My 4.6 pony needs SERIOUS help! - Mustang Evolution

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Old 04-18-2010, 03:13 PM   #1
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Unhappy My 4.6 pony needs SERIOUS help!

Hello all, I stop in from time to time looking for answers to my problems but I need to ask everyone for some input on this.

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!!!!
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Old 04-18-2010, 04:39 PM   #2
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Re: My 4.6 pony needs SERIOUS help!

What exactly does it feel like when you are taking off?
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Old 04-18-2010, 04:52 PM   #3
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Re: My 4.6 pony needs SERIOUS help!

It stutters really really bad and if I dont take my foot off the gas and lay into very slow and smooth, it will keep stuttering then give about 2-4 backfires through the tailpipe.
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Old 04-18-2010, 06:15 PM   #4
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Re: My 4.6 pony needs SERIOUS help!

Have you had the fuel rail pressure sensor checked? Anything over 1/4 throttle with this blown will lead to the same issues you are describing.
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Old 04-18-2010, 06:27 PM   #5
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Re: My 4.6 pony needs SERIOUS help!

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Have you had the fuel rail pressure sensor checked? Anything over 1/4 throttle with this blown will lead to the same issues you are describing.
I have not had this checked. I can lay off the gas when its acting up and apply smooth acceleration to get it straightened out sometimes, but if it were fuel starved, it would make sense the way it runs. I'm going to go look under the hood but can anyone point me in the proper direction?
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Old 04-20-2010, 02:03 PM   #6
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Re: My 4.6 pony needs SERIOUS help!

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 (and love the sound of my uncatted Violator exhaust)
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Old 04-22-2010, 10:25 AM   #7
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Re: My 4.6 pony needs SERIOUS help!

I could be wrong but my dads F-150 was having that problem last year and the problem was the throttle body was clogged up a little. We cleaned it out and it has run right since then. Ive never heard it with a mustang so Im not sure. Hope it helps
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Old 04-22-2010, 10:50 AM   #8
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Re: My 4.6 pony needs SERIOUS help!

Thanks for thw reply. I pulled the throttle body and plenum last year and cleaned them pretty good but that didnt change anything.

This weekend i will be changing a few parts and inspecting the ignition thoroughly just to make sure thos 2 years old wires arent shorting
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Old 04-22-2010, 11:02 AM   #9
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Re: My 4.6 pony needs SERIOUS help!

i had the same somewhat of the same issue in my 04 v6 a while back and i had two of my spark plug wires that had fallen loose and got burned...

good luck!
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Old 04-23-2010, 11:06 PM   #10
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Re: My 4.6 pony needs SERIOUS help!

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....
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Old 04-23-2010, 11:46 PM   #11
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Re: My 4.6 pony needs SERIOUS help!

Trans shudder can be caused by engine performance issues

Something's not right with yours, and even moreso that it's not tripping codes for it..

Try unplugging the MAF, starting the car and see if the car runs (you can't floor it, it'll stall) but driving around easily if the MAF is an issue, it'll run quite smooothly
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Old 04-24-2010, 12:12 AM   #12
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Re: My 4.6 pony needs SERIOUS help!

Unplug the MAF and take it for a short cruise around the block?
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Old 04-24-2010, 01:03 AM   #13
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Re: My 4.6 pony needs SERIOUS help!

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Unplug the MAF and take it for a short cruise around the block?
Precisely.. With the MAF unplugged the car will run based off of other signals but it will run, if the MAF is messed up (causing your issues) this will bypass that.. You won't have any guts as you're not metering air but if the car runs smooth you might have found your culprit

And again you'd be surprised what a poorly functioning engine will do to transmission feel..
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Old 04-25-2010, 04:52 PM   #14
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Re: My 4.6 pony needs SERIOUS help!

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 instinctively feather 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 their input!!
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Old 05-24-2010, 09:18 PM   #15
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Question Re: My 4.6 pony needs SERIOUS help!

Quote:
Originally Posted by MonteCitan View Post
Precisely.. With the MAF unplugged the car will run based off of other signals but it will run, if the MAF is messed up (causing your issues) this will bypass that.. You won't have any guts as you're not metering air but if the car runs smooth you might have found your culprit

And again you'd be surprised what a poorly functioning engine will do to transmission feel..
I disconnected the MAF sensor on my 02 Mustang GT and it runs the same with or without it. is it messed up
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Old 05-24-2010, 11:06 PM   #16
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Re: My 4.6 pony needs SERIOUS help!

I was actually going to post tonight because its running pretty good finally. After my last "success" post, the same old problem cropped up and actually got worse. Last weekend I swapped the 2 coils to opposite sides of the engine, went through the firing order, inspected the wires, pulled the plenum off cleaned it again and removed the plenum spacer, re-cleaned the MAF, and put it all back together. Boy was it running like crap all week. So Wednesday night, as it backfired and choked, I laid into it and lo and behold I FINALLY got an engine code. It was P1443 (evap emissions device as usual) and cylinder 1 misfire. I bought some slick 50 fuel system cleaner, dielectric grease, anti seize compound and Seafoam. Last night I pulled the #1 plug and looked it over. Besides the gap looking big, the plug was clean. I put it back together and put some DE grease on the injector plug and bent the terminals a little bit to get a positive connection then proceeded to Seafoam her for 30 minutes. When I took it out for a test drive to blow out the Seafoam, HOLY CRAP!! I dont EVER remember it running this good. Today I was able to pull the tires loose on dry pavement and drive without a hitch. There is still a little slippage in the tranny but the engine pulls it up out of the slippage zone quickly and easily and feels like a new car.

Was is the reseating of the plug wire and injector harness or did the Seafoam work the injector clean? I am at a loss as to what fixed it, but right now I have a whole shopping cart of parts at latemodelrestoration.com that I wont feel bad about blowing my bonus on if it continues to run this good, including a NEW set of injectors.

Even with the full Violator no cat exhaust, it idles much quieter and smoother now. It used to sound reminiscent of a mildly cammed car at idle (which was sex to the ears with O/R X and Violator mufflers) but now it purrs soft and ultra stable. I do need to tune out some of the mid/top end noise because its just TOO freakin loud, but for now, I'm going to driver her and love her all over again.
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Old 05-25-2010, 06:10 AM   #17
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Re: My 4.6 pony needs SERIOUS help!

Good news!
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Old 05-25-2010, 11:42 AM   #18
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Re: My 4.6 pony needs SERIOUS help!

Awesome! Glad you got it figured out.
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