Sluggish/backfiring only when warmed up? Need help quick!

[95_5.0_stang]

Well, I've been having these rich/lean problems for awhile now. The car seems to run good for the first minute or so after starting it up when cold. I pulled the codes and got both banks running rich and lean. So I replaced 02 sensors. That fixed it for a day and a half, and then all of a sudden I am driving and it starts bogging down and back firing and it's barely drivable home.

I pulled codes again and it's saying right side is running lean. I've talked to sorscode (Danny) on the phone for a long time about this problem, and we can't seem to find a solution. Brand new plugs, wires, o2 sensors, 40 psi fuel pressure, 10 degrees timing on 87 octane, vacuum is 18 pounds nice and steady. I pulled the spout and set timing to 30 degrees. It runs better then before, but still very sluggish and back fires once in awhile. Any suggestions at all? I'm trying to get the car running good before prom tommorrow, so help as soon as possible is appreciated. Thanks a lot!

BTW, I have a small exhaust leak on right side between header/h-pipe. This wouldn't happen to cause the problem would it? I pulled 02 sensors and they have a small amount of carbon/exhaust on them but look normal.

 

[red95gtconvert]

I just fixed a problem very similar to yours about an hour ago, ended up being the gasket between the upper and lower intake. Get a can of starting fluid and spray around all the gaskets and vacuum lines and listen for a change in RPM. It's worth a shot. Good luck.

 

[95_5.0_stang]

I just fixed a problem very similar to yours about an hour ago, ended up being the gasket between the upper and lower intake. Get a can of starting fluid and spray around all the gaskets and vacuum lines and listen for a change in RPM. It's worth a shot. Good luck.

Yea, I've went through hell and back with the upper to lower intake gasket. I finally got it so I don't have a vacuum leak. Or so I don't think, I'll give that a shot in the morning though. Thanks, any other suggestions?

 

[red95gtconvert]

Starting fluid is a very helpful diagnostic tool

 

[95_5.0_stang]

Starting fluid is a very helpful diagnostic tool

Indeed....

 

[red95gtconvert]

Oh yeah I forgot, have you tried cleaning you mass air meter. Remove the meter from the air cleaner housing and unscrew the torx screws, pull the meter out from the housing and using alcohol and a q-tip very carefully clean the wires and the diodes. Put everything back together in reverse of disassembly.

 

[95_5.0_stang]

Oh yeah I forgot, have you tried cleaning you mass air meter. Remove the meter from the air cleaner housing and unscrew the torx screws, pull the meter out from the housing and using alcohol and a q-tip very carefully clean the wires and the diodes. Put everything back together in reverse of disassembly.

Oh yea, that was one of the first things on the list. We've, thought of just about everything.

 

[MI95Cobra]

whats your timing at??? have you adjusted your throttle??? do you have a fuel pressure regulator????

 

[95_5.0_stang]

whats your timing at??? have you adjusted your throttle??? do you have a fuel pressure regulator????

10 degrees timing. Adjusted throttle? As in idle? Yes, I have a fuel pressure regulator, it's at around 40 psi with vacuum unplugged.

 

[1TallMF]

Couple things I'd try-out (if you haven't yet):

1. Check the TPS voltage throughout the throttle opening range, making sure there are no spikes or dead spots in the signal voltage.

2. Run a cylinder balance test using a code scanner, might give a pointer as to whether or not a particular cylinder is to blame.

3. Test the resistance on the primary and secondary circuits on the coil when it is hot.

4. Douce the PIP with electronic contact cleaner, sometimes they can get crap built-up on them and get a slightly messed-up signal.

5. Unplug MAF while the car is running and see if anything changes or kills it. If it keeps running more or less the same, its probably the problem.

6. Check the resistance accross the terminals on the ECT when the engine is cold and when it is hot.

As a last resort, rent a limo for the prom.