coils with the delphi wiring harness and see if i still get the check engine light. i will just throw on a extra warm coat tonight!

tom falco

Must say why do people think the stock coils wont WORK????? What is the reason for the swap????? Does the coils do something different????? Just curious. If it fires the plugs what is the reason to update the coils????????? MORE HP AND MILAGE?????? HOW. Just my .02$$$

senorbob999

i have 206K on my truck and the stock coils on my truck are going bad. serveral ls1 gearheads, gen 3 and gen 4 guys swap oout their coils for the ac delco type because they are more powerful and can add some horses to your engine. ive seen articles in camaro magazines that did the swap and ls1 fbody guys get between 10-15hp by doing the swap. and they coils that i am swapping are not aftermarket....they are oem coils just a different type. msd coils blow out quickly and have a long list of problems. accel makes a decent aftermarket coil but they have weak mounting brackets on them and they fall off the bracket often. im simply trying to make my old high mileage engine run a lil smoother and hopefully last a bit longer. im not doing it for racing or to have the biggest ***** out truck on the block. if it works then it works, if not then i screwed myself over and will have to buy another set of coils. no harm done!

senorbob999

sucess!!! i finally figured out how to sucessfully do the coil swap! NO MORE CHECK ENGINE LIGHT OR SLUGGISH FEELING WHEN YOU DRIVE!!! im going to have to do a write up for all of those who are interested in doing this same swap. if you have a set of delphi coils (square shaped) and you want to swap them out for the more powerfull and better performing ac delco coils (barrel type) then you will need to do the following. i will try to do a more in depth write up later but for the mean time this will have to do.

to put it simply...you need a set of 8 ac delco coil, a ac delco coil bracket, and you use your oem delphi coil wiring harness (just install the old wiring harness onto the new bracket and install the new coils).

#1 get a set of new or low mileage ac delco coils (barrel type)
#2 get a pair of ac delco coil monting plates/brackets (the delphi coil brackets are non compatible with the ac delco coils!)
#3:disconnect your negative cable of your battery
#4 locate the ignition coil wiring harness on your truck and carefully unplug the small blue locker.
#5 after that slowly and carefully unplug the coil wiring harness from the main harness.
#next carefully remove the spark plug wires from your oem coils (if you plan to do a tune up this is the time to just take all the cables off and then take off the spark plugs).
after that there are 5 10mm screws that hold the oem coil bracket to the valve cover. they come off counter clockwise. remove all 5.
#6 the oem coil bracket has 2 clips on the driver side that hold the engine wiring harness in place and the fuel injector harness in place. carefully with a small flathead screwdriver pop the clips open and release the engine harness and fuel injector harness.
#7 if your truck has a.i.r injection and a egr valves (stupid) then with 1 hand you will have to hold the oem coils and bracket and with the other carefully pull the metal air injection tube outwards to make clearence for the coils to come out of. if you have a friend that can help this makes it a whole lot easier to do. watch out for the engine main wiring harness and the other lil wires that can get caught on the coils.
#8 once the oem coils and bracket are out you must get a tiny flat head screwdriver and flip the bracket over and wedge out the wiring harness plug. it is held on by a metal clip that is extremely easy to break in you put too much pressure. slowly and steadily place the screw driver under the clip and twist the screw driver left and right to wedge off the clip. once the clip comes off there are 4 small black lil push in clips that are part of the wiring harness itself on the front of the bracket that also need to be carefully remove. with a pair of needle nose pliers compress the clip and at the same time push down. the clips will pop out.
#9 once the oem delphi coil harness is off the bracket install it on the ac delco coil bracket. make sure that the ac delco coils are not installed on the ac delco bracket yet. it makes installing the delphi wiring harness tougher when the ac delco coils are on. the delphi harness installs on the ac delco bracket just like the delphi bracket. 1st you must insert the metal clip of the harnes plug onto the bracket. there a special little slot in the middle of the ac delco bracket for the clip to go onto. you will need to use the small flathead screwdriver to get the clip to hold onto place. slide the clip all it can go (dont push hard or you will break it and then your screwed!) once you cant slide it down further wedge the small flathead under the clip and open the clip a lil bit so that the clip can slide down the ac delco bracket all the way. once thats done make sure that the 4 coil connectors on the wiring harness are over the bracket and not under it (if the connectors are under the bracket it will be impossible to bolt down the bracket onto the valve cover later on!).
#10 now you can install you ac delco coils onto the ac delco coil bracket. each one is held on by 2 7mm screws. hand tighten snug and once all 4 are done connect all 4 coils to their respective coil connector on the harness.
#11 so to sum up so far you have a set of ac delco coils on a ac delco coil bracket but you are using a delphi coil wiring harness instead of the ac delco wiring harness. this would be a lot easier with pics and i plan to do a full color write up later on to help my fellow ls1'ers and truck guys.
#12 once the coils are on and all connected they are ready to be put back onto the valve cover. like mentioned before. if you have air injection and egr this will be a lil tougher cause you have to lift up the metal pipe for the air injection to make clearence for the coils and bracket. make sure that on the drivers side that the main engine harness and fuel injector harness dont get tangled up in the coils or get stuck underneath them. the holes for the new ac delco brackets line up exactly the same as the oem delphi brackets so there no need to drill and thread new holes. line up the ac delco coil bracket with the holes on the valve cover and by hand place and tighten the screws on both ends and the screw right in the middle. once all 3 screws are hand tightend you can screw in the other 2. using a 10mm socket or wrench (a rachteting wrench makes this part tons easier because there is no space at all on rear coils, save yourself the headache and buy a 10mm ratcheting wrench!!!!!).
#13 once the screws are tightened down reconnect all 4 spark pug wires to the new coils.
#14 once the spark plugs are on then go ahead and plug the main power source back onto the coil wiring harness. make sure to set in and place the blue locker so that the plug wont pop off later on.
#15 and thats it. just do the same for the other side. one special note. on the passenger side the coil bracket has a special lil bracket that comes off of it that hold the heater core lines in place. amke sure to reuse this bracket and save the 10mm nut that holds it down!
#16 reconnect you negative battery cable and start your truck. let it sit there for about 5-10 minutes before you drive it. then your done!

