- Dec 11, 2014
- 5
- 0
- 1
Ok, after researching the net for months, countless forums, tech help from ford, etc etc, I'm at wits end.
I have a 1997 Mustang GT, 4.6L 2V, Manual trans, 3.73 gear, Magnaflow cat-back. K&N factory replacement filter. Everything else stock.
It's developed worse over the last few years.
Here's the whole story. bought the car used about 60k miles ago. Seemed to run fine to my knowledge.
Within the last year or so, power has dropped. Acceleration mainly. Can not even get it to squeak in 1st gear with 3.73's!
Idles fine. Will idle all day long. In neutral, rev's up like any other car. Hit's top end no problem. Sounds great.
Cruising at highway speed, no problems. Cruise all day. 300 miles trip didn't skip a beat.
Accelerating, sucks. I had an 80's suburban waste me on an onramp to the interstate. My boss at the auto parts store is a retired racecar driver, says it sucks. My friends Kia Rio will waste my stang.
Upon accelerating, light touch seems better than pushing the pedal. Hammer the pedal a lil, and it bogs down, flutters, seems like it wants to go, but is being held back. Just can't break free. For example, I can ONLY get it to 3800 rpm staying in 3rd gear. There is so much knocking/pinging/rattling noise and the stang won't go past it! Shifting to 4th I can go faster, but cannot get anywhere close to redline. Now, if I drop it into 5th, she starts to chug for a couple of seconds, buck/stagger and clean up and cruise. When I'm cruising at any speed, push clutch in, push the gas, she'll rev right up to redline no problem, quick as could be. Drop her back to 4th or 5th, she misses, chugs, etc.
Dual exhaust, passenger side tailpipe black, driver side clean as when I installed it. Always had me baffled.
Driver side has a new O2 sensor upstream, due to wiring harness connector corrosion. (This had caused similar issues, but a lot worse, backfiring, could barely drive it, it had a corroded terminal)
No Check Engine lights. - However, I finally threw a code, light is NOT on, but my scantool says MIL is on. MIL lights up when you start the car, so bulb is good.
A friend of mine hooked up a professional scanner, Cyl #5 had 25k misfires in a 30 minute drive, and cyl's 6, 7 & 8 had misfires, but less than 10K.
Swapped out both ignition coils with my 98 F-150, which runs just perfect, no change in power.
I then changed my wires, after noticing in the dark the northern light. Replaced with Motorcraft. Partial increase in power.
Changed my worn Autolite double plats to Motorcraft plugs. Very slight change, however after test driving, it finally threw a PO300 code.
Swapped out MAF from my truck, no change.
Did the propane trick for vacuum leaks, did not detect any change.
On the PO300 code, freeze frame data read:
RPM 1789
87.1 Load
LTFT1 18%
STFT1 10.9%
LTFT2 -2.3%
STFT2 10.9%
55mph.
Did another test, idling vs 2500rpm
Idle
LTFT1 0.0
STFT1 Between 1 and 4%
LTFT2 -3.9%
STFT2 hovered around 1%
At 2500 rpm
LTFT1 7.8%
LTFT2 -7.8%
STFT1 and 2 stayed about the same.
PCM calibration is 6-19C. No revision printed on tag on door pillar.
No engine noises, even with stethoscope.
133,000 miles. I bought it 8 years ago with about 75k on it.
My upstream O2's switch as normal according to my scantool's live data.
Any help would be just awesome, considering most of you prolly fell asleep reading this post. This is my baby, my pride, my joy, and would like to have my 200+hp back....
I have a 1997 Mustang GT, 4.6L 2V, Manual trans, 3.73 gear, Magnaflow cat-back. K&N factory replacement filter. Everything else stock.
It's developed worse over the last few years.
Here's the whole story. bought the car used about 60k miles ago. Seemed to run fine to my knowledge.
Within the last year or so, power has dropped. Acceleration mainly. Can not even get it to squeak in 1st gear with 3.73's!
Idles fine. Will idle all day long. In neutral, rev's up like any other car. Hit's top end no problem. Sounds great.
Cruising at highway speed, no problems. Cruise all day. 300 miles trip didn't skip a beat.
Accelerating, sucks. I had an 80's suburban waste me on an onramp to the interstate. My boss at the auto parts store is a retired racecar driver, says it sucks. My friends Kia Rio will waste my stang.
Upon accelerating, light touch seems better than pushing the pedal. Hammer the pedal a lil, and it bogs down, flutters, seems like it wants to go, but is being held back. Just can't break free. For example, I can ONLY get it to 3800 rpm staying in 3rd gear. There is so much knocking/pinging/rattling noise and the stang won't go past it! Shifting to 4th I can go faster, but cannot get anywhere close to redline. Now, if I drop it into 5th, she starts to chug for a couple of seconds, buck/stagger and clean up and cruise. When I'm cruising at any speed, push clutch in, push the gas, she'll rev right up to redline no problem, quick as could be. Drop her back to 4th or 5th, she misses, chugs, etc.
Dual exhaust, passenger side tailpipe black, driver side clean as when I installed it. Always had me baffled.
Driver side has a new O2 sensor upstream, due to wiring harness connector corrosion. (This had caused similar issues, but a lot worse, backfiring, could barely drive it, it had a corroded terminal)
No Check Engine lights. - However, I finally threw a code, light is NOT on, but my scantool says MIL is on. MIL lights up when you start the car, so bulb is good.
A friend of mine hooked up a professional scanner, Cyl #5 had 25k misfires in a 30 minute drive, and cyl's 6, 7 & 8 had misfires, but less than 10K.
Swapped out both ignition coils with my 98 F-150, which runs just perfect, no change in power.
I then changed my wires, after noticing in the dark the northern light. Replaced with Motorcraft. Partial increase in power.
Changed my worn Autolite double plats to Motorcraft plugs. Very slight change, however after test driving, it finally threw a PO300 code.
Swapped out MAF from my truck, no change.
Did the propane trick for vacuum leaks, did not detect any change.
On the PO300 code, freeze frame data read:
RPM 1789
87.1 Load
LTFT1 18%
STFT1 10.9%
LTFT2 -2.3%
STFT2 10.9%
55mph.
Did another test, idling vs 2500rpm
Idle
LTFT1 0.0
STFT1 Between 1 and 4%
LTFT2 -3.9%
STFT2 hovered around 1%
At 2500 rpm
LTFT1 7.8%
LTFT2 -7.8%
STFT1 and 2 stayed about the same.
PCM calibration is 6-19C. No revision printed on tag on door pillar.
No engine noises, even with stethoscope.
133,000 miles. I bought it 8 years ago with about 75k on it.
My upstream O2's switch as normal according to my scantool's live data.
Any help would be just awesome, considering most of you prolly fell asleep reading this post. This is my baby, my pride, my joy, and would like to have my 200+hp back....