SES with AC on

[JonJon]

Well I had that funky idle problem which I fixed by messing with the idle screw. It ran great for a few weeks until I used the AC last week.

I turned the AC to defrost the windows and my SES came back on. I'm assuming it's the same lean codes. My car started to idle all crazy again, but only when the AC was on. When it was off, it idled fine. With the AC on, my RPMs hang horribly when I shift. With the AC off, the car idles at 700 and doesn't hang on shifts.

Here's the original thread.
http://forums.stangnet.com/showthread.php?t=450426

Any ideas?

 

[cjones]

recheck the codes (may be a different prob than before) and recheck the IAC(the computer uses that to compensate for the extra load of the A/C).

 

[Red mustang Gt 46]

Have you checked the TPS to see if it's reading the correct voltage at idle? Each time you adjust the screw, the voltage should be checked at the adjusted position. To check it, turn ignition on (not running) and install volt meter probes into the ground wire and signal wire (rear of plug). At idle position, the reading should be between 0.05 to 1.0 volt. With someone else pressing the gas pedal, the reading should increase to 4.0 to 5.0 volts...if it doesn't, replace the TPS. Just a thought...

 

[JonJon]

recheck the codes (may be a different prob than before) and recheck the IAC(the computer uses that to compensate for the extra load of the A/C).

On Tuesday I'm going to go get the codes pulled again. It should be the same thing since the car idled all crazy and a few minutes later up came the SES. I'll check the IAC too. Thanks.

Have you checked the TPS to see if it's reading the correct voltage at idle? Each time you adjust the screw, the voltage should be checked at the adjusted position. To check it, turn ignition on (not running) and install volt meter probes into the ground wire and signal wire (rear of plug). At idle position, the reading should be between 0.05 to 1.0 volt. With someone else pressing the gas pedal, the reading should increase to 4.0 to 5.0 volts...if it doesn't, replace the TPS. Just a thought...

Hmm... I've never checked the TPS. No one even suggested it in my previous idle problem thread... I'll have to do that. Thanks.

Oh, I just got that TPS this spring when I got my Accufab TB...

 

[twogts4us]

Have you eliminated the possibility of the Densecharger as being part of the problem, JonJon? I'm just curious cause I'm still interested in buying one for my wife's 01 GT...but not if turns out to be the source of your issues. I remember you saying it idled fine with the OEM air tube.
Check that TPS...hopefully that is where your problem lies...I guess(?)

 

[JonJon]

Have you eliminated the possibility of the Densecharger as being part of the problem, JonJon? I'm just curious cause I'm still interested in buying one for my wife's 01 GT...but not if turns out to be the source of your issues. I remember you saying it idled fine with the OEM air tube.
Check that TPS...hopefully that is where your problem lies...I guess(?)

I haven't yet... I have finals tmw and tuesday. On Tues I'm going to try the listed techniques above and if that doesn't help, I'll try the stock pipe. I dread getting the stock pipe back on, it took my roomate and I 30 minutes to get it onto the 75mm TB. But, it'll help me find the problem real quick. I'll post back.

Oh, when I called DeMolet (Densecharger pipe makers) they said no one had ever called with such a problem. So hopefully it's something else.