'04 3.4 Liter Swap in '01 Monte Carlo...Stalling Issues

[ChevroletR]

Hello all. Hopefully somebody can offer some help with this one since I'm about out of options.

This past summer, my mom's 01 3.4 Liter Monte Carlo blew a head gasket/cracked head with over 160,000 miles on it so we bought a 3.4 Liter out of a salvage yard out of a 2004 Impala and swapped in. Everything runs and works great, however we have an intermittent stalling. We have found no pattern to stalling (turning, a/c on/off, braking, accelerating, etc) however it seems to be mostly when stopped or coming to a rolling stop and getting back on the gas to pull out in traffic, however my mom claims it stalled on her while rounding a merging loop once.

No DTCs, and it happens so fast I can't record anything on the Tech II snapshot. I have pretty much swapped out everything I thought possible including IAC, TPS, both crank sensors (and performed a crank relearn via Tech II), coils and ignition module. Performed an injector balance test, fuel pressure test, exhaust back pressure, injector cleaner service and throttle body cleaning.

My mom took it into the dealer and my friend was working on it and called GM TAC and when he told them the engine was a 2004, the TAC guy went "Oh!" as if that may not be a good thing. I'm wondering if there is a different calibration or PCM confliction going on. The ONLY thing I can see different is the newer 2004 cam position sensor being that the new one has the connector actually on the sensor instead of the 2001 and older 3.1/3.4's having the cam sensor with the wires coming out of it and across the upper plenum. We checked part numbers and the camshafts and PCM's and found they have different part numbers between 2001 and 2004, which would have to do with the reluctor ring on the camshaft, however the Tech II reads a 'Valid Camshaft position signal' so I figured that was ruled out.

I thought about finding the matching PCM out of the 2004, however I don't think the car would start and enable theft deterrent since the VINs wouldn't match. I certainly don't want to spend $300 or abouts (that's the price from advance auto/aftermarket!) on a PCM and program it to find out it doesn't fix our problem.

Anybody ran into this or heard of a issue as such? Any information or help would be GREATLY appreciated. Thanks!

Ryan Washington

[MrCritical]

You can't get a fail code without a snapshot?

At the very least you will either need a PCM or the old one recalibrated.

[ChevroletR]

What do you mean I can't get a fail code without a snapshot? There are no codes/DTCs and when I drove it while trying to manual snapshot, the stalling happens so quick and quietly that the car stalls before I can snapshot it. I one thing I forgot to mention is that while idling, when I snap the throttle in park, the engine takes a big gulp of air and the RPMs drop to about 400-500 and then the RPMs go up along with the throttle position finally (A hesitation). I actually got the car to stall while sitting in park one time and playing with snapping the throttle. My buddy who looked at it at the dealer said he compared that with another 3.4 and said it seemed normal. I disagree and think this 'gulping' or hesitation has to do with the stalling, but again don't know what it is.