JGA

Hi

Changed out my headers to the stock manifolds, cats and Y pipe to get my car through the local sniffer test.

Car is running great, but when I floor it (WOT) I get a bad missfire. I am not really sure if it is a missfire, bang or pop. It's quite loud. I can drive it on the highway at 100 mph and it is smooth. It is only when I am accellerating at WOT. I looked under the car for any hitting or contact and there is plenty of clearance on all the exhaust pipes.

Is it possible I could get this problem from a leaking AIR or EGR gasket? I assume an exhaust leak would make a ticking noise, but not a loud pop or engine missfire.

I did add some carbon cleaner to the fuel system because I had a fair bit of carbon deposits. Should I be looking at the plugs or ignition system first?

Any help appreciated.

Thanks JA

2K2WS6TA

iTrader: (2)

Try changing plugs, you might have cracked one when you changed the exhaust around, also make sure the wires are on tight 2 clicks on the coil side one click on the plug side

NHRAMAN

iTrader: (1)

Where are you located..why not just add cats for sniffer..do you have a visual also ??? ....[ he's right..check for plug crack.]

JGA

Hi

Thanks for the help everyone.

Not a usual case. Had Mac headers and Cat y pipe. When way, way, way over on HC and NOX. Had the **** scanned out of it at three different shops and could not find anything wrong. Checked EGR, AIR, plugs, wires, coils, fuel filter, vacuum leaks, etc. Also tried tuning it with HP Tuners. Even with the fuel trims adjusted it still failed. Actually it did worse after the tuning.

Unfortunatley I could not find anyone that could get it past for me. No one in the area has the software or any tuning experties (No ls1 culture established in my area). Not being able to insure it was not an option, so I gave up after about 4 months of screwing around and swapped the old exhaust back in.

Now I have a missfire, so I still have problems to solve before I can try the sniffer test.

JA

NHRAMAN

iTrader: (1)

headers shouldn't affect those readings all that much with cats...sounds like you have bigger problems...???

JGA

Hi

I agree, but the headers were like a stone wall or barrier. 2 GM dealers refused to work on the car, and the other placers I tried gave up after doing the basic scanning. Everything had been replaced: plugs, wires, fuel filter, O2s, air filter, etc. The thing is the car was running great and its hard to fix somthing unless it actually fails. Evey day I was hopping for an SES light would come on and then give me an idea of what to look at. It has never come on.

I was realy at the point where all I could do was start replacing parts wholesale. Try a computer here an EGR valve there. Atleast now I can get it into a GM dealer with a Tech 2 and find out what is realy wrong. I have about 6 months left on the warrantee so I can get the repairs paid for.

I have really learned the hard way, as it is costing me a lbit.

Thanks JA.

NHRAMAN

iTrader: (1)

....NO SES..??. ...you should have driven to a tuner....2-5 hours driving would do it I would think...the places here are few and far between also...there is a big speed shop that just moved to a new location and new building with a dyno and full shop..but they still are learning the ropes with newer cars...lots of muscle...not many computer-controlled muscle. .....all my friends drive hot cars....strokers, 454, 455, 426 even...only a few hot vettes and f-bodys. [for some reason there are not many fast furds here.] ....... .....Where are you located...maybe someone can help you..!!!!!!!!!!

thechef

iTrader: (13)

are you running a stock cam???

if so go to the dealer and have your pcm reflashed to STOCK
with your car being tuned by several tuners everything is way off base if you put the stock parts back put a stock tune back in and if ya have no SES light you should be good to go, and if that doesnt do it look into the waiver program im sure the state has one which will exempt you

NHRAMAN

iTrader: (1)

VERY good advice.

sdbrown84

iTrader: (22)

Yep. Most states have a one time waiver form. However, if you are more than DOUBLE the allowed limit you will be forced to fix the vehicle. Every state is different.

JGA

Hi

I noticed the forum deleted your reference to mopac. They have absolutely no tuning software for any type of car. They installed my headers in the first place. After I started having problems they refused to work on my car period. I am not just talking about tuning but basic diagnostics or help. They have a sales guy their who is a real dishonest ****. Also, they bent my stock Y pipe when they removed it.

I found a guy with HP Tuners and a wideband. We did a basic VE tune and got the trims right (I think he got them 0 to - 5). It helped the HC but actually made the NOx worse. I have the stock program loaded back in now.

I think the closest shop with software is in Ablerta. I was not willing to do the 10 hour drive each way. There are a few dyno shops near Mission, but they do not have software.

The car feels very strong now and runs much better after putting the stock manafolds back on and stock program. I think all I have to do is get rid of this misfire and it should pass. I will keep my fingers crossed.

Thanks JA

NHRAMAN

iTrader: (1)

I deleted it.....Check out the guys at Vancouver F-Body.....