Changed my spark plugs now truck skips and runs rough

[Sleezy Moto]

Here recently like 2 days ago I replaced my spark plugs in my new 2003 Chevy Silverado with 4.8. I pulled the plugs. While loosening all of them I realized they were tighter than Godzilla’s anus. After I was able to remove all plugs they looked horrible. Previous owner didn’t change them in 4 years. Broke 2 coil wires so I bought a new set. Ppl at oreilys asked if it was circle or square. Me confused thinking they were talking about the boots I said circle. (I have square coils). I installed NGK V POWER PLUGS. installed the new wires. Started the truck and it kept wanting to die and was idling below 500. Removed plugs and found they were not gapped. Gapped then to 0.40 reinstalled. Disconnected the battery for 30 seconds. Started truck and still had same problem. Restarted truck and it was idling smooth. I let it idle for 30 mins. Came back put it in reverse. Tapped the gas a little and it was like the throttle got stuck I had to push the brakes to the floor to get it to stop. Drove around and noticed at certain speed it would throw you forward then smooth out. Also my oil pressure is way below 40 and doesn’t shoot up when driving. Someone please help. 

[15SilvyHC]

Have you verified whether they were the correct plug wires or not? That is where I would start. If they aren't right will def cause problems. 

[riverbanks]

There is no better plug than a/c Delco,stick with the tried and true

[15SilvyHC]

1 hour ago, riverbanks said:

There is no better plug than a/c Delco,stick with the tried and true

Agreed. These engines are notoriously finicky when it comes to spark plugs. Best to just use the oem delcos. That was going to be my next suggestion if he used the right spark plug wires and they were wired correctly.

Edited November 3, 2020 by 03pewterZ

[txab]

NGK brand were OE in some vehicles also. I'm not familiar with the "Power Plug" description, looks to be that their G-Power line is a Platinum plug, which is what you want. Was this the number(s)? 3186 #TR5GP

[riverbanks]

Throw the old plugs back in,that would prove where the problem is

[Grumpy Bear]

Listen to txab. He's on the right track. Plugs and wires, if not the right ones can/will cause RFI and drive your PCM nutty. 

[Sleezy Moto]

I talked with the people on the phone at oreilys where I got the plug wires and they said the only difference in the square coil and circle coils are the length do I need the longe ones to make it run properly bc the ones i took off were longer than the new ones. Idk if it makes a difference tho. Also I already ordered ac del I thinking that’s is my problem I will test my luck when I get them. Keeps suggestions flooding other people will need help with this too in the future. 

[Sleezy Moto]

3 hours ago, txab said:

NGK brand were OE in some vehicles also. I'm not familiar with the "Power Plug" description, looks to be that their G-Power line is a Platinum plug, which is what you want. Was this the number(s)? 3186 #TR5GP

They are the v power I didn’t check the numbers and description doesn’t say if they platinum or iridium 

[txab]

Well looks like the "V" Power line is a nickel plug. It has of course a little v groove in the tip of the center electrode. Also according to NGK the number for the V power is:

NGK 2238 TR5 V-Power Spark Plug

The number for the platinum plug came from Rockauto

 

 

At least it's not a plug that has the triple ground electrode. those are worthless imo and cause issues in many engines.

 

I'd run a Platinum or double platinum plug. you would be surprised what some of these aftermarket plugs will do to running performance, especially at idle. But you got these so see what happens

Edited November 4, 2020 by txab

[txab]

58 minutes ago, Sleezy Moto said:

I talked with the people on the phone at oreilys where I got the plug wires and they said the only difference in the square coil and circle coils are the length do I need the longe ones to make it run properly bc the ones i took off were longer than the new ones. Idk if it makes a difference tho. Also I already ordered ac del I thinking that’s is my problem I will test my luck when I get them. Keeps suggestions flooding other people will need help with this too in the future. 

Longer would be better but as long as they are long enough to fit tightly with being stretched and possibly pull off as the motor vibrates/moves

[MaverickZ71]

Best to stick with AC Delco plugs and wires (of the proper length).  You can enter your VIN on the online acdelco.com parts catalog and it will tell you the exact part numbers for all available factory replacement parts on your truck.  If you're buying said parts at O'Reillys, they should be good, genuine parts.  Beware of buying them on Ebay or some other online sources, as some folks have paid good $ for what turned out to be Chinese fake parts in what appeared to be AC Delco boxes.  

Edited November 6, 2020 by MaverickZ71

[newdude]

Get a set of OEM/ACDelco plugs and wires and re-test.  

[Colossus]

Did you replace ALL of the coils?  If not, I would.  Coils, plugs, wires.  Plugs need to be AC/Delco, wires need to be AC/Delco or equivalant.  Coils should be AC/Delco too.  Here's why:

 

The coils get weak over time just like the plugs do.  But as the plug wears, so does the coil so putting in a new plug on an old coil will likely be trying to shoot the plug with less than adequate power.  This will often set a CEL light.  You get 8 new plugs, 8 new wires, and 8 new coils, (or 4, if the coils are split) you get a nice clean baseline to work off of, and I'm betting ya, that eliminates the problem.  The foolish old adage of "If it is not broken or setting a CEL, don't repair it" Is just that, foolish.  Preventative maintenance.  (which is what you were trying to do in the first place) 

 

The engine was designed and engineered using AC/Delco (or whomever manufactures the plugs, wires, and coils for AC/DELCO and stamps the AC/Delco name onto them) gear, so when it comes to things like plugs sensors, and such, sticking with the specs the engine was designed around is the best way to go.  There are certain things that are fine to go aftermarket on, such as oil filters, air filters, and such.  But stick with AC/Delco plugs and wires and coils. 

 

Hope this helps

 

 

 

 

Edited November 6, 2020 by Colossus

[ftwhite]

You might check that you seated the wires fully. Fitting them on the coil requires a bit of force until it "clicks" and seats on the post inside the coil insulator that the boot wraps on. I found this out because with vibration, if not seated fully, they tend to slide off and form a slight gap. This can cause the engine to stutter and stall at idle, or sometimes only with light load as the computer tries to sort out what's wrong. 

I just replaced my plugs and wires after 44k miles. I used MSD wires (33828) and NGK plugs (LTR5AHX). Runs great. You might also measure the wires to see if they are low resistance/in spec.  

 

Not a fan of the ACDelco wires. after 44k and 3 years, they were brittle, had very high resistance (in all fairness, they might have gotten worse in the effort to get them off), and are not well made IMO. Taylor and MSD are much higher quality. Plugs...ACDelco is great. I went with NGK. I'll report if I have problems, but 200 miles so far and no issues, idles like it was new. 

I have considered replacing the coils too, but have no good reason to do so yet, and would do it in steps to feel the difference. I did on a old Suburban when two broke, and the MSD ones were great for over 50k miles.