Some may remember that I've been having intermittent stalling trouble since my harness/ECM swap. It happens about every 2 weeks, and was due last week, so the car HAD to decide to wait until the day before I finally get it in for inspection to act up again, as I was returning from the junkyard with the parts I need to pass inspection (IAC motors, digital EGR). What happens is that when I'm cruising at any speed, the engine will give a hard miss, run normal for a bit, miss again, and continue missing until it stalls. If I let out the clutch, the engine speed will flutter through about a 400 RPM range (generally around 1500 RPM) and will surge up to about 2500 and down to about 8-900 RPM a couple of times before I have to pull over because it's dead. I let it sit for a minute or 2, and restart, and it's fine again for about 2 minutes before it does it again. I got home, and let the engine run until it died again so I could test some things (injector hot resistance, power to coil and ignition module, etc), and found out that my DMM is AWOL (of course!). The other thing the ECM does is when the engine stalls, the ECM intermittently kicks into the ALDL codes flash mode and starts the coolant fan and turns the SES off to flash the codes. Today, however, unlike the other times, I put the jumper in the ALDL and got nothing. I flashed the ECM codes by connecting my test light between the test terminal on C207 and ground. And, towards the end of the day, even that didn't work. Since I have 2 spare MEMCALs from FWD cars, I popped the factory one out and put one of them in, and got codes from the ALDL. I put the old one back in, and got codes all of a sudden. However, when I tried to start the engine, it acted as though I was getting a code 46 and kicked over only for a split second before it just cranked. Keep in mind the engine was running not even an hour before this... I switched to a backup ECM with one of the FWD MEMCALs and got the same result. I plan on switching out the ignition module with a spare I have in the morning. One thing I'm thinking is that maybe the MEMCAL is shot?

I finally got to pull the codes this time, and I'm getting 13 (open O2S), 15 (LOW CTS), 35 (IAC error... that's what the replacements are for as I don't think it even worked with the old system), and 45 (rich O2). I'm thinking there is a short somewhere in the works between these connectors and the others (but not the ECM... I've checked). I've already repaired the (almost) broken TPS/IAT wire in B5 where the insulation and half of the wires were split in 2 places, within an inch of each other, close to the ECM connector, and no other wires are damaged in the vicinity (unwrapped the harness already). The thing I'm thinking is that when I originally installed the harness, it was routed just a smidge too close to the exhaust pipe on the pass side, and the outer loom melted. I checked the wires inside when I replaced the loom, but I didn't see any melted wires or anything. Guess I'll look again.

Another thing to keep in mind is that I can drive 400+ miles straight on the 302 system, and I am NOT putting that back in for anything. I'll take the car off the road and walk to work for months until I get this figured out before I do that as it is too much of a pain to repin the C221 and C207 connectors AGAIN. The only code/problem I get with that system is 45, probably because the sensor is contaminated or something...

I'm looking at my 92 FSM and am completely in the dark here. Any light would be appreciated.

 

..have you replaced the cts..it could be dumping fuel in the engine thats not needed causing it to flood,did the miss start all at once?..as a rule of thumb any electrical is all of sudden and mechanical is spread over time..yours sounds mechanical especially if you have replaced the mentioned parts.Pretty sure you checked the basics,so im thinking its maybe a short?..could still be the ecm..the eclipse i had would leak capacitors and cause all sorts of problems,,easy to check to just smell it n see if its like raw fish.Mine jerks when i try to hold a steady speed,,havent found the cause yet(thinking still could be my pick up coil),when i got my 92 it would run to operating temp then shut off,had air in the system,so i drained it with new antifreeze and problem solved.do you think yours might be losing compression?

 

I'm also thinking a short, probably by the exhaust where the loom melted a couple of months ago. Other than that, I'm lost. The thing is, like I said above, the car ONLY does this with the 730 system. The only problem with the 302 system is the code 45. Well, not the only one... The reason I swapped the harnesses in the first place was because the 302 never seemed to want to properly control my idle speed. I would start the car and have to wait at least a full 30 seconds before the idle speed dropped below 1500 RPM. But that system never threw a code 35, which is why I'm stumped as to why it seems that the IAC control was slow with the 302 system and nonexistant with the 730 system. At least the 302 system had a controlled hot idle speed of 700 RPM, whereas the 730 system throws a code 35, keeps me out of closed loop, and idles at 1200 RPM no matter how hot the CTS is reading.

BTW, I'm also going to pull the O2S and find out if it's contaminated or not.

Also, neither 730 ECM smells of burnt electronics, and, believe me, I know what those smell like... I've burned up a few resistors and diodes in my day.

:edit: Another thing... Last time I checked my compression, I was above 160 in all 6 cylinders, with #6 (with leaking valve seals) having about 186 PSI. And yes, redoing the valve guides is on my to-do list for when I get some decent money going (if ever).

