Power loss and gain from one minute to the next?!?!
Ok here's the thing.. I bought this 01' GT 2 weeks ago. I test drove MANY mustangs before coming back to this one. Out of all the car I drove (including 5 speed cars) this was the strongest of them all. It had way more power than the rest I drove. So, I purchased the car the dealer filled the tank up for me (it was almost completely empty). When I left the car was running fine. But about an hour later it lost a LOT of power. I mean it went for killing the tires on take off to not even been able to force them to spin. Even the engine sounded different, choked out sounding or something. Then it started running right again a little while later (full power back). I thought maybe the dealer just put cheap gas in it, but when it ran out I put good gas in it with no change. Since then it has got worse and now doesn't ever run as good as the day I bought it. The engine still runs very clean, but it sounds different and has less power. The engine light has not come on to pull any codes from. I changed the air filter, no difference. I have had all 5.0's so I don't know any tricks to these 4.6's has anyone experienced anything like this? If so what was the problem?
I was thinking cats maybe, but if they were messing up the engine light should come on right? I got off road H-pipes for it anyway to make sure. I will be installing them this weekend if the Lord wills.
Anyway, any info would be great! Thanks and God bless!
Bobby
ok you said "the dealer might have put cheap gas in it". what kind did you put in. keep in mind that car is supposed to have 87 octane. other than that i have no clue at all. how many miles are on it?
The car only has 65,000 miles on it, so if it's anything like the 5.0's it's just barely broke in at that milage. I have never had a 4.6 car before, but I have had many mustangs as well as other cars and I haven't had a car yet that ran better on 87 than it did on 93 octane gas. There's not that much difference between them really, but the 93 always seems to run better and more efficient. However I am willing to try about anything, so my next tank of gas I will run some 87 through it and see what happens. I am open to any other suggestions as well. God bless!
Bobby
Start by changing the fuel filter and testing fuel pressure. I would also inspect the plugs and change them while I was in there, check the coils as well.
recalls! always check your recalls from the dealer, make sure they have been done. coil, and or intake gasket. intermittent problems could be electrical related. pinging under hard acceleration can be a fuel issue.
vacuum loss may be a gasket issue.
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DSS 331 stroker, AFR 185 heads, Performer rpm 2 intake, Accufab 75 mm race TB, 30lb injectors, 80 mm Pro-M mass air, Extreme energy cam 266.
Anderson ford power pipe the big one, Ford motor sport shorty headers, Bassani x pipe custom cat back with flows, World class T5, center force duel friction clutch.
if your spinning tires your traction control will kick and cut your power down alot. also depending on how long you spin your tires is how long it stays on, so if your going from stop light to stop light spinning tires everytime you take off that could be your problem.
I drive the car normal. it's only on occasion that I lay into it from a dead stop. I always have the traction control OFF. It being an automatic car with stock gears won't be spinning from light to light, right now it won't spin at all. I don't try to spin the tires, I was just stating that before from a dead stop it had enough power to spin the tires and barked second gear. It's doesn't do that now. I was told to run 93 octane in these, where can I go that actually tells what is suposed to be used or what ever?
There is no pinging or anything like that, it runs very smooth and very clean, it just isn't making as much power and sounds a little different.
I so much like carb cars better than fuel injection cars, grrrr.....lol
Thanks and God bless!
Bobby
Sounds like the same thing mine did, after fuel filter, new coil packs, wires, plugs, MAFS, air cleaner, and TPS I took it to the dealer and found out it was a cracked intake.
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1997 Mustang GT- Sniper NO2, Bassani Off-road X pipe, Flowmaster Catback, C Springs, tons of other little things-
I hope it isn't that... It was actually cold here today and it ran really rough when I first started it up... Related?!?! I haven't had time to really get down and search out the problem yet, hopefully this weekend I'll have some free time. Wish me luck. God bless!
Bobby
Power loss and gain from one minute to the next?!?! 
