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Backfiring from exhaust under load

  • Thread starter Thread starter Huff890
  • Start date Start date Nov 15, 2021
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Huff890

Member
Jul 2, 2018
35
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Jacksonville
Nov 15, 2021
#1
  • Nov 15, 2021
  • #1
91 mustang lx 5.0 2nd and 3rd wot around 2500 and above can't get out of its on way backfires then launches and back fires again shift to 3rd same thing can smell gas where do I start? Plugs,for, where let me know please thanks
 

General karthief

wonder how much it would cost to ship you a pair
5 Year Member
Aug 25, 2016
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polk county florida
Nov 15, 2021
#2
  • Nov 15, 2021
  • #2
Need more info.
How long have you had the car?
Miles?
Originally a V8 car?
Any other modifications?
 
H

Huff890

Member
Jul 2, 2018
35
1
8
Jacksonville
Nov 15, 2021
#3
  • Nov 15, 2021
  • #3
General karthief said:
Need more info.
How long have you had the car?
Miles?
Originally a V8 car?
Any other modifications?
Click to expand...
122k stock yes original 5 0
 
H

Huff890

Member
Jul 2, 2018
35
1
8
Jacksonville
Nov 15, 2021
#4
  • Nov 15, 2021
  • #4
Huff890 said:
122k stock yes original 5 0
Click to expand...
Had the car for 2 years
 

General karthief

wonder how much it would cost to ship you a pair
5 Year Member
Aug 25, 2016
27,869
10,542
203
polk county florida
Nov 15, 2021
#5
  • Nov 15, 2021
  • #5
Check the common things, plugs, wires, cap and rotor, fuel pressure, and timing, I would go as far as a compression test.
 

JD1964

there is enough sticking out to grab on to
15 Year Member
Jun 28, 2013
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Nov 17, 2021
#6
  • Nov 17, 2021
  • #6
I’d begin by checking for proper fuel pressure
 

General karthief

wonder how much it would cost to ship you a pair
5 Year Member
Aug 25, 2016
27,869
10,542
203
polk county florida
Nov 17, 2021
#7
  • Nov 17, 2021
  • #7
Oh, checked for codes?
 

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor
Admin Dude
Jan 4, 1985
42,963
21,132
234
Box behind Walmart
Nov 17, 2021
#8
  • Nov 17, 2021
  • #8
Codes first:

It's likely in limp mode.

The throttle position sensor is probably bad. Your code check will help to confirm.
 

Mustang5L5

That is…until I whipped out my Bissell
Mod Dude
Feb 18, 2001
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Nov 18, 2021
#9
  • Nov 18, 2021
  • #9
There's a few things that can cause this.

First step: Dump codes. I'd also check fuel pressure and perform a smoke test to check for vacuum leaks. A slipped intake gasket can sometimes cause this. I'd do some basic troubleshooting first before firing off the parts cannon
 
H

Huff890

Member
Jul 2, 2018
35
1
8
Jacksonville
Nov 18, 2021
#10
  • Nov 18, 2021
  • #10
Noobz347 said:
Codes first:

It's likely in limp mode.

The throttle position sensor is probably bad. Your code check will help to confirm.
Click to expand...
Codes I got were 11 33 and 13
 

Mustang5L5

That is…until I whipped out my Bissell
Mod Dude
Feb 18, 2001
43,216
17,899
224
Massachusetts
Nov 18, 2021
#11
  • Nov 18, 2021
  • #11
Huff890 said:
Codes I got were 11 33 and 13
Click to expand...

Are those engine off, or engine running codes
 
H

Huff890

Member
Jul 2, 2018
35
1
8
Jacksonville
Nov 18, 2021
#12
  • Nov 18, 2021
  • #12
Mustang5L5 said:
Are those engine off, or engine running codes
Click to expand...
Engine off
 

Mustang5L5

That is…until I whipped out my Bissell
Mod Dude
Feb 18, 2001
43,216
17,899
224
Massachusetts
Nov 18, 2021
#13
  • Nov 18, 2021
  • #13
Huff890 said:
Engine off
Click to expand...

