Car is backfiring

Chris951 · May 7th, 2009, 07:28 PM

So ever since I got my car it will backfire through the exhaust. It only does it on WOT runs when I'm shifting around 5k. Otherwise it won't do it if I keep the rpms down. But the past couple months now it has been backfiring through the intake when its cold. It will only do it once in a while though like once a week and when it happens it will only do it once maybe twice. I know I need to set my timing but could I be running lean or rich? I can't really tell myself because I have an o/r h-pipe and dumps so it always smells. I was thinking about getting an adjustible fpr. Would that help along with setting my timing?

mxnate116 · May 7th, 2009, 10:14 PM

depends on what your fuel pressure is now. if its high or low an adjustable could help, but so could a new stock one.

i put a new fpr on mine and it ran amazing for two weeks then slowly went back to shit(popping through the intake all the time). i need to check my fuel pressure again to see if it crapped out again.

dr.gonzo! · May 7th, 2009, 10:20 PM

How long has it been since you had a tune up? Any exhaust leaks or loose header bolts?

Ntv69 · May 7th, 2009, 11:38 PM

Subscribing here, i have same problem with my 87. You still runnin speed density system? Mine also backfires around 5k also when about to shift. I too have a off road x pipe, and have to real smelly exhaust and fuel smell. I bought plugs,rotor,cap,wires,k&n filter cleaner. Gonna tune up, sdjust timing, change oil, flush rad clean up my dirty k&n. Im hoping if i put on a short belt and eliminate the smog pump it will help with the exhaust smell.

Chris951 · May 7th, 2009, 11:54 PM

Originally Posted by dr.gonzo

How long has it been since you had a tune up? Any exhaust leaks or loose header bolts?

Actually yeah, Both the bolts came out at one point on the #4 cylinder and I think the bolt holes in the head are warped because I cannot get new ones in.

And I did a tune up when I bought it in september. New plugs, cap and rotor, cleaned the TB and iac, etc. I've also seafoamed it like 3 times lol.

Jackson · May 7th, 2009, 11:56 PM

Originally Posted by Chris951

So ever since I got my car it will backfire through the exhaust. It only does it on WOT runs when I'm shifting around 5k. Otherwise it won't do it if I keep the rpms down.

My car did the same thing after I installed my O/R H pipe until I removed my smog pump. Im not exactly sure why it made a difference (I have a few theories but Im not a mechanic so i can only guess) but as soon as i yanked the pump, put on a short belt and capped the smog stuff it quit backfiring...

Chris951 · May 7th, 2009, 11:57 PM

Originally Posted by Ntv69

Subscribing here, i have same problem with my 87. You still runnin speed density system? Mine also backfires around 5k also when about to shift. I too have a off road x pipe, and have to real smelly exhaust and fuel smell. I bought plugs,rotor,cap,wires,k&n filter cleaner. Gonna tune up, sdjust timing, change oil, flush rad clean up my dirty k&n. Im hoping if i put on a short belt and eliminate the smog pump it will help with the exhaust smell.

Yeah I'm still on SD. Sounds like we have a similar problem because mine backfires right in the middle of shifts at 5k.

Chris951 · May 7th, 2009, 11:58 PM

Originally Posted by Jackson

My car did the same thing after I installed my O/R H pipe until I removed my smog pump. Im not exactly sure why it made a difference (I have a few theories but Im not a mechanic so i can only guess) but as soon as i yanked the pump, put on a short belt and capped the smog stuff it quit backfiring...

I'm currently running a short belt. My smog pump seized a few months ago.

PolishSasquatch · May 8th, 2009, 12:39 AM

im getting backfriing over 4000 rpm. but im running an 85 carbed motor, with no exhaust on it ( open pipe after the car, its only temporary untill i can afford mufflers). Could it be a lean out backfire?

Ntv69 · May 8th, 2009, 12:43 AM

Originally Posted by Chris951

I'm currently running a short belt. My smog pump seized a few months ago.

What size belt? power steering? i assume no ac with the t-roofs

Chris951 · May 8th, 2009, 12:56 AM

Originally Posted by Ntv69

What size belt? power steering? i assume no ac with the t-roofs

83.5" belt. I have power steering and ac but the ac will be gone soon because it doesn't work

93mustank · May 8th, 2009, 01:44 AM

Originally Posted by Chris951

I know I need to set my timing but

hmmmmmmm......

flattusmaximus78 · May 8th, 2009, 10:57 AM

When my car pops through the intake it's due to lean conditions. Often low fuel pressure. It did it more often in the winter now. If you have an adjustable fpr make sure that once it's adjusted, that the nut is tight.

I had m y car tuned on 40psi or so. When back for a slight retune and it was going leaner and leaner. Turned out my fpr nut was loose and it was slowly dropping over the course of a month.

hopper · May 8th, 2009, 03:32 PM

yes ther are AC on t-tops,
Also i had the same prob with the back fireing although it was a carbed engine.
this would only happen under load at 5K.
found out there was a very very very small crack in the boot of one of the plug wires, onced changes no problems any longer

Chris951 · May 8th, 2009, 06:05 PM

Originally Posted by flattusmaximus78

When my car pops through the intake it's due to lean conditions. Often low fuel pressure. It did it more often in the winter now. If you have an adjustable fpr make sure that once it's adjusted, that the nut is tight.

