Idle and check engine light problems, help plz =[

[PhLoBuS]

Recently I have been getting a really strange idle on my car. Usually it sits at a nice 750rpm and stays there. Now its either there randomly or at a 1000+rpm and not being steady at all. Rpms likes to jump around and I notice that the amp meter for my battery randomly drops down alot. And sometimes Air Bag flashes and I have no clue why. Only thing I have changed recently was the brake pads. I changed my battery cables no luck with that. Any ideas or clues on whats wrong let me know please. thanks!

 

[HISSIN50]

I would go get the alternator tested. Even thought the puter uses 5 volts for its ref voltage, voltage variances can cause issues in the systems which do use 12 volts. This is, unless you think that the idle dropping and U/D's are responsible for the voltage dips.

ANy codes?

Good luck.

 

[PhLoBuS]

definetly not the alternator its brand new

 

[jrichker]

definetly not the alternator its brand new

I'm sure Hissin will agree that there are a lot of "new" alternators that have problems right out of the box. Do yourself a favor and have it checked.

 

[HISSIN50]

I'm sure Hissin will agree that there are a lot of "new" alternators that have problems right out of the box. Do yourself a favor and have it checked.

You know me well Joe. Matter of fact I was just complaining to Daggs yesterday [I think it was him] about that.

On one particular vehicle, I went through a couple alternators in two weeks (one was bad right out of the box, one died within about 10 days and the last is still on there).
I just bought a reman'd alt Sunday for a serious DD (otherwise I would have gotten an aftermarket unit online. This is a well regarded brand too - not cheapie stuff) and it has some bearing noise right out of the box. Also has slightly low output. It will get swapped again once temps drop below 105* here.

As I know JR has said before and will tell you, it is wise to have all alts, starters and batteries bench tested before purchase. I learned my lesson with two of those three in my younger years. And even then, you can still have one that tests ok but it not quite up to par.

Good luck.

 

[Rerun]

HISSIN, what's up dude!~

Anyhow, my LX had a charging problem once, bought 2 brand new alternators, which after being tested were found to be bad. So what I did was rip the alternator out, took it to my local Auto Electric shop and had it tested. If it tests good atleast you can count that out.

Is the battery light in your dash coming on?

 

[garystocker]

The autozone/pep-boys alternators are crap. The new 130 amp and up 3G's are really good. don't you think? Beefy, quality right out of the box.

 

[HISSIN50]

Justin, how ya been?!

I have not seen you in here much. I think the last time was when the front end of your stang sank in mud or something like that.

Gary, I think it is a bit of a crap shoot. I have had good luck on the first try with some reman'd alts and really bad luck with others. They are LLT for a reason.

I have a 170 amper in the '88 which does well - decent lookin alt too.

On my last go-around here, a new alt was not even available at any parts stores in town. A new OEM one online from a discount dealer was ~250 bucks. What can ya do.

 

[Rerun]

Same old **** bro, although I just recnetly picked up a custom 66 fairlane. I'll post pics when I get home. What have you been up too? I got the mustang parked on dry ground, haven't really been driving her much but I feel the urge now!

Getting the stang painted finally, should come out nice!

Sorry, didn't mean to take over this thread.

 

[kennebell331]

The autozone/pep-boys alternators are crap. The new 130 amp and up 3G's are really good. don't you think? Beefy, quality right out of the box.

I don't know about autozone/pepboyz, but NAPA has bad alternaotrs, regardless new or reman. I don't like selling them, cuz I know hes gonna come back. :damnit:

Check if your battery cables are tightly snugged onto the battery, believe it or not, very common problem.

 

[PhLoBuS]

I have a new 3G alternator 150 amp one. Also would a bad alternator cause Check Engine, Low Coolant and Air Bag to come up? I dont think it would...

 

[kennebell331]

Possible. it seems like you have a bad electrical problem if you got those lights flashing.

 

[jrichker]

Check the grounds - all of them...

Grounds are important to any electrical system, and especially to computers.

1.) The main power ground is from engine block to battery: it is the power ground for the starter & alternator.

2.) The secondary power ground is between the back of the intake manifold and the driver's side firewall. It is often missing or loose. It supplies ground for the alternator, A/C compressor clutch and other electrical accessories such as the gauges. Any car that has a 3G alternator needs a 4 gauge ground wire running from the block to the chassis ground where the battery pigtail ground connects.

3.) The computer has its own dedicated power ground that comes off the ground pigtail on the battery ground wire. Due to it's proximity to the battery, it may become corroded by acid fumes from the battery. It is a black cylinder about 2 1/2" long by 1" diameter with a black/lt green wire.

4.) All the sensors have a common separate ground. This includes the TPS, ACT, EGE, BAP, & VSS

5.) The O2 sensor heaters have their own ground (HEGO ground) coming from the computer. This is different and separate from the O2 sensor ground. It is in the fuel injector wiring harness and comes out under the throttle body. It gets connected to a manifold or head bolt.

6.) The TFI module has 2 grounds: one for the foil shield around the wires and another for the module itself.

7.) The computer takes the shield ground for the TFI module and runs it from pin 20 to the chassis near the computer.

8.) The computer's main power ground (the one that comes from the battery ground wire) uses pins 40 & 60 for all the things it controls internally.

See http://www.fluke.com/application_notes/automotive/circuit.asp?AGID=1&SID=103#volt for help troubleshooting voltage drops across grounds

 

[PhLoBuS]

Okay thanks for the info I will check that stuff out asap. Only thing I have done recently to the car was new rotors, brakes and calipers. And earlier this summer I put a trickflow upper/lower intake with 75mm tb and valve covers.