Can you run the engine running codes as well? Those will likely be more informative
 
H

Huff890

Member
Jul 2, 2018
35
1
8
Jacksonville
Nov 18, 2021
#14
  • Nov 18, 2021
  • #14
Mustang5L5 said:
Can you run the engine running codes as well? Those will likely be more informative
Click to expand...
It came up as a 4
 

Mustang5L5

That is…until I whipped out my Bissell
Mod Dude
Feb 18, 2001
43,216
17,899
224
Massachusetts
Nov 18, 2021
#15
  • Nov 18, 2021
  • #15
Wasn’t a valid test.

Do the koeo and cm codes. Once done, start the engine. The idle should go up, display a 4 or 8 and the start spitting out codes shortly after. A pass is code 11. No codes, or no code 11 and it was not done correctly.
 
H

Huff890

Member
Jul 2, 2018
35
1
8
Jacksonville
Nov 18, 2021
#16
  • Nov 18, 2021
  • #16
Mustang5L5 said:
Wasn’t a valid test.

Do the koeo and cm codes. Once done, start the engine. The idle should go up, display a 4 or 8 and the start spitting out codes shortly after. A pass is code 11. No codes, or no code 11 and it was not done correctly.
Click to expand...
Running codes
11
22
44
41
22
19
44
 

Mustang5L5

That is…until I whipped out my Bissell
Mod Dude
Feb 18, 2001
43,216
17,899
224
Massachusetts
Nov 18, 2021
#17
  • Nov 18, 2021
  • #17
Huff890 said:
Running codes
11
22
44
41
19
Click to expand...
Plus KOEO codes 13 and 33


Code 22: BAP sensor
Code 41: O2 sensor indicates lean (i forget which bank)
Code 44 is the air pump, you can ignore this
Code 33 is the EGR. Wont affect how car is running
Code19 is typically set when your idle speed is set about 725.

Code 19 - Engine off - No Vehicle Power (pins 37 + 57) or bad PCM VPWR Diagnosis. This is a wiring problem that is from a bad ECC power relay, bad connection, bad fuse link or a bad computer. The ECC relay is located on top of the computer under the passenger side kick panel. Pull the connector off any fuel injector and measure the voltage on the red wire: if its 12 volts or better, the ECC relay is OK. If the ECC relay is OK, pull the kick panel off and measure the voltage at pins 37 & 57. If it is 12 volts or more, then the computer's diagnostic firmware has taken a dump and is defective.
 
H

Huff890

Member
Jul 2, 2018
35
1
8
Jacksonville
Nov 18, 2021
#18
  • Nov 18, 2021
  • #18
So I'd need to get a new pcm if the firmware is defective correct
 

JD1964

there is enough sticking out to grab on to
15 Year Member
Jun 28, 2013
3,431
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Maryland
Nov 18, 2021
#19
  • Nov 18, 2021
  • #19
Huff890 said:
So I'd need to get a new pcm if the firmware is defective correct
Click to expand...
These ECU’s are known for the internal capacitors going bad. They can be repaired. Some diyers have been successful at repairing them. I tried but it didn’t work for me. I then sent it in to an exchange service. You send yours in and they either repair it or send you another that’s been repaired. I’ve had good luck with this service. So, “if” it’s your ECU acting up you could consider this path

A9L A9P C3W A3M X3Z MUSTANG ECU PCM COMPUTER REPAIR SERVICE 5.0 REPAIR & RETURN | eBay

Mustang ECU Repair Service. Quick turn around after the computer is received. Easy repair process. If we are unable to repair your computer, WE CAN HELP! 701 La Veta Dr. Crank, no start?.
www.ebay.com
 

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor
Admin Dude
Jan 4, 1985
42,963
21,132
234
Box behind Walmart
Nov 18, 2021
#20
  • Nov 18, 2021
  • #20
Mustang5L5 said:
Code 33 is the EGR. Wont affect how car is running
Click to expand...
Unless the diaphragm is torn then it's a vacuum leak.
 
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