I had m y car tuned on 40psi or so. When back for a slight retune and it was going leaner and leaner. Turned out my fpr nut was loose and it was slowly dropping over the course of a month.

I'm gonna get an adjustable fpr when i can get some money.

Ntv69 · May 8th, 2009, 07:50 PM

Does a kirban adj regulator attach right too stock fuel rails? Anyone runni a pressure gauge beside it??

flattusmaximus78 · May 8th, 2009, 11:14 PM

kirban bolts right in on the rail. I put my guage on the rail were the shrader vavle went. I just put a nos fitting in.

May 7th, 2009, 07:28 PM	#1
Chris951 Hardcore Enthusiast 1991 mustang 5.0 Join Date: Aug 2007 Location: Mesa, AZ Posts: 1,938 iTrader: 0 reviews	Car is backfiring So ever since I got my car it will backfire through the exhaust. It only does it on WOT runs when I'm shifting around 5k. Otherwise it won't do it if I keep the rpms down. But the past couple months now it has been backfiring through the intake when its cold. It will only do it once in a while though like once a week and when it happens it will only do it once maybe twice. I know I need to set my timing but could I be running lean or rich? I can't really tell myself because I have an o/r h-pipe and dumps so it always smells. I was thinking about getting an adjustible fpr. Would that help along with setting my timing?

May 8th, 2009, 10:57 AM	#13
flattusmaximus78 I Post Entirely Way Too Much 1993 5.ohhhh 12.97 @140mph Join Date: Apr 2006 Location: Gatorland Posts: 6,122 iTrader: 3 reviews	When my car pops through the intake it's due to lean conditions. Often low fuel pressure. It did it more often in the winter now. If you have an adjustable fpr make sure that once it's adjusted, that the nut is tight. I had m y car tuned on 40psi or so. When back for a slight retune and it was going leaner and leaner. Turned out my fpr nut was loose and it was slowly dropping over the course of a month. __________________ 02 Pewter z28, hoosiers/lid/exhaust/spray...125mph 1993 gt Sold, already missed --Moates Quarter horse $225-- --Cobra intake $150-- --tremec 3550 bell and shifter $1100--

May 8th, 2009, 07:50 PM	#16
Ntv69 Regular 1987 Mustang GT 5.0 5spd Join Date: May 2008 Location: Alberta Posts: 118 iTrader: 0 reviews	Does a kirban adj regulator attach right too stock fuel rails? Anyone runni a pressure gauge beside it?? __________________ 1987 Mustang GT 5.0 5spd t-roofs, FRPP 4.10 gears, MM subframe connectors, FRPP a arms, Tokico Hp struts/shocks, alum rad, electric fan, dcc fan control unit, 6g alternator

May 8th, 2009, 11:14 PM	#17
flattusmaximus78 I Post Entirely Way Too Much 1993 5.ohhhh 12.97 @140mph Join Date: Apr 2006 Location: Gatorland Posts: 6,122 iTrader: 3 reviews	kirban bolts right in on the rail. I put my guage on the rail were the shrader vavle went. I just put a nos fitting in. __________________ 02 Pewter z28, hoosiers/lid/exhaust/spray...125mph 1993 gt Sold, already missed --Moates Quarter horse $225-- --Cobra intake $150-- --tremec 3550 bell and shifter $1100--

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May 7th, 2009, 10:14 PM	#2
mxnate116 Hardcore Enthusiast SVTfocus, F250 Join Date: Jun 2007 Location: Spokane, WA Posts: 2,971 iTrader: 1 reviews	depends on what your fuel pressure is now. if its high or low an adjustable could help, but so could a new stock one. i put a new fpr on mine and it ran amazing for two weeks then slowly went back to shit(popping through the intake all the time). i need to check my fuel pressure again to see if it crapped out again.

May 7th, 2009, 11:38 PM	#4
Ntv69 Regular 1987 Mustang GT 5.0 5spd Join Date: May 2008 Location: Alberta Posts: 118 iTrader: 0 reviews	Subscribing here, i have same problem with my 87. You still runnin speed density system? Mine also backfires around 5k also when about to shift. I too have a off road x pipe, and have to real smelly exhaust and fuel smell. I bought plugs,rotor,cap,wires,k&n filter cleaner. Gonna tune up, sdjust timing, change oil, flush rad clean up my dirty k&n. Im hoping if i put on a short belt and eliminate the smog pump it will help with the exhaust smell. __________________ 1987 Mustang GT 5.0 5spd t-roofs, FRPP 4.10 gears, MM subframe connectors, FRPP a arms, Tokico Hp struts/shocks, alum rad, electric fan, dcc fan control unit, 6g alternator

May 8th, 2009, 12:39 AM	#9
PolishSasquatch Regular Join Date: Mar 2009 Posts: 97 iTrader: 0 reviews	im getting backfriing over 4000 rpm. but im running an 85 carbed motor, with no exhaust on it ( open pipe after the car, its only temporary untill i can afford mufflers). Could it be a lean out backfire?

May 8th, 2009, 03:32 PM	#14
hopper Regular Join Date: Apr 2007 Posts: 390 iTrader: 0 reviews	yes ther are AC on t-tops, Also i had the same prob with the back fireing although it was a carbed engine. this would only happen under load at 5K. found out there was a very very very small crack in the boot of one of the plug wires, onced changes no problems any longer

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