Why must you die?

[ShiftTheDrift]

Here we have a 1994 Cobra with a basic engine rundown as follows:

-Stock 302ci
-E303 Cam
-TF Heads
-MAS calibrated for 24# injectors
-JMS Custom Chip
-70mm TB

My question is this. The car idles good, doesn't hang, operates, as it should once going. However, I've noticed often that just simply turning on the A/C will kill the motor or drop significant RPMs including backing out of the driveway or especially coming to an abrupt stop.

Can anybody explain what's causing this?

I've thought that it might be an injector, fuel pump, alternator, or the AFPR. I haven't done anything about testing anything. Just looking for direction right now.

Thanks!

 

[jermy82]

Did this start after doing any of your mods, or did it occur before? If it was after a mod, which one?

 

[91LX_5L]

sounds like a voltage problem to me, check battery and or alternator. could also be a vaccume issue?

 

[ShiftTheDrift]

Did this start after doing any of your mods, or did it occur before? If it was after a mod, which one?

This seems to be a problem that has just recently developed. All modifications aside.

 

[ShiftTheDrift]

I just recently replaced the battery. The symptoms were present before doing so.

 

[belzebub2u]

shot in the dark

check to see how easy the compressor moves. im not a mechanic in the least but if your compressor is trying to freeze up it could affect it.

 

[epracmetcon]

My car does the same thing, sounds like either your ac compressor is locked up along with the clutch. My guess is that it does the same thing when your defrost is on as well too huh?

 

[ShiftTheDrift]

Not necessarily. I just added that turning on the A/C is just one of a few things that causes this problem.

UPDATE: Something I seriously forgot to mention, the voltage gauge "doesn't" always show a neutral or positive charge. In this case, it's showing a negative reading. Does this help?

voltage regulator?

 

[WhiteDevil]

Mine used to do stuff like that too. Now mine surges but only when the A/C is on. Not a bad surge. If im idling it will surge up to like 900rpm then go down and idle fine then like 10 seconds later it does it again. Only when the A/C is on. Its really wierd.

 

[krahkin]

I had replied to this earlier, and it didnt show up? Anyway, before the voltage edit, I suggested checking your idle air set-screw. Mine had closed itself due to vibration and my car kept dying exactly as you described. I had also suggested checking fuel pressure.

The low voltage will kill your idle. I had a failing altenator, and once your ignition voltages begin to drop, say bye bye to running smooth. You can check your alt and battery pretty easily with a multimeter. Hope thishelps you figure out your problems.

 

[ShiftTheDrift]

I agree. I've looked at the idle-air bypass screw and the fuel pressure. The screw seems to be right where I left it and the fuel pressure is 39psi with the vacuum off.

If I were to purchase a new voltage regulator, I assume 130 amps?

 

[ProKiller]

you have a cobra right? the cobras have 24# injectors, but mass air sensor has to be calibrated for 19#s. the computer adjusts accordingly. You said you had the mass air calibrated for 24s. that could cause a problem, don't know if that is why its dying, but regardless.

 

[ShiftTheDrift]

Oh really???

Hmm, this is a JMS custom chip and I distinctly remember the paperwork indicating the MAS was calibrated for 24# injectors. How will this make the ECC function?

 

[91LX_5L]

try cranking the wheel to the left? or is it the right? anyways try both, does your voltage drop, or rpms drop bad almost causing stall or stalling the car???

 

[EHunt]

My car wouldn't idle when I turned on the a/c and the compressor kicked on and after researching the problem I found that some people pulled off the iac valve off the side of the throttle body and cleaned the inside of it with carb cleaner. I did this and my idle problems went away. Maybe try the same thing? Hope that helps.

 

[ShiftTheDrift]

try cranking the wheel to the left? or is it the right? anyways try both, does your voltage drop, or rpms drop bad almost causing stall or stalling the car???

Yes. In fact that's one of the most annoying things of all. Got an idea?

EHunt, already tried that one. But thanks for the idea!

 

[93 teal terror]

Mine did the same thing when I bought the car. I didn't know until after I bought it. Turned out the coil just needed to be replaced. Not saying thats your problem, but it fixed mine and 4 years later its never happened again.

 

[chefster]

check ground wire connections