Backfiring is getting worse

Chris_H · 10-31-2002, 08:51 PM

Ok, a couple of months ago the car started to backfire from time to time. it didn't happen a lot, but it would happen once a week or so. Seems when I ghet on the gas pretty good, usually full throttle, and then let off, it would backfire. I turned down the fuel pressure the other day from 38psi to 35psi. I drove to work, got on the gas, slowly let off, and got a pretty good backfire. Sounds like I am shooting off cannons from the car. Even when just crusing in the neighborhood the other night, and letting off the gas for the stop sign it backfired. It doesn't do it all the time, but it does it enough to where I am starting to get concerned. Anybody have any thoughts on this, or know how I can fix this? I know this can't be all that good for the car, but can it cause any problems? Any help is greatly appreciated.

Thanks
Chris

Stang_Crazy · 10-31-2002, 09:31 PM

We have an old Hillbilly truck at work that used to backfire...we would make it backfire when we would pass a jogger or someone walking and scare teh s$it outta them hehe... About a month ago, I went to backfire it and it sounded like a damn cannon went off. We stopped teh truck and looked under it...the muffler was blown apart. Right at the seam. blown wide open. I'm not saying this is what's gonna happen to your car (God, I hope not), but it can happen...

sn95gt19 · 10-31-2002, 10:17 PM

i have a buddy that has a billy truck that does the same thing. it shoots 3 ft flames out the tail pipe if you pump the gas then let off. my guess is that you need new plugs/ wires/ 02's/ or maybe your timing is out of wack. either way something is making the gas go through the exhaust without getting burnt.

CB93LX · 10-31-2002, 11:32 PM

Id check for exhaust leaks.

Chris_H · 11-01-2002, 12:00 AM

Well I know for a fact I have an exhaust leak. About 3 weeks ago I needed to trailer the car over to a friends so we could put it up on his lift and work on it. When I was driving it up on this trailer ( I swear it had tractor tires on it) I dragged the H-pipe on it. After getting it on the lift I noticed the pipe has about a 18" dragged dent/scrape in it, about 1/8" deep, but it didn;t look like it cut the pipe. There is a leak though so either the pipe seperated or there is a cut in it. So this would be causing the backfiring?

Chris

CB93LX · 11-01-2002, 12:35 AM

Id put money on it. Theres your trouble right there. Get that fixed and she'll be back to growling instead of coughing. Good luck.

88fivepointoh · 11-01-2002, 11:49 PM

check your mass air sensor.. your running lean.. an exhaust leak won't cause backfiring.. its fuel mixture issue.. your probably running lean.. of you have a sticking valve or timing chain failure is on the way... I would check the mass air sensor out first.. any codes? let me know what u find...

srv1 · 11-02-2002, 12:07 AM

Quote:

Originally posted by 88fivepointoh
check your mass air sensor.. your running lean.. an exhaust leak won't cause backfiring.. its fuel mixture issue.. your probably running lean.. of you have a sticking valve or timing chain failure is on the way... I would check the mass air sensor out first.. any codes? let me know what u find...

ok guys i have the same problem as he does and i have NO exhuast leaks. mine does it when i nail the throttle and then go to shift at high rpms. come to find out it may be my sloppy timing chain or i have seen this same problem on another mustang and it was the pickup in the distributor that broke.

my cars still does it. waiting for heads and a cam swap so it will give me an excuse to change the chain!

Hope that helped Chris.

srv1 · 11-02-2002, 12:08 AM

oh i almost forgot. Chris, how many miles on your motor?

CB93LX · 11-02-2002, 01:58 AM

88FIVEPOINTOH If you get on the gas and then let off suddenly and it backfires, it CAN be an exhaust leak.

