Originally Posted by DUB

First off...you are not "pissing me off"...I am still willing to do all I can to help you...and if that means explaining how to use a scanner and read the data...that is fine also. But also with that written...IF you are someone who does not know this 'stuff'...would it not be in your best interests to give the information requested that people ask for??? I do not mind waiting for it due to your work schedule...but not replying to it and possibly thinking that it means nothing is something else entirely...don't you agree?? Moving on.

The term 'integrator' is a term that you will see on the screen of the scanner...and it is mentioned in the service manual. In a 'perfect world' your engine should be running at an integrator value of 128. This value is outlined in the trouble code 16 for your Oxygen sensors. And I sue this value to let me know if there is a vacuum leak AFTER the throttle body...where your IAC is located which is controlling the idle and and leaks AFTER IT.

TRUST ME...I have had more customers than I can count that threw EVERY part at their engine and only to find out that NONE of them helped. And often times installing a less expensive NON-GM/ACDelco parts have been a problem also....in my experiences. This is where trying to fix something without the knowledge and the tools to give you the information needed. SO...unless you want to waste a lot of your hard earned money...do as you wish....you might get lucky and fix it.

If you have a FACTORY Service Manual...you might need to...when you can find time...is to do some reading to familiarize yourself with some of the information.

I am still here....but I need information. Without it I am "FLYING BLIND' and can not offer anything else.

Keep in mind that this car really needs good power to keep it running right. So this issue with your alternator would be TOP on my list to get fixed.

DUB

Originally Posted by Cliff Harris

In my opinion you need certain basic tools to diagnose a problem like this (and many others):

1 - fuel pressure gauge
2 - timing light
3 - digital voltmeter

If you are missing any of those it will be much more difficult to troubleshoot problems with your car.

An ALDL (Assembly Line Diagnostic Link) cable and scanning software for a computer would also be helpful. A dedicated scan tool can also be used, but that's less flexible and doesn't allow data logging.

Originally Posted by wedgeheaded

I have a 90 vert with the L98. It has nearly 200K on the clock thought the motor was rebuilt and runs better than great, most of the time. It has a stumble just off idle. I've been pursuing it as being related to the EGR or IAC. It's none of that, nor injectors. I have the receipts to prove it. My FSM suggests low voltage as a cause of low idle/just off idle throttle response issues. The battery is fairly new. What about my alternator, can I be getting low output at low RPMs? If I am, wouldn't the battery pick up the slack? How can I prove it WO buying an alternator? Thanks in advance.

Originally Posted by pcolt94

Unless I missed something, it is not verified that there is a alternator or voltage problem. This all stems from information from the FSM. Nowhere do I see that any voltage has been made at idle or any other RPM. I think several voltage measurements need to be made to see if anything is even wrong with the charging voltage.

Depending when the car is started, the charging voltage for the first start of the day will be higher since the battery has been sitting over night. It will probably charge about 14.5 volts. And after a while will probably start to drop off after a full charge is acquired. Might go down to the high 13s or so. If you are in the 12s, then there might be a problem assuming you don’t have the headlights, blower motor and accessories running. But even then, if the alternator is OK, at a higher RPM it should be a 14.0 or so.

Measure the battery voltage at the battery to get the measurements. That way if the voltage is OK, we can move on with some other suggestions. This is a real simple test to do.

Originally Posted by DUB

If his alternator is charging in the 12's.....regardless if the headlight and any other accessory is on...there is a charging problem...regards of RPM. It should charge ...at least in the mid 13's when idling....and that is assuming that the battery is fully charged.....if the battery is low...then it will go into the 14.'s.

You can use the gauge in your cluster for checking the voltage initially. Checking a the battery like pcolt94 mentioned is also a good suggestion.

AND...form experience...I have repaired so MANY Corvettes due to the cables being loose and arcing occurring and corrosion building up. SO...'wedgeheaded'...unless you have done so and VERIFIED that they are in excellent condition...remove your battery cables and VISUALLY inspect the condition of the cable ends where it makes contact with your battery terminal area....and when you put it back on...make sure it is tight and the cable will NOT move when completed.

Then...also VISUALLY check and verify that the large red wire that connects to the back of your alternator is good and tight and that it has not been messed with or the wire looks like it is broken or damaged....along with the connector that plugs into the alternator.

REMEMBER that if you go to remove the large red wire from the alternator....DO NOT....REPEAT...DO NOT allow the stud in the alternator that this red wire gets attached to....is allowed to spin....which can happen if you do not hold the terminal on the wire securely. IF this stud turns...it can effect/damage the inside of the alternator where parts are connected to the backside of this stud.

DUB

Originally Posted by wedgeheaded

OK, small progress but not what I'd hoped to see. I tried to PU a pressure gauge for my fuel line but couldn't locate one. I did check my alt at idle, 15.23 V. That's not my problem. 4 12s this week then going to OK for a week to visit my daughter and son-in-law. As our weather is getting too cool for top down driving, I'm probably going to dog this off till spring. I am going to pursue finding somebody local who is good with these motors. There has to be somebody. Not knowing what I'm doing, I think it's my best shot. If it had a carb I'd be looking at the transition circuit. But it doesn't. Thanks for all your time and trouble. I will be back.

Originally Posted by DUB

I know you are going to stop until spring....BUT...I personally do not like the volts when at idle....they are really high. 16 volts is really not good. I think I would be looking at the alternator. YES...it is under the 16 volts max that you do not want....but it is not that far from it.

Best of luck finding someone who KNOWS what they are doing. Because you let someone who DOES NOT know what they are doing and wants to work on it so they can say "they worked on a Corvette"...could be catastrophic....ONLY because I get Corvettes in that were worked on by people who should not be allowed to possess a tool box.

DUB

Originally Posted by wedgeheaded

That's kinda what got me into this and most of my messes. I don't mind paying for a job well done but it bugs me to pay for something and it ends up being done less professionally than I would have done. So, I end up swapping out suspect parts and hope I get lucky. Or, I educate myself. This won't beat me.
As for the alt reading, I read it at the red wire terminal and the neg on the battery. I thought it seemed high but figured the voltage reg would enter in somehow. I'm a Mopar guy and owning this Corvette is all new to me and I find myself troubleshooting like it's a mopar. To some extent, it's fine. But sometimes not. If it were a mope, I'd know who to go to and where I could take it. Lots to learn. I'll get it though.

Originally Posted by DUB

Regardless if it is a Mopar or not....the physics of the charging system are the same. I do not know Mopar's...but I know it needs to have a charging system....which I would believe that Mopar has not come up with some unique 'twist' on changing DC currents to there own electrical system because they still use a DC 12 volt battery. Correct???. What would you do if your Mopar was charging way higher than you know it should ..or so close to the 'danger zone'???? Most major auto parts stores have an alternator testing machine and will test it for free.

Check the battery also....it could possible have shifted plates or a problem in one cell. Perform a load test and see if it is OK. Usually when a battery is low on voltage....the alternator will be a bit higher until the battery is at full strength...BUT being at almost 16 volts when charging...it can be a low battery or the alternator is going bad on the voltage regulator area in it....and having a power drain...I would have the alternator tested.

I know you have to do what you have to do.....BUT ...HONESTLY....I get many customers that 'swap parts' hoping that get it right. And they finally throw in the towel and bring it to me and I find something that has nothing to do with what they spent all that money on.

DUB

Originally Posted by ToniJ1960

Just a thought, the red wire from the alternator where you read the voltage from. Can you read the voltage across both ends of that wire while its running?