backfiring after mod install

**razer900** · 04-14-2010, 05:11 PM

Installed headers, ory, magnaflo catback, ported tb, new 55 plugs, mail order tune(Frost), deleted air and egr. Install went smooth with no issues. Car fired right up and idled nice and smooth. Apon test drive, under hard acceleration the car slighty jerks and backfires rapidly like a machine gun. Car has great power but i dont think its up to it full potential. Hooked up my handheld code reader,(not an expensive one) but was suprised to see no numerical codes. But... the yellow light came on meaning there is a possible problem. Three flashing icons showed up: "OH" Oxygen Sensor Heater Monitor, "EV" Evaporative System Monitor, and "O" Oxygen System Monitor. I checked all possible lines and wire connections to make sure i didnt unplug something accidently. Everything looks ok. Car seems to get worse as it gets warmer. Can somebody point me in the right direction, Iam stumped with the codes it is giving me. Thanks in advance

**c5z28** · 04-14-2010, 05:13 PM

Did you have him tune out any o2's that may or may not still be on the car?

**razer900** · 04-14-2010, 05:50 PM

Originally Posted by c5z28

Did you have him tune out any o2's that may or may not still be on the car?

front two o2's are still in there, the rears are tuned out

**Y2KPewterSS** · 04-14-2010, 05:57 PM

Have you checked to make sure all your plug wires are making good connections, and also to make sure the plugs aren't loose.

**razer900** · 04-14-2010, 06:02 PM

Originally Posted by Y2KPewterSS

Have you checked to make sure all your plug wires are making good connections, and also to make sure the plugs aren't loose.

three times already... the reader said nothing about any misfire either, but like i said, its popping like a machine gun under acceleration. Makes me wonder if it isnt a plug or wire?

**0rion** · 04-14-2010, 07:51 PM

did you swap plugs and did you leave the plugs in when you were putting the headers in? Not real hard to crack the ceramic on the plugs hitting them with the headers. What you're describing sounds like a backfire and not a misfire to me. My experience is that a backfire is normally fuel related such as a burnt O2 wire, vacuum leak, or MAF issue. I would check your O2 harness and make sure everything is plugged in and away from the headers. Also check to make sure you plugged the front O2's into the front harness and not the rear.....it's been done many times before.

What type of extensions did you use for the headers? Store bought or did you manually extend the harness?? I've seen this give people all kinds of problems too.

**Ws6islife** · 04-14-2010, 08:45 PM

well actually im having the same problem, i have headers,ory, and magnaflows as well just installed them, just as you install whent great, i also did plugs and wires, i rechecked them but i still get a pop, mine isnt at acceleration tho its when at rest at a red light i get a pop and the car jerks a bit, i checked my maf, i also checked my plugs like i said, checked for exhaust leaks, i deleted the air pump, pulled the fuse. But i still have the problem have not checked the O2's tho but i storebought harnes.

**razer900** · 04-15-2010, 06:22 AM

Originally Posted by 0rion

did you swap plugs and did you leave the plugs in when you were putting the headers in? Not real hard to crack the ceramic on the plugs hitting them with the headers. What you're describing sounds like a backfire and not a misfire to me. My experience is that a backfire is normally fuel related such as a burnt O2 wire, vacuum leak, or MAF issue. I would check your O2 harness and make sure everything is plugged in and away from the headers. Also check to make sure you plugged the front O2's into the front harness and not the rear.....it's been done many times before.

What type of extensions did you use for the headers? Store bought or did you manually extend the harness?? I've seen this give people all kinds of problems too.

Ya Orion, i put on the new plugs right before i threw the lts on. Newbie mistake... i figured it was easier that way cuz i did the whole install by myself. No doubt i could have cracked a plug, i assumed the code reader would have picked it up tho? Its not a build up boom backfire. More like a constant rapid popping under acceleration. Not ruling out a vac leak either tho, but i checked physically three time over and everything looks allright. The MAF looks good and clean too. The car ran perfect bfore the install... Gonna take it to a mechanic tonight and read the codes with a good scanner and hope it will tell me something. Thanks for the reply Orion

**0rion** · 04-15-2010, 10:33 AM

I'm guessing you also checked the spark plug boots to make sure they all "clicked" when they went on? Very easy to think they're on when in fact they're not quite all the way on....especially that number 8 plug.

