"Popping" Under Acceleration
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Teching In
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From: Bangor, ME
"Popping" Under Acceleration I just installed Pacesetter LT, a Pacesetter ORY, and a TSP lid last weekend. I already had a magnaflow cat back. Other than that the car is stock. It seemed to be running fine up till today. Today, about halfway through a 140 mile trip, it started making a popping sound under hard acceleration in 1st gear back at the rear of the car. Any idea what could be causing this?
Also, I think the car has always done this, but it idles at 800 rpm or so until you start rolling. At that time it will go up to around 1400 and won't come down until you stop again. Is this normal? Thanks for your help.
Also, I think the car has always done this, but it idles at 800 rpm or so until you start rolling. At that time it will go up to around 1400 and won't come down until you stop again. Is this normal? Thanks for your help.
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Teching In
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From: Bangor, ME
It's possible, but the car seems to be pulling as hard as ever when the sound is occuring. It originates in the back left of the car...probably backfiring out of the left tailpipe and not the right?? I'm certainly not a mechanic, so I need some help figuring this out. I just want to make sure that a) I'm not hurting the car, and b) there is nothing internally wrong with the motor that might be causing this to happen.
If it helps any, it doesn't back fire on deceleration.
If it helps any, it doesn't back fire on deceleration.
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From: Vancouver,[KITSILANO].B.C. Canada *WestCoast*
does it do this at 1800-3000 rpms and sounds like maybe a header gasket leak or something ?? mine is doing this but all the bolts are tight and i used good gaskets... 
When you hit the cat overtemp protection the PCM will
dump fuel, perhaps to the point of exhaust popping
(though I've never noticed that). Perhaps there is some
additional element (fouled plug, weak plug wire, etc.)
that makes for worse firing when over-enriched.
Stock exhausts are an I-pipe that splits later so why
anything would be different on the left than the right
(other than the muffler being basically straight-through
in that branch while the right side has to make a U-ey)
I dunno.
dump fuel, perhaps to the point of exhaust popping
(though I've never noticed that). Perhaps there is some
additional element (fouled plug, weak plug wire, etc.)
that makes for worse firing when over-enriched.
Stock exhausts are an I-pipe that splits later so why
anything would be different on the left than the right
(other than the muffler being basically straight-through
in that branch while the right side has to make a U-ey)
I dunno.
i had a customer that had a bad contact on one of his coil packs & it was causing a misfire which ended up sounding like popping or backfires...thats why i assume its a missfire.
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Originally Posted by XRno1
I just installed Pacesetter LT, a Pacesetter ORY, and a TSP lid last weekend. I already had a magnaflow cat back. Other than that the car is stock. It seemed to be running fine up till today. Today, about halfway through a 140 mile trip, it started making a popping sound under hard acceleration in 1st gear back at the rear of the car. Any idea what could be causing this?
Also, I think the car has always done this, but it idles at 800 rpm or so until you start rolling. At that time it will go up to around 1400 and won't come down until you stop again. Is this normal? Thanks for your help.
Also, I think the car has always done this, but it idles at 800 rpm or so until you start rolling. At that time it will go up to around 1400 and won't come down until you stop again. Is this normal? Thanks for your help.
Re:misfire under WOT
Check the connections at the coils and plugs first.
I just had the same problem. It was a bad high tension wire. I changed the set and everything was fine. If you are doing your own work, I would get a multi-meter and check them for resistance. I had one wire with high resistance at the connector to the coil.
If you are not doing your own work and will have to pay labor, you might consider replacing the whole set, if they are old. It actually takes a fair bit of time to replace them at a shop. The labor will be more then a wire set costs.
JA
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Verdad Gallardo Thread Starter
Teching In
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From: Bangor, ME
Ok, I will check the plug connections. I had all the plug wires off when I was doing the header install, so that's a possibility. The other possibility is that it was not possible to keep one of the plug wires (2nd from front) from touching one of the EGR tubes that came off the passenger side headers. It doesn't appear to be affected by this visually, but perhaps the heat is damaging it inside? Any solution to keeping this wire from touching the header with Pacesetters?
Also, if it were a plug wire or plug type problem, would it not be missing/backfiring/running on 7 cylinders all the time rather than just the limited time that I'm having this problem? To my ear, it sounds like everything is running great until I floor it in 1st at low RPM. I'm a newbie, so I apologize if these are poor questions.
Also, if it were a plug wire or plug type problem, would it not be missing/backfiring/running on 7 cylinders all the time rather than just the limited time that I'm having this problem? To my ear, it sounds like everything is running great until I floor it in 1st at low RPM. I'm a newbie, so I apologize if these are poor questions.
Check your plugs too. I had a set of NGK TR6 that cracked down the porcelin. It was making a popping sound but I knew it was missing. The bad thing about it was that I was at the track seeing how it ran after header install.
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From: Bangor, ME
Ok, so I took my car to a friend of mine who has a regular scanner (not for tuning, just checking codes etc.). At idle, or even when revving in neutral it would not misfire. We tried riding around, and I got the scanner to show that it was misfiring on #4. This was an odd coincidence because #4 was the wire that was touching my header and I figured it was probably just burned. So, I changed the plug wire and figured I'd be all set. Wrong. It's still doing it! I then, after much cursing and swearing, removed and replaced the #4 plug. That didn't fix it. It still is doing the same thing. It seems like it has to be missing from what everyone is saying, but I'm starting to second guess that diagnosis.
If you nail the throttle in 1st at about 2000 RPM, it will start making that popping/backfiring sound out the exhaust and it accelerates but it feels like it's "hitching." It's obviously not accelerating at full speed. As the RPMs climb and you continue to stay in the throttle it will come out of it...maybe 4,500 RPM. When you hit 2nd it might pop a little but usually not. It just seems to be when the RPMs are climbing really rapidly in 1st that it will do it. If you floor it in 3rd at 2000 RPM, it will not do it. It just starts to pull like it normally would, although obviously the RPMs are not climbing nearly as fast 3rd. Some people I know are trying to tell me it's a "lean" bog...is this possible?
I'm baffled here. Any help I can get would be appreciated.
If you nail the throttle in 1st at about 2000 RPM, it will start making that popping/backfiring sound out the exhaust and it accelerates but it feels like it's "hitching." It's obviously not accelerating at full speed. As the RPMs climb and you continue to stay in the throttle it will come out of it...maybe 4,500 RPM. When you hit 2nd it might pop a little but usually not. It just seems to be when the RPMs are climbing really rapidly in 1st that it will do it. If you floor it in 3rd at 2000 RPM, it will not do it. It just starts to pull like it normally would, although obviously the RPMs are not climbing nearly as fast 3rd. Some people I know are trying to tell me it's a "lean" bog...is this possible?
I'm baffled here. Any help I can get would be appreciated.
Thread Starter
Teching In
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From: Bangor, ME
I should also mention that the car has not thrown any codes through all of this. It only has 24,000 miles on it, and I have O2 Sims on the back sensors. Could the Front O2's possibly be bad, or is it possible that they are being thrown off by their new position so far back in the exhaust stream and are tricking the computer?? It seems like any of these things would probably throw some sort of code, but I really don't know much about PCMs. Thanks again.
