Headers, catted y, cat back... Popping? Missing?

**Whamhammer** · 01-21-2016, 03:20 PM

Hey guys,

Christmastime, I had a set of Kooks emissions long tube headers, catted y, Magnaflow cat back, NGK TR55 plugs and Corvette style front 02's. When I am driving under light load in 5th and 6th (at 45-65 mph 1-1.5k rpm or so) and I try to accelerate past 1/3 throttle or greater, it feels like the engine is missing. Today, I decided to get-into-it a bit, so I was doing full throttle, and it started popping-missing above 5k or so. The car feels really good at 1/3-1/2 at 2-3k rpm though and I really havent suffered gas milage wise and no codes, the only real changes programmed into the tune is to give the 02s more time to heat up before throwing a code. This all happens when the cars at proper operating temps.

Everywhere that I have read, with a full exhaust upgrade, a tune is beneficial but not mandatory. Is my car just more sensetive than most? I would thinks the way its acting, I'd almost think the TPS was off, but I'd figure a code would be thrown though.

**DarrenWS6** · 01-21-2016, 05:34 PM

Sounds like a not so happy coil pack.

**Whamhammer** · 01-21-2016, 05:37 PM

Originally Posted by DarrenWS6

Sounds like a not so happy coil pack.

Wouldnt that throw a code?

If theres no code, and without buying a new coil and moving it around to different cylinders until it doesnt act up anymore, how would one test/find it?

**pajeff02** · 01-22-2016, 03:28 AM

Go back over your ignition wiring. Remove and reinstall all the plug wires and ensure that you can hear/feel one "click" at each plug and two "clicks" at each coil pack. It does sound like a misfire -- under load the spark plug requires more juice to light off the air/fuel mixture in the combustion chamber and a bad connection could be the culprit. Misfire detection is based upon a sensor that can detect each the "push" each cylinder gives the crankshaft when it combusts. Could be that it is enough to be noticeable, but for some reason is not being picked up by the PCM to trigger the SES. Other potential issues would be fueling, a vacuum leak, or a MAF that is acting up. To test the MAF simply unplug it and take the car for a ride. This will force the PCM into speed density mode. The test will also trigger the SES so you will need to clear the code after the fact.

**35th-ANV-SS** · 01-22-2016, 04:01 AM

My guess is if it just started right after the header install it's likely something to do with that; such as a loose plug wire. Might want to make sure while you're looking things over that no wires are close to the headers.

**Whamhammer** · 01-22-2016, 11:28 AM

Originally Posted by 35th-ANV-SS

My guess is if it just started right after the header install it's likely something to do with that; such as a loose plug wire. Might want to make sure while you're looking things over that no wires are close to the headers.

I did check the wires this morning and it did not seem that any were close to the headers, I also pushed the wires towards its connection points and didn't feel any slack there either, of course, the rear wires were hard to get to/see at 6 sumthin' AM. I checked the main harness to the coil pack harness connectors too, they seemed fine as well. When Snowmagedon is done with us, hopefully Sunday, I will try to double check the wires again, and if it doesn't change, I will try disconnecting the MAF and see what that does. Push comes to shove, I'll drop it off at my shop that did the install and see what they can find.

Hopefully its something fairly simple, stuff happens, I just which it would have thrown a code to make it easier to find the "stuff".

**DarrenWS6** · 01-22-2016, 05:17 PM

Originally Posted by Whamhammer

I did check the wires this morning and it did not seem that any were close to the headers, I also pushed the wires towards its connection points and didn't feel any slack there either, of course, the rear wires were hard to get to/see at 6 sumthin' AM. I checked the main harness to the coil pack harness connectors too, they seemed fine as well. When Snowmagedon is done with us, hopefully Sunday, I will try to double check the wires again, and if it doesn't change, I will try disconnecting the MAF and see what that does. Push comes to shove, I'll drop it off at my shop that did the install and see what they can find.

Hopefully its something fairly simple, stuff happens, I just which it would have thrown a code to make it easier to find the "stuff".

Perhaps a battery terminal reset? Shot in the dark. I know with Ford's and their coil packs that a low grade misfire can occur and be felt while driving, and not trigger a CEL. Did you add some dielectric grease to the coils? Perhaps a spark plug wasn't gapped properly? Kinked plug wire?

**Whamhammer** · 01-23-2016, 03:59 AM

Originally Posted by DarrenWS6

Perhaps a battery terminal reset? Shot in the dark. I know with Ford's and their coil packs that a low grade misfire can occur and be felt while driving, and not trigger a CEL. Did you add some dielectric grease to the coils? Perhaps a spark plug wasn't gapped properly? Kinked plug wire?

