The first thing I thought of when reading the beginning of that post is ALTERNATOR. Id be willing to bet that the voltage regulator is generating a lot of noise. You also have to remember that it also acts as an AC generator when the alternator is stationary. This is required to excite the windings so the alternator will energize when the engine starts. You can, if its quiet, hear the alternator being energized at KOEO. Its a high pitched buzz, maybe 1 kHz. See if thats what yours sounds like. If it sounds real erratic, then you got a bad regulator. Something like that could make tons of electrical interference if it goes bad.

 

Seeing that I don't have a good used one readily available to rob off something and try on mine I'm going to make it a really nice tin foil hat and see what happens. Damn those underhood solar flares. This would also explain the excellent radio reception in accessory and why it goes to hell in run engine off or on.

 

Just unplug the field and see if the noise goes away.

 

I didn't unplug it but I did make it a very nice little aluminum foil hat out of reynolds wrap that was several layers thick. Went for a drive and after the BLMs came around (had the battery unhooked) I made a good pull with it and wouldn't you know it pulled smoothly up to 5000 and then only had a subtle hesitation to it. I'm not so sure that wasn't air fuel ratio induced since I was nearing 14.5:1 when I got that high. I'm still in closed loop with PE disabled at the moment. I did it a few more times and it only got better with each run. It seemed better all around. This got me to thinking probably a year or more ago the air bag light came on which is almost unheard of on such a truck and it said system over voltage detected. I'm not so sure its not putting some AC voltage back in the system as well. I've got my receipt and I'm going to pull it off as soon as it cools down and make them give me a "new" one. I bet it fixes the damn thing. If it does I may be so damn happy I go try to blow it up just because it finally runs good.

 

So, after all that, you've got a dirty alternator !
A single leaking diode in it can do that. ( as well as make it run REALLY hot )

So, one of the real first symptoms was noise in the radio !
Noise on any of the sensor lines, or on the battery lead, can cause ALL of what you were seeing.
Good job staying with it.

 

I'm not going to jump to conclusions just yet but this is the most promising lead yet. Seeing that is has a good drive cycle under its belt I should be able to unplug it and take a short drive to see if its really the problem or not. I'm sure it is but it would be nice to know for sure.

 

This isn't a good idea. The battery acts as a damper to the electrical system. If the thought is that the alternator is bad. It is much better to disconnect it, both field plug and output cable (insulate well!).

And disconnect it with the engine off. Then start engine or do the key-on, engine-off radio test.

RBob.

 

I was saying it had been sitting for a week with the battery unhooked and when I reconnected and went for a test drive it had to do some relearning before it ran right.

I just pulled it off and may go get a replacement tomorrow, or I may just wait until tuesday. Got too much house work that needs to be done and its too hot out to be working in the garage for very long.

 

For future reference, the way to check it is to simply unplug the 4-pin connector on the alternator. That will disable it, and allow you to just run off the battery.

Also, any time you hear anything at all in the radio, its automatically a sign of trouble. The radio is the electrical system equivalent of the canary in the mineshaft. Its the first thing to have trouble since its got a big long whip designed to pick up RF.

One test I usually do is switch it to AM as well. That can tell you how much noise is coming from the alternator, as well as the ignition. A little hum and buzz is normal in these older cars and trucks, but anything more is a sign of leakage. If it actually manages to scramble the FM as well, then there are serious problems with EMI as at that point, your basically either overloading the front end, or generating lots of RF in that spectrum where the station is located.

 

Incidentally, how long has the radio been acting like that?

 

Its been a long time. The reception has never been great but within the last two years its gotten worse. I never listen to AM but I tried it just to see and its basically pure static. If you're lucky you might be able to hear some voices or something over the static. On FM I can pick up stations that located within 30-40 miles from here pretty clearly, sometimes with static though. Everything from the antenna lead to the antenna base and mast were replaced several years back to restore the reception which at that time it did but then it went to hell again hopefully due to this alternator.

