1997 Ford Mustang My Engine stutters right around 4000 RPM

Tiny
HUSKERS75
  • MEMBER
  • 1997 FORD MUSTANG
  • V8
  • 2WD
  • MANUAL
  • 129,000 MILES
I have a 1997 Ford Mustang GT. I have a problem that has been bugging me for a long time. It doesn't have the power that it used too. When I accelerate I have most of my power until about 4000 RPM then it stutters badly and the RPMS rise very slowly. Or if I'm in high gear at low RPMS. If I press my foot down on the accelerator there will be a really bad stutter and sometimes a pop that sounds like its coming out of the intake. I'm not throwing any codes either. I have brand new spark plug wires, just got a new fuel filter a while ago also.
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Sunday, October 18th, 2009 AT 11:29 AM

7 Replies

Tiny
RACEFAN966
  • EXPERT
Ok so tell me what all have you replaced? What have you checked? Do you have a digital multi meter is we need it? Is there any performance mods? Get back to me with as much info as you can and we will go from there.
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Tuesday, October 20th, 2009 AT 10:34 AM
Tiny
HUSKERS75
  • MEMBER
Let's see I've put in new spark plugs, new spark plug wires, new fuel filter. I have a K&N Cold Air Intake, Steeda Underdrive pulleys, Accufab Throttle Body, Accel Coil Packs. I just cleaned my M.A.F. I'm starting to think that I'm running lean. I just checked my spark plugs and the tips of all of them were white.
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Tuesday, October 20th, 2009 AT 5:53 PM
Tiny
RACEFAN966
  • EXPERT
Ok I would like to test the TPS. To do that you will need a paper clip and a digital multi meter. Now at the tps you will need to use the paper clip to back probe the gray wire with the white stripe. Now hook up you meter set it on volts. Now turn the key on engine off and check voltage should be around.8 volts. Now slowly open the throttle the voltage should increase as you open it, it should increase with no drops or glitches and should read about 4.5 volts at wide open throttle. Get back to me with what you find. We will see what to check next. I would like to know if this does this all the time or does it seem to do this more when the engine is cooler or warmer? Did this start after any of the power adders? If not then when did it start? What spark plugs did you install? I have done a few bolt ons with my 98 and have more to do as money permits. Anyway get back to me and we will see what to do next.
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Wednesday, October 21st, 2009 AT 10:17 AM
Tiny
HUSKERS75
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I will try this today. Nope it didn't happen after any of the power adders. It did it a long time after the power adders. It started doing it about a year ago. It gets worse as the car warms up. Like if I take my car out on the highway right after I started it up on a cool morning I will have almost all my power.
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Wednesday, October 21st, 2009 AT 11:05 AM
Tiny
RACEFAN966
  • EXPERT
Ok I would also like you to check the air charge temp sensor and the coolant temp sensor. Just simply unplug them with key off engine off and ohm them. Do this when it is cold and give me the ohm's and the temp at the time you check it. Now if you have a way to read the engine temp then do the coolant temp sensor when it is warmed up too and give me ohms and engine temp with that test.
Here is a pic of the temp sensor it should be near or on the thermostat. The air charge temp sensor looks very simular except it is either in the intake tube or on the intake manifold.


http://www.2carpros.com/forum/automotive_pictures/249564_101777_1.jpg

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Thursday, October 22nd, 2009 AT 9:51 AM
Tiny
HUSKERS75
  • MEMBER
Ok try and figure this one out. I borrowed a SCT SF3 / XCal3 Power Flash Mustang Tuner. I did a 91 octane tune and to my amazement the stutter was completely gone! I had pretty much all my power. However there is still a slight stutter above 5000 RPMs but its nothing like what it was. Also its strange but now it seems to run worse when its cold. It will idle rough. But when its warmed up it idles smooth and doesnt stutter at all with the tune I did. What could the tuner of fixed?
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Saturday, October 24th, 2009 AT 1:36 AM
Tiny
RACEFAN966
  • EXPERT
Ok as I have asked check the coolant temp sensor and the air charge temp sensor. Get me the ohms of those sensors and the temp at the time you tested them. Do this when the engine is cold and give the air temp at the time you checked them.
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Saturday, October 24th, 2009 AT 9:00 AM

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