Car is BackFiring, has a High Idle, and Reeks of Gas. Exhaust Leak? Bad O2's? Help!

fawcett

Member
Sep 10, 2003
380
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16
Cohasset, Ma
So my car is running pretty well, except for the fact that it is backfiring when i rev it high (happens when idle is falling). The high idle is ok, i can deal with it. My car wont stall with it set this high, and i dont loose any vacuum at low rpms.

On the otherside i would like my car to smell, well... not like exhaust. it reeks, how bad for my health is this? i may have an exhaust leak or two. i remember when i installed my mgw shifter and test drove it without the shifter boot or cover that it sounded like my exhaust was leaking from where my shorties meet my o/r h pipe or before that...

should i just take it to an exhaust shop?
would an exhaust shop like midas do a better job replacing my exhaust gaskets, tighten everything down and fix any or all of the leaks? how do you tell if your headers are leaking? i know that i need to have the h section of the h pipe widened. the piping doesnt tuck into the trany brace like it should, it's not wide enough and my exhaust hangs low. again would midas do this better than some regular mechanic?

what about my o2 sensors? how do i tell if they are going bad? are they expensive to replace? can someone recomend a reputable brand to go with if i do need to get a new set? i think i have heard that the bosch's(spl?) are good

-fawcett

1995 gts frpp 340bhp 302, gt40x heads, e-cam, aeromotive fpr set at 38-39psi, 190lph fuel pump, 65mm frpp tb, prom80, track heat intake w/ spacer, unequal length shorties, o/r h pipe, flows, full mallory hifireVI ignition, fluidyne radiator(new and nice!), 24lb frpp injectors, d&d viper spec t56, mgw shifter, afm super king cobra clutch, afm alum flywheel, d&d alum ds, march pulleys, brembos all around, cobra r's
 
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Yeah if your o2s are bad your car wouldve thrown you a CE light. To check for a leak, make sure your car is cold. Start it, and put your hands around where you think the leaks would be (Header to H pipe meeting), if you feel air pulsing out, then youve got your leak.
 
Would i get a code if my Pro-M 80 is going bad? What else would pulling codes do for me?
I have heard that going to AutoZone or where ever is bad b/c their scanners can mess our cars up... is this right?
-fawcett
 
urban96 or anyone,
can you tell me which are the good ones or cheapo's?
i am usually willing to spend the extra couple bucks for the good stuff but if these will do...
By the way thanks for that site, that is where i will order i think
-fawcett
 
fawcett said:
what tools are needed to change O2 sensors? they sell them on the site.
i do need anything special, do they need to be welded in or anything special like that?
no experience in this area,
-fawcett
im pretty sure bosch are who makes the OEM so i would go with them

no need for welding, just soak the old ones down pretty good with PB blaster or other penatrating oil and let it sit for a little. you can remove/install them with an open end wrench. you may need a hammer to tap on the wrench to break the stockers lose
 
so i went to autozone to use a scan tool and see if my computer is throwing any codes. one of the kids working there came out with me to give me a hand. he looked for the hook up to plug his scanner and couldnt find it. he said it was ripped out? where could it be? i know i didnt rip it out.... maybe when it was at a shop sometime? why would a shop do that though?

anyways, since there was no plug to be found he said start it up. but even before i did that he mentioned how much it stank. so i cranked it over and held the rpms at like 3500. he said it was the heater pipe on my exhaust manifold that was leaking. he also said that this has happened to him before and he passed out behind the wheel. i drove it home with the windows wide open and i plan on taking it to a exhaust shop tomorrow. im going to hold off on the o2's until my exhaust is leak free.

does this sound right to you guys? i have no experience in this area so if anyone knows anything please share the wealth - i need it!
thanks,
-fawcett
 
Fawcett, a common reason for your backfiring could possibly be that you have an offroad h-pipe, but you still have your smog pump connected.
Try this...look by your passenger side valve cover, you will see a tube running under your A/C lines that is black and a little over an inch thick. Is it connected to a small canister down there? If it is, disconnect it, and check to see if you still get those backfires. Just a thought....
 
There is also a obd 2 plug on our cars in the driver's footwell but I believe they are not hooked up being our cars are obd1 computer management. They installed them there to get ready for 1996 when the government made that a mandatory thing.