Im not sure what you mean about "battery terminal reset", are you suggesting that I do that?

My speed shop did the full exhaust/plugs install, so I cant say if they used dielectric grease.

A few weeks ago, I did go back to the shop because I was hoping they could increase the clearance between the y pipe and the ground ( it was as good as it got), and thats when I had him check the low end, top gear acceleration missing, in which he rode with me with his computer and saw that the knock sensor was picking up some mild knocking but he believed some of it was because I was bogging the engine (trying to accerate in sixth at 1-1.k rpm.) and that the full exhaust moved the torque band/curve up and made the bogging more noticable than before, which made some sense to me.

I never experienced the full throttle problem because I have had snow tires on since the install and drive more conservatively than usual on these tires.

Of course, theres about two feet or so of snow surrounding my car, and still snowing, so I cant mess with it yet. Can someone tell my company approvea massive pay raise for me, so I can buy a house with a (heated) garage?

**0rion** · 01-25-2016, 09:20 PM

first thing I would do is take it back and let them figure out what they did wrong....definitely something on the install side isn't right. Could be a few things really. I wouldn't rule out a fueling issue from an exhaust leak or something like that either. Almost sounds like it's doing it when it goes into PE. Do you have anything to log it with and see what your fuel trims look like? Like I say though....I would start with the installers.

**Whamhammer** · 01-26-2016, 03:04 PM

Originally Posted by 0rion

first thing I would do is take it back and let them figure out what they did wrong....definitely something on the install side isn't right. Could be a few things really. I wouldn't rule out a fueling issue from an exhaust leak or something like that either. Almost sounds like it's doing it when it goes into PE. Do you have anything to log it with and see what your fuel trims look like? Like I say though....I would start with the installers.

If it hadnt've snowed a metric $h!7 ton, I would have already have taken it back. I am going to give a few more days to get the roads okay. He knows that it was doing it down low but I havent had a chance to talk about it with him for when I was flooring it, it litteraly snowed the next afternoon and I was finally able to drive it today. I will talk to him Thursday, so he can get back to normal first.

**slims00ls1z28** · 01-28-2016, 09:10 AM

Coolant temperature sensor is probably broken or not connected, been there done that. Right after a header install matter of fact. Never threw a code but ran like ass and backfired a lot WOT.

**0rion** · 01-28-2016, 03:06 PM

Originally Posted by slims00ls1z28

Coolant temperature sensor is probably broken or not connected, been there done that. Right after a header install matter of fact. Never threw a code but ran like ass and backfired a lot WOT.

anytime I've ever seen that happen it would idle perfect and then go to complete ass when it went to closed loop. Sounds like his is running fine until it's under load.

**Whamhammer** · 01-28-2016, 05:12 PM

Originally Posted by 0rion

anytime I've ever seen that happen it would idle perfect and then go to complete ass when it went to closed loop. Sounds like his is running fine until it's under load.

Went down to the shop today and we took the car out for a spin with his computer hooked up. One cylinder showed a markedly higher rate of misfire, so he pulled the plug, and low and behold the ceramic was cracked. He put a new plug in and its running much better.

I am very happy I chose this shop, I called him on the phone and told him about the problem, he made the time for me and knocked the whole thing out in no-time. Lets face it guys, most shops these days would want to set up an appointment first.

**0rion** · 01-28-2016, 10:33 PM

Originally Posted by Whamhammer

Went down to the shop today and we took the car out for a spin with his computer hooked up. One cylinder showed a markedly higher rate of misfire, so he pulled the plug, and low and behold the ceramic was cracked. He put a new plug in and its running much better.

I am very happy I chose this shop, I called him on the phone and told him about the problem, he made the time for me and knocked the whole thing out in no-time. Lets face it guys, most shops these days would want to set up an appointment first.

That had actually crossed my mind as a possibility. That's more common than you would think...people wrestle those headers in and end up whacking a plug with them. Always a good idea to pull those plugs until the headers are bolted up. Glad they did you right and glad you got it worked out.

**Whamhammer** · 01-29-2016, 05:01 AM

Originally Posted by 0rion

That had actually crossed my mind as a possibility. That's more common than you would think...people wrestle those headers in and end up whacking a plug with them. Always a good idea to pull those plugs until the headers are bolted up. Glad they did you right and glad you got it worked out.

Thanks Orion. I am very happy with the shops service. To be honest, the shop removed the old Gm iridium plugs for the install, and put these NGK coppers in after the put the headers on, so we think that the plug had been dropped somewhere between manufacturing and installation.