My car is backfiring so loud it sounds like a gunshot! HELP - Saturn Sky Forums: Saturn Sky Forum
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post #1 of 13 (permalink) Old 06-23-2010, 03:06 AM Thread Starter
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My car is backfiring so loud it sounds like a gunshot! HELP

Here is the deal. I have had a RPI Exhaust and Dp on the car for about 8,000 miles. My car has 21,000 miles on it.

For awhile the car sounded fine with the set-up and for about a month it started gurgling. I rather liked the sound of the gurgling and it got worse everyday.

Last night I was driving my car and when I changed gears from 2-3 with RPM's at 3-3.5 my engine started backfiring, or maybe it was the exhaust. I'm not really a gearhead type so the technical aspects of all this elude me.

The backfiring was a popping sound, but really really loud. When I say loud I'm talking 5x louder than a 70's muscle car with a straight pipe and no cat. I will just say it doesn't sound good at all. It sounds as though the muffler or dp have something to do with it.

One thing I will mention is my turbo solenoid and factory blowoff valve (RECIRCULATING VALVE) may not be opening and closing properly and solenoid not working.

-When I stop the car it usually stops until the revs get above 4k rpms
-It stops or is much quieter if I keep revs low
-It doesn't happen when my foot is lightly on the gas.
-It still happened if I engage the clutch and put shifter in neutral, but when the engine winds down it is quiet again while cruising
-**WHEN I PULLED INTO A PARKING LOT AND PUSHED THE PEDAL TO KICK UP THE RPM'S THE ENGINE BACKFIRED, SOUNDED FUNNY AND WOULDN'T BREAK ABOVE 4000RPMS. It will run up to redline if I am on it with no problems except MAYBE the backfire...

QUESTION: Is it normal for a "stainless" exhaust to have rust on it after less than 1.5 years and are exhausts warrantied?
QUESTION: Is RPI a sponsored vendor? Sorry for the drawn out msg
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post #2 of 13 (permalink) Old 06-23-2010, 05:51 AM
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1st of all, what calibration you have on your ECU? OEM/GMPP/Aftermarket?
2nd I would do some logs to read if everything is ok in the engine and if the problem comes because of the exhaust.

Loud backfire you say?


At 00:20, that is caused because of the WOT Box, wot shifting from 2nd to 3rd

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post #3 of 13 (permalink) Old 06-23-2010, 07:21 AM
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Backfiring is generally combustion of the mixture into the intake. This is usually a condition caused by a lean fuel mixture. But I kind of doubt that could occure easily with SIDI. A check of the sensor data would show faulty baro data or faulty MAP data. Popping or ignition in the exhaust can be caused by a light-off of a rich mixture. The conditions to set this up are not uncommon in boosted applications but you also need extra oxygen to make this happen. In that regard, I'd be looking for a leak in your exhaust system. You can also get popping in the exhaust from an overly-advanced ignition but I don't see how that could be with a properly functioning computer.

But with a malfunction in your BOV you could be experiencing compressor surge which sounds more like a bad stutter in the intake system. Of course, you'd want to address this since there's little point chasing down the problem when you know you have something that's not right in the system and what affects it may have.

Also, I doubt a misfire condition since that would immediately set a MIL.

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post #4 of 13 (permalink) Old 06-23-2010, 05:51 PM
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I'd say check your entire exhaust for loose connections. If it's that loud then I think it's as Gerry stated, it could be a light-off in the exhaust, which would cause a very loud bang. I experienced a VERY loud backfire on my motorcycle for a while whenever I let off the gas and pulled the clutch in. It turned out to be caused by loose/missing bolts on one of the pipes, allowing air to get in at the engine/pipe connection.

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post #5 of 13 (permalink) Old 06-24-2010, 10:36 AM Thread Starter
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Update:
GMPP+Wester's Upgrade
GMPP CAI
SOLO DP
RPI EXHAUST
STOCK IC

UPDATE: When you completely press down the accelerator for a few seconds car goes into limp mode. Turn off the key and restart sky it is back to normal until you floor it again..

Last night when I was driving it seems as though the accelerator was sticking and it was driving with the RPM's at 2k and the they would stick when I disengaged the clutch.

When I drive the rpm's up to 4k when I push clutch it seems to take far longer than normal for the rpm's to drop.

Send computer back twice because I had issues and it was throwing an overboost code last year Lyndon said it wasn't the computer, and send it back. I took it to saturn and after throwing it on their scanner they said I needed the Turbo Regulator Solenoid (with throw rubber tubes going into it and it is partially covered by the valve cover) They also said I needed a new Recirculating Valve (Factory BOV). I had already opened this piece up to see if it was ripped or damaged, but it was in perfect condition. I know Dejon Dave sells uprated springs. The tech THOUGHT the limp mode could be the spring because of high boost loads which the begins leaking at the recirculating valve due to the weak spring which upon letting the boost go could cause the computer to go into the protection mode it's in.
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post #6 of 13 (permalink) Old 06-24-2010, 10:37 AM Thread Starter
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Quote:
Originally Posted by Kelu View Post
1st of all, what calibration you have on your ECU? OEM/GMPP/Aftermarket?
2nd I would do some logs to read if everything is ok in the engine and if the problem comes because of the exhaust.

Loud backfire you say?