Chris_H · 11-02-2002, 08:22 AM

Well I've got about 70,000 give or take a thousand on the motor. Still a pretty good motor in my eyes. I have an A/F ratio gauge in the car, but with the FMU, I seriously doubt its running lean. When I nail it, the 2nd ro 3rd green light on the A/F gauge is about where it sits. Its only on deceleration that it back fires, not between shifts as SRV1 says his does. I have the stock mass air meter in it still because I can't get the car to run right with the 73 C&L. I am heading to Phoenix today, so I will talk with Tom at All Mustang and see what he has to say. I will be back tomrrow, so if you guys still have suggestions, let me know please!!

Thanks a lot,
Chris

88fivepointoh · 11-02-2002, 10:31 AM

try another mass air meter, and check your timing.. run a different octane gas in her.. 93+ see what that does..

srv1 · 11-03-2002, 12:30 PM

Quote:

Originally posted by Chris_H
Well I've got about 70,000 give or take a thousand on the motor. Still a pretty good motor in my eyes. I have an A/F ratio gauge in the car, but with the FMU, I seriously doubt its running lean. When I nail it, the 2nd ro 3rd green light on the A/F gauge is about where it sits. Its only on deceleration that it back fires, not between shifts as SRV1 says his does. I have the stock mass air meter in it still because I can't get the car to run right with the 73 C&L. I am heading to Phoenix today, so I will talk with Tom at All Mustang and see what he has to say. I will be back tomrrow, so if you guys still have suggestions, let me know please!!

Thanks a lot,
Chris

sorry Chris, but i failed to read your mods!

anyways, sounds like a timing problem to me or the FMU needs to be reworked. it may be running too rich and causing it to ignite with unburnt gas in your exhaust.

Chris_H · 11-04-2002, 10:08 AM

As far as the timing is concerned, I haven't touched it since Jan when we put the Novi in. Unless it has changed on its own, I don't see how this has become the problem, but I will check the timing anyway.
As far as the gas. We can only get 91 octane here, pretty pathetic I know. But I have gotten gas at the same station for the past 3 years. Unless they have had bad gas for the past month, then I don't see this as an issue either, but it's time for the octane boost anyway. I even got gas in Phx this weekend, and I still had the same issue.
I don't know if the exhaust leak could be the cause of this, but the leak has come in the past month, along with the more consistent backfiring. I know I need to get that fixed, its just a matter of time.
I will take off the mass air meter, mess with it a little, and try it again.

Thanks for the help
Chris

CB93LX · 11-04-2002, 06:14 PM

Im not trying to discount these other opinions on the problem and its hard to tell for sure without being there. But 9 times out of 10 if you punch the gas and get them RPMs up and then let off and thats when it backfires and you know you have an exhaust leak then thats the trouble. Id get that fixed before I messed with anything else. Well, Is your car running good as far as performance? If so, Why mess with timing,mass air or anything else and then have to get it all "right" again? An exhaust leak will cause this.

muskrat · 11-04-2002, 07:22 PM

Car is backfiring because timing is retarding to much. This is caused by a defective distributor module. Autozone sells one for around $44.00.

Chris_H · 11-04-2002, 07:47 PM

For what its worth, I don't know if I mentioned this the first time or not, but the car will backfire when I quickly let off the gas after punching it, and it will also backfire when I am cruising at 75-80mph on the highway in 5th and just completely let off the gas. Keep in mind this isn't happening everytime, which is fine with me, but it happens enough that I am worried about it. Sometimes its a cannon blast, other times it a softer "pop." Sometimes it sounds like its comming out of the tailpipes, sometimes it sounds like its comming from under the hood/passenger side of the car somewhere. I know this is not helping much, but this is what its doing. I appreciate all the replies so far. You guys are great.

Chris

88fivepointoh · 11-04-2002, 07:58 PM

swap out that mass air.. I had the exact same issues... Leaning out.. Try a new mass air sensor or run teh car with out installed.. the car will idle funny but it should pop as bad if not at all.. let me know.

