2.3L stall after idle

1995 2.3L DOHC 115,000 miles, motor rebuilt at 103,000 miles ...

here's whats going on, drive the car from point A to point B no problems ... drive the car from point A to point B let idle for more then 10 mins and it starts to miss, then dies. If you start it right away it will miss like crazy then die, If you let it cool down (1+ hrs summer, 40 mins in winter) it will start up & run like new.

Parts that have been replace are as follows
crank, pistons, 1 rod, engine bearings, water pump, timing chain, oil pump, balance shaft bearings, exhaust & cat, crank position sensor, head (rebuillt), fuel pressure regulator, oil pressure sensor, thermostat.

here is what I know, after the rebuild it wasn't running right ... cam was one tooth off (fixed this), the car just doesn't seem to be running to its full potential (it runs ok, just not as strong as it should be), it has spark on all 4 cylinders ... during the summer when it died on me I tried swaping (coils, coil housing, & ignition control module) (I had the spare assembly with me at the time, didn't make a difference). While sitting there the temp doens't get over 200 degree (so its not like its overheating). The only explanation I can give is its like the car is loading up with fuel (thats my guess). Where would you start? Injectors? O2 sensor? Is it possible one of the injectors is stuck open? can the injectors be cleaned & where & how much?

thanks in advance ... this has been driving me nuts ... im either going to fix it or the car is going up in flames! (and I don't mean to collect insurance money, just for the pure joy of seeing this thing die!)

Well sounds like something electrical shorting when it gets warmed up.

Since you have replaced alot of stuff already, I would start by testing you cam position sensor when you get the miss.

After the rebuild did you replace any of the ignition components ?
This is usually the culprit of a mysterious miss though it could be many things.

So I'd start with those two and then start on the fuel system/injectors.
Thier are places that can clean them, but this doesnt always help then you wasted you money. Testing them with an ohm meter is a good way to see how they are pulsing. If you have acess to a nice scann tool these too can tell you at what % they are or arent working.

Well sounds like something electrical shorting when it gets warmed up.

I would start by testing you cam position sensor when you get the miss.

After the rebuild did you replace any of the ignition components ?

cam position sensor? you mean crank position sensor? there is no cam position sensor on the 2.3L quad4's. If your talking crank position sensor thats kinda hard to get to when everything is warm.

"ignition components" you mean coils, coil housing, & ignition control module? second to last time I had a failure I swapped all three (had one I knew was good in the trunk & just enough tools to change it), results were nothing changed it still wouldn't fire ... I thought maybe the ignition control module was getting hot causing problems ... not the case since the cold one from the trunk didn't change anything.

if your talking ignition as in "keyed ignition" in the steering column ... the answer would be no ... could this really be the problem ... seems to only happen when the motor gets hot (200 +), yes the fan works at 220 or 230 can't remember ...

all injectors tested very close to the same ohms at the time of the rebuild, how do you test them to read the pulses?

scan tool, I have to pull alot of strings to get one of them, since its pre 97 (its a 95) its the old OB1 scan tool, autozone can't scan it, and my mechanic buddy is pretty busy. maybe i'll have to break down & pay for a scan ...

on a side note ... even during the summer with the hood open I couldn't get it to heat up enough to miss, 5 mins with the hood down & it did ... maybe the solution is put vents in the hood like they used to on the 60's & 70's cars! I'm not above cutting up this car!

I did mean Cam but forgot the 2.3 didnt have one.
You can test the Crank sensor from the wire harness but you replaced that so I wouldnt think it would be bad already.

I did mean coils & ingnition Module. Since you just had it laying in the trunk either one or both could be bad.

On testing injectors pulse requires some special tool(s).
Try this link (http://www.asashop.org/autoinc/dec2000/mech.htm), it explains testing in more details. And here is another link (http://www.factorypro.com/services/injector_clean_match.html)that discusses pulse testing.

Since it is heat related I'd check the wire casings on your ignition module and the injector wires. Sometimes they get breaks in the casings or the wires break inside the wire case and as it heats they seperate and then when it cools the make contact. And the plug-in connectors on these components.

I was not realy talking about an autozone scann tool, thiers are crapy, and dont usually read all codes.
I was speaking more on the line of something like AutoTap or a Mac/Snap on scanner.

As you already know sometimes these troubles are dificult to locate, but by testing a few components when you have a no start issue or a bad miss will help narrow it down.

edit
Also double check your engine grounds(injectors harness, coils, ignition mod),
as they can loose connection sometimes when heated or dirty.

How about the plug wires? I had to change them on my 95, and it had the same problems. Turned out one of the boots was cracked and was arcing when it got hot. Also, check the ignition module, make sure the correct grease is installed on the mounting surface. When they get hot they don't like to work all that well. That was more a f*rd problem than a gm problem, but it doesn't hurt to check.

thanks guys some great things to check there ...

you know i've never even thought of changing out the injector harness, I know thats one thing that does go bad on these ... wow, just called the dealer, $523.89 for the harness ... thats an expensive guess, I have a noid light, maybe I can replicate the problem & test with the noid light. then maybe i'll look into one from a junk yard ...

plugs & plug wires were changed on the rebuild also ... so im guessing they are still good

will check all the electrical connections ...

thanks for the input, might be a little while before I get around to doing the test, leave next week for vacation for 10 days

$523.89 for the harness :yikes:

You sure that wasnt the entire wiring harness for the car?

I'd just inspect the injector wires for breaks/cracks.
If you find one damaged just use a butt connector with some shrink tube over it.

Good Hunting !