intermittent engine stalling/stumbling

[dawgpound818]

My 96 I30 had a check engine light on and recently started having what seemed like an intermittent misfire/stalling problem. Sometimes it idles fine, sometimes it idles really hard and stalls. It stumbles hard on acceleration sometimes and does OK other times. The exhaust odor smells like it is running rich and not burning all of the fuel it's getting. I took my car to Autozone and had the OBDII scanner hooked up. It read the code for a failed bank 1, sensor 1 O2 sensor, as well as a knock sensor (I believe this code was due to the misfire problem, not a bad knock sensor?), and a P1320, "Ignition Signal Primary Circuit Fault" code. I changed my plugs (NGK platinum like OEM) which were much needed after 109k on the originals. I also changed my failed bank 1, sensor 1 O2 sensor. I then returned to Autozone and had the codes cleared. My engine light went off, but my engine continues to intermittently stall, stumble, run rich, and fall on its face when accelerating. It seems to do it equally cold or hot. I'm thinking (based on what I've read here on NICO that this could be due to IACV being clogged or excessively dirty, but I had no engine light code (DTC) for anything related to that part. Could this be a PCM issue or has anyone else had this problem? HELP, PLEASE!!!!!! And thank you in advance!

[halcyon87]

I've had similar intermittent stalling/stumbling as well when in coming to a stop or idling. when I finally took it to a dealer, because local mechanics were not able to figure the problem out the dealer told me it was the "mass air flow sensor" and this did not trip the CEL, so you might want to check that out as well and see.

[Chris93se]

-check your coilpacks for corrosion?-vacuum leaks-as you said IACV-MAF

all i got

[maximaman]

I recently have the exact same problem on my 96. i took apart the iacv and the maf and cleaned the shyt out of them and it got 90 percent better. So basically its one of those. Just to narrow it down for you. Oh, and it shot no codes for months until recently.

[dawgpound818]

Cleaned the hell out of the IACV, not much better (though it was filthy!). The second I starttd messing with the MAF to pull and clean it, it took a crap. Seems like it was working its way there and I just helped it along...hahaha. Engine would not rev over 2500rpm and stalled like crazy. Replaced MAF with 2 different junkyard MAF's...no change. Returned junkyard MAF's and bought new (reman.) MAF from Autozone (with warranty) and the problem is gone! I'm glad it needed the plugs, O2 sensors, and IACV cleaned anyways because the last thing I messed with ended up being 99.9% of my problem. Car runs like new again, plenty of power, and marked MPG improvement. Thank you all for your help!