YouTube - Fiat Coupe Turbo vs Opel GT

At 00:20, that is caused because of the WOT Box, wot shifting from 2nd to 3rd
I can get mine to be just as load with continous popping.
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post #7 of 13 (permalink) Old 06-24-2010, 10:38 AM Thread Starter
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Quote:
Originally Posted by Kelu View Post
1st of all, what calibration you have on your ECU? OEM/GMPP/Aftermarket?
2nd I would do some logs to read if everything is ok in the engine and if the problem comes because of the exhaust.

Loud backfire you say?

YouTube - Fiat Coupe Turbo vs Opel GT

At 00:20, that is caused because of the WOT Box, wot shifting from 2nd to 3rd
I can get mine to be just as load with continous popping.

So it's possible it could be due to my DP?
How about a blown muffler (It certainly doesn't sound healthy as it did when I first bought it)
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post #8 of 13 (permalink) Old 06-24-2010, 10:56 AM
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Question

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Originally Posted by BoxsterGuy View Post
I can get mine to be just as load with continous popping.

So it's possible it could be due to my DP?
How about a blown muffler (It certainly doesn't sound healthy as it did when I first bought it)
I thought that RPI system uses 2 separate not mufflers, but are like uhhh, baffles??

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post #9 of 13 (permalink) Old 06-24-2010, 01:14 PM Thread Starter
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Originally Posted by MidniteBlues View Post
I thought that RPI system uses 2 separate not mufflers, but are like uhhh, baffles??
My RPI exhaust has tubes, not mufflers. The tubes get about 1.5 inches wider around from a 3 inch pipe for about 1.25 feet in length and goes out again into 3 inch pipes.
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post #10 of 13 (permalink) Old 06-24-2010, 05:03 PM
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its not en exhaust issue. its a tune issue, or turbo issue.

peace out.
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post #11 of 13 (permalink) Old 06-24-2010, 05:25 PM
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Tune? Turbo?
How come a tune can "brake" if it was working fine until now?
His symptoms sounds like running very rich how come turbo is responsible for running rich?
I would call many other things like MAF but not the turbo.

BoxsterGuy: check the exhaust for leaks, read your DTCs and try to log your engine with something like HPTuners.

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post #12 of 13 (permalink) Old 06-24-2010, 07:46 PM Thread Starter
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Originally Posted by Kelu View Post
Tune? Turbo?
How come a tune can "brake" if it was working fine until now?
His symptoms sounds like running very rich how come turbo is responsible for running rich?
I would call many other things like MAF but not the turbo.

BoxsterGuy: check the exhaust for leaks, read your DTCs and try to log your engine with something like HPTuners.
I mentioned before I think that the spring in my factory recirculating valve MAY not be retaining boost which would make sense since under partial throttle it doesn't go into limp mode while under full throttle it does after several seconds of seeing high boost.

I seem to remember Dejon Dave selling a heavier spring so I'm going to check myself.

My dealer has the car now, and I mentioned everything I've pulled from the forum just to help him out. To be honest he doesn't seem VERY educated in regards to the car, but I will give him the benefit of the doubt.

The car no longer has it's factory bumper to bumper so this is entirely out of pocket. Tomorrow they will call me and I'll give you a heads up with the condition my car has..

IS THROTTLE A TERM USED WITH A CAR? IT SOUNDS MORE LIKE A MOTORCYCLE!
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post #13 of 13 (permalink) Old 06-25-2010, 02:48 PM
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Yes

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Originally Posted by BoxsterGuy View Post
I mentioned before I think that the spring in my factory recirculating valve MAY not be retaining boost which would make sense since under partial throttle it doesn't go into limp mode while under full throttle it does after several seconds of seeing high boost.

I seem to remember Dejon Dave selling a heavier spring so I'm going to check myself.

My dealer has the car now, and I mentioned everything I've pulled from the forum just to help him out. To be honest he doesn't seem VERY educated in regards to the car, but I will give him the benefit of the doubt.

The car no longer has it's factory bumper to bumper so this is entirely out of pocket. Tomorrow they will call me and I'll give you a heads up with the condition my car has..

IS THROTTLE A TERM USED WITH A CAR? IT SOUNDS MORE LIKE A MOTORCYCLE!
A throttle is the mechanism by which the flow of a fluid is managed by constriction or obstruction.

In a car - the gas pedal is either mechanically linked usually via a cable to the moving parts making up the throttle assembly - or electronically as in most modern cars to the computer which in turn controls the moving parts that control fuel flow etc. On a motorcycle - the term throttle is typically used to refer to the portion of the handle which is twisted to perform the same function as the gas pedal in a car - whether all motorcycles are mechanical or some are "drive by wire" I do not know - but the throttle on a motorcycle is in fact more than just that control surface that you interact with - and includes the cables (or electronics) and moving parts connected to the fuel and air intake systems of the engine. I don't know the history of why we use the term throttle on a motorcycle rather than something more like gas-handle - or why we use gas pedal on a car instead of throttle pedal - but any engine of any sort has some throttle mechanism - even if it is an electric engine you could call the rheostat or other mechanism to control the input voltage/current a throttle.

or you could say that the automotive gas pedal and the motorcycle twist handle are actually throttle control devices whereas the actual throttle assembly is separate and connected via cable or computer - but then you'd have to come up with a catchy name other than twisty handle control - it is easy to use throttle on the motorcycle to include both the actual throttle as well as the throttle input control

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