Mustang Backfiring at 4000 RPM

[62thunderbird]

Well this is my second post. I was driving my mustang the other day and I wanted to get on it and the car at 4 Grand the car started to backfire like it was missing. It does this once and a while. I hate to mess with these new cars. I pulled a plug and it was a very light color almost white Running lean. I was looking and bank two spark plugs looks like I will have to take the intake manifold off to get them out? I cannot get my socket down there. Could it be the plugs, plug wires or a injector or a fuel rail? I was nervous when it did this. I am also the 5th owner. I will probably end up trading it in for a 07 GT or try to get a bullitt.
Thanks any suggetions please.

 

[Hardtop68]

Mine did that it was the fuel pump... as my car was already 135.000+ miles I replaced the whole fuel pump... of course, I had already ruled out:

- Spark plugs were OK...
- Coils were OK... check impedance (do a seach on the forums on this matter.)
- New fuel filter OK...
- Injectors just serviced were OK...
- No fault codes on the computer...

Use a long extension on your spark plug socket to get them out... no need to remove anything else to do it (the COP of course!)

 

[62thunderbird]

I pulled a code p1131 O2s no switch lean. Should I replace my O2S. I cleared it and has not come on again it has been two months since. My problem is that my manifold is covering up part of the spark plug hole and I cannot get the socket down there it won't even go through. If it was your pump was the bad one making noises. Also to throw this is my car smells like sulfer or rotton eggs I was thinking it is the cats? when the car runs lean would it make the cats smell? Should I run a fuel injector cleaner through it? Lucas fuel injector cleaner. I like that stuff because it is a non solevent and says it will not hurt the cats.

 

[Hardtop68]

The old one had no noise but it was not pumping enough gas when the tank gas below 3/4 full... also the pump suction strainer was too dirty...

Get your tank full to the top and see it the problem happens again...

Regarding the rotten smell, do a search on the forum... this issue was discused some days ago!

 

[62thunderbird]

Thanks for the help. I get what you mean about filling it up. to see when exactly it starts doing it.