HELP Alternator noise(?) problem, also, I ain't got no MAP sensor

[sporqster]

3800 SC Stalker here. First, I didn't build my 7 mysef, so I'm learning about the idiosyncrasies as I go. And there are idiosyncrasies. When I bought this car, it ran perfect, idled nice and had smooth power right up through all the power band I had the guts to experience.

 

But then a regulator failure blew up the ECM, ICM, and well, nothing has been quite the same since.

 

After replacing the ECM, ICM, and of course the alternator/regulator, I found that my new alternator wasn't charging. After taking it back and testing it at the chain parts store verified there was nothing wrong with it, I dug into the harness to find that the "IG" and "S" wires were spliced together right behind the connector to the alternator with a crimp connector that had just let go of the wires. Well, actually, the observation was that the IG and S wires going to the alternator were both loose in the loom, and there was only one wire in the loom close to there with a crimp connector on it connected to nothing, which was connected to a ignition-switched 12 volts, so I'm putting 2+2 together. Replaced the crimp connector and all is well, right? Unfortunately wrong.

 

The car runs like total crap with the alternator running plugged in. Backfires, hesitates, barely idles. And I can verify this by pulling the fuse on the wire to the IG/S circuit as shown on the attached and immediately the car runs better. (It really needs a better tune as the one that's in there is clearly not as good as the one Dennis Brunton put on the ECM that got fried, but it's much OK-er). The CEL reads P1361 & P1362, "TDC sensor 1 no signal" and "TDC sensor 1 Intermittent interruption." I replaced the TDC sensor. Probably wasn't anything wrong with it, but I like collecting the RockAuto magnets, apparently.

 

Is the way this alternator is wired likely the cause of electrical noise that is wrecking the TDC sensor? Or some other cause? I'm not an electrically inclined person, but I know how to use a multimeter. What might be up here? 

 

Also, the code reader is throwing P0107 "Manifold Absolute Pressure Circuit Low", which is interesting, because on my set up, there is a MAF, but I don't have a MAP sensor. Yeah I know, SEEMS like it would want a MAP, but looks like this Stalker was built without one. Stalker owners - is that typical? As I said, I had to replace the ECM in this car because of an earlier electrical regulator failure, was there something special on the old ECM that ignored the lack of a MAP sensor and made it just work?

 

Thanks for reading this far! Hoping to get this sorted out before the weather warms up!

[Rosteri]

Hi, if IG and S are spliced together between the alternator and the ign switch, then turning off the engine (ignition…) might cause troubles within the regulator, as it doesn’t see the battery voltage anymore while the alternator still runs. I’d fix that. 
 

I’d also try a second alternator on the engine to rule out the alternator as a problem source, if somehow possible.
 

Second thing that comes to mind is, that alternators do take quite a bit of power when charging (plugged), so if the problems are only at idle, then the engine might just be out of tune/ too low idle rev. Stuttering/running bad at low revs can easily create the TDC code, so it isn’t necessary the reason for the running problems, just a sign.

 

What is the battery voltage when engine is running without/with alt plugged?

 

Then if possible check the shielding of the trigger wires, or just make sure that none of the alternator wires are close to other wires.  But somehow I doubt this is the cause.

 

 

 

 

[sporqster]

IG/S splice: Already have that on the short list to fix, I've already had one very costly regulator failure, after all.

 

Re power: It's not just the power its pulling at idle, it really is causing timing issues, it doesn't drive well above idle either, like it has terrible timing or something.

 

Without the alt plugged in, it's just under 12 according to the dash gauge, and it'll sink to 10.5 on a trip to the parts store and back, so basically, as expected? It is a pretty small battery.

 

I like to think it isn't shielding wires as it USED to run well, before the regulator "incident". So scratching my head too.

 

Part of me wants to pull every piece of wiring out, create a new harness, and install a megasquirt, as the OEM ecms are kinda a black box to me and I can tune a MS with my phone. But I've not quite made it to that place yet.