Just wondering. Was the car moving or stationary at the time? Are you aware that the PCM makes different decisions about idle speeds depending upon IF the car is moving or not? The PCM has two idle speeds with higher if the car is moving. The slow idle will be activated once the car comes to a complete stop.another issue i have is my idle sometimes is at 1100/1200 rpm. i tap the throttle and it kicks down to 750/800 rpm. like kicking off a choke on a carb engine. Any ideas?
Are you positive that the noise is coming from engine and not from the rear end?02 mustang gt, under acceleration i get a sssss noise. it is noticeable only under a load.
Another thought.. How did the issues present themselves, started & escalated over a time period, or just occurred suddenly one day while driving? Did you notice (1) of the (2) issues occurring before the other, or at the same time? Any DTC’s?
-John
Just wondering. Was the car moving or stationary at the time? Are you aware that the PCM makes different decisions about idle speeds depending upon IF the car is moving or not? The PCM has two idle speeds with higher if the car is moving. The slow idle will be activated once the car comes to a complete stop.
Further the speed of idle that the PCM selects also depends upon the throttle mode. Closed throttle or part throttle. Soooooooo if the TPS closed throttle signal is unstable this can cause an elevated idle.
Here's more information on how the IAC/idle works and how to trouble shoot.
Troubleshoot IAC idle problems 1996-2004
Troubleshoot IAC idle problems 1996-2004
Back to the basics. Check for blown fuses. Especially fuse F2.2 and F2.8 in the Central Junction Box (CJB 1999-2004 MY). Confirm key on power using a known good ground. 1999-2004 MY fuse panel schedule...www.stangnet.com
Are you positive that the noise is coming from engine and not from the rear end?
Just wondering. Was the car moving or stationary at the time? Are you aware that the PCM makes different decisions about idle speeds depending upon IF the car is moving or not? The PCM has two idle speeds with higher if the car is moving. The slow idle will be activated once the car comes to a complete stop.
Further the speed of idle that the PCM selects also depends upon the throttle mode. Closed throttle or part throttle. Soooooooo if the TPS closed throttle signal is unstable this can cause an elevated idle.
Here's more information on how the IAC/idle works and how to trouble shoot.
Troubleshoot IAC idle problems 1996-2004
Troubleshoot IAC idle problems 1996-2004
Back to the basics. Check for blown fuses. Especially fuse F2.2 and F2.8 in the Central Junction Box (CJB 1999-2004 MY). Confirm key on power using a known good ground. 1999-2004 MY fuse panel schedule...www.stangnet.com
Are you positive that the noise is coming from engine and not from the rear end?
Hi,
Likely a Vacuum leak in your Intake piping between the MAF sensor and the Throttle body, or within lines connected to either.
1) Check the IAC for function, leaks or wear.
2) Verify TB is tight to plenum, no sticking opening/releasing throttle by hand.
3) Check Throttle linkage for binding.
Lube.
4) Inspect and replace any damaged vacuum lines, repair less than optimal connections.
-Possible to replicate leak origin with hood open engine running by snapping the throttle open. Likely an obvious issue you’ll spot quick. Good opportunity to clean your Filter.
Good luck.
-John
Hi,I thought I found it but a road test proved me wrong. The car has a after market intake. The pcv from the driver side had a bad connection to the intake tube. I repaired it and thought it was it.
Hi, Glad to hear she’s running strong. If the air cleaner is quite dirty, it may cause the engines demand for vacuum to get pulled from an area that may not normally leak, a vacuum line, etc. Similar to a vacuum cleaner with a clogged tipThe clutch is working as it should. It cycles on for 14-17 seconds and off for 7-10 seconds, just counting in my head and not by a stopwatch. The clutch will cycle when in defrost mode or ac mode.
I was fixated on the compressor because to me it sounded like a ac compressor clutch engaging or disengaging. Every now and then I get this noise under the hood.
The motor runs great now that the iac has been replaced. The hiss noise is there under load. While giving it gas and not under load there is no hiss. The air cleaner is filthy, has to be cleaned and oiled. I did notice a different noise at the air cleaner. With the hood open and giving it gas by the intake, it changes tone at the air cleaner when coming back down to idle. . I recorded it but you cant hear it.
i cleaned the air filter and oiled it up. this made my idle off again. i drove it for a little while then disconnected the battery and drove it again and the idle is back. i disconnected the ac and the noise is still there. I will try to disconnect the fan and try that. the sound is hard to describe, ac compressor clicking on, a sudden bang, relay or valve shutting hard?Hi, Glad to hear she’s running strong. If the air cleaner is quite dirty, it may cause the engines demand for vacuum to get pulled from an area that may not normally leak, a vacuum line, etc. Similar to a vacuum cleaner with a clogged tip
These air cleaners are also vulnerable to cracks where they slide onto the tube & are clamped, also causing the same annoying “hiss”, more under load during hard acceleration. There’s a few filters out there that actually make noises as described, brand new- out of the box.SR is of these. What system are you running, ?
Any possibility it’s an electric cooling fan that’s making a cycling noise & contributing to the confusion? If you want to rule out the A/C compressor clutch isnt engaging when nof necessity, you could disconnect that electromagnetic power source connector, temporarily, see what occurs.
Good luck!
-John
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