**razer900** · 04-15-2010, 11:02 AM

Originally Posted by 0rion

I'm guessing you also checked the spark plug boots to make sure they all "clicked" when they went on? Very easy to think they're on when in fact they're not quite all the way on....especially that number 8 plug.

they all clicked, also put a speck of grease on the ends of the wires. Maybe i put a little too much on one of them? More i think about it seems spark related. Hope the mechanics reader will pick it up tho. I still dont know why it was throwing the codes tho? I will post my results tonight. Thanks again for the help. Quite difficult for me to explain and for all you guys to fix my car over the internet, but i thank you all for any suggestions

**razer900** · 04-15-2010, 05:52 PM

Originally Posted by 0rion

I'm guessing you also checked the spark plug boots to make sure they all "clicked" when they went on? Very easy to think they're on when in fact they're not quite all the way on....especially that number 8 plug.

Just an update... Car goes like a bat outta hell now. Orion you were on the right track the whole time, #6 plug was cracked(the ceramic fell on the ground when i pulled the wire off) Put new plug in and instantly ran awesome. Thanks to you guys for all your advice and help!! Special BIG "Thank You" to Frost for your tune, now I know why your name and services are highly recommended. Thanks again everybody! Iam one happy man now!

**0rion** · 04-15-2010, 07:54 PM

Originally Posted by razer900

Just an update... Car goes like a bat outta hell now. Orion you were on the right track the whole time, #6 plug was cracked(the ceramic fell on the ground when i pulled the wire off) Put new plug in and instantly ran awesome. Thanks to you guys for all your advice and help!! Special BIG "Thank You" to Frost for your tune, now I know why your name and services are highly recommended. Thanks again everybody! Iam one happy man now!

glad to hear you got it fixed. Like I said, not hard at all to break or crack that ceramic if you don't pull the plugs or put them in before the headers. I always pull them whether someone is putting new ones in or not. You're right in your other post.....it is tough to explain, diagnose, and fix a car through the internet so usually we just go by symptoms and what's been the cause in the past. Some stuff just happens more than others but it's still hard to get it figured out on the boards although you'd be surprised at just how often it gets worked out on here eventually. I'd like to see the success rate but it has to be way up there like 90% or better. Most of it is due to you guys that are willing to go out and work on it and keep after it until the problem gets figured out.

**razer900** · 04-16-2010, 05:40 AM

Originally Posted by 0rion

glad to hear you got it fixed. Like I said, not hard at all to break or crack that ceramic if you don't pull the plugs or put them in before the headers. I always pull them whether someone is putting new ones in or not. You're right in your other post.....it is tough to explain, diagnose, and fix a car through the internet so usually we just go by symptoms and what's been the cause in the past. Some stuff just happens more than others but it's still hard to get it figured out on the boards although you'd be surprised at just how often it gets worked out on here eventually. I'd like to see the success rate but it has to be way up there like 90% or better. Most of it is due to you guys that are willing to go out and work on it and keep after it until the problem gets figured out.

Ya iam kind of stubborn that way. I caused the problem so i wanted to fix it. (with the help of all you friendly folk) I sort of threw in the towel with my "cheapo" code reader tho, it wouldnt pick up the misfire code. The mechanics reader picked it up reight away. Damn glad it wasnt back passenger side plug!!!!

**Cutlass** · 04-16-2010, 05:36 PM

Originally Posted by razer900

Ya iam kind of stubborn that way. I caused the problem so i wanted to fix it. (with the help of all you friendly folk) I sort of threw in the towel with my "cheapo" code reader tho, it wouldnt pick up the misfire code. The mechanics reader picked it up reight away. Damn glad it wasnt back passenger side plug!!!!

I was gonna say, what the heck kind of a code reading displays "OH" "EV" and "O" instead of actual trouble code numbers...toss that thing in the garbage