10-31-2002, 08:51 PM	#1
Chris_H Registered Member Join Date: Oct 1999 Location: New Mexico Posts: 488	Backfiring is getting worse Ok, a couple of months ago the car started to backfire from time to time. it didn't happen a lot, but it would happen once a week or so. Seems when I ghet on the gas pretty good, usually full throttle, and then let off, it would backfire. I turned down the fuel pressure the other day from 38psi to 35psi. I drove to work, got on the gas, slowly let off, and got a pretty good backfire. Sounds like I am shooting off cannons from the car. Even when just crusing in the neighborhood the other night, and letting off the gas for the stop sign it backfired. It doesn't do it all the time, but it does it enough to where I am starting to get concerned. Anybody have any thoughts on this, or know how I can fix this? I know this can't be all that good for the car, but can it cause any problems? Any help is greatly appreciated. Thanks Chris __________________ 1987 LX, Best times: 13.47 @ 102.49, 1.80 60ft 6900' DA

10-31-2002, 09:31 PM	#2
Stang_Crazy It's never clean enough! Join Date: Jan 1999 Location: Shaler, PA Posts: 1,542	We have an old Hillbilly truck at work that used to backfire...we would make it backfire when we would pass a jogger or someone walking and scare teh s$it outta them hehe... About a month ago, I went to backfire it and it sounded like a damn cannon went off. We stopped teh truck and looked under it...the muffler was blown apart. Right at the seam. blown wide open. I'm not saying this is what's gonna happen to your car (God, I hope not), but it can happen... __________________ ~Dan 2001 SVT Lightning 89' GT : Taking up garage space and waiting for a buyer... Rice Hater's Club - Member #11

10-31-2002, 10:17 PM	#3
sn95gt19 motors done......woohooo Join Date: Mar 2002 Posts: 799	i have a buddy that has a billy truck that does the same thing. it shoots 3 ft flames out the tail pipe if you pump the gas then let off. my guess is that you need new plugs/ wires/ 02's/ or maybe your timing is out of wack. either way something is making the gas go through the exhaust without getting burnt. __________________ 95gt lazer red (98 cobra clone) Rice Haters Club Member #116

11-01-2002, 12:00 AM	#5
Chris_H Registered Member Join Date: Oct 1999 Location: New Mexico Posts: 488	Well I know for a fact I have an exhaust leak. About 3 weeks ago I needed to trailer the car over to a friends so we could put it up on his lift and work on it. When I was driving it up on this trailer ( I swear it had tractor tires on it) I dragged the H-pipe on it. After getting it on the lift I noticed the pipe has about a 18" dragged dent/scrape in it, about 1/8" deep, but it didn;t look like it cut the pipe. There is a leak though so either the pipe seperated or there is a cut in it. So this would be causing the backfiring? Chris __________________ 1987 LX, Best times: 13.47 @ 102.49, 1.80 60ft 6900' DA

11-02-2002, 12:08 AM	#9
srv1 Get down..... Join Date: Apr 2001 Location: Room 103 Posts: 2,095	oh i almost forgot. Chris, how many miles on your motor? __________________ Cobra brakes are on! Finally..... ------------------------------------------------

10-31-2002, 11:32 PM	#4
CB93LX Registered Member Join Date: Oct 2002 Location: Eastern N.C. Posts: 50	Id check for exhaust leaks.

11-01-2002, 12:35 AM	#6
CB93LX Registered Member Join Date: Oct 2002 Location: Eastern N.C. Posts: 50	Id put money on it. Theres your trouble right there. Get that fixed and she'll be back to growling instead of coughing. Good luck.

11-01-2002, 11:49 PM	#7
88fivepointoh Registered Member Join Date: Aug 2002 Location: Rochester Posts: 553	check your mass air sensor.. your running lean.. an exhaust leak won't cause backfiring.. its fuel mixture issue.. your probably running lean.. of you have a sticking valve or timing chain failure is on the way... I would check the mass air sensor out first.. any codes? let me know what u find...

11-02-2002, 01:58 AM	#10
CB93LX Registered Member Join Date: Oct 2002 Location: Eastern N.C. Posts: 50	88FIVEPOINTOH If you get on the gas and then let off suddenly and it backfires, it CAN be an exhaust leak.