i hope this helps anyone in the future that wants to do this swap. thanx to the guys that responded and shared my pain in this situation!

senorbob999

if your truck has a ecu tuner (hypertech, diablo, superchips, etc) you will need to return your truck back to stock tuning before you remove your delphi (square shaped) coils. if you dont de-tune your truck back to stock you will get the "CHECK ENGINE LIGHT" when you turn your truck on with the new coils. once you de0tune your truck back to stock and install the new coils you can once agin use your programmer and tune your truck back the way it was. i have a slp ecu tuner for my truck and i found this out the hard way!!

tom falco

Coils do get week from time to time. But with that being said i would like to know how a coil that fires a plug successfully is any different than any other one that does the same?????? In 46 years in the business i find it hard to believe that a coil can give an engine HP. My question is HOW. The dyno testing we have done on this subject is always the same. No matter how hard we try we cant get one ounce of HP difference by changing coils. That is if the stock coil can fire the mixture and is not defective. In supercharged and turbo motors sometimes plug gap is a problem but thats IT. Once again i am a funny guy with thousand of dyno hours under my belt. Please give me one technical reason how a coil change increases HP. If the plugs fire they fire. The gm coil setup or for that matter any engine coil is ok as long as the spark is there and up to manufacturers spec. Closed end wafer coils like the ones that are on our cars are totally fine. remember there are 8 coils(v8 engine) on modern cars that have plenty off time to recover from saturation. Not like the old days when one coil fired all 8 plugs in 2 revolutions. NOT BUYING IT. I have done several dyno pulls on this subject and found NO HP DIFFERENCE. To gain 10-15 wheel HP is not easy to do. And for someone to claim that with a coil change is really pushing IT. Just my .02$$$

69LT1Bird

iTrader: (1)

X10, not gonna happen. There are several posts on here about the subject already, internet myths are so much fun. Someone car runs bad, they put new parts on and now they "Gained" horsepower, maybe you just returned the engines power to normal.

tom falco

Totally correct 69. Changing a coil cant fix a bad injector. Or changing automatic tranny fluid will not fix a slipping transmission. Love those old WIVES TALES.