- With this level of engine change (going from an L67 to an L36), was the PCM re-programmed OR switched? If not, problem #1.
- To my knowledge, the Security system does not try to disable the injectors, when it does not want you driving the car, it will NOT start as the injectors are simply OFF.
- When Taz suggested co-workers playing pranks, this is more the dumping crap in the gas tank. Such as, have you checked to ensure ALL your plug wires are still firmly connected? If it's mis-firing, that's a QUICK and EASY check.
- You mentioned new plugs were put on the donor motor. Were they BOSCH plugs? If so, change'em. BOSCH has had a history of being poor performers for me and my friends on GM engines (or they die suddenly 6 months later resulting in horrible mis-fires).
- Potentially, it could be a failing coil pack. If the car is throwing a Check Engine light, it may reveal one or more cylinders mis-firing. If it's 2 cylinders, see if they share a coil pack.
- Could be a failed plug, injector, coil (coils are NOT common failure points from my experience).
- Could be a damaged plug wire arcing (inspect for damage on the wires, like a cut sheething).

 

I would start with the check engine light that should point you in a direction, like stated before it could be the upstream o2 sensor, bad plugs coil pack or plug wire, I'm also thinking it could be your maf (mass air flow sensor) if you unplug the maf it will make your car run rich but it might make it drivable for a few days but replace it asap if it is the culprit otherwise you will face serious drop in mpg's. Few other things to check is vacuum leaks, fuel pressure and your catalytic converter

 

Thanks Maniac! The check engine light is on. But it has been on for quite sometime.

MwJames, could you tell me the location of the MAF? Since you mentioned that I do remember how my previous Volvo did the same thing at idle, Haha MPG isn't important to me I live 2 miles from work, it will be a lot better to unhook it and drive until Advance can have the part in for me. Please help me locate the sensor.. Thank you!

 

Part 1 -MAF Sensor Test (P0101, P0102, P0103): GM 3.8L (1996-2005).

Hi `Brad, click above link...I hope it helps...Good Luck

 

So your car has been throwing a check engine code for a while?? Any idea what the code is? Just because it's had a code thrown for a while and ran does not mean it's not part of your current problem. It could be the problem got WORSE.

If you look at the throttle body, the MAF sits right on top of it (roughly rectangular, not very thick, the probe hangs down into it). It uses 2 security torx screws to hold it in (recommend replacing those things with stainless hex heads).
If you see the black item on this throttle body, that's the MAF:

 

My friend fixed the issue! It was the vacuum line that goes to the fuel pump and the map sensor had partially fallen off! (The hose that's on the opposite side of the MAF sensor) Anyone know what this piece is exactly called? From the recent hot temperatures the glue that was holding the seal together (guessing it failed at one point) finally just gave up and was leaking air. Saved me tons of money! Now it's back to fixing the security and replacing the hub. Thanks for the help everyone! Hopefully this will help someone someday!

 

Good to hear you got it fixed! Love yellow montes looks good!