11-02-2002, 08:22 AM	#11
Chris_H Registered Member Join Date: Oct 1999 Location: New Mexico Posts: 488	Well I've got about 70,000 give or take a thousand on the motor. Still a pretty good motor in my eyes. I have an A/F ratio gauge in the car, but with the FMU, I seriously doubt its running lean. When I nail it, the 2nd ro 3rd green light on the A/F gauge is about where it sits. Its only on deceleration that it back fires, not between shifts as SRV1 says his does. I have the stock mass air meter in it still because I can't get the car to run right with the 73 C&L. I am heading to Phoenix today, so I will talk with Tom at All Mustang and see what he has to say. I will be back tomrrow, so if you guys still have suggestions, let me know please!! Thanks a lot, Chris __________________ 1987 LX, Best times: 13.47 @ 102.49, 1.80 60ft 6900' DA

11-02-2002, 10:31 AM	#12
88fivepointoh Registered Member Join Date: Aug 2002 Location: Rochester Posts: 553	try another mass air meter, and check your timing.. run a different octane gas in her.. 93+ see what that does..

11-04-2002, 10:08 AM	#14
Chris_H Registered Member Join Date: Oct 1999 Location: New Mexico Posts: 488	As far as the timing is concerned, I haven't touched it since Jan when we put the Novi in. Unless it has changed on its own, I don't see how this has become the problem, but I will check the timing anyway. As far as the gas. We can only get 91 octane here, pretty pathetic I know. But I have gotten gas at the same station for the past 3 years. Unless they have had bad gas for the past month, then I don't see this as an issue either, but it's time for the octane boost anyway. I even got gas in Phx this weekend, and I still had the same issue. I don't know if the exhaust leak could be the cause of this, but the leak has come in the past month, along with the more consistent backfiring. I know I need to get that fixed, its just a matter of time. I will take off the mass air meter, mess with it a little, and try it again. Thanks for the help Chris __________________ 1987 LX, Best times: 13.47 @ 102.49, 1.80 60ft 6900' DA

11-04-2002, 06:14 PM	#15
CB93LX Registered Member Join Date: Oct 2002 Location: Eastern N.C. Posts: 50	Im not trying to discount these other opinions on the problem and its hard to tell for sure without being there. But 9 times out of 10 if you punch the gas and get them RPMs up and then let off and thats when it backfires and you know you have an exhaust leak then thats the trouble. Id get that fixed before I messed with anything else. Well, Is your car running good as far as performance? If so, Why mess with timing,mass air or anything else and then have to get it all "right" again? An exhaust leak will cause this.

11-04-2002, 07:22 PM	#16
muskrat Registered Member Join Date: Mar 1999 Location: va Posts: 35	Car is backfiring because timing is retarding to much. This is caused by a defective distributor module. Autozone sells one for around $44.00.

11-04-2002, 07:47 PM	#17
Chris_H Registered Member Join Date: Oct 1999 Location: New Mexico Posts: 488	For what its worth, I don't know if I mentioned this the first time or not, but the car will backfire when I quickly let off the gas after punching it, and it will also backfire when I am cruising at 75-80mph on the highway in 5th and just completely let off the gas. Keep in mind this isn't happening everytime, which is fine with me, but it happens enough that I am worried about it. Sometimes its a cannon blast, other times it a softer "pop." Sometimes it sounds like its comming out of the tailpipes, sometimes it sounds like its comming from under the hood/passenger side of the car somewhere. I know this is not helping much, but this is what its doing. I appreciate all the replies so far. You guys are great. Chris

11-04-2002, 07:58 PM	#18
88fivepointoh Registered Member Join Date: Aug 2002 Location: Rochester Posts: 553	swap out that mass air.. I had the exact same issues... Leaning out.. Try a new mass air sensor or run teh car with out installed.. the car will idle funny but it should pop as bad if not at all.. let me know.

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