 

Correct, in more ways than one.
In this context, the battery can be thought of as a very, very large capacity filter capacitor.
( in truth, a capacitor and a battery act much the same in nearly all circumstances )

If running on battery only, all of the noise is gone, and the ECM is suddenly behaving, it's a real good indication you've found the source of the problem.

 

.

 

Got it, I misunderstood what you were doing.

RBob.

 

I put the "new" alternator on monday and finally got around to driving it this evening. I hate to say its fixed but I'm pretty damn certain its fixed. I'm still running around in closed loop with PE disabled so I'm targeting 14.7 under all loads and I was getting just a few light misfires from 5000-6000 at times but it was running in the neighborhood of 15:1 on the wideband so I didn't get too concerned about that. Need to go back to PE again.

It still has issues though. I let it idle about 10 minutes and ran it off idle some before I drove it. I made it half a mile or so then it started its plunge on both the BLM and INT. The BLM eventually made it down to 90 and the INT to 40 and stayed there. Scannerpro was showing a pulse width of 0.00 and I was at 10% throttle and holding steady at 14.7:1 AFR. I let off and it died. I coasted to the intersection got pulled over and restarted it. Had to hold my foot to the floor to get it to start then it was all happy. After that the BLMs came right in line averaging in the 124-134 range. Why the hell it does this everytime the battery is disconnected is beyond me.

The other stupid thing its doing is the throttle is sticking. I had put bushings in it a while back and actually still have just a hair of play on the drivers side of the throttle body due to some wear on the throttle shaft and the passengers side when I reassembled it was pretty snug. Put some anti seeze on it and it worked smooth and has been up until now. It got so tight while driving it hung at 15% and I had to smack the pedal a few times before it let go. I guess I will take it back apart and put some lapping compound on the shaft and try to loosen up that bushing a little. I swear its always something.

 

You still running Batt discnnect or something happens after batt disconect?

 

I never ran with the battery disconnected? Why would I do that? Nobody does that. All I ever meant by that and still mean is I unhook it so the pcm goes dead and erases all its memory.

 

I was just confused what you meant. It was talked about to disconnet altenator earleier, can,t figure out why you dissconected batt. Just trying to keep up...

Did your radio noise go away?

 

You know I never even turned the radio on. I'm still having to play with the injector offset and VE's and figuring out what the ideal fuel pressure is going to be for 74# injectors. Today I had it idling at 600 rpms, the pulse width way holding steady at 0.40 which is too low really to the point of being nearly closed at all times, and it was idling at 13.5:1 and it was trying its best to bring it back down to 14.7 but it was perfectly smooth. Not a hint of chop or surge or anything. Not bad for a LT4 hot cam. I'm at 25 psi now WOT and at idle with vacuum connected I'm at 18 psi. I may have to back the pressure down a little more but it calculates out to be about 450 hp worth of fuel. I doubt I'm at that but I can't find my low pressure FPR spring at the moment so I'm as low as I can go for now. I still think I should be able to get a workable pulse width both at idle and at WOT at this pressure. I was running the injector offset at 650 mv compared to the stock of 396 mv at 11.2-14.4 actual system voltage. I'm going to try 525 mv tomorrow and see if that doesn't calm things down a little more.

 

OK your a good tuner, that's why I read your stuff, but we were chasing a strange electrical noise you thought was casuing the problem and could even hear it in the radio. I would really like to know if it's still there. Besides my curiousity and love of challenge to find this **** (hands on) I think you should focus on if the noise is gone or any other electrical glitches you thought were involved from charging system and if they are now gone or still there. Then you can go back to tuning OK, I promise...

 

This is simply not possible, UNLESS fuel is getting to the intake by some other means. You simply can not have no fuel and still run.
Methinks you have a fuel leak.

