My 4.6 pony needs SERIOUS help!

[VadenKwinn]

Too much time, money and effort wasted on my 96 stang. I have worked my rear off on this thing but its still terrible and I need help.

1996 4.6 Mustang GT w/ Auto (yuck)
112000 miles

Ok, here goes!! I bought it used with 48k on the clock and for the first year it ran great, but there was ALWAYS a little stumble off the line. In the last 2 years I have replaced the plugs, wires, coils and 1 bad injector but nothing ever cleared up the issue. Last summer it started running BAD. Backfires through the exhaust when I lay on it (anything over 1/3 throttle) and jerks like an SOB. I bought some refurb injectors on Ebay and installed them one night only to have it dump tons of fuel into the exhaust so I swapped in the originals again and got it running the way it was before. I had to, at that point replace the TPS because it was dieing at idle. TPS went in, I measured the voltages on it and they are dead on. I also installed an AM CAI and 1" plenum spacer along with a complete front to back Pypes Violator system. None of this helped with power or clearing up the backfiring and hesitation.

This morning I replaced the MIL Eliminators because one came loose and laid on the X pipe, melting it in half. I took it for a spin, some street and some highway and the MIL stayed off (YAY!! apparently last year AM sold a bad batch of MIL Eliminators and I got one ) but it still backfires and chokes/hesitates and has no power. I'm at least another 2 years out from a new car and really REALLY need help getting this thing running decently. Right now, I drive 4 miles each way to work so fuel mileage isnt a huge issue but if I have to drive farther it absolutely sucks gas like crazy.

To summarize...2 new coils, new wires, 3rd set of plugs, new TPS, fuel filter, MIL Eliminators, CAI, Pypes Violator full exhaust system, 1 inch plenum spacer (plenum to intake, not TB)

I am at a total loss. I dont want to blow my whole bonus check this year on this damned car, but if I could get it running RIGHT, I wouldn't mind as much.

HELP!!!!:disgust:

 

[SteveR]

Are the injectors in the car what the tune is set for?

 

[oxfordgt]

Have you checked your regulator? Data log the fuel pressure.

 

[VadenKwinn]

They are the factory injectors, the refurbs I purchased were orange hats like the current ones but the "slimmer" design. I got a refund on those since they clearly didnt work.

For datalogging the FP, what ridiculously expensive equipment would I need?

The more I've been reading and checking online, it sounds like this may be a problem with the regulator or FP sensor, but replacing them "just to see" is a fairly expensive deal in itself, though its quickly becoming my last hope.

 

[Midnight2V]

Swap a stock ECM with the same 4 digit alphanumeric code. A lot ECM failures start with these exact symptoms.

 

[wmburns]

Any DTC codes? Have you checked ALL of the fuses? Frequently buring through the O2 sensor leads will short out the O2 heaters thus blowing the fuse and affecting the O2 sensors as will as any other sensor on the same circuit.

For backfire the 1st thing to check is ignition. Next check timing. If you sure that the ignition is in tip top shape, consider checking the CAM sensor.

Clean the MAF. Use cleaner designed for this.

 

[VadenKwinn]

After replacing the MIL eliminators, I havent had a CEL since. I do expect it to come on in the next few days though, I have had the intermittent P0442 (or something like that) for evaporative emissions control thats very sporadic. My problems still remain though it run starts and idles a bit smoother, there is still the serious bogging andjerking under throttle unless i take my foot off the gas and lay in slow and smooth. Im going to replace the fuel pressure regulator and cam sensor this weekend and see how it goes, they are both relatively cheap and I am getting desparate to have my pony running for the summer relatively cheap (and love the sound of my uncatted Violator exhaust)

 

[mrmhrm9598]

Cab someone tell me exactly what a MIL is? Sorry to jump in on the post.

 

[VadenKwinn]

MIL stands for Malfunction Indicator Light, also known as a CEL or check engine light, ALSO known as "that stupid ******* orange light that wont go out!!!"