 

Deff check the hot spot near the loom,if it was a problem once then it could be doin it again,when you said the 302 took 30 seconds to drop rpm was that from a cold start or after it ran,shut off,then started again?,,and i would just replace the o2 while you have it out unless its new then you have a source to go by for a contaminated O2 sensor,plus you know the IAC is controlled by the ecm no matter which system you have..you have checked the IAT..which also might still be a problem in the wiring,then again any wires near the block is at risk.And lettin it sit for a couple of minutes then runs for a while sounds electrical too,too little time for anything mechanical to cool down,maybe a wire breaking down,,or maybe somethin the ecm cant/wont pick up like vac leak,fuel pump,pick up coil, so a completely melted wire may not be a problem.You said that at one time the ALDL was goin into diagnostic mode,,check the connector,,maybe the two wires that are used in that are touching somewhere,couldnt hurt.

 

302 system took 30 seconds from "cold" start to drop to proper engine speed. I say "cold" because it will do this after sitting for a couple of hours, whether it's slightly warm or not. If the engine is hot, the 302 won't do this... I can start it in half a crank and it drops right to where it's supposed to be. I don't have any vacuum leaks, and I've smoke tested the system to make sure.

Update: Swapped back to old harness even though I REALLY didn't want to, but getting TO inspection is more important. Misfiring like a bear now, I think it's a bad connection with a plug wire or something (good thing I have spares), but will check tomorrow after work. I'm going to unloom the entire harness one piece of loom at a time and go through every inch of every freaking wire until I find out what the problem is. I KNOW the problem isn't the hardware (sensors and motors/solenoids, except possibly the O2S) because the other system runs just fine with the exception of the IAC thing. It's not the fuel pump, either... The OPS continues to run the pump until the pressure drops when the engine is going nuts (I have a very loud pump you can almost hear over the engine when you're working under the hood, and it's been that way for quite a while).

I have to replace the O2S anyways... Kind of forgot to disconnect it when I yanked the harness and the wire came out of the sensor . I was probably going to have to replace it anyways, so, eh, no big deal. BTW, anyone have a dizzy to coil wire (the 2 wire one between the module and the coil, or just the module end of this wire)? The wire is good, the retaining tab isn't... Dangit.

Thing with the diagnostic mode is funny. When I first got home yesterday after the problem kicked in again, I didn't get codes out of the ALDL, and had to secondary jump the codes wire to ground. I got as far as code 35 before the light just went and stayed full on (without my having disconnected my test light from either the ground or the white/black wire or anything). I went and swapped MEMCALs later, and the system worked just like it's supposed to. And, like I said, the ECM intermittently puts itself into diagnostic mode when it's screwing up and not running. I don't know... the whole thing is making me go nuts. One minute it runs fine, the next, it's dead as dead gets, and all the running gear is good. Freaking wiring!

It's like the car doesn't want to be inspected this year... First the pass outer tie rod end craps out, then the brake light comes on because the rears aren't self adjusting. So I finally get the brake light out, and the engine controls die. Go figure. The only good luck I've had this last couple of months was finding an A/C delete box on the 84 4-banger at the junkyard (and it's all mine when I can get it out! ).

 

Might be a longshot, but I just fixed a problem with my '89 2.8L V-6 Firebird. The car would all of a sudden die - even at highway speed and would not start for a few minutes. Also, the alternator output was low. I checked everything over, belts, tensioner, etc., replaced the alternator, tightened engine grounds and little improvement. And the stupid thing still stalled every so often.

So......I replaced the coil wire to the distributor (the one marked A B that sits to the front of the coil) and problem solved!!!! Kind of makes me wonder if some of those "heat soak" problems of the past were due to that stupid wire and not to starter solenoids, etc.

Anyway, something else to consider on a car with wiring that is approaching 20+ years.

 

The alternator was repaired a couple of months ago, but I have no way to test the output at the moment. The thing that bugs me is that I've put 2 separate sets of diode rectifiers in the thing, and it's still putting out an AC current . I'm going to pick up a heavy duty rectifier and see what happens.

I repaired the coil to dizzy wire you mentioned 2 years ago (when my AC/Delco ignition module crapped out I noticed the coil end of the wire was hanging on by 2 strands of wire and then it broke) and replaced it completely since. I have a spare one (if I haven't tossed it and I can find it), but I seriously don't think that is the problem. Keep in mind that I mentioned that the 302 system works just fine, but it's the 730 system that keeps stalling out on me whenever it feels like (usually when it's least convienient, like when it died the first time at the intersection of 2 major roads in our county seat).

BTW, my car is over the 20 year hump... It's 23 this model year.

 

Mav...if you need a MEMCAL to try, I have my old AUJ(?) in the house. Let me know and I'll send it to you. I got a 3.1 V6 auto,

Ken

 

Thanks. That could help. However, I am looking for a BAUX MEMCAL, for the 5-speed. Doubt I'll find one, though, so I'll take what I can find.

Got her going... Rewired the C221 wrong and didn't have power to the pass side fuel injectors, along with crossing the 3 and 5 plug wires again . Now I just have to get the oxygen sensor replaced... I don't seem to recall putting it in THAT tight. Mileage is kind of crappy right now, and the starter needs to be reshimmed along with having the bolt holes retapped. I can deal with that after inspection, though.

I started to go through the 730 harness a couple of days ago, but didn't get very far yet. I'll let you know what happens with that.