1995 T/A LT1 Stalls at Idle when hot...

[95transAm]

-The car has been stalling out at idle when stopped for any duration of time over a minute or so. It happens when the outside temperature is warmer, especially when in traffic. It has been happening for over 2 years now but only in the summer months, due to the temperature. It does not stall out all the time once it gets up to temperature, because the car will get hot and not stall out sometimes so it is not DIRECTLY temperature related. The following has been done to the car and has not had any effect on the problem, in other words I have done this work and the problem is still happening….

-new fuel pump
-new fuel filter
new fuel pressure regulator
-new EGR valve
-new EGR solenoid
-new air filter
-new distributor
-new spark plugs
-new spark plug wires
-new water pump
-new drive belt

-I have had a 180 and 160 thermostat in the car, neither affects the problem

-This only happens after driving the car for like over an hour or so, usually after a long cruise at speeds over 55, if I just drive it around town for 45 minutes, it NEVER stalls out. After a long drive, the car will start to idle rough and it seems to be worse when the car is in drive but will stall out in ANY gear. I have tried to press the gas during this rough idle and the car feels like it is being bogged down by a bad air/fuel mixture or something, appears to be leaning out…It does not happen all the time, but after the car gets hot if you let it sit at idle it will eventually stall out. The car will crank after it stalls out but normally not start immediately but after 5-10 mins it will start up again and then idle smooth for a short period of time, and then it will idle rough again and stall out again, it happens a lot more often and faster once it has happened once.

I have had it on a scanner before while it was stumbling and all the readings were ok, as far as another garage was concerned. Also, I might just be going crazy but it seems like my voltage readings have dropped lately but not dramatically.

SOOOO, what's next? PCM, ICM, cat, o2, temp sensor? vac leak? ANY IDEAS?

[OverTrained]

Hows your injectors? If you got one or two clogged up with shit the engine will run like doody. You may be getting fuel into the cylinders sometimes and then other times nothing. This would cause your lean condition if your reading the plugs. Just my $.02

[red 95 lt1 z28]

if ya have someone with some spare parts, i would check the coil, icm and 02 sensors, easy to swap out, and wont cost a thing if your borrowing, i have some o2 sensors if you would want to try, what brand opti is on the car?

[Cause4panic]

do the icm cooling mod http://shbox.com/1/4th_gen_tech2.html#ICM_cooling

See if it helps before spending any more money

[95transAm]

i just put in a GM Opti like 2,000 miles ago, and I am definitely gonna investigate the ICM and try to create some space between it and the block, the GM part is only 95 bucks from GmPartsDirect and then I will probably get an MSD coil if I wind up replacing...anyone have an ICM they are lookin to sell?

[tkayrc3]

TPI's & LT1's: replace all 8 injectors first, then diagnose the problem, if it still exists which in most cases it won't.

[96WhiteZ28]

I agree with John... The LT1 and TPI injectors commonly get coil problems. TPI more so than LT1. What happens is the injectors work fine until the coil gets hot, then it starts to short out giving you intermittent injector operation. I always test LT1 injectors after cleaning for 20 minutes or so because they are nice and hot from the cleaning process and show problems that don't appear when cold.

Put in a set of Ford Blue tops instead of the factory Multecs and you'll never have to worry about it again. I have sets of either available but recommend the Fords and can get you a good deal on them so you can shoot me a PM and I'll hook you up.

[OverTrained]

Originally Posted by 96WhiteZ28

I agree with John... The LT1 and TPI injectors commonly get coil problems. TPI more so than LT1. What happens is the injectors work fine until the coil gets hot, then it starts to short out giving you intermittent injector operation. I always test LT1 injectors after cleaning for 20 minutes or so because they are nice and hot from the cleaning process and show problems that don't appear when cold.

Put in a set of Ford Blue tops instead of the factory Multecs and you'll never have to worry about it again. I have sets of either available but recommend the Fords and can get you a good deal on them so you can shoot me a PM and I'll hook you up.

Stop acting like you know a thing or two about injectors