00 gt idle mess up

explicitone · 03-17-2003, 05:23 AM

I (with the help of a friend) installed my mac prochamber on sat. and since it went on, the car idles funny but only with the heat on. the idle will be fine then all of a sudden it will go up to 1000 then down to 500 then be fine again for awhile some of the times it dropped so low it almost died. what could this be? I dont see how the prochamber would cause a idle problem.

stangt00 · 03-18-2003, 07:44 AM

The prochamber can have alot to do with it. No cats right? Well, the air fuel probably isnt right, and the computer is trying to compensate. Best way to fix it is to have a computer chip installed and custom tuned so they can get the air/fuel mixture right. If your planning on other mods in the near future, and you can wait, do them first then have it tuned.m Also, try resetting the computer by disconnecting the battery for about 5 mins or so, then reconnecting it. Good luck.

explicitone · 03-18-2003, 08:24 AM

I see your point but what I dont under stand is why only when the heat is on and after driving it for a few days it seems like its only when the defroster is on

blue00gt · 03-18-2003, 12:20 PM

Does it only do it with the defrost on or the heater, too? My car had the same problem - idle was erratic with the defroster on and would alternate between 500 and 1000 or so. The defroster uses the A/C to dehumidify the air and it turned out on mine that the A/C was low on refrigerant so the compressor kept kicking on and off and causing the idle to change. Mine was low enough that I could tell myself by turning the A/C on high and feeling that it wasn't blowing very cold.

Red Mustang Gt 46 · 03-19-2003, 08:39 AM

When your a/c compressor kicks on, the EEC compensates by raising the idle (because of the load imposed by the compressor). If this is what your talking about...

stangt00 · 03-19-2003, 09:18 AM

As I said, the ECC is already trying to compensate for the enriched fuel/air mixture that the prochamber created. When you trun on the defroster it has to increase the idle, and does this by adding fuel to the mixture whenever the compressor kicks on, thus making the fuel/air even worse. Then it has to compensate by leaning it out, but then its not idling right so it enriches it but then its too rich so it leans but then it's not idling right etc... Get the point? You have to have the fuel/air at idle corrected so when you turn on the defroster, it will raise the idle properly and maintain a decent fuel/air ratio.

blue00gt · 03-19-2003, 12:36 PM

I don't believe that the Prochamber could change the air/fuel ratio apppreciably. The freed up exhaust just allows the motor to pump air and fuel through at a higher rate - this extra air coming in is measured by the mass air meter, so there should be no problem there. Even without cats the mil eliminators should be feeding the right voltage to the sensors, and the O2 sensors are only responsible for fine-tuning the mixture and indicating problems and should not be able to have that drastic of an effect on idle speed even with no cats and no mil eliminators. Also, if the computer were hunting and causing the problem, the cycle time of the problem he describes would be alot faster.
If the problem coincides with the A/C compressor coming on with the defroster you should be able to hear a loud click when it turns on and the idle speed drops. Getting the refrigerant refilled on my GT fixed the problem without doing anything else. I'm just saying to look into it because I had the exact same problem and that's what it turned out to be with my car, silly as it sounds. I don't know why having low refrigerant would make the idle change when it kicks in any more noticeable that when the system is filled - maybe it was just that it kept coming on and off alot more often.

stangt00 · 03-19-2003, 03:05 PM

You sure about that? When I put mine on, my air/fuel was way screwed up. You could smell it in the exhaust. After my chip was reburned, it was much better. Now that I think about it, I had almost the same problem when I turned of my defroster. Not as rough, but erratic none the less and it went away after the tune. Since I have a Prochamber, and have had it tuned, I think I have grounds for what I am saying. Wanna check? put an air/fuel gauge on it and see how far off it is.

03-17-2003, 05:23 AM	#1
explicitone Registered Member Join Date: Apr 2002 Location: racine ,wi Posts: 691	00 gt idle mess up I (with the help of a friend) installed my mac prochamber on sat. and since it went on, the car idles funny but only with the heat on. the idle will be fine then all of a sudden it will go up to 1000 then down to 500 then be fine again for awhile some of the times it dropped so low it almost died. what could this be? I dont see how the prochamber would cause a idle problem. __________________ RUN IT STAIGHT AND RUN IT HARD ________ Novi 2000 60' 1.46 1/4 10.67 mph 126.5 _________

03-18-2003, 07:44 AM	#2
stangt00 Registered Member Join Date: Dec 2002 Location: Philadelphia PA Posts: 143	The prochamber can have alot to do with it. No cats right? Well, the air fuel probably isnt right, and the computer is trying to compensate. Best way to fix it is to have a computer chip installed and custom tuned so they can get the air/fuel mixture right. If your planning on other mods in the near future, and you can wait, do them first then have it tuned.m Also, try resetting the computer by disconnecting the battery for about 5 mins or so, then reconnecting it. Good luck. __________________ 2000 GT 80mm Pro-M mass air, 24lb injectors, 75mm BBK T/B, K&N Filter Cold Air, 1/2" Phenolic intake spacer, Underdrive Pulleys, Dyno Tuned Autologic Chip, FMS Shorty Headers, Mac Prochamber 2 1/2" Off Road H pipe, 2 Chamber Flowmasters, Steeda lowering springs. Steeda Tri-Ax Short Throw shifter, Steeda Power slot rotors w/ Hawk Pro pads, 3.73 FRP Gears. Headwork and Comp cams install in progress.