 

[VadenKwinn]

Well, shes nothing if not consistent. Threw a code on the way home last night, so I took it to autozone and got the computer read and it was the P0442 (or something like that lol) for the evaporative emissions control. I have seen this online numerous times and no one has ever narrowed down what part is bad or what can be done to fix it. Its the sort of thing that I can clear and it wont come back for a week or two sometimes, and sometimes clears itself a few days after tripping, and rarely if ever trips when the weather goes down to 40F or below. I know I have a bad filler neck grommet (cant fill it up to 1/2 without leaking bad). Since the MIL Eliminators it does start and run a lot better but I still cant mash the pedal.

Now, heres the real question...
My tranny has been bad for years now, it shudders when switching gears, usually 1-2 or 2-3 unless i'm standing on the throttle. Could the tranny be bogging the engine down so bad at times that its causing misfires and apparent lack of power?? I can definitely tell the difference between bad shift and engine stuttering/backfiring and a lot of times they coincide with each other (more noticable now that I got the computer happy with the MIL eliminators) I has the VSS changed about 6 years ago and the tranny hasn't been right since. Like I said, if I were to get my bonus and had to blow it on my car, I wouldn't mind if I actually got it running good again. With the tranny and engine all working off of the computer that counts on proper signals from both to keep it all running fine, I've been wondering if the trans may be the root cause.....

 

[wmburns]

Sooo you don't think the leaky filler neck grommet has something to do with the EVAP DTC code?

If there is a leak large enough for gas to run on the ground, the tank is not air tight. The EVAP DTC code is basically saying the gas tank not air tight.

 

[VadenKwinn]

Im not doubting thats that the problem, im in the hopefull optimism stage. Its on my list of summer repairs, but I dont want to put my hopes on it only to be let down if it doesnt fix it. This pony has given me a lot of that lately. I would gladly put up with that though if I could get it running right.

 

[Midnight2V]

Your grommet being damaged is not going to cause these problems. Its either a misfire due to spark loss or an ignition timing problem, and since you have already changed your plugs, plug wires and coil packs that eliminates the misfire as being a result of lack of spark leaving you only with improper ignition timing. Three things control the ignition timing....your crank trigger, crank sensor, and your ecm. Since your crank trigger is just a piece of metal on your crank, and your cars does in fact run, you can pretty much rule it out. Since your car does in fact run, the sensor (a magnet more or less) is operating correctly unless the bracket it is mounted in has come loose and it has shifted, so check that, it shouldn't move. After that, its all ECM. I had this exact same problem in my 96, I tried all the same stuff you have as well. In fact, I probably had the same 4 digit code on my ECM as well. This is a KNOWN problem. Swap the ECM.

Also, just FYI, the VSS would not affect the functioning of your tranny, unless whoever changed the VSS also changed the tranny at the same time and forgot to tell you (OOPS!). In other words they stole your tranny and gave you a trashed one in its place. Yes, it does happen.

 

[VadenKwinn]

OK, update we all (at least me!) have been waiting for. I swapped out the cam sensor and fuel pressure regulator today. The regulator didnt leak from the nipple but the vacuum line had a strong raw gas smell coming from it. I reset the computer, buttoned her up and hit the road. She started a little better and drove pretty good. I put some fresh gas in and hit the expressway and opened it up only to find that I still had some flat spots, but there was a huge difference. I can feel every little slip of the tranny and feather the throttle around the flat spots.

So I get it home and pull in the garage, pop the hood and check for leaks. WTF!! I LEFT THE REGULATOR VACUUM HOSE OFF!!! Dumbass....

Needless to say I slid it back on, reset the computer again and hit the road. WOW what a difference!!Smooth, flat, hard pulling, with a SMOOTH idle and MUCH better tip in from idle. Now I can feel EVERy little jerk or skip the tranny puts out. All of the flat spots that I insitcively fleather the throttle to avoid (I'm so used to because I've been driving it like that for so long) are gone gone gone!! I hit 90MPH before I even knew it, I cant even remember the last time that it ran this good. The CAI and Violator exhaust really make a big difference now. So when the new regulator had no vacuum supply, it ran pretty much like it did before changing it and once it was reconnected it ran great. I'm banking on the fact that that was the issue. When listening to it from the rear at idle, its so much smoother and doesn't have the little "pops" and stutters that it had before.

After all this, one problem did crop up though, its one that I havent had in at least 2 years. No traction in the rain and fishtailing off the line. I guess its just something I'll have to live with...

Thanks to everyone for there input!!