My rig is running 80# injectors at 24 PSI. At a 500 RPM idle I have a pulse duty cycle around 2%, and it idles smooth, and passed E-check yesterday.
( the third time through. E-check didn't like hollow cats. (( a three year old problem. No clue how it passed 2 years ago, but it did )) )

 

That could be. When I first put the 74# injectors in I had a pretty substantial leak on the injector pod gasket. It was the same gasket thats been in there for years and been apart who knows how many times but it leaked. Replaced it and thought I had it all sealed up but maybe not. Really though I think its more of a PCM being stupid issue than something actually wrong. For what its worth rather than using a narrow band I'm using my widebands narrow band output for closed loop 02 based fuel correction and it could be something to do with that.

 

Your kidding...right? Not to be unkind, but REALLY?

You have ANY idea how lost this **** is?

We love Red, but be real.

 

That's one reason I run both sensors, separately, simultaneously.
One cross-checks the other. If they don't agree, I know something went wonky with one of them. ( it has happened )
Still, your BLM, INT, and pulsewidth all say the ECM is doing it's best to cut fuel, and it's still running, says fuel leak into the intake, somehow. ( gasket, stuck injector, something. )

 

The problem I had with the narrow band is it was being fooled due to cam overlap. I tried adjusting the voltages but never could make it do what it was supposed to. Depending on the load and engine speed it may be targeting 14.7 but may actually be at 13:1 or as lean as 16:1. It was suggested I try using the narrow band output on the wideband and in doing that it actually runs at the commanded 14.7:1 and aside from this taking fuel away issue after a PCM reset seems to be working. I never said I was good but I'm slowly figuring it all out. When you've got so many variables and things that may or may not be working as intended its hard to know what way to go with it.

 

How far apart ( physically ) did you have the NB and WB ? Heated NB ? And, how far from the collector, or manifold out ? How far down the pipe ?

Something many of us have in common !

When that happens to me, I back up. Just the other day, I reverted back 23 tunes to get back to a definite known set of conditions. Not perfect, or even real good, but known.

 

The wideband is in the left bank about 2 feet back from the collector. The narrow band is in the right bank about a foot back from the collector. Both are probably too far back I know.

 

Not to hijack but where IS a "good" place for an O2 sensor to go? I was planning to run a NB (heated) and WB on my setup. There are provisions for an O2 in both collectors of the headers. Should one go in each? Or should I put them just after my Y-pipe (single exhaust)? And what would be a good distance?

 

Since they are both heated, anyplace ahead of about a foot from the tailpipe outlet should be fine.
My unheated NB is about 8 inches or so from the #7 exhaust valve in the manifold outlet. My WB about 8 feet beyond that. Both in the left bank. No crossover, so my right bank isn't monitored, but the bungs are there in case I feel a need.
Note that any exhaust leak renders them questionable, and an exhaust leak ahead of the sensor renders it useless for any data collection at all.

In Red's case, I'd *really* want to know why the NB wouldn't work, especially when the WB seems to. Something isn't right with that.

 

I'd probalby be best putting them both right after the Y-pipe, but I could get away with putting one in each header collector. I will decide when I get around to fabbing the exhaust.

 

Finally the 2 1/2 year long saga is over. After sitting for at least a month I finally finished getting it all switched back to the old speed density setup, even back to the dual snorkel air cleaner and 5 inch tall lid/filter setup. I even put some 1.6 roller rockers on it while I was at it. I kept having this really bad drivability issues. I was lucky if it idled and come to find out the Borg Warner injectors that were supposed to be for a 92 model 454 engine (74#) were not spraying worth a damn. I don't know if it was some weird injector offset issue or what but I put the stock 61s back in, set the pressure at 30, stock injector offset and all is well. I took it for a drive tonight and it pulled without a single hiccup to 5500 and the VE's still aren't completely perfect. I do believe after all this it was the alternator to blame.

 

Can you post a picture of the Borg Warner injectors? They may not be Rochester but another brand of TBI injectors.

RBob.