03-18-2003, 08:24 AM	#3
explicitone Registered Member Join Date: Apr 2002 Location: racine ,wi Posts: 691	I see your point but what I dont under stand is why only when the heat is on and after driving it for a few days it seems like its only when the defroster is on __________________ RUN IT STAIGHT AND RUN IT HARD ________ Novi 2000 60' 1.46 1/4 10.67 mph 126.5 _________

03-18-2003, 12:20 PM	#4
blue00gt Mustang Addict Join Date: Jan 2001 Location: McKinney, TX Posts: 1,294	Does it only do it with the defrost on or the heater, too? My car had the same problem - idle was erratic with the defroster on and would alternate between 500 and 1000 or so. The defroster uses the A/C to dehumidify the air and it turned out on mine that the A/C was low on refrigerant so the compressor kept kicking on and off and causing the idle to change. Mine was low enough that I could tell myself by turning the A/C on high and feeling that it wasn't blowing very cold. __________________ Strike down the unroadworthy! 2000 GT Atl. Blue: '03 Cobra motor - 465rwhp/473rwtq, T-56 6-speed, full MM TA/PH & tubular K-member suspension, Saleen body, 17" Torq-Thrust II's, M/T ET Street radials, and lots more '94 Rio Red Cobra: All the bolt-ons, 3.73s

03-19-2003, 08:39 AM	#5
Red Mustang Gt 46 13.3 @ 103 Join Date: May 2001 Location: Maryland Posts: 253	When your a/c compressor kicks on, the EEC compensates by raising the idle (because of the load imposed by the compressor). If this is what your talking about... __________________ Equipment by: Steeda C&L COMP CAMS FRPP MSD Bassani Magnaflow MAC

03-19-2003, 09:18 AM	#6
stangt00 Registered Member Join Date: Dec 2002 Location: Philadelphia PA Posts: 143	As I said, the ECC is already trying to compensate for the enriched fuel/air mixture that the prochamber created. When you trun on the defroster it has to increase the idle, and does this by adding fuel to the mixture whenever the compressor kicks on, thus making the fuel/air even worse. Then it has to compensate by leaning it out, but then its not idling right so it enriches it but then its too rich so it leans but then it's not idling right etc... Get the point? You have to have the fuel/air at idle corrected so when you turn on the defroster, it will raise the idle properly and maintain a decent fuel/air ratio. __________________ 2000 GT 80mm Pro-M mass air, 24lb injectors, 75mm BBK T/B, K&N Filter Cold Air, 1/2" Phenolic intake spacer, Underdrive Pulleys, Dyno Tuned Autologic Chip, FMS Shorty Headers, Mac Prochamber 2 1/2" Off Road H pipe, 2 Chamber Flowmasters, Steeda lowering springs. Steeda Tri-Ax Short Throw shifter, Steeda Power slot rotors w/ Hawk Pro pads, 3.73 FRP Gears. Headwork and Comp cams install in progress.

03-19-2003, 12:36 PM	#7
blue00gt Mustang Addict Join Date: Jan 2001 Location: McKinney, TX Posts: 1,294	I don't believe that the Prochamber could change the air/fuel ratio apppreciably. The freed up exhaust just allows the motor to pump air and fuel through at a higher rate - this extra air coming in is measured by the mass air meter, so there should be no problem there. Even without cats the mil eliminators should be feeding the right voltage to the sensors, and the O2 sensors are only responsible for fine-tuning the mixture and indicating problems and should not be able to have that drastic of an effect on idle speed even with no cats and no mil eliminators. Also, if the computer were hunting and causing the problem, the cycle time of the problem he describes would be alot faster. If the problem coincides with the A/C compressor coming on with the defroster you should be able to hear a loud click when it turns on and the idle speed drops. Getting the refrigerant refilled on my GT fixed the problem without doing anything else. I'm just saying to look into it because I had the exact same problem and that's what it turned out to be with my car, silly as it sounds. I don't know why having low refrigerant would make the idle change when it kicks in any more noticeable that when the system is filled - maybe it was just that it kept coming on and off alot more often. __________________ Strike down the unroadworthy! 2000 GT Atl. Blue: '03 Cobra motor - 465rwhp/473rwtq, T-56 6-speed, full MM TA/PH & tubular K-member suspension, Saleen body, 17" Torq-Thrust II's, M/T ET Street radials, and lots more '94 Rio Red Cobra: All the bolt-ons, 3.73s Last edited by blue00gt; 03-19-2003 at 12:43 PM..

03-19-2003, 03:05 PM	#8
stangt00 Registered Member Join Date: Dec 2002 Location: Philadelphia PA Posts: 143	You sure about that? When I put mine on, my air/fuel was way screwed up. You could smell it in the exhaust. After my chip was reburned, it was much better. Now that I think about it, I had almost the same problem when I turned of my defroster. Not as rough, but erratic none the less and it went away after the tune. Since I have a Prochamber, and have had it tuned, I think I have grounds for what I am saying. Wanna check? put an air/fuel gauge on it and see how far off it is. __________________ 2000 GT 80mm Pro-M mass air, 24lb injectors, 75mm BBK T/B, K&N Filter Cold Air, 1/2" Phenolic intake spacer, Underdrive Pulleys, Dyno Tuned Autologic Chip, FMS Shorty Headers, Mac Prochamber 2 1/2" Off Road H pipe, 2 Chamber Flowmasters, Steeda lowering springs. Steeda Tri-Ax Short Throw shifter, Steeda Power slot rotors w/ Hawk Pro pads, 3.73 FRP Gears. Headwork and Comp cams install in progress.

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