I have an 02 Firehawk that is completely stock(for now) down to the SLP muffler still on it. It's an auto.

Here's what i need help with.
When the car is idling in park/neutral and the ac is on the charging system is doing what it's supposed to. When it is put into gear and idling it seems like it cannot keep up. The system drops to about 13v and the ac doesn't cool as well as it should or as well as it does in park/neutral. The blower speed seems allowed down as well. When driving down the road everything works as it should as the voltage is above 14.5.

Has a new alternator. Just seems like the computer isn't compensating for the load at idle. Did the same thing with the old alternator.

Also has a slight misfire at idle, but no codes. There are no codes at all. Has new plugs, wires, and coils. Can see the misfire on the tech 2 misfire graph.

Any thoughts or ideas. Thanks in advance.

Ben

 

Check your grounds.

 

i had some charging issues with my 02 WS6. After i had the fans tuned for a 160 t-stat the voltage would drop when they would turn on at 185. So i upgraded the big 3 and bought a Powermaster CS-130D 165 amp alternator and thought that would help but nope. I still had voltage drops and the interior lights would dim when i would put my headlights on. I ended up getting the AD244 220 amp alternator. That is a huge upgrade and now with the AC on full blast and headlights on my voltage never drops. If your car doesn't have the AD244 i would definitely get that.

 

Also consider that the stock voltage gauge in the instrument cluster often reads up to 1 volt lower than the actual voltage at the battery terminals.

 

Alright. So the grounds are good. I also did a check by adding a ground from the head to the ground stud the battery hooks to.

Watching the tech 2 when idling in p/n it is commanding a 650rpm idle. The moment it is put in gear; it's being commanded to 550rpm at idle. That seems low. I cannot find info on what the idle speed are supposed to be. Does anyone have that info? Any thoughts on why it would be doing this low of an idle? Thanks in advance.

Ben

 

This is exactly as it should be. Stock idle speed for all LS1 F-bodies is 650rpm P/N, 550rpm in gear. For manuals it's 800rpm. This is the factory setting for all examples 1998-02.

You can raise idle speed with tuning, but it really shouldn't need a higher idle speed if the cam is stock.

You can also upgrade to an alternator that makes more amperage at lower engine speeds, and/or swap to a smaller pulley (but then max rpm is limited, or alternator damage could result - not really a concern if your shift points are still stock though).

But if the engine seems to have a misfire at idle, I'd look into correcting this first. Even if there are no codes, your scanner should show cylinder specific misfire counts. So if it registers the misfires on a general graph, look for the cylinder specific data and see what (or which) cylinder(s) is/are responsible. If the cylinder specific counts don't show anything noteworthy for any specific cylinder, then look at the fuel trim data and see if the LTFTs are elevated on either (or both) banks. They shouldn't really be more then +/- 5% or so on a good running stock car (I'd call +/- 10% the upper limit). If the trims are at all elevated, then you might want to look at fuel pressure next. Could also be that an injector or two or three are a bit gummed up if the fuel system has been neglected (such as very old, untreated fuel left in the system) at any point in its life.

 

This is exactly as it should be. Stock idle speed for all LS1 F-bodies is 650rpm P/N, 550rpm in gear. For manuals it's 800rpm. This is the factory setting for all examples 1998-02.

Thanks for the idle specs and it's doing what it's supposed to. You can raise idle speed with tuning, but it really shouldn't need a higher idle speed if the cam is stock.

I'm trying to get everything corrected before i do any tuning. You can also upgrade to an alternator that makes more amperage at lower engine speeds, and/or swap to a smaller pulley (but then max rpm is limited, or alternator damage could result - not really a concern if your shift points are still stock though).

i put a new 165 amp alternator on the car last weekend. The problem carried over from the last alternator. Voltage from the alternator on p/n at idle is about 14v with the ac on or off. In gear it's hovering about 12.8v and with the ac on it's down to 12v. But if the engine seems to have a misfire at idle, I'd look into correcting this first. Even if there are no codes, your scanner should show cylinder specific misfire counts. So if it registers the misfires on a general graph, look for the cylinder specific data and see what (or which) cylinder(s) is/are responsible. If the cylinder specific counts don't show anything noteworthy for any specific cylinder, then look at the fuel trim data and see if the LTFTs are elevated on either (or both) banks. They shouldn't really be more then +/- 5% or so on a good running stock car (I'd call +/- 10% the upper limit). If the trims are at all elevated, then you might want to look at fuel pressure next. Could also be that an injector or two or three are a bit gummed up if the fuel system has been neglected (such as very old, untreated fuel left in the system) at any point in its life.

Long term in p/n ac on is:
-2 for bank 1
-1 for bank 2

ac on is:
-3 bank 1
-2 bank 2

in gear ac off:
Both banks -2

in gear ac on:
-2 bank 1
-2 bank 2

I'm gonna get the battery tested next. If you guys see anything with this numbers; let me know. I will really appreciate it.

Ben

 

Battery tested good

 

Need to make a correction.

once everything is fully hot after a drive. Idling in gear with the ac on and blower speed max the voltage is down to 11.5.

the misfires seem to be gone. Even on the tech 2 graph.