popping sound in my exhaust?
08-16-2001, 11:46 PM
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popping sound in my exhaust?
Help! My cat was clogging my muffler so i had to replace both the cat and the muffler. As soon as i had the new cat and muffler put on, the car runs fine untill i hit about 5000rpms. My Z is making a poping noise under hard acceleration? H e l p 
08-16-2001, 11:52 PM
#2
Hmm, well, when I first saw the topic, I was thinking exhaust leak when you let off. But, since its under hard acceleration, Im not sure, is it a surging/hesitation popping? 
-Roshambo
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-Joe
1988 Pontiac Trans Am WS6 - 305 TPI, 700R4, 3.23 Posi, Digital Dash, Leather Seats, Maui Blue with Silver GFX, T-tops, Tinted Glass, Gutted MAF, TB Coolant Bypass, K&N Cone Filter, Hi Flo Cat, 3" Cat-Back, MSD Super Coil, L98 Aluminum Heads, Ported and Polished Plenum, Siamesed Intake, Edelbrock 3 point Strut Tower Brace.
-Roshambo
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-Joe
1988 Pontiac Trans Am WS6 - 305 TPI, 700R4, 3.23 Posi, Digital Dash, Leather Seats, Maui Blue with Silver GFX, T-tops, Tinted Glass, Gutted MAF, TB Coolant Bypass, K&N Cone Filter, Hi Flo Cat, 3" Cat-Back, MSD Super Coil, L98 Aluminum Heads, Ported and Polished Plenum, Siamesed Intake, Edelbrock 3 point Strut Tower Brace.
08-17-2001, 12:03 AM
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Just trying to get some advise..... I have posted this topic on the tpi fourm. no reply's and hoping my crew could help me out here? I'm kindof stuck
08-17-2001, 12:57 AM
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Car: '89 Firebird
Engine: 7.0L
Transmission: T56
When was the last time you relaced your oxygen sensor? They should be replaced every 30K miles. Do you have a reading or your air/fuel ratio? You might need to bump up your FMU just a tad. You may have not needed the extra fuel before because of the inefficient exhaust system. I would hesitate going full throttle for a bit... especially if you're still on cast pistons.
08-17-2001, 11:03 AM
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Sup Quick Trip!
I have only put 14K on my car in the last 2.5yrs since i have owned it. It has 74k on it now and the O2 sensor was replaced when i put the tes headers on which was last year. I suspect the car is running way too rich because the cat went bad and my tailpipes were black. I Thought backfiring in the upper rpms was an indication of a lean condition? And i'm sceared to death to say bad exhaust valves, flat cam etc.... But my vacume is steady 20inches at idle...needle does not fluctuate! And i do not have a scantool If i did, I would definately be able to see if the car is running lean or rich. Thanks for the help! Anyone else???
I have only put 14K on my car in the last 2.5yrs since i have owned it. It has 74k on it now and the O2 sensor was replaced when i put the tes headers on which was last year. I suspect the car is running way too rich because the cat went bad and my tailpipes were black. I Thought backfiring in the upper rpms was an indication of a lean condition? And i'm sceared to death to say bad exhaust valves, flat cam etc.... But my vacume is steady 20inches at idle...needle does not fluctuate!
And i do not have a scantool If i did, I would definately be able to see if the car is running lean or rich. Thanks for the help! Anyone else???
08-17-2001, 11:06 AM
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Engine: 5.7L V8
Transmission: 700R4
Wait, I thought the popping sound was from running too rich? Unburned fuel is going through the headers and sometimes igniting... it usually happens when you let off the throttle at high RPMs.
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08-17-2001, 01:59 PM
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K...took of my FMU and it runs fine. It does feel like it lost some power without the fmu. I'm going to get a kit to down grade the fmu from a 8:1 to a 6;1 or even a 4;1...Thanks everyone!
08-17-2001, 02:28 PM
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Car: '89 Firebird
Engine: 7.0L
Transmission: T56
Popping in the exhaust is usually associated with a lean condition. A large backfire is commonly because of a rich condition. Craiger... NEVER run that car in a boost condition without the FMU. 
You have too much to lose if you burn the valves or most likely the pistons. Instead of ordering extra kits for the FMU you might consider simply purchasing the Super FMU which is fully adjustable with the turn of some screws. You should probably talk to Glen on this one. He'll likely hone in on the problem very quickly. 
You have too much to lose if you burn the valves or most likely the pistons. Instead of ordering extra kits for the FMU you might consider simply purchasing the Super FMU which is fully adjustable with the turn of some screws. You should probably talk to Glen on this one. He'll likely hone in on the problem very quickly.
08-17-2001, 05:38 PM
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Quicktrip... Everyone who has the same setup as i have...paxton sn2000 they do not use the fmu. They do run an aux fuel pump at 48-52psi. I set mine at 54psi untill i get the rebuild kit which will come on wensday. I would normally agree with you but as i have no detonation what so ever with out my fmu, plus i have 24lb injectors so that could be my saving grace. However, i have turned up my boost retard a little an plan not to boost it untill i get the rebuild kit. I wish i would have purchased a super fmu! They sell a kit that has the fixings to set my fmu from a 4:1 all the way to a 12;1. Thanks for all the help!
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