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Not sure also whether it is the alternator as well. I added a voltage booster and then the alternator rewire just to try and get around some of that issue along with the pulsing lights I'd get sometimes. Things seem a bit better.
A vac canister is a great Idea with a larger cam.
The reason for this is that below a certain RPM your pcm removes the 5 volt's that excites the alternator field, effectivly shutting off your alternator. Hence the low voltage and fluctuation.
I'm gonna bet that the problem with low charge voltage at 600-700 rpm, is either a weak alternator or too much load on the charging system at those rpms. Considering youv'e got an electric water pump, I'm going to guess the latter.
Fix the idle stability problem and you'll solve the charging issue.
Interestingly, your idle stability problem sounds much like the the idle problem I had with my mod'ed 01. It's discussed in a thread to which we both posted at: http://forum.camarov6.com/showthread...49#post1011749
Since the tables one needs to access to tune idle spark are not accessible with the HPT 2.22 or 2.23, I simply added 6-8° to the base spark tables in the cells at which the engine idles. My idle stability was much improved and throttle response improved a ton.
How can I measure vacuum? Is anyone familiar with the Aeroforce scan gauge? is the HG/psi my vacuum? If so it says I'm pulling roughly -6- (-8) at idle? is this really bad?
I have 2 Aeroforce gauges, they don't read vac. though, you need a Vac./boost gauge.
08' L76 6.0L 4X4 Chevy EXT.Cab LTZ Vortec MAX with Snug top cover, Dynomax exhaust,Hptuners& K&N intake
96' Camaro M5 to A4 conversion, alot of mods . GT35R Turbo full suspension. Built engine
I have this issue with my car as well... I've noticed it's only when I'm coasting down without the clutch in and AC off... But I sit at 18v regularly, and drop to under 13, and idle goes to about 400, from 750.
I do not think this voltage-drop issue has anything to do with vacuum, high octane fuel or any of that. My car has always done this also, and I bought the car new. If you look in the Haynes manual, on p. 12-30, on the PCM section there is a brown wire labeled Generator Control. It appears to me that the PCM is controlling whether the alternator is putting out power. For some reason, I think the PCM is cutting off the signal, causing the alternator to stop putting out power. A moment later, the PCM turns it back on again. Also, watch the voltage gauge when you first start the car. On mine, the voltage always comes up a couple of seconds after startup. It's as if the PCM is programmed to only let the alternator kick on after the engine has reached idle speed. None of my other cars have done this. On these other cars the alternator has always run as long as the engine is running. However, the stupid Haynes manual does not show where this brown wire goes to. It just shows "Starting/Charging System". Well, the only wire I see to the alternator is a tiny red wire. Who knows where this brown wires goes. I'm thinking that if the PCM is bypassed, and the alternator receives the 12V signal from a key-on source, that the voltage-drop issue will go away.
I had a chipmunk munching on wires in my car, one was the smaller wire on the alternator. He chewed right through it. I started my car and my volts were down and stayed down no matter what RPM my engine was in. I knew exactly what it was because I forgot to plug that wire in when I changed my alternator before.
Interesting idea though. We should get someone with a multimeter to test that wire. Couldn't a constant charging alternator over charge the battery though?
I had a chipmunk munching on wires in my car, one was the smaller wire on the alternator. He chewed right through it. I started my car and my volts were down and stayed down no matter what RPM my engine was in. I knew exactly what it was because I forgot to plug that wire in when I changed my alternator before.
Interesting idea though. We should get someone with a multimeter to test that wire. Couldn't a constant charging alternator over charge the battery though?
Yes, it can damage the battery, and the coils in the alternator.
I do not think this voltage-drop issue has anything to do with vacuum, high octane fuel or any of that. My car has always done this also, and I bought the car new. If you look in the Haynes manual, on p. 12-30, on the PCM section there is a brown wire labeled Generator Control. It appears to me that the PCM is controlling whether the alternator is putting out power. For some reason, I think the PCM is cutting off the signal, causing the alternator to stop putting out power. A moment later, the PCM turns it back on again. Also, watch the voltage gauge when you first start the car. On mine, the voltage always comes up a couple of seconds after startup. It's as if the PCM is programmed to only let the alternator kick on after the engine has reached idle speed. None of my other cars have done this. On these other cars the alternator has always run as long as the engine is running. However, the stupid Haynes manual does not show where this brown wire goes to. It just shows "Starting/Charging System". Well, the only wire I see to the alternator is a tiny red wire. Who knows where this brown wires goes. I'm thinking that if the PCM is bypassed, and the alternator receives the 12V signal from a key-on source, that the voltage-drop issue will go away.
There is as set rpm range that the alternator operates whitin, to low and it is shut off by the PCM. And if I remember correctly the alternator receives a 5 volt to energize the coils, not 12. The PCM doesnt just decide to "cut power", some outside variable that is causing this to happen, as it is all based on tables and values. No need for a bandaid if you fix the cause.
I have had plenty of hands on experience with this problem and I have found it to have a direct coralation with idle and vacum. As I progressed to bigger cams with more overlap the problem has become much more pronounced.
I will add to this later when i have more time.
I was reading more about alternators last night, and it seems that most later model cars now have PCM-controlled alternators, whereas older cars had internal voltage regulators. So, if our alternators do not have internal regulators, we cannot just hook it up to 5V or 12V because it probably would overcharge. It may even have uncontrolled voltage. The solution would probably be to switch the alternator for one that is internally regulated. But then, would that mess with the PCM if it is no longer allowed to control the voltage? Who knows.
I have a stock cam and my car does something similar randomly. The voltage and RPM will drop and then it'll "catch itself" and the volts/RPM will surge up past idle. It'll keep yo-yoing like this until I give it a bit of gas, then it settles